DIY Audio Projects Forum

The Naked Amplifier
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Author:  Soundbrigade [ 09 Oct 2009, 15:25 ]
Post subject:  The Naked Amplifier

Don't take this literally, the title is just a working title for something that for half a day was supposed to be a naked amplifier. Naked, in tjis case, meant an amp with all components mounted on standoffs on an aluminium base, slightly like a piece of art. But as soin as I started looking up what pieces I had for the project I ran into an old chassis, drilled for another, now scrapped amp and got a completely different idea.
This project is still on the drawing board, though I have the all components (bought them 4 years ago!). There is some work to make holes in a chassis, which is done in an hour or two but becuase of the drill burrs, I tend to postpone this work as long as I can.

Some info on the project:
The amp is a simple 10-12W pushpull amplifier based on a pair of 832, twin beamtetrodes. For each channel one such twin tube is required, which , I read somewhere is very much like a twin 6V6. There's an 12AT7 as phase splitter but I will try to find an equivalent in an octal sockel. On the pics below is a 12SJ7 posing to show my ideas.
So here's the schematic:

The pics:
The box is a mediumsized Hammond steel chassis, which was drilled for another, now scrapped project. I will turn it upside-down and use an aluminium plate , or brass or steel. The OP trannies are from a company in Stockholm, bought 10 years ago at least, and the mains trannies are custom-made for another project. I am not sure how the specs are, have a paper somewhere. There should be a 12VAC winding but that was "lost in translation". Instead, there's a 5V winding.

The tubes have top anodes but where to find connectors for those. However I have some nice connectors but they are sitting in my Priboi-amp. When I swap tubes in that one, I can solve this problem, but I am not there. Yet! Another solution is to use crocodiles.

It woudl be great to find suitable dual triodes with metal cans. Often 12V tubes are housed in metal, but I leave that for the time being; must do som research here. As the 832 looks like tubes-from-another-planet I don't mind having the input/phase splitter tubes in a matching UFO-style. Compactron tubes are a choice. Btw, I nothiced there was a tube with three triodes that electrically were much like 12AT7.

As I wrote, just, don't expect this project to progress that fast.

Author:  Geek [ 09 Oct 2009, 15:48 ]
Post subject:  Re: The Naked Amplifier

That's not only going to be a cute one, but they look really cool in the dark :D


Author:  Gio [ 09 Oct 2009, 18:31 ]
Post subject:  Re: The Naked Amplifier

That sure will look neat. BTW - where is the output iron from?

Author:  Soundbrigade [ 10 Oct 2009, 01:49 ]
Post subject:  Re: The Naked Amplifier

The output irons are from a company some 50 miles N of where I live. I think they were made for an EL84-PP amp named Edison 12 (constructed by Audio Innovation's Erik Andersson). I got them from a small repair shop in Stockholm long time ago.
Actually I have three pairs of suitable transformers for this project; a pair froma butchered Heathkit amp and a pair of new iron from, but therese were the ones most "accessable".
I also have a pair of 829 that will be tested with my Hammond 1627SE, but propably I will try something completely different later.

Author:  CrazzyAbtTubes [ 10 Oct 2009, 06:29 ]
Post subject:  Re: The Naked Amplifier

This looks as bizarr as the idea of making a 3-500Z amplifier! :shock: except this one would look even cooler! :thumbsup:

Author:  Soundbrigade [ 10 Oct 2009, 09:02 ]
Post subject:  Re: The Naked Amplifier

I have a schematic for an amplifier based on this little creature:

It has be cooled by a fan all the time.

Author:  Geek [ 10 Oct 2009, 16:16 ]
Post subject:  Re: The Naked Amplifier

Ah! A weired tube thread now :D

Lighthouse tubes are neat.

Here's one of four 6442 oddballs kicking around the bench.



Author:  TDMalcolm [ 16 Nov 2009, 09:51 ]
Post subject:  Re: The Naked Amplifier

Hi All, Just as a bit of fun ;) and not quite as nice looking, you could try a ELL80 double pentode :shock: .... capable of about 3-5 watts se... 8-) shame i've only got one of them...their are rare now :(

Author:  Bennybuis [ 21 Nov 2009, 15:33 ]
Post subject:  Re: The Naked Amplifier

Hallo everybody,

I just bought a pair of those GU32 - 200 MHz - Qa 15 W. I'll attach a picture. I hope someone will help me make something nice of it I am a newbe. Greetings from Holland.

GU32 - 200 MHz - Qa 15 W .jpg

Author:  Bennybuis [ 21 Nov 2009, 19:42 ]
Post subject:  Re: The Naked Amplifier

Hallo everybody,

I know now that the GU 32 are the Russian version of the 832 transmitting tetrodes and they are easy and inexpensive to get. Around 11 € each. If anybody is interested, I can hook you up. I have 4 coming, not two like I said in my last post, so I am excited, I wanna try this schematic push pull, too. Good listening.

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