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Old 14th May 2009, 12:28 AM   #1
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Question Single ended amp, EL34, KT88 ideas??

Ok...the next project I'm mulling in my pointy head is an SE amp using EL34 or KT88 outputs and a very simple circut. Anyone have any ideas and/or schematics/plans ? Since my area of interest is mainly musical instrument amplifiers, it would ideally be something designed for or easily adapted for that purpose. I am relative novice-level having rebuilt/overhauled a couple dozen amps and scratch built...with a lot of help from this forum..one screamin' banshee of a mutant Fender circut. I like cathode bias amps for their touch sensitivity...also I would like to easily swap tubes with other compatable types...i.e. KT90, KT100...I appreciate all your suggestions...I have a file full of those so far.
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Old 14th May 2009, 12:44 AM   #2
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I'll state the obvious one that seems to fit all of those: Tubelab Simple SE.
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Old 14th May 2009, 12:48 AM   #3
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Default Russ..re Simple SE

That's a PCB amp ? I'd prefer PP ...can I get a schematic and build it from scratch ? Would that be easily adapted to instrument amplifier...i.e. 1 meg input?
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Old 14th May 2009, 01:16 AM   #4
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About the most straightforward SE amp design you can write
down is described here:

http://diyaudioprojects.com/Tubes/KT88/

A nice discussion of various modifications can be found here:

Improvements for the Mikael Abdellah KT88???

If you make the cathode bias at least partly adjustable, you can handle
almost any output tube in the 6L6/KT66/KT88 family.
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Old 14th May 2009, 01:24 AM   #5
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Default Re: Russ..re Simple SE

Quote:
Originally posted by bereanbill
That's a PCB amp ? I'd prefer PP ...can I get a schematic and build it from scratch ? Would that be easily adapted to instrument amplifier...i.e. 1 meg input?
Yes, it's a PCB amp. You could build one PtP, of course. The schematic and everything is there, but you said simple, so...

Alex's KT88 SE amp on diyaudioproject.com is the one I was planning to build before coming across the SSE. It's a bit simpler than the SSE to boot.
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Old 14th May 2009, 01:52 AM   #6
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lex's amp looks like a good possibility ! Looks like only i/2 of the preamp tube is being used, no ? That would allow for some artistic license on my part...adding a gain stage...maybe switched as a boost???
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Old 14th May 2009, 02:53 AM   #7
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It is designed as half of a stereo amp, so the other half of
the preamp tube is used for the second channel. If you are
imagining this for a instrument amp, you could use the other
half to drive a tone stack with no net loss in gain.
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Old 14th May 2009, 10:20 AM   #8
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Default Torrence

Yeah, I see that now...A tone stack would probably be the more logical use for the second half...I need a way to get some crunch at a reasonable volume. Would an MV be ok with this amp ya think ? Lots of times it squishes these lower powered amps....
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Old 14th May 2009, 10:20 PM   #9
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I built this one. Very nice sounding.

http://db.audioasylum.com/cgi/m.mpl?...ght=proud+papa
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Old 15th May 2009, 06:00 AM   #10
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It sounds like you are looking for a high powered Fender Princeton clone. Try this schematic and instead of the 6V6 use a EL34. Allen Amplifiers has transformer (TO11C) that is perfect for a SE EL34 output. You can find it here:

http://www.allenamps.com/parts.php#transformers

If you want more gain then I would use a additional 6SL7 gain stage and wire it up as a pre and post gain. That will give you all the "crunch" that you want. I had a schematic drawn up for such a beast but I can't seem to find it. I'll keep looking though. You will need to boost the voltage for the output stage also.
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