My 4Mhz amplitude modulated audio sstc
Reaching, Mon May 05 2008, 05:45PMa while ago i thought that i had to start something new. drsstc design is great but after 12 drsstcs i said "hey, what am i doing here.?" so this was the day i started reading. richies site and his 4mhz sstc project made me thoughtfully.
but i wanted something new, something cooler. so i started reading about amplitude modulating. well, here it is.
In detail its just a basic Class e amplifier like richie burnett used. i simplified his shematic and played around and this is what i came up with.
the 4 mhz class e part works great and at the moment i still think about the idea to get rid of the big transformer for the audiosignal. unless it sounds really great.
this was the first test of the prototype, so its all really basic.
what i want to try is to use a linear regulator like everyone here knows, for powersupplys etc. the linear regulator is set to around 90% of the input voltage. with a smallsignal amplifier the audiosignal is amplified and then fed to the gate of the linear reg causing the output voltage to change. like this.
in theory i should have a output voltage which isrelatively stable over a wide current range with a modulated audiosignal on top of the dc voltage. in my simulations it all works really great and with the amplification factor and output voltage carefully set, the power dissipation should be less than 30Watts for 120Watss output power. my first tests showed me that the class e part works best with an input voltage of around 50 volts,.
im on holiday now, so this project will be updated as soon as i tried this linear reg. for sure, the shematics shown here are just for showing what i mean. the final circuits are much more complex.
Re: My 4Mhz amplitude modulated audio sstc
..., Mon May 05 2008, 11:01PM
Sounds like a great project, you should be able to get some really nice sounding audio out of it with such a nice high Fo. It is hard to judge audio quility from a youtube video, but it sounds like you have some kind of nonlinearity in your system (saturating the audio transformer?) that is causing some distorsion.
I hope you can get the liner reg to work!
..., Mon May 05 2008, 11:01PM
Sounds like a great project, you should be able to get some really nice sounding audio out of it with such a nice high Fo. It is hard to judge audio quility from a youtube video, but it sounds like you have some kind of nonlinearity in your system (saturating the audio transformer?) that is causing some distorsion.
I hope you can get the liner reg to work!
Re: My 4Mhz amplitude modulated audio sstc
Steve Conner, Tue May 06 2008, 10:50AM
You'll need some kind of RF bypass capacitor between the output of the modulator and the primary coil of the Class-E stage. It's hard to see how it could have worked well without one.
Steve Conner, Tue May 06 2008, 10:50AM
You'll need some kind of RF bypass capacitor between the output of the modulator and the primary coil of the Class-E stage. It's hard to see how it could have worked well without one.
Re: My 4Mhz amplitude modulated audio sstc
Reaching, Tue May 06 2008, 11:20AM
mh, maybe i was lucky with the settings. this is my first class e project, so what kind of rf bypass capacitor do you mean? a cap in parallel with the primary, tuned at resonant frequency? ok, the mosfet got warm in my circuit but i ran it for some hours and nothing bad happend. input voltage is around 40-50volts but i tested 100volts as well. sure, the design is not perfect, but for now it works fine.
maybe someone who already build class e stages can give me some hints to improve my circuit.
well, there was some disortion due to the audio transformer in my previous circuit. the dc current flowing through the transformer caused the transformer to saturate very quickly, and maybe the bad quality of the selfmade mosfet amp caused more disortion.. thats why i try to get rid of it with this linear reg design. today i want to build it and do some research and tests with different loads to see how rugged it is and how much power dissipation i have to expect.
theres still a lot to do, and thats why i thought to open a project thread to get some suggestions from you
Reaching, Tue May 06 2008, 11:20AM
mh, maybe i was lucky with the settings. this is my first class e project, so what kind of rf bypass capacitor do you mean? a cap in parallel with the primary, tuned at resonant frequency? ok, the mosfet got warm in my circuit but i ran it for some hours and nothing bad happend. input voltage is around 40-50volts but i tested 100volts as well. sure, the design is not perfect, but for now it works fine.
maybe someone who already build class e stages can give me some hints to improve my circuit.
well, there was some disortion due to the audio transformer in my previous circuit. the dc current flowing through the transformer caused the transformer to saturate very quickly, and maybe the bad quality of the selfmade mosfet amp caused more disortion.. thats why i try to get rid of it with this linear reg design. today i want to build it and do some research and tests with different loads to see how rugged it is and how much power dissipation i have to expect.
theres still a lot to do, and thats why i thought to open a project thread to get some suggestions from you
Re: My 4Mhz amplitude modulated audio sstc
..., Tue May 06 2008, 06:48PM
I think that he means you need to add a cap from the v+ side of L3 to ground, because as it is the inductance/resistance/losses in general of the audio transformer is being added to L3.
The size for that cap is tricky because having too large of one will kill the high frequency performance.
Also, something that would be interesting to see would be to run this coil strait off of a 'real' audio amplifier. If you coil is drawing 100w at 50v that is 25omhs of impedance--which should be able to work with an audio amplifier without too much trouble. I suppose the biggest problem would be dealing with the nonlinearities of the coil, although it should be possible to inject a DC bais after the dc blocking cap in the amp, although by the time all of that is working it would probably have been easier to just build your own modulator they way you were planning....
..., Tue May 06 2008, 06:48PM
I think that he means you need to add a cap from the v+ side of L3 to ground, because as it is the inductance/resistance/losses in general of the audio transformer is being added to L3.
The size for that cap is tricky because having too large of one will kill the high frequency performance.
Also, something that would be interesting to see would be to run this coil strait off of a 'real' audio amplifier. If you coil is drawing 100w at 50v that is 25omhs of impedance--which should be able to work with an audio amplifier without too much trouble. I suppose the biggest problem would be dealing with the nonlinearities of the coil, although it should be possible to inject a DC bais after the dc blocking cap in the amp, although by the time all of that is working it would probably have been easier to just build your own modulator they way you were planning....
Re: My 4Mhz amplitude modulated audio sstc
uzzors2k, Tue May 06 2008, 09:07PM
Awesome, I'm looking forward to seeing what you come up with!
Sorry, but no constructive criticism.
uzzors2k, Tue May 06 2008, 09:07PM
Awesome, I'm looking forward to seeing what you come up with!
Sorry, but no constructive criticism.
Re: My 4Mhz amplitude modulated audio sstc
Marko, Wed May 07 2008, 10:17AM
Richie Burnett got around all this a much simpler way as I recall -
He just used two class E amplifiers in push pull, and phase modulated one amplifier with audio.
I don't know how he done that, possibly with some sort of crazy PLL circuit.
Power levels and frequencies were of course immense (18Mhz and >1000W with just two IFP460's, I think. Hope I'm not letting out any of his secrets here
).
I don't know much more than that but apparently it is not really worth trying to use some kind of huge amplifier for audio modulation.
I'm not sure how this phase shift modulation sounds, but it may be suffering from supply voltage sag since there's no feedback of any kind to compensate it.
