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Old 12th February 2004, 08:46 AM   #1
GeirW is offline GeirW  Norway
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Default comments on this design..

ciao..

i was just looking on bonavoltas site..
and this design/circiut made me curious.

EL84 Quad SE

what gives.. any information would be of interest..


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Old 12th February 2004, 09:00 AM   #2
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Default Re: comments on this design..

Quote:
Originally posted by GeirW
ciao..

i was just looking on bonavoltas site..
and this design/circiut made me curious.

EL84 Quad SE

what gives.. any information would be of interest..


Nice!! ...Paralel Push-Pull penthode connected EL84...concertina phase splitter...averall feedback...DC in the heatters...

It's Fine!!!
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Old 12th February 2004, 09:01 AM   #3
Jax is offline Jax  Sweden
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It looks like a quick hack, a PPP design quickly rewired for SE operation. The concertina splitter is used as a buffer with gain 1.

Poor design in my opinion.
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Old 12th February 2004, 09:10 AM   #4
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Quote:
Originally posted by Jax


It looks like a quick hack, a PPP design quickly rewired for SE operation. The concertina splitter is used as a buffer with gain 1.

Poor design in my opinion.
Yes!!...i have not remarked that...the phase invertion is in the output transformer...and the grids of the output tubes are
feed with signals in phase...

4 eyes are better than 2 ...

The second half part of the ECC83 is doing nothing...only increasing noise...better if it was used as a follower for to drive the parallel output with lower impedance...
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Old 12th February 2004, 05:33 PM   #5
GeirW is offline GeirW  Norway
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ciao.

so.. is there anything to do for adjustment/improvement..
or is the curcuit just stillborn..

as jax said.. paralell PP "disguised" as a SE..
(nothing to gain..?)


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Old 12th February 2004, 08:03 PM   #6
Jax is offline Jax  Sweden
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Well, there are a few things that can be done.

Remove the 470k and 2.2M connected to the grid of the second '83. Connect the second 83 grid directly to the plate of the first. Remove the 47k from plate to supply on the senond 83 and connect plate directly to the supply.

Connect the two 100nF coupling capacitors to the cathode of the second 83.

Also (error in the schematic?) connect the 100k from first 83 grid to ground and connect input directly to the grid.

You will now have a circuit where the first 83 is an amplifier directly connected to the second 83 which is now a cathode follower happily driving the grids of the four output tubes.

Note the feedback, you will need to phase it correctly.
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Old 13th February 2004, 08:24 AM   #7
GeirW is offline GeirW  Norway
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ciao.

Quote:
Well, there are a few things that can be done
i slightly got the feeling that this is a design
isn`t your cup of tea..

i assume the point behind this circuit.. is to try to
get the best from PP & SE ?
(remember am a newbie)

or perhaps there is some artifacts with PPP design
he wanted to kill. i mean.. what would be the purpose
of rewire it as SE.? why not make a big SE.
what did he try to do.?


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