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[email protected] alesynkin@gmail.com is offline
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Default Direct-Coupled SE Amplifier using the EL509/6KG6

On Wednesday, November 20, 2002 6:15:18 AM UTC-8, Denis wrote:
(Jon Yaeger) wrote in message ...
Denis,

That being said, do you have a recommended alternative?

Spasebo,

Jon


Yes, I have. I'm sure this is a cathode-feedback (CFB), or by other
words, distributed loading pentode stage. I've already posted much
about this technique here in RAT. This equally works with PP and SE,
but I prefer PP amplifiers and all my designs up to date are PP. I use
CFB circuit much similar to that introduced by Peter Walker in QUAD
tube amps.
A small (from 10 to 20%) portion of the primary winding is connected
to the cathode of the power tube thus providing a precisely tailored
amount of local negative feedback in the output stage. The screen grid
of a pentode is tied to a constant B+ supply, and the Eg2 in general
case can differ from Ep. Moreover, when a pentode or ray tetrode
operates at Eg2 Ep, the distortion spectrum remarkably simplifies,
and it is possible to almost completely suppress 3rd and higher order
harmonics over a considerable portion of dynamic range.

The internal resistance of a pentode with such small percentage CFb is
nevertheless very low, and the speaker damping is already sufficient
without adding global NFB. At the same time, the g1 driving voltage is
comparable, or even lower than that for DHTs like 300B.

If we take for comparison a possible SE CFB stage with EL509 against
some typical 300B amp (this is especially interesting as these two
tubes have comparable plate dissipation limits), the EL509 CFB SE amp
will have less than 1/10 of 300Bs distortion with same benigh spectrum
and supposedly 1/3 of 300Bs Ri. Moreover, EL509 will give more than 6
dB of plate current headroom in respect to the 300B - like 9W output,
and will better handle reactive loads. So there is something to think
of.

EL509 has also other special features which place it well above other
known tubes, both pentodes and triodes.

Best regards,

Denis N. Afanassyev

www.cortmi.com.ua/omak







In article ,
(Denis) wrote:

"Simon van de Laak" wrote in message

...
Hello RATs,

Has anybody build the Direct-Coupled SE Amplifier using the EL509/6KG6
designed by Bob Danielak?
(
http://www.geocities.com/bobdanielak/technoteNo33.html). What are your
remarks/tips on this design? Did you have any problems building this design?

Thanks.

Simon

EL509 certainly asks for better amp design than this one.

No need to lobotomy this magnificient tube!

Denis.


Hello Denis!
Any realization of Your suggestions? Spasibo!
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