I hope Richie can explain this better some time,
Marko
Marko, Wed May 07 2008, 10:17AM
Richie Burnett got around all this a much simpler way as I recall -
He just used two class E amplifiers in push pull, and phase modulated one amplifier with audio.
I don't know how he done that, possibly with some sort of crazy PLL circuit.
Power levels and frequencies were of course immense (18Mhz and >1000W with just two IFP460's, I think. Hope I'm not letting out any of his secrets here
).I don't know much more than that but apparently it is not really worth trying to use some kind of huge amplifier for audio modulation.
I'm not sure how this phase shift modulation sounds, but it may be suffering from supply voltage sag since there's no feedback of any kind to compensate it.
I hope Richie can explain this better some time,
Marko
Re: My 4Mhz amplitude modulated audio sstc
Reaching, Wed May 07 2008, 01:23PM
well. ive build the linear reg and was surprised.
its really difficult to adjust, but it works quite well. its obviously not that powerful than the audio transformer design, mostly due to the induced extra voltage in the transformer design.
40volts is fine, but the modulation ratio is really small and so on the volume is not as good as i expected.
now, that i know, that this design is worth a try, i want to go further. a new linear reg design for voltages up to 100v is the goal.
after that, the prototyping is almost done and i can start working on my stereo design
Reaching, Wed May 07 2008, 01:23PM
well. ive build the linear reg and was surprised.
its really difficult to adjust, but it works quite well. its obviously not that powerful than the audio transformer design, mostly due to the induced extra voltage in the transformer design.
40volts is fine, but the modulation ratio is really small and so on the volume is not as good as i expected.
now, that i know, that this design is worth a try, i want to go further. a new linear reg design for voltages up to 100v is the goal.
after that, the prototyping is almost done and i can start working on my stereo design
Re: My 4Mhz amplitude modulated audio sstc
GeordieBoy, Wed May 07 2008, 02:54PM
If you want to go down the linear high-level AM route I would recommend investigating the Class-H modulator. This arrangement uses a split rail supply and two linear pass elements to give a very respectible efficiency and low distortion for typical audio signals. The modulation efficiency at the quiescent operating point can be nearly 100% because one pass element is in saturation and the other is in cutoff. Excursions of the audio signal either take one device closer to cutoff, or the other device further towards saturation depending on the polarity of the audio waveform. This situation is a significant improvement on a Class A high-level modulator, but without the complexity of a full-blown PWM switching amplifier.
Some info is here:
(It also doesn't require the special modulation transformer to resist saturation due to the DC flowing in the secondary.)
The dog's bollox of high-level AM modulation is the polyphase Class D switching amplifier, but things like this are difficult for a hobbyist to design, build and set up. Or as Marko eluded there are alternative low-level means of introducing modulation such as FM and out-phasing.
-Richie,
GeordieBoy, Wed May 07 2008, 02:54PM
If you want to go down the linear high-level AM route I would recommend investigating the Class-H modulator. This arrangement uses a split rail supply and two linear pass elements to give a very respectible efficiency and low distortion for typical audio signals. The modulation efficiency at the quiescent operating point can be nearly 100% because one pass element is in saturation and the other is in cutoff. Excursions of the audio signal either take one device closer to cutoff, or the other device further towards saturation depending on the polarity of the audio waveform. This situation is a significant improvement on a Class A high-level modulator, but without the complexity of a full-blown PWM switching amplifier.
Some info is here:
(It also doesn't require the special modulation transformer to resist saturation due to the DC flowing in the secondary.)
The dog's bollox of high-level AM modulation is the polyphase Class D switching amplifier, but things like this are difficult for a hobbyist to design, build and set up. Or as Marko eluded there are alternative low-level means of introducing modulation such as FM and out-phasing.
-Richie,
Re: My 4Mhz amplitude modulated audio sstc
Reaching, Wed May 07 2008, 05:23PM
hey thanks. maybe i´ll try it.
finished the linear regulator prototype and build everything on a larger heatsink.
made a new video with a better cam so you can imagine how well this thing sounds. :)
Reaching, Wed May 07 2008, 05:23PM
hey thanks. maybe i´ll try it.
finished the linear regulator prototype and build everything on a larger heatsink.
made a new video with a better cam so you can imagine how well this thing sounds. :)
Re: My 4Mhz amplitude modulated audio sstc
Firefox, Wed May 07 2008, 08:36PM
Wow, that is awesome! Could you add some values to the schematic? This looks exceedingly simple, and I would like to build one like it to show off in physics class.
Firefox, Wed May 07 2008, 08:36PM
Wow, that is awesome! Could you add some values to the schematic? This looks exceedingly simple, and I would like to build one like it to show off in physics class.
Re: My 4Mhz amplitude modulated audio sstc
Reaching, Wed May 07 2008, 09:13PM
yeah, its pretty simple. next week or so i can get the shematics finished. the shematics shown above do not represent the whole circuit. its a bit more complex than that but compared to other circuits its really simple.
Reaching, Wed May 07 2008, 09:13PM
yeah, its pretty simple. next week or so i can get the shematics finished. the shematics shown above do not represent the whole circuit. its a bit more complex than that but compared to other circuits its really simple.
Re: My 4Mhz amplitude modulated audio sstc
Reaching, Fri May 09 2008, 10:30AM
New Video
I build a new secondary and tuned the class e circuit.i nearly doubled the power and now i think its fine :)
Reaching, Fri May 09 2008, 10:30AM
New Video
I build a new secondary and tuned the class e circuit.i nearly doubled the power and now i think its fine :)
Re: My 4Mhz amplitude modulated audio sstc
Dago, Fri May 09 2008, 11:23AM
Looks and sounds great, looking forward for more information about it. Does the interference (the sizzle or something that appears in the chorus of the first song) come from the coil or does the camera/microphone just get interference from the coil?
Dago, Fri May 09 2008, 11:23AM
Reaching wrote ...
New Video
I build a new secondary and tuned the class e circuit.i nearly doubled the power and now i think its fine :)
New Video
I build a new secondary and tuned the class e circuit.i nearly doubled the power and now i think its fine :)
Looks and sounds great, looking forward for more information about it. Does the interference (the sizzle or something that appears in the chorus of the first song) come from the coil or does the camera/microphone just get interference from the coil?
Re: My 4Mhz amplitude modulated audio sstc
Reaching, Fri May 09 2008, 11:44AM
this noise that appears from time to time is due to the disortion of the microphone. sorry, but i have no better cam for recording. in reality it sounds like some of this ultra high fidelity speakers.
Reaching, Fri May 09 2008, 11:44AM
this noise that appears from time to time is due to the disortion of the microphone. sorry, but i have no better cam for recording. in reality it sounds like some of this ultra high fidelity speakers.
