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Hazmatt_(The Underdog)

Thu Dec 06 2007, 11:23PM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

The reason not to use a tube rectifier like 5AU4 or similar is that Hammond doesn't always put a 5V winding on the power transformer. Then you have to scramble for a 5V 4A transformer and they just aren't that common now. Of course you might say "well just tap off the 6.3V winding" Well no, its not that simple. You need 1A/ 6L6 or EL34 and with a lot of preamp tubes the current adds up fast too.

To get the 'sag' of a rectifier tube you would be able to use a 30-50R power resistor after the rectifier bridge and use the transformer without the 5V winding.

Otherwise you just buy the transformer with the 6.3V and 5V winding.

EDY19

Sat Dec 08 2007, 12:00AM

Registered Member #105 Joined: Thu Feb 09 2006, 08:54PM
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Posts: 408

What ways do you use to limit inrush current into the capacitors when using diodes? I always find myself in a bind when building power supplies, because the inrush is so great. Hamfest is comin up though, it'll be my first one, i'm pretty excited:-)

ShawnLG

Sat Dec 08 2007, 06:31AM

Registered Member #286 Joined: Mon Mar 06 2006, 04:52AM
Location:
Posts: 399

"In my opinion I think hybrid designs are much cooler."

I have repaired a modern tube amp for someone and it was a hybrid. There was few diodes, transistors and an, IC. I was thinking about a hybrid design, so I would have the best of both worlds. My micro VTTC is definitely a hybrid. ;)

"Hamfest is comin up though, it'll be my first one, i'm pretty excited:-)"

Be prepaired to have a nerdgasm, and bring lots of money.

Steve Conner

Sat Dec 08 2007, 05:06PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

ShawnLG wrote ...

Be prepaired to have a nerdgasm, and bring lots of money.

Lol

I thought I better mention a few things:

You can't connect the heater of a rectifier tube to the same heater supply as all the other tubes. It will cause a tubesplosion. Except for a few indirectly heated rectifiers with extra-strong heater-cathode insulation like the EZ80.

I've never needed to use inrush current limiting on tube amp power supplies. The winding resistance of the P.T. seems to take care of it, though if I ever build this 300 watt monster, it may be a different story!

I also like hybrids, my first amp used op-amps in the EQ and a MOSFET regulated B+. This one will be all tube though, apart from the rectifier diodes and panel LEDs...

EDY19

Sat Dec 08 2007, 07:26PM

Registered Member #105 Joined: Thu Feb 09 2006, 08:54PM
Location:
Posts: 408

I was already planning on bringing lots of money

I think my main objective is going to be finding a 115V : 240V >120VA transformer, and I'll keep an eye out for some cool caps and tubes

I'm pretty excited though, just have to get through exams first, however I got 100% on my last physics one, so I'm not toooo worried about that one

ShawnLG

Wed Dec 12 2007, 05:10AM

Registered Member #286 Joined: Mon Mar 06 2006, 04:52AM
Location:
Posts: 399

After doing some research on tube distortion. A tube amp would squeeze the top of the sinewave when driven into saturation. A logarithmic amplifier can do the same "squeezing" effect. I have built my own tube effect circuit using all silicone. Some Tube FX boxes out there uses a simular ciruit such as the Ibanez Tube Screamer.

The "tube" distortion sounds very clean without any intermodulation. It also has good sustain.

Yay for silicon!

mod edit: 400pxplz kthx

Steve Conner

Sun Dec 16 2007, 10:59PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Nice work ShawnLG, but does it smell like tubes too?

Anyway, progress has been slow, I'm busy at work, but I got the LED lighting working today... I think I hear Leo Fender spinning in his grave!

BTW, this is my 2001th post - open the pod bay doors, Chris!

Marko

Mon Dec 17 2007, 12:26AM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Steve, that looks MEAN.

Carbon_Rod

Mon Dec 17 2007, 01:41AM

Registered Member #65 Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155

Nice project,

Also done a few amp repairs for some people over the years. Some musicians pay an extraordinary amount of money to keep the original sound of their instruments. The tube-amp can arguably be considered part of the instrument.

Dalus

Mon Dec 17 2007, 01:30PM

Registered Member #639 Joined: Wed Apr 11 2007, 09:09PM
Location: The Netherlands, Herkenbosch
Posts: 512

That looks sick Steve

. Shawn, thanks for the circuit I will sure try it with my alsis ra 500

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