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Old 21st April 2007, 11:13 PM   #1
haziz is offline haziz  United States
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Default Very Basic EL84 or EL34 DIY Amp

What is a basic DIY EL84 or EL34 amp design? It should sound good, preferably in ultralinear mode (with possibly a triode option). Output preferably in the 16-50 W range though since I have a number of speakers may be somewhat flexible there; I would like to be able however to preferably drive 88 dB/W/m speakers. Using commercial made amps I have found that I actually prefer UL EL84 or EL34 amps (Manley Stingray and Snappers) to SETs (at least 1 amp with 2 parallel 300B tubes).

My ability to read schematics is very limited and my patience for extensive bodywork is very limited (I also don't own anything more sophisticated than a very basic drill). I did briefly start the Bottlehead Paramour kit but never finished it.

I know I am throwing out a lot of caveats but I am confident the ingenuity of the DIY gurus here should be able to accommodate.

Thanks.

Sincerely,

Hany.
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Old 22nd April 2007, 02:59 AM   #2
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My suggestions:

You might want to finish the 2A3 SET amp first before you tackle a more complicated PP circuit. Two reasons: first, the experience will be invaluable on later efforts. Second, those few Watts of SET will actually play at a good moderate level on 88dB speakers.... great for jazz, acoustic, etc. I find that about 15 to 20 Watts of tube power is plenty for loud concert passages. (I used to have 88dB efficient speakers). You might look up SY's Red Light EL84 circuit here on the forum, it looks good to me. But I would finish the kit before starting something from scratch, which takes a lot more effort and patience!

Good Luck,
Kent
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Old 22nd April 2007, 04:05 AM   #3
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A beautiful amplifier is the velleman kit K4040
http://www.vellemanusa.com/us/enu/pr...iew/?id=350535

also the Jolida SJ502 is a very good schematics (I think)
http://www.drtube.com/schematics/jolida/sj-502a.gif

Triode mode switch can be easy added...
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Old 22nd April 2007, 04:11 AM   #4
jduffy is offline jduffy  United States
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Default Re: Very Basic EL84 or EL34 DIY Amp

Quote:
Originally posted by haziz
I did briefly start the Bottlehead Paramour kit but never finished it.

I know I am throwing out a lot of caveats but I am confident the ingenuity of the DIY gurus here should be able to accommodate.

Just curious to know why you weren't able to finish the Bottlehead kit? I did one of their kits and thought it was very well laid out. It took about two nights to complete it and was my first kit.

Doing something from scratch and using just a schematic is a very different experience. I recently finished a preamp which came out perfectly but it took a lot more time and energy than say the Bottlehead kit.

I'm the reverse of you in that I like SET much more than PP. My next amp will be the Abdellah KT88 (you can do a search here) which appears to be a simple build, but I'll probably substitute the tube and use the EL34. Different strokes for folks and all that.

Good luck with your search.
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Old 23rd April 2007, 12:25 AM   #5
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Default Re: Very Basic EL84 or EL34 DIY Amp

Quote:
Originally posted by haziz
I did briefly start the Bottlehead Paramour kit but never finished it.
Well worth finishing...

dave
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Old 23rd April 2007, 01:37 AM   #6
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Quote:
my patience for extensive bodywork is very limited
Same here!

A way around that problem, apart from buying a kit, could be to buy a used amp (e.g. from ebay) and cannibalize it for the chassis and transformers and, possibly, the tubes if they're still OK. You would probably want to replace most of the other stuff in there, especially the capacitors, pots and resistors. The layouts of most PP amps will lend themselves to implementing other designs, within reason.
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Old 23rd April 2007, 12:01 PM   #7
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You can always go for the DIY Paradise Simple EL84. Can't beat that for simplicity in PP configuration.

http://www.diyparadise.com/simpleel84.html

I'm waiting for the prices of the transformer set from my custom winder company to start building one.

I know it's an overkill, but you can always use a 19" rack case, or another commercialyl available box, you just have to drill for the tubes (or leave them inside the box with some vent holes) and the volume pot and other connectors. Say, 4 driliings max, 3 of 6mm for the RCAs and pwoer cord and one of 10 for the pot.
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Old 24th April 2007, 04:49 AM   #8
gofar99 is offline gofar99  United States
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Greetings, I agree with Simpleton, The Simple EL84 is hard to beat for simplicity. There are three versions of the amp. I would start with the basic one and leave room for the parts to upgrade to the other versions as you got experienced.

Good listening
gofar99
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Old 24th April 2007, 01:49 PM   #9
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Hmmm... I wonder if that self splitting topology from the DIY paradise EL34 amp could be used to ease the drive requirements of transmitting tubes for high power PP.

mike
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Old 24th April 2007, 04:52 PM   #10
gofar99 is offline gofar99  United States
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Greetings, I suspect that this is off topic, but maybe. The issue would be bias complications. Transmitters often run in class C and audio gear in variations of A and B. It could be very difficult to bias the tubes in the configuration of the simple el84 to run class C. I would be interested to see how it could be done. Anyone out there have thoughts on this?

Good listening
gofar99
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