Re: My 4Mhz amplitude modulated audio sstc
Dr. H., Fri May 09 2008, 12:43PM
Awesome Reaching. It will be very cool when you box it
Cheers Huben
Dr. H., Fri May 09 2008, 12:43PM
Awesome Reaching. It will be very cool when you box it
Cheers Huben
Re: My 4Mhz amplitude modulated audio sstc
WaveRider, Fri May 09 2008, 01:55PM
Very nice! The transformer modulation scheme in the drain circuit is a good old-fashioned AM transmitter method for very linear modulation. The drawback is that the audio amplifier must be powerful enough to provide the depth of modulation you need...up to 50% of the total AM signal power for 100% modulation as well as a big enough transformer to avoid saturation (altho' air-gapping the core reduces this effect)...
If you are going to the trouble to design a regulated DC powersupply, why not design a system where you apply the modulation to the regulator feedback. In effect, using the regulator as an audio amplifier that also handily provides DC bias? Then you would only need a small audio signal...and the feedback would help linearity too!
Also, with deep modulation, you get power-dependent detuning of the tesla coil as the discharge size/temperature is modulated. This introduces non-linearities in the acoustic generation. For this reason, a tracking oscillator using a power oscillator or PLL circuit are recommended.. (in fact, most plasma tweeters I have seen use vacuum-tube power oscillators that are "self-tuning"..)
Great work!!!!!
WaveRider, Fri May 09 2008, 01:55PM
Very nice! The transformer modulation scheme in the drain circuit is a good old-fashioned AM transmitter method for very linear modulation. The drawback is that the audio amplifier must be powerful enough to provide the depth of modulation you need...up to 50% of the total AM signal power for 100% modulation as well as a big enough transformer to avoid saturation (altho' air-gapping the core reduces this effect)...
If you are going to the trouble to design a regulated DC powersupply, why not design a system where you apply the modulation to the regulator feedback. In effect, using the regulator as an audio amplifier that also handily provides DC bias? Then you would only need a small audio signal...and the feedback would help linearity too!
Also, with deep modulation, you get power-dependent detuning of the tesla coil as the discharge size/temperature is modulated. This introduces non-linearities in the acoustic generation. For this reason, a tracking oscillator using a power oscillator or PLL circuit are recommended.. (in fact, most plasma tweeters I have seen use vacuum-tube power oscillators that are "self-tuning"..)
Great work!!!!!
Re: My 4Mhz amplitude modulated audio sstc
GeordieBoy, Fri May 09 2008, 03:46PM
Yeah, that is basically what the Class H modulator does. Except it makes use of a split rail supply so that dissipation in the modulator is minimised around the quiescent operating point (normal carrier level.)
By the way, has anyone investigated using Carrier Level Control (DCC) on an audio-modulated Tesla Coil? It would seem like a good way to reduce power draw, minimise corona hiss during quiet passages, and maximise the peak audio volume achieveable with a given set of power semis.
-Richie,
GeordieBoy, Fri May 09 2008, 03:46PM
If you are going to the trouble to design a regulated DC powersupply, why not design a system where you apply the modulation to the regulator feedback. In effect, using the regulator as an audio amplifier that also handily provides DC bias?
Yeah, that is basically what the Class H modulator does. Except it makes use of a split rail supply so that dissipation in the modulator is minimised around the quiescent operating point (normal carrier level.)
By the way, has anyone investigated using Carrier Level Control (DCC) on an audio-modulated Tesla Coil? It would seem like a good way to reduce power draw, minimise corona hiss during quiet passages, and maximise the peak audio volume achieveable with a given set of power semis.
-Richie,
Re: My 4Mhz amplitude modulated audio sstc
Reaching, Sun Jun 15 2008, 10:13AM
ive been working on this project for weeks now and made a board, which includes the whole circuit.
its fully analog, without an ic or something. there is a crystal oscillator with 4 mhz for the drive signal. amplified by a simple bc546 transistor and a push pull stage of bd139/140, then fed to a gdt to the class e stage.
the audiosignal is amplified by another simple bc546 with emitter current feedback to provide simple adjustment. a dc bias pot with a smal cap in parallel is for adjusting the dc bias of the linear regulator. you adjust this pot for around 30 to 35v output. the amplifier stage is adjusted to provide around 20-30% modulation of the mosfet gate.
both mosfets are cheap irf630, and all the other parts are easily availiable too. all you need is to plug it in and enjoy :) a transformer with 30V AC and 3-4A current is recommned. the ac voltage is rectified on board and smoothed with 13200µF 50V of capacity.
Reaching, Sun Jun 15 2008, 10:13AM
ive been working on this project for weeks now and made a board, which includes the whole circuit.
its fully analog, without an ic or something. there is a crystal oscillator with 4 mhz for the drive signal. amplified by a simple bc546 transistor and a push pull stage of bd139/140, then fed to a gdt to the class e stage.
the audiosignal is amplified by another simple bc546 with emitter current feedback to provide simple adjustment. a dc bias pot with a smal cap in parallel is for adjusting the dc bias of the linear regulator. you adjust this pot for around 30 to 35v output. the amplifier stage is adjusted to provide around 20-30% modulation of the mosfet gate.
both mosfets are cheap irf630, and all the other parts are easily availiable too. all you need is to plug it in and enjoy :) a transformer with 30V AC and 3-4A current is recommned. the ac voltage is rectified on board and smoothed with 13200µF 50V of capacity.
Re: My 4Mhz amplitude modulated audio sstc
Myke, Sun Jun 15 2008, 05:34PM
Looks very cool. Nice work.
Myke, Sun Jun 15 2008, 05:34PM
Looks very cool. Nice work.
Re: My 4Mhz amplitude modulated audio sstc
uzzors2k, Sun Jun 15 2008, 06:56PM
Wonderful. Is the sound quality really crystal clear, and is there much/any noise from the streamers? My PLL class E coil is useless for audio modulating because the streamers hiss so loudly. I'm not sure if it's the PLL, my PSU or the low frequency that does it.
uzzors2k, Sun Jun 15 2008, 06:56PM
Wonderful. Is the sound quality really crystal clear, and is there much/any noise from the streamers? My PLL class E coil is useless for audio modulating because the streamers hiss so loudly. I'm not sure if it's the PLL, my PSU or the low frequency that does it.
Re: My 4Mhz amplitude modulated audio sstc
Reaching, Sun Jun 15 2008, 07:06PM
the streamers are almost silent, and around 2cm long. there is no hiss from the flame itself
sound is wonderful, crystalclear, yes. :)
Reaching, Sun Jun 15 2008, 07:06PM
the streamers are almost silent, and around 2cm long. there is no hiss from the flame itself
sound is wonderful, crystalclear, yes. :)
Re: My 4Mhz amplitude modulated audio sstc
Firefox, Mon Jun 16 2008, 02:02AM
That is a beautiful thing *starts scrounging for parts*.
Firefox, Mon Jun 16 2008, 02:02AM
That is a beautiful thing *starts scrounging for parts*.
Re: My 4Mhz amplitude modulated audio sstc
Arcstarter, Mon Jun 16 2008, 02:49AM
Arcstarter, Mon Jun 16 2008, 02:49AM
Firefox wrote ...
