EL 34 / 6L6 SE Guitar Amp Project - diyAudio
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Old 13th February 2014, 08:56 PM   #1
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Default EL 34 / 6L6 SE Guitar Amp Project

This project is with One 6V6 EL 34 or 6L6 tube . It is a 5Y3 or 5U4 Rectifier and 6SQ7 pre-amp tube ! .

I had most of these parts already and I basically just made this amp out of my savage parts that were laying around .

Chassis was too small , I decided to make another chassis and take the 100 dollar guitar amp challenge !
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Last edited by Gary Vee; 22nd February 2014 at 09:51 AM. Reason: new info
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Old 17th February 2014, 04:55 AM   #2
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Gary,
These little amps can be gorgeous.
Would have thought you may be struggling for gain with a single 6SQ7 for the preamp.

If so you may condsider trying a 6SJ7 pentode.

For your reference (and possible interest) here is one from a 1940's design.
Clever tone control around the output tube (6V6) which would also work with the 6L6 for sure and probably with the EL34 too.
The 80 rectifier is forerunner to the 5Y3. The 6J7 are ST shape with a grid top cap. 6SJ7 is equivalent. Input 6J7 is triode strapped, 2nd is pentode mode. This one sounded stunning with my Telecaster. That schematic is accurate except for a 15K grid stop resistor on the 6V6.

Cheers,
Ian
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Old 17th February 2014, 10:12 PM   #3
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Default The amp was too small , some 6SQ7's can work !

Thanks Gingerwood for the input and diagram . The 6SQ7 tubes have a microphonic problem and it took me 3 of them to find a good one - A GE ! .
A very Nice sounding guitar tube ! . The tube is Not loud enough on it's own though - it needs another tube to help increase the volume up some more .
The Quality of tone and everything else a guitarist could want was there with a 6SQ7 , It worked best with a EL 34 and a 5U4 rectifier .
I'm Building a bigger chassis for it right now and I'm not really done with this tubes testing yet ! . The biggest problem that I see is the microphonic tube issue ! ,
It does have a father tube a grid clip 6Q7 - 100 gain that was made in a small GT size glass , these may actually be a much better option due to the microphonic issue.
I will compare the diagram you posted to a Gretch model G6156 diagram that I found and see which one of them seems to be the best one to build .
The Gretch design is push pull 6V6 , the hum was pretty loud with this SE amp ,
so I think maybe the Gretch's design built with 6L6's instead of 6V6 or EL 34 is how I should go with it ?
With a smaller power transformer then mine - I think it could work out good in SE ! .
I like SE sound but the hum is just a little bit too much for me to handle.
I ordered a PP output transformer for it to try it again using two output tubes .
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Old 8th March 2014, 01:15 AM   #4
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Ian,

Interesting schematic.

Wondering if you have some pics?
and a larger schematic?

Also with the FC outputs,

I can't recall can those be modded to
not use them?

Or

Do you just find a FC with a vintage speaker?
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Old 11th March 2014, 02:21 AM   #5
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The Field Coil Speaker was original on this amp.
I've since collected about 8 of these Field Coil Speakers from 8" up to 12". I think Field Coil Speakers do something special for guitar.

The schematic is from Australian "Radio TV and Hobbies" magazine, June 1942, a article titled "Two High gain Amplifiers". The article has full schematics and construction details. I have a 7 MByte scan of that magazine. PM me with an email address if you want it. Half of it is interesting valve design stuff and half of it is war propaganda (WW2).

Otherwise this is all I have.

Cheers,
Ian
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