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Old 28th October 2004, 01:11 PM   #1
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Default el84 amp

I want to build a new amp...I've bought four el84 but I'm not sure which is the best way to use them. I need 7/10W so the I think that the options could be:
1) sep, pentode connection with local negative feedback
2) push pull, maybe ultraliner connection.

For push pull design I like solution like this:

http://www.meta-gizmo.com/Tri/interstage.html

What's about phase splitting by using an interstage transformer ? I think this could be an interesting solution, perhaps better than pse pentode connection

Thankyou in advance

Mark
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Old 28th October 2004, 01:20 PM   #2
SY is offline SY  United States
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Using an IT can work, but is (IMO) unneccessarily expensive and removes many design options. The nice thing about EL84s is that they don't require much drive- difficult tubes are a better argument for ITs.

If it were me, I'd build a simpler, more classic design. Have you seen the Bevois Valley amp in Morgan Jones's book?
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Old 28th October 2004, 01:32 PM   #3
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If it where me...I would build http://www.meta-gizmo.com/Tri/interstage.html as well..

can't get any simpler than that.. and to me it IS a classic design.
It sure is a little more expensive...but what is 200$ for something that provides you with years and years of problem free amplification......and the phase splitting does not suffer through time like I suppose a tube based phase splitter does. Plus I happen to believe that adding feedback is like castrating your amp. (Term stolen from the Positive Feedback review of the sixpacs amps...http://www.positive-feedback.com/Issue6/sixpac.htm).

The Bevois valley apparently sounds quite good But is actually quite complex and therefore less suited as a first time build IMO.


Cheers,
Bas
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Old 28th October 2004, 10:31 PM   #4
mcs is offline mcs  Denmark
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This simple amp works well: http://stiftsbogtrykkeriet.dk/~mcs/EL84_Amp.html

It would be quite easy and cheap to make, if you want to try something simple first.

Best regards,

Mikkel C. Simonsen
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Old 30th October 2004, 07:48 AM   #5
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You could use the "Simple EL84" design from www.diyparadise.com (the site is down - bandwidth exceeded). From memory... it's a UL push-pull design with the output serving as phase-splitter since the tubes are mounted in differential.

No idea how it sounds... or how good the phase splitting balance is when done this way

Will check if I saved the schematic

It has been assumed that this is mark_titano's first amp. He hasn't said this
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Old 30th October 2004, 08:10 AM   #6
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schematic:
Attached Images
File Type: gif ecc99el84c.gif (6.0 KB, 1776 views)
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Old 30th October 2004, 08:54 AM   #7
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Quote:
Originally posted by Bas Horneman
It sure is a little more expensive...
This little beauty does a good job for almost no money...

http://www.edcorusa.com/transformers...wsm10k-10k.htm

dave
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Old 30th October 2004, 08:55 AM   #8
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Quote:
Originally posted by mcs
This simple amp works well: http://stiftsbogtrykkeriet.dk/~mcs/EL84_Amp.html
That is the same topology as the Morgan Jones amp which SY mentioned. Morgan's amp probably has the detail down better.

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Old 30th October 2004, 08:57 AM   #9
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Quote:
Originally posted by audiousername
You could use the "Simple EL84" design from www.diyparadise.com
An elegant amp, but you oonly get half the power.

dave
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Old 1st November 2004, 10:38 AM   #10
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Thankyou All

It seems that pse design is not a good idea...hehehe
Ok I will try push pull, I never built one ( I'm listening an El34 SE, my second diy amp), I think this could be a good experience.
Maybe I'll try pse design later...

I think that I'll try somethink like this:

http://www.audiodesignguide.com/my/pp3.html

Maybe with better power supply...ccs source for the el84...and battery bias for the input stage.
What's about?

I found two LL1671 (second hand) for 100Euro:

http://www.lundahl.se/pdfs/datash/1671.pdf

what you say? I buy them? I'm not sure that they are ok for small triode like 5842...

Thankyou in advance
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