That is a beautiful thing *starts scrounging for parts*.
Haha i do the same thing every time i see someone else's projects.That is a beautiful thing *starts scrounging for parts*.
Re: My 4Mhz amplitude modulated audio sstc
teslacoolguy, Mon Jun 16 2008, 03:56AM
Can you post the pcb files for this thing?
teslacoolguy, Mon Jun 16 2008, 03:56AM
Can you post the pcb files for this thing?
Re: My 4Mhz amplitude modulated audio sstc
GeordieBoy, Mon Jun 16 2008, 10:01AM
Reaching - What material are the two toroids? I assume the RF drive transformer is Mn:Zn ferrite, and it looks like your RF choke is using the same material? A closed ferrite toroid is not really the best choice for the PA's drain choke, because it can saturate due to the DC current component. You might see better performance (better efficiency and cooler PA MOSFET) using a Type-2 iron powder toroid, or a gapped ferrite or stick inductor here. These generally work better as RFCs than ferrite with no air-gap.
Just a comment. Cool project and a nice PCB too!
-Richie,
GeordieBoy, Mon Jun 16 2008, 10:01AM
Reaching - What material are the two toroids? I assume the RF drive transformer is Mn:Zn ferrite, and it looks like your RF choke is using the same material? A closed ferrite toroid is not really the best choice for the PA's drain choke, because it can saturate due to the DC current component. You might see better performance (better efficiency and cooler PA MOSFET) using a Type-2 iron powder toroid, or a gapped ferrite or stick inductor here. These generally work better as RFCs than ferrite with no air-gap.
Just a comment. Cool project and a nice PCB too!
-Richie,
Re: My 4Mhz amplitude modulated audio sstc
Marko, Mon Jun 16 2008, 12:48PM
Hi guys,
Yes, for drain chokes, best to use are the yellow-white iron powder toroids from SMPS output chokes. The choke only sees DC so there is no need to be worried about dissipation on it.
One thing I was personally wondering about from time to time - what *assures* that volt-seconds on the link choke remain constant in class E amplifier? While device is the choke sees full bus voltage for full time, but during off-time wouldn't it see sinusoidal voltage slope?
Why doesn't this disbalance the Vs on the choke?
Marko
Marko, Mon Jun 16 2008, 12:48PM
Hi guys,
Yes, for drain chokes, best to use are the yellow-white iron powder toroids from SMPS output chokes. The choke only sees DC so there is no need to be worried about dissipation on it.
One thing I was personally wondering about from time to time - what *assures* that volt-seconds on the link choke remain constant in class E amplifier? While device is the choke sees full bus voltage for full time, but during off-time wouldn't it see sinusoidal voltage slope?
Why doesn't this disbalance the Vs on the choke?
Marko
Re: My 4Mhz amplitude modulated audio sstc
GeordieBoy, Mon Jun 16 2008, 02:24PM
No don't use yellow/white iron powder (type-26) for Radio Frequency chokes (or green/blue type-52 for that matter! These materials are very lossy above a few hundred kHz and will turn a nice crispy brown colour quite quickly when exposed to rapid large flux excursions. You ideally want carbonyl iron powder like the red/clear type-2 toroids commonly used by radio hams. I forget the other type, maybe 6 or 8? Gapped ferrite is okay though.
The drain choke sees a voltage equal to the supply voltage minus the drain voltage of the MOSFET. The time-averaged value of the applied voltage is zero. Energy that is pumped into the magnetic field when the switch is closed, is released to the resonant tank circuit when the switch opens. It is similar to a boost or flyback converter in that respect.
-Richie,
GeordieBoy, Mon Jun 16 2008, 02:24PM
No don't use yellow/white iron powder (type-26) for Radio Frequency chokes (or green/blue type-52 for that matter! These materials are very lossy above a few hundred kHz and will turn a nice crispy brown colour quite quickly when exposed to rapid large flux excursions. You ideally want carbonyl iron powder like the red/clear type-2 toroids commonly used by radio hams. I forget the other type, maybe 6 or 8? Gapped ferrite is okay though.
The drain choke sees a voltage equal to the supply voltage minus the drain voltage of the MOSFET. The time-averaged value of the applied voltage is zero. Energy that is pumped into the magnetic field when the switch is closed, is released to the resonant tank circuit when the switch opens. It is similar to a boost or flyback converter in that respect.
-Richie,
Re: My 4Mhz amplitude modulated audio sstc
Marko, Mon Jun 16 2008, 02:30PM
I don't see what is the problem, how you mean this? Since DC link choke carries only DC current with very small ripple, although it sees AC voltage. I always use them on royer oscillators without any problems.
Matt Bingham has used them a lot for class E amplifiers at very high frequencies without any problems too.
I thought you used them as well Richie, for class E amps. Why aren't all our chokes frying then?
Long ago I was also afraid of using the powder toroids for link chokes thinking they are 'lossy' but everyone assured me against that.
And indeed they work rather well, once enough inductance is used to keep ripple small... (??)
High frequency actually seemed to be beneficial by allowing to use less inductance.
Marko, Mon Jun 16 2008, 02:30PM
No don't use yellow/white iron powder (type-26) for Radio Frequency chokes (or green/blue type-52 for that matter! These materials are very lossy above a few hundred kHz and will turn a nice crispy brown colour quite quickly when exposed to rapid large flux excursions. You ideally want carbonyl iron powder like the red/clear type-2 toroids commonly used by radio hams. I forget the other type, maybe 6 or 8? Gapped ferrite is okay though.
I don't see what is the problem, how you mean this? Since DC link choke carries only DC current with very small ripple, although it sees AC voltage. I always use them on royer oscillators without any problems.
Matt Bingham has used them a lot for class E amplifiers at very high frequencies without any problems too.
I thought you used them as well Richie, for class E amps. Why aren't all our chokes frying then?
Long ago I was also afraid of using the powder toroids for link chokes thinking they are 'lossy' but everyone assured me against that.
And indeed they work rather well, once enough inductance is used to keep ripple small... (??)
High frequency actually seemed to be beneficial by allowing to use less inductance.
Re: My 4Mhz amplitude modulated audio sstc
GeordieBoy, Mon Jun 16 2008, 03:09PM
It depends on the power level you are running at Marko. Type-26 is the cheapest crapiest grade of iron-powder for use in very high-volume low-cost SMPSUs operating the tens or low hundreds of kHz. If it suffices for any other particular application then great, because it is dirt cheap, but there are many better materials for RFCs.
My point was that at high power levels and high frequencies where only the right materials will survive, type-2 Fe powder is best for minimal heating as the drain choke.
GeordieBoy, Mon Jun 16 2008, 03:09PM
It depends on the power level you are running at Marko. Type-26 is the cheapest crapiest grade of iron-powder for use in very high-volume low-cost SMPSUs operating the tens or low hundreds of kHz. If it suffices for any other particular application then great, because it is dirt cheap, but there are many better materials for RFCs.
