the Reversal SRPP

Stee · 11:24 PM

my last project is a SRPP tube preamplifier
with a special input and output buffer:
cathode follower with a current source

that is to have a compensation of "triode tone mark"
in other word appear technically unnecessary but "magic for music"

Allen Wright · 12th May 2010, 11:13 PM

Hi,
I see a circuit with an input and an output cathode folllower, with a SRPP gain stage between.

I see no point in having either cathode follower, the input one is not needed to drive a pot and a SRPP input, and the output Z of the SRPP should be low enough to drive a cable without the extra CF.

Why add them? KISS is my key principle, and a CF (even with a CCS load) still is not 100% transparent.

Regards, Allen

Sch3mat1c · 13th May 2010, 12:34 AM

V1a, V2b and V3b can be replaced with resistors.

Tim

kevinkr · 13th May 2010, 01:12 AM

I have to agree with Allen.. It seems needlessly complex which can't IMHO help the sound. Simpler is usually better.

Stee · 13th May 2010, 06:47 PM

of course
but I think the success of the SRPP is just replacing the anode resistor load with a triode:
an active load is good for the cathode in terms of sound
it is true that the principle of character's compensation is not measurable
but your ear will notice a more realistic scene
just because works another identical unit in opposition of phase
a too modern concept for designers more orthodox

Allen Wright · 13th May 2010, 07:04 PM

I have no argument with your use of the SRPP topology as a gain stage, but cannot see why you need a CF buffer before it AND after it. Pointless IMO.

Regards, Allen

Miles Prower · 14th May 2010, 05:12 AM

Input cathode follower: do not need. Ditch it.

Output CF: use a proper CCS tail load, either cascoded, discrete BJTs, a CCS IC, or if you insist on a "no sand" solution, a high g(m) pentode CCS. Triodes are horrible as CCSs.

Arnulf · 14th May 2010, 07:31 AM

Stee, how does this thing sound with 150V B+ ?

Allen Wright · 14th May 2010, 10:12 AM

Quote:

Originally Posted by Miles Prower

Input cathode follower: do not need. Ditch it<<

Agreed.

>>Output CF: use a proper CCS tail load, either cascoded, discrete BJTs, a CCS IC, or if you insist on a "no sand" solution, a high g(m) pentode CCS. Triodes are horrible as CCSs.

Miles, why does he even need an output CF? A well designed SRPP's purpose is to act as a active load AND a "CF" with a low OPZ.

But if you want to do a really sonically transparent CF, I believe you need to use my SLCF, which can be seen as the last section of my FVP-5A schematic, linked here:

http://www.vacuumstate.com/index.tpl...271.4389191557

Regards, Allen

316a · 14th May 2010, 01:21 PM

I can't see how this thing can work . Look at the grid arrangement on the input stage V2A .

316A

13th May 2010, 12:34 AM	#3
Sch3mat1c diyAudio Member Join Date: Jan 2003 Location: Milwaukee, WI	V1a, V2b and V3b can be replaced with resistors. Tim __________________ See my Electronics webpage -- the home of Vacuum Tube Drag Racing. The key to being a successful Audiophile: "I reject your reality and substitute my own!"

13th May 2010, 01:12 AM	#4
kevinkr diyAudio Moderator Join Date: Sep 2004 Location: Boston, Massachusetts Blog Entries: 6	I have to agree with Allen.. It seems needlessly complex which can't IMHO help the sound. Simpler is usually better. __________________ www.kta-hifi.net

13th May 2010, 06:47 PM	#5
Stee diyAudio Member Join Date: Jul 2005 Location: milan	Simpler is usually better of course but I think the success of the SRPP is just replacing the anode resistor load with a triode: an active load is good for the cathode in terms of sound it is true that the principle of character's compensation is not measurable but your ear will notice a more realistic scene just because works another identical unit in opposition of phase a too modern concept for designers more orthodox __________________ visit my best audio idea http://www.esafono.it/DACTONE.htm

14th May 2010, 05:12 AM	#7
Miles Prower diyAudio Member Join Date: May 2005 Location: USA Blog Entries: 2	Input cathode follower: do not need. Ditch it. Output CF: use a proper CCS tail load, either cascoded, discrete BJTs, a CCS IC, or if you insist on a "no sand" solution, a high g(m) pentode CCS. Triodes are horrible as CCSs. __________________ There are no foxes in atheistholes www.dolphin-hsl.com

14th May 2010, 07:31 AM	#8
Arnulf diyAudio Member Join Date: Feb 2009	Stee, how does this thing sound with 150V B+ ? __________________ mod verb, transitive /mod/ to state that one is utterly clueless about the operation of device to be "modded" and into "fixing" things that are not broken; "My new amplifier sounds great so I want to mod it."

12th May 2010, 11:13 PM	#2
Allen Wright R.I.P. Join Date: Dec 2001 Location: Schaffhausen Switzerland	Hi, I see a circuit with an input and an output cathode folllower, with a SRPP gain stage between. I see no point in having either cathode follower, the input one is not needed to drive a pot and a SRPP input, and the output Z of the SRPP should be low enough to drive a cable without the extra CF. Why add them? KISS is my key principle, and a CF (even with a CCS load) still is not 100% transparent. Regards, Allen

13th May 2010, 07:04 PM	#6
Allen Wright R.I.P. Join Date: Dec 2001 Location: Schaffhausen Switzerland	I have no argument with your use of the SRPP topology as a gain stage, but cannot see why you need a CF buffer before it AND after it. Pointless IMO. Regards, Allen

14th May 2010, 01:21 PM	#10
316a diyAudio Member Join Date: Dec 2002 Location: West London	I can't see how this thing can work . Look at the grid arrangement on the input stage V2A . 316A

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