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Old 30th March 2004, 06:39 AM   #1
dimitri is offline dimitri  United States
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Default Which triode is the best for preamp?

While I made a lot of tube amps/preamps they have disappeared from my workbench too quickly to compare them It seems impossible now to gather them in one place and listen. I would like to construct hybrid amp with SS linear output stage(current amp) and tube driver(voltage amp).
My question is: which triode(pentode) is considered as the most appropriate(musical) for the preamplifier with gain 20-30? I have heard that low Gm triodes are the best, as high Gm triodes sound granular. The SRPP stage produces enlarged amount of higher harmonics. Is it so?
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Old 30th March 2004, 07:30 AM   #2
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hi dimitri,

Quote:
The SRPP stage produces enlarged amount of higher harmonics. Is it so?
No, the SRPP stage is a good stage and produces the same
(or less) amount of higher harm. than a simple common catode stage, irrespective of the load and of the level.
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I call this an SRPP, with or without bypass cap.
in parallel to the cath res of the lower triode, but
with the out from the cath. of the upper one and
not from the plate of the lower.

Ciao
Federico
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Old 30th March 2004, 08:06 AM   #3
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Default Pentode Mu stage

An alternative to the triode Mu, would be the pentode or MOSFET Mu stage, by all accounts this is an excellent preamp stage
The diagrams below come from Allan Kimmels article on Mu stages
Well worth looking at!

The output impedence can be very low, and the gain approaching that of the triode
You have a choice of many great pre-amp triodes like the 6sn7 or 6sl7 even one of the newer Russian 6H2n/1n should perform well
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Old 30th March 2004, 08:11 AM   #4
Jax is offline Jax  Sweden
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A vintage 6SN7 would be my first choice with 100-150V/8mA.

Others are E80CC, 12BH7, 6CG7, 6FQ7.

Yet another is ECC88 if you drive it at 85V/10mA and 22k load.

ECC99 looks good but I have no experience of it myself.

ECC82 has higher distortion than any of the above.
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Old 30th March 2004, 09:09 AM   #5
dimitri is offline dimitri  United States
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What about Gomez stage?

http://digilander.libero.it/paeng/srpp_vs_gomez.htm
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Old 30th March 2004, 03:15 PM   #6
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Quote:
What about Gomez stage?
hi

this is the implementation I prefer,
particularly for its distortion performance
with low res load.

Federico
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Old 30th March 2004, 05:36 PM   #7
MaciekP is offline MaciekP  Poland
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Hell,
5687 is good and powerfull sounding.
Very good tube preamp output stage has Audio note DAC with ECC88/6DJ8 in SRPP config and low voltage. Excellent sound.
http://mparvi.republika.pl/DAC2sig_small.gif

Maciej
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