My point was that at high power levels and high frequencies where only the right materials will survive, type-2 Fe powder is best for minimal heating as the drain choke.
Re: My 4Mhz amplitude modulated audio sstc
Reaching, Mon Jun 16 2008, 04:40PM
its almost impossible to try everything out. thats why i used a "normal" ferrite core for the choke. from my expierience with this circuit that material worked very well without too much heating. i dont know the exact type of material though. just some cheap ferrites. the drain choke is getting hot after a few minutes, around 40°C and remains at this temperature, . thats ok i think. i just dont wanted to try more out, cause i was worried that the wrong core material and inductance can distort the audiosignal modulated on the dc voltage. and the streamers are long enough. i wanted to build a high quality plasma speaker and thats it.. if you think, that other core material can improve efficiency in audio quality and volume, i´ll try it out for sure. but longer streamers can distort the audio so im not aiming for long sparks.
Reaching, Mon Jun 16 2008, 04:40PM
its almost impossible to try everything out. thats why i used a "normal" ferrite core for the choke. from my expierience with this circuit that material worked very well without too much heating. i dont know the exact type of material though. just some cheap ferrites. the drain choke is getting hot after a few minutes, around 40°C and remains at this temperature, . thats ok i think. i just dont wanted to try more out, cause i was worried that the wrong core material and inductance can distort the audiosignal modulated on the dc voltage. and the streamers are long enough. i wanted to build a high quality plasma speaker and thats it.. if you think, that other core material can improve efficiency in audio quality and volume, i´ll try it out for sure. but longer streamers can distort the audio so im not aiming for long sparks.
Re: My 4Mhz amplitude modulated audio sstc
Reaching, Mon Jun 16 2008, 04:44PM
Sorry for doubleposting. heres the improved shematic i use.. the layout is the same, just a few changes in resistor values and gdt and choke
Reaching, Mon Jun 16 2008, 04:44PM
Sorry for doubleposting. heres the improved shematic i use.. the layout is the same, just a few changes in resistor values and gdt and choke
Re: My 4Mhz amplitude modulated audio sstc
teslacoolguy, Mon Jun 16 2008, 09:46PM
What can the bc546 be substuted for? (I am assuming that a bc550 will work just fine.)
Edit: Also i was wondering what awg is the secondary? And what are the specs, diameter, hight and also what kind of heatsinks do you need for the fets.
teslacoolguy, Mon Jun 16 2008, 09:46PM
What can the bc546 be substuted for? (I am assuming that a bc550 will work just fine.)
Edit: Also i was wondering what awg is the secondary? And what are the specs, diameter, hight and also what kind of heatsinks do you need for the fets.
Re: My 4Mhz amplitude modulated audio sstc
Marko, Tue Jun 17 2008, 12:45PM
Oh, OK then. Still with low cost and availability of those toroids, why not use them as long as they work?
As far as I think I understand, the *ripple current*, that is, the AC component of current, is what makes the core get hot. To reduce the ripple I want higher inductance, but inductance is limited by max ampere turns before the core goes into saturation.
So, if I need more power I can use several cores stacked or as separate inductors in series to reduce cookage.
Material 2 has mu relative of only 10 though, bug I heard it's praised for RF use. Can it also be used as AC current choke or transformer core at it's rated(2-20Mhz) frequencies?
Marko, Tue Jun 17 2008, 12:45PM
It depends on the power level you are running at Marko. Type-26 is the cheapest crapiest grade of iron-powder for use in very high-volume low-cost SMPSUs operating the tens or low hundreds of kHz. If it suffices for any other particular application then great, because it is dirt cheap, but there are many better materials for RFCs.
Oh, OK then. Still with low cost and availability of those toroids, why not use them as long as they work?
As far as I think I understand, the *ripple current*, that is, the AC component of current, is what makes the core get hot. To reduce the ripple I want higher inductance, but inductance is limited by max ampere turns before the core goes into saturation.
So, if I need more power I can use several cores stacked or as separate inductors in series to reduce cookage.
Material 2 has mu relative of only 10 though, bug I heard it's praised for RF use. Can it also be used as AC current choke or transformer core at it's rated(2-20Mhz) frequencies?
Re: My 4Mhz amplitude modulated audio sstc
GeordieBoy, Tue Jun 17 2008, 03:25PM
By all means use type-26 for any application that you can get away with! Just watch out for any initial signs of heating because the organic binding material is susceptible to thermal degradation. This aging further increases core loss and can ultimately lead to thermal runaway.
You can increase inductance by stacking iron-powder cores, although keep in mind that this increases the volume of magnetic material in the field and therefore increases total core loss again. Micrometals design software is excellent for quickly assessing these tradeoffs although it does contain a few bugs.
Although the drain choke is designed to approximate a constant current source, "more inductance" isn't always better. I would specify the drain RFC to have a ripple of about +/-5% of the DC supply current at the chosen operating frequency. If you make the RFC too big you can run into problems with squegging and sub-harmonic oscillations in the power amplifier.
The inductance of the drain choke also plays a very important role in limiting how quickly you can modulate the PA in designs like this with high-level Amplitude Modulation. Too large an RFC will act too strongly to keep the drain current constant and will prevent rapid modulation of the amplitude of the RF output. The drain choke and power amplifier essentially form a series RL network from the point of view of the modulator, so the choice of L affects the bandwidth of the audio that can be modulated onto the carrier.
Type-2 could in theory be used at any frequency although you would need a lot of turns to get a useful inductor for operation in the kHz or Hz. Such a device would have high copper loss and be indicative that a better material choice should be made for more balanced copper vs core losses.
-Richie,
GeordieBoy, Tue Jun 17 2008, 03:25PM
By all means use type-26 for any application that you can get away with!
Just watch out for any initial signs of heating because the organic binding material is susceptible to thermal degradation. This aging further increases core loss and can ultimately lead to thermal runaway.You can increase inductance by stacking iron-powder cores, although keep in mind that this increases the volume of magnetic material in the field and therefore increases total core loss again. Micrometals design software is excellent for quickly assessing these tradeoffs although it does contain a few bugs.
Although the drain choke is designed to approximate a constant current source, "more inductance" isn't always better. I would specify the drain RFC to have a ripple of about +/-5% of the DC supply current at the chosen operating frequency. If you make the RFC too big you can run into problems with squegging and sub-harmonic oscillations in the power amplifier.
The inductance of the drain choke also plays a very important role in limiting how quickly you can modulate the PA in designs like this with high-level Amplitude Modulation. Too large an RFC will act too strongly to keep the drain current constant and will prevent rapid modulation of the amplitude of the RF output. The drain choke and power amplifier essentially form a series RL network from the point of view of the modulator, so the choice of L affects the bandwidth of the audio that can be modulated onto the carrier.
Type-2 could in theory be used at any frequency although you would need a lot of turns to get a useful inductor for operation in the kHz or Hz. Such a device would have high copper loss and be indicative that a better material choice should be made for more balanced copper vs core losses.
