Amp Prototyper

mayfly

Senior member
Messages
8,302
The pedal prototyper reminded me of a tube amp prototyper that I had built about 10 years ago.  I had forgotten it until that thread, but I just dug it out to show you all.

Do NOT attempt to build anything like this unless you really know what you are doing.  Doing otherwise will burn your neighbor's house down, kill your cat/dog, and fry your private bits off

With that out of the way, here it is.  There are three separate boxes for maximum reconfigurability: the power supply, pre-amp, and the power amp:

n527102111_1688020_9934.jpg


The power supply uses a hammond transformer and has a 300VDC B+ supply, a -56VDC bias supply, 6VAC heater supply, and a 6VDC regulated heater supply.  The latter I threw in to see what difference it really makes under certain circumstances.  The dust on this unit really shows how long it's been since I've used it!

n527102111_1688023_846.jpg


Here's the inside.  Plenty of decoupling (those are 100uf 400V caps), and a big fuse block.  Those who know tube amps know that you don't want to dick around with safety - so those are fast blow fuses on each leg of every supply.

n527102111_1688021_251.jpg


Here's the pre-amp.  This was the circuit that went through the most experiments.  It's a two channel pre, with a black face type clean channel, and a mesa-style lead channel.  The main thing that I learned from this unit was I didn't like Mesa-style preamps  :icon_biggrin:

n527102111_1688026_1738.jpg


and here's the inside - again plenty of decoupling.  I kinda went overboard, but I didn't want to be driven crazy with 60Hz hum

n527102111_1688025_1450.jpg


The power amp went though several changes as well.  Here it is configured for 6V6 tubes, fixed bias.  There are switches for flipping it into triode mode, and the pots are for master volume and feedback loop experiments.  It has also seen cathode bias, 6L6 and EL34 Tubes.  From this unit I realized that I was not a fan of fixed bias amps  :icon_thumright:

Here's the outside:

n527102111_1688027_2038.jpg


and here's the inside:

n527102111_1688028_2356.jpg



So, where did all that experimentation lead?  To these things:

n527102111_1688031_3304.jpg

n527102111_1688034_3608.jpg


This is an AC30 style amp, with top boost channel, normal channel, and a EL84 based output stage with cathode bias, master volume, and no feedback loop.  This is a 15 watt version.

I made several of these in both 30 and 15 watt versions.



 
K

kreig

Guest
Show-off :icon_jokercolor:

Where can we buy one and how much?

You're alot cleaner in your execution, I can tell in the photo's ... :hello2:

Did I already call you a show-off? :icon_scratch:

:headbang1:
 

mayfly

Senior member
Messages
8,302
Well, I don't really do this anymore.  When I started in the Boutique amp biz there was matchless, Dr Z, Victoria - and not much else.  I think Top Hat was just starting out - not sure.  I build the amp mostly because I was not happy with amps that you could buy so I decided to build my own.  Other folks liked them, so I started making them in quantity.

I got out of it for several reasons.  The main one is that now you can buy off the shelf stuff that does what I want.  Also, the boutique market has gotten pretty crowded.  It seems like there's a new player starting up every month.  It's tough to stand out when the market is that tight. Besides, you can get a real VOX AC30 these days that has a master volume and all the other features that I designed into my amps.  Once that happened I figured that there really was no point.  Besides, as I discovered in my journey, I'm  not really into manufacturing.

If I were to do it all over again, I'd get someone else to do the majority of the building - Ceritone comes to mind.

But - been there, done that.  Don't need to do it again.
 
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