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Registered Member #3989
Joined: Thu Jul 07 2011, 05:10PM
Location: In a van down by the river.
Posts: 52
I want to build a direct coupled tube amp that has a very wide frequency response and be able to use it for a guitar amp and also be able to use it for cb radio base station, ham radio or AM radio staion etc. Is that possible?
Registered Member #1792
Joined: Fri Oct 31 2008, 08:12PM
Location: University of California
Posts: 527
You could use it as an audio amplifier for said radio stations, it would not be practical to to design an amplifier to work at both audio and radio bands.
Registered Member #3989
Joined: Thu Jul 07 2011, 05:10PM
Location: In a van down by the river.
Posts: 52
Mattski wrote ...
You could use it as an audio amplifier for said radio stations, it would not be practical to to design an amplifier to work at both audio and radio bands.
Practical? Maybe not but I want to try and do it anyway because according to the some of the books here, a dc coupled vacuum tube amplifier should be capable of amplifacation over a very very wide range. Seems like a fun project to me, and useful too as I need a new guitar amp and have 12 or so various common pentode tubes including one my favs, an 8417. I could rig up a switch on the front of the control panel between sets and listen and talk to truck drivers... :)
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
I haven't read your sources but in my experience; - building low power amplifiers with no feedback and a bandwidth of dc to GHz is surprisingly easy - when high power is required efficiency becomes important and that usually means transformers are required, so leakage inductance (and 'stray' capacitance) becomes a bandwidth-limiting factor. - I find it difficult to build a linear PA using transformers for just one decade bandwidth!
I would say that a transformer-less PA is certainly possible for dc to 27 MHz (or more) but it will be very inefficient / need a lot of cooling. So it is better to build a good audio amp with feedback for audio quality and a separate hf amplifier with tuned output stage for a cb PA. (try using feedback in a 10's of MHz PA .. not easy)
Registered Member #3989
Joined: Thu Jul 07 2011, 05:10PM
Location: In a van down by the river.
Posts: 52
[quote]
Sulaiman wrote ...
I haven't read your sources but in my experience; - building low power amplifiers with no feedback and a bandwidth of dc to GHz is surprisingly easy - when high power is required efficiency becomes important and that usually means transformers are required, so leakage inductance (and 'stray' capacitance) becomes a bandwidth-limiting factor. - I find it difficult to build a linear PA using transformers for just one decade bandwidth!
I would say that a transformer-less PA is certainly possible for dc to 27 MHz (or more) but it will be very inefficient / need a lot of cooling. So it is better to build a good audio amp with feedback for audio quality and a separate hf amplifier with tuned output stage for a cb PA. (try using feedback in a 10's of MHz PA .. not easy)
Thank you for the replies, maybe have a switch or something to use the transformer on the output in audio range mode and then switch to bypass the ot in antenna mode? I won't need any negitaive feedback with a guitar amp would I? I mean distortion could help the sound depending on how you look at it, since I am creating music and not just reproducing it. Good to know it is possible!
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combo unit: guitar amp/linear amplifier. Would it work?