-Richie,
Re: My 4Mhz amplitude modulated audio sstc
Reaching, Tue Jun 17 2008, 05:02PM
The primary is 4 turns with 6cm diameter and 1,5mm². i dont know the awg cause here in germany every wire thickness is given in "mm" or mm²"
the secondary is 5cm in diameter and 8 cm in height, wound with 0,5mm enameled copper wire.
for the bc546 you can use just any small signal npn transistor you have. it should stand up voltages up to 80v and currents of around 100mA, nothing special. you can use 60v types for sure
Reaching, Tue Jun 17 2008, 05:02PM
The primary is 4 turns with 6cm diameter and 1,5mm². i dont know the awg cause here in germany every wire thickness is given in "mm" or mm²"
the secondary is 5cm in diameter and 8 cm in height, wound with 0,5mm enameled copper wire.
for the bc546 you can use just any small signal npn transistor you have. it should stand up voltages up to 80v and currents of around 100mA, nothing special. you can use 60v types for sure
Re: My 4Mhz amplitude modulated audio sstc
teslacoolguy, Fri Jun 20 2008, 02:47AM
What kind of heatsinking is needed for the mosfets?
teslacoolguy, Fri Jun 20 2008, 02:47AM
What kind of heatsinking is needed for the mosfets?
Re: My 4Mhz amplitude modulated audio sstc
Firefox, Sun Jun 22 2008, 05:25AM
I was trying to translate the writing on the schematic and there were only two things I couldn't understand on it, one was the description of the heatsink; Q5, Q6 mount on a good heatsink At least 3.2K/W?. What is the 3.2 K/W? Also, on C11, what does the description 4.7N 630V FKP1 mean? I assume its 4.7 nF 630V, but what is FKP? I hope my questions aren't too much trouble.
Firefox, Sun Jun 22 2008, 05:25AM
I was trying to translate the writing on the schematic and there were only two things I couldn't understand on it, one was the description of the heatsink; Q5, Q6 mount on a good heatsink At least 3.2K/W?. What is the 3.2 K/W? Also, on C11, what does the description 4.7N 630V FKP1 mean? I assume its 4.7 nF 630V, but what is FKP? I hope my questions aren't too much trouble.
Re: My 4Mhz amplitude modulated audio sstc
teslacoolguy, Sun Jun 22 2008, 05:28AM
Im using a very big heatsink but im having problems with the audio coming into the coil. The bias pots work but i dont get any audio modulation or breakout.
teslacoolguy, Sun Jun 22 2008, 05:28AM
Im using a very big heatsink but im having problems with the audio coming into the coil. The bias pots work but i dont get any audio modulation or breakout.
Re: My 4Mhz amplitude modulated audio sstc
Reaching, Sun Jun 22 2008, 11:44AM
The coil is difficult to tune, so its out of question that you need some time to make things right. you´ll need some time to get the right resonant frequency.
my tip. use a long copper wire, around 10cm on top of your secondary. measure the voltage on drain of the first mosfet and adjust the pot for maximum output voltage. the first thing you have to do is to get the right frequency, otherwise its extremely difficult to get breakout.
put the copper wire on top of your secondary and watch out for the current being drawn on the 50v line. then cut the copper in say 1cm pieces and watch the current. it should get higher to around 1,5A-2A where you should get breakout.
the grounding of your secondary coil is another tricky part. in one of my circuits it was enough to ground it on the mains, but for some reason it can be better to connect the secondary ground to the circuit ground.
the complicated part in this circuit is to get breakout. when youve done you can adjust the bias pot to around 30v and then you can adjust the pot for the amplifier. thats it.
the circuit has no feedback or something else in cause of simplicity, so tuning the secondary to 4mhz is the tricky part.
the heatsink of 3,2k/W is a standartised formula for heat dissipation here in germany. it means that for a given dissipation of say 1watts into the heatsink the heatsink is getting 3,2kelvin warmer. for 10watts its 32kelvin or 32degree celsius.
try reversing the primary. that can help too. the primary coil is difficult too. i had best performance with the primary put 1,5cm above the first secondary winding
fkp1 is a pulse capacitor from a german capacitor facility. you just have to use a good cap here cause the whole current is floing through it. just use a good foil cap
hope that helps
Reaching, Sun Jun 22 2008, 11:44AM
The coil is difficult to tune, so its out of question that you need some time to make things right. you´ll need some time to get the right resonant frequency.
my tip. use a long copper wire, around 10cm on top of your secondary. measure the voltage on drain of the first mosfet and adjust the pot for maximum output voltage. the first thing you have to do is to get the right frequency, otherwise its extremely difficult to get breakout.
put the copper wire on top of your secondary and watch out for the current being drawn on the 50v line. then cut the copper in say 1cm pieces and watch the current. it should get higher to around 1,5A-2A where you should get breakout.
the grounding of your secondary coil is another tricky part. in one of my circuits it was enough to ground it on the mains, but for some reason it can be better to connect the secondary ground to the circuit ground.
the complicated part in this circuit is to get breakout. when youve done you can adjust the bias pot to around 30v and then you can adjust the pot for the amplifier. thats it.
the circuit has no feedback or something else in cause of simplicity, so tuning the secondary to 4mhz is the tricky part.
the heatsink of 3,2k/W is a standartised formula for heat dissipation here in germany. it means that for a given dissipation of say 1watts into the heatsink the heatsink is getting 3,2kelvin warmer. for 10watts its 32kelvin or 32degree celsius.
try reversing the primary. that can help too. the primary coil is difficult too. i had best performance with the primary put 1,5cm above the first secondary winding
fkp1 is a pulse capacitor from a german capacitor facility. you just have to use a good cap here cause the whole current is floing through it. just use a good foil cap
hope that helps
Re: My 4Mhz amplitude modulated audio sstc
Firefox, Sun Jun 22 2008, 05:37PM
Thank you Reaching, that helps a lot. About tuning the secondary to the 4Mhz crystal, why not use a NE555 or TL494 and tune the primary to the secondary circuit so that you don't have to be perfectly at 4MHz?
Firefox, Sun Jun 22 2008, 05:37PM
Thank you Reaching, that helps a lot. About tuning the secondary to the 4Mhz crystal, why not use a NE555 or TL494 and tune the primary to the secondary circuit so that you don't have to be perfectly at 4MHz?
Re: My 4Mhz amplitude modulated audio sstc
Reaching, Sun Jun 22 2008, 07:41PM
a ne555 and a tl494 cant get higher than max 2mhz, and at these frequencies, the discharge makes still a lot of noise. 4mhz is totally silent. i used a crystal oscillator cause it was easier, but for sure you can use a 74hc4046 or some other high frequency pll to tune for the right frequency.
but at class e its difficult and makes not a lot of sense to tune the oscillator, cause you have an adjusted class e circuit which is only efficiently at a given fres, so i thought, why not tune the seondary to a given primary frequency with good adjusted and efficient class e circuit.
its really easy to tune the secondary and it makes a lot more sense, in case of simplicity and efficiency.
Reaching, Sun Jun 22 2008, 07:41PM
a ne555 and a tl494 cant get higher than max 2mhz, and at these frequencies, the discharge makes still a lot of noise. 4mhz is totally silent. i used a crystal oscillator cause it was easier, but for sure you can use a 74hc4046 or some other high frequency pll to tune for the right frequency.
but at class e its difficult and makes not a lot of sense to tune the oscillator, cause you have an adjusted class e circuit which is only efficiently at a given fres, so i thought, why not tune the seondary to a given primary frequency with good adjusted and efficient class e circuit.
its really easy to tune the secondary and it makes a lot more sense, in case of simplicity and efficiency.
Re: My 4Mhz amplitude modulated audio sstc
GeordieBoy, Sun Jun 22 2008, 07:50PM
I designed my 4MHz and 8MHz HF-SSTC units with the same viewpoint. I used a fixed crystal oscillator and set up all the gate-drive and matching networks to work correctly at the operating frequency. The only things that needed tuning were:
1. The Fres of the secondary
2. The coupling factor to get correct Class-E waveform with a soft-landing
3. The shunt cap across the MOSFET to set the power level.
The optimum shunt capacitor value actually varies depending on the supply voltage. This is one of the things that hampers efficiency and degrades linearity when high-level Amplitude Modulation is applied to a class E amplifier.
I also agree with Reaching's statements about tuning and layout becoming more critical with increasing frequency. The coil became a lot more sensitive to its surroundings at 8MHz than at 4MHz. And at 18MHz things get very finicky.
-Richie,
GeordieBoy, Sun Jun 22 2008, 07:50PM
I designed my 4MHz and 8MHz HF-SSTC units with the same viewpoint. I used a fixed crystal oscillator and set up all the gate-drive and matching networks to work correctly at the operating frequency. The only things that needed tuning were:
1. The Fres of the secondary
2. The coupling factor to get correct Class-E waveform with a soft-landing
3. The shunt cap across the MOSFET to set the power level.
The optimum shunt capacitor value actually varies depending on the supply voltage. This is one of the things that hampers efficiency and degrades linearity when high-level Amplitude Modulation is applied to a class E amplifier.
I also agree with Reaching's statements about tuning and layout becoming more critical with increasing frequency. The coil became a lot more sensitive to its surroundings at 8MHz than at 4MHz. And at 18MHz things get very finicky.
-Richie,
Re: My 4Mhz amplitude modulated audio sstc
Firefox, Sun Jun 22 2008, 11:40PM
Would this circuit work better in a Faraday cage to take away environmental EM interference then? In any case, I see your point about using the fixed frequency oscillator.
Firefox, Sun Jun 22 2008, 11:40PM
Would this circuit work better in a Faraday cage to take away environmental EM interference then? In any case, I see your point about using the fixed frequency oscillator.
Re: My 4Mhz amplitude modulated audio sstc
teslacoolguy, Mon Jun 23 2008, 12:12AM
Ok i tried to make the layout very low inductance and todays testing just led to a mosfet explosion
and i am glad you told me that the shunt capacitor has to be of high quality. I dont have any pulse rated caps of that value so im probably going to end up sampling some cde caps for that.
teslacoolguy, Mon Jun 23 2008, 12:12AM
Ok i tried to make the layout very low inductance and todays testing just led to a mosfet explosion
and i am glad you told me that the shunt capacitor has to be of high quality. I dont have any pulse rated caps of that value so im probably going to end up sampling some cde caps for that.Re: My 4Mhz amplitude modulated audio sstc
Myke, Sat Jun 28 2008, 05:59PM
If I wanted to make the same coil without the audio modulation section and also change the oscillator frequency, would I have to change T1, C4, and C5? Also what does C10 do? If I were to use a different MOSFET would I have to use a different cap (C10)?
really late edit:
HAHA. I laugh at myself now for asking these questions. It's a class E amp on the output so yeah, I would have to change stuff so everything switched at the right time.
Myke, Sat Jun 28 2008, 05:59PM
If I wanted to make the same coil without the audio modulation section and also change the oscillator frequency, would I have to change T1, C4, and C5? Also what does C10 do? If I were to use a different MOSFET would I have to use a different cap (C10)?
really late edit:
HAHA. I laugh at myself now for asking these questions. It's a class E amp on the output so yeah, I would have to change stuff so everything switched at the right time.
Re: My 4Mhz amplitude modulated audio sstc
eniyuki, Tue Dec 22 2009, 05:22AM
eniyuki, Tue Dec 22 2009, 05:22AM
Reaching wrote ...
Sorry for doubleposting. heres the improved shematic i use.. the layout is the same, just a few changes in resistor values and gdt and choke
can anyone tell me what is that QG1 there? i can see 1 4mhz xtal and a chipSorry for doubleposting. heres the improved shematic i use.. the layout is the same, just a few changes in resistor values and gdt and choke
Re: My 4Mhz amplitude modulated audio sstc
Experimentonomen, Tue Dec 22 2009, 09:22AM
Its a crystal oscillator module, looks like a little rectangular metal box with four legs.
Experimentonomen, Tue Dec 22 2009, 09:22AM
Its a crystal oscillator module, looks like a little rectangular metal box with four legs.
Re: My 4Mhz amplitude modulated audio sstc
eniyuki, Tue Dec 22 2009, 03:42PM
oh i see, didnt see one before. thank you
eniyuki, Tue Dec 22 2009, 03:42PM
oh i see, didnt see one before. thank you
Re: My 4Mhz amplitude modulated audio sstc
eniyuki, Fri Dec 25 2009, 11:53AM
is this the right part for QG1 in the schematic?
eniyuki, Fri Dec 25 2009, 11:53AM
is this the right part for QG1 in the schematic?
Re: My 4Mhz amplitude modulated audio sstc
Experimentonomen, Fri Dec 25 2009, 12:55PM
I´d say yes.
Experimentonomen, Fri Dec 25 2009, 12:55PM
I´d say yes.
Re: My 4Mhz amplitude modulated audio sstc
eniyuki, Fri Jan 22 2010, 06:06PM
can i use 2 irfp250 or 450 instead of irf630? dont have 630 here locally
eniyuki, Fri Jan 22 2010, 06:06PM
can i use 2 irfp250 or 450 instead of irf630? dont have 630 here locally
Re: My 4Mhz amplitude modulated audio sstc
eniyuki, Wed Jan 27 2010, 09:26AM
any one? Can i use irfp450?
eniyuki, Wed Jan 27 2010, 09:26AM
any one? Can i use irfp450?
Re: My 4Mhz amplitude modulated audio sstc
mb, Wed Jan 27 2010, 12:32PM
For Q5 you can use a IRFP450.
For Q6 i wouldn't use a IRFP450
because Ciss is four times higher as Ciss from the IRF630
this means you need more power to drive the mosfet.
look at this guy ,he build a 4Mhz class e sstc with a IRFP460
(look under sstc 4)
mb, Wed Jan 27 2010, 12:32PM
For Q5 you can use a IRFP450.
For Q6 i wouldn't use a IRFP450
because Ciss is four times higher as Ciss from the IRF630
this means you need more power to drive the mosfet.
look at this guy ,he build a 4Mhz class e sstc with a IRFP460
(look under sstc 4)
Re: My 4Mhz amplitude modulated audio sstc
eniyuki, Wed Jan 27 2010, 07:18PM
eniyuki, Wed Jan 27 2010, 07:18PM
mb wrote ...
For Q5 you can use a IRFP450.
For Q6 i wouldn't use a IRFP450
because Ciss is four times higher as Ciss from the IRF630
this means you need more power to drive the mosfet.
look at this guy ,he build a 4Mhz class e sstc with a IRFP460
(look under sstc 4)
thanks for the link! Can I add audio modulation to sstc4? in the above link?For Q5 you can use a IRFP450.
For Q6 i wouldn't use a IRFP450
because Ciss is four times higher as Ciss from the IRF630
this means you need more power to drive the mosfet.
look at this guy ,he build a 4Mhz class e sstc with a IRFP460
(look under sstc 4)
Re: My 4Mhz amplitude modulated audio sstc
eniyuki, Wed Feb 03 2010, 07:36AM
sorry for double post, but can i add audio modulation to sstc4 (link above)? if so, what pin should i use?
eniyuki, Wed Feb 03 2010, 07:36AM
sorry for double post, but can i add audio modulation to sstc4 (link above)? if so, what pin should i use?
Re: My 4Mhz amplitude modulated audio sstc
eniyuki, Thu Feb 04 2010, 05:42PM
eniyuki, Thu Feb 04 2010, 05:42PM
mb wrote ...
For Q5 you can use a IRFP450.
For Q6 i wouldn't use a IRFP450
because Ciss is four times higher as Ciss from the IRF630
this means you need more power to drive the mosfet.
look at this guy ,he build a 4Mhz class e sstc with a IRFP460
(look under sstc 4)
sorry for bumps. anyone can answer my question? For Q5 you can use a IRFP450.
For Q6 i wouldn't use a IRFP450
because Ciss is four times higher as Ciss from the IRF630
this means you need more power to drive the mosfet.
look at this guy ,he build a 4Mhz class e sstc with a IRFP460
(look under sstc 4)
Re: My 4Mhz amplitude modulated audio sstc
Arcstarter, Thu Feb 04 2010, 09:03PM
Apologizing does not excuse acting against the rules, and doing it twice certainly does not help...
No, with that circuit there is not a way to audio modulate it... If you checked the data sheets for each part and took some time to understand it (instead of building something you do not understand) then you could answer it yourself. This forum is mostly for help with something that has not been fully documented, or you cannot find an easy answer, or a dilemma between two different possibilities.
Arcstarter, Thu Feb 04 2010, 09:03PM
Apologizing does not excuse acting against the rules, and doing it twice certainly does not help...
No, with that circuit there is not a way to audio modulate it... If you checked the data sheets for each part and took some time to understand it (instead of building something you do not understand) then you could answer it yourself. This forum is mostly for help with something that has not been fully documented, or you cannot find an easy answer, or a dilemma between two different possibilities.
Re: My 4Mhz amplitude modulated audio sstc
teslaozone, Fri Aug 05 2011, 07:15PM
Hello, Im planning on building this for my highschool science fair. Does anyone know if there is an english schematic? I do have experience building tesla coils, but i have never built something off a schematic before, and it doesnt help that it its a different language. Thanks
teslaozone, Fri Aug 05 2011, 07:15PM
Hello, Im planning on building this for my highschool science fair. Does anyone know if there is an english schematic? I do have experience building tesla coils, but i have never built something off a schematic before, and it doesnt help that it its a different language. Thanks
Re: My 4Mhz amplitude modulated audio sstc
SKA, Mon Aug 08 2011, 12:15PM
Hi teslazone
I'll try to translate the schematic for you:
The Notes on the right side of the shematic:
-C6 and C8 are high-pass capacitors. If you want to hear the higher frequencies of the audio-input you should choose 100nF types
-R5, R7, R8 and R13 are high precision trimmer-resistors
-Q5 and Q6 should be mounted on a heatsink with a thermal conductivity of maximal 3,2K/W
-The 50V Power supply should have a minimum of ripple voltage. Use a capacitor with at least 10000µF. The current is about 1,8 to 2,3 Amps
The current of the 12V Power supply is about 0,3 Amps
R13 regulates the bias voltage for the Mosfet (Q5). Set this voltage to about 30 to 35 V
L1 is a 570µH Inductor, wounded on a 26mm toroidal ferrit core (17 windings of 0,8mm Wire)
C11 should be a high peak current type like a FKP1. (we often use these capacitors in germany)
T1/GDT is also wound on a 26mm toroidal ferrite core
I hope, you understood everything, because my english is not quite good
Stefan
p.s. @ reaching: warum nennst du dich hier nicht auch CTC, so wie in den deutschen Foren?
SKA, Mon Aug 08 2011, 12:15PM
Hi teslazone
I'll try to translate the schematic for you:
The Notes on the right side of the shematic:
-C6 and C8 are high-pass capacitors. If you want to hear the higher frequencies of the audio-input you should choose 100nF types
-R5, R7, R8 and R13 are high precision trimmer-resistors
-Q5 and Q6 should be mounted on a heatsink with a thermal conductivity of maximal 3,2K/W
-The 50V Power supply should have a minimum of ripple voltage. Use a capacitor with at least 10000µF. The current is about 1,8 to 2,3 Amps
The current of the 12V Power supply is about 0,3 Amps
R13 regulates the bias voltage for the Mosfet (Q5). Set this voltage to about 30 to 35 V
L1 is a 570µH Inductor, wounded on a 26mm toroidal ferrit core (17 windings of 0,8mm Wire)
C11 should be a high peak current type like a FKP1. (we often use these capacitors in germany)
T1/GDT is also wound on a 26mm toroidal ferrite core
I hope, you understood everything, because my english is not quite good
Stefan
p.s. @ reaching: warum nennst du dich hier nicht auch CTC, so wie in den deutschen Foren?
Re: My 4Mhz amplitude modulated audio sstc
Chris_Knight, Tue Feb 23 2016, 12:59PM
Reaching's RFC value is 560uH. With type 2 material, that's about 120 turns. Why such a high inductance value compared to other class e implimentations? It was my understanding that the value of the RFC was pretty non-critical, just large enough to block hi freq ac.
Richie and uzzors2k have RFC values of 47 and 56uh
Chris_Knight, Tue Feb 23 2016, 12:59PM
Reaching's RFC value is 560uH. With type 2 material, that's about 120 turns. Why such a high inductance value compared to other class e implimentations? It was my understanding that the value of the RFC was pretty non-critical, just large enough to block hi freq ac.
Richie and uzzors2k have RFC values of 47 and 56uh
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