6sn7 operating points

AudioGeek · 6th September 2005, 03:55 AM

whats a good operating point for an input stage?

probably not bypass cathode resistor.

will be cap coupling to 6BX7 into a 1:1/1 phase splitter tranny.

power supply voltage is around 260v.

Is 100-130v too low for plate voltage on 6SN7? voltage output will be very low so does it really matter?

will be for a 6SN7 cap coupled to 6BX7 to drive PP 6B4G's.

any help would be appreciated as I don't know that much about 6SN7's and 6BX7's except what is said about how they sound.

billr · 6th September 2005, 10:12 AM

hi, like they say, it all depends

here's a URL to a site that has typical bias points for the 6sn7. this is taken from the RCA handbook.

you may find it useful.

http://www.triodeel.com/rca_c13.gif

another way to do this is to look at circuit diagrams that use this valve. also look at the triodeel main page on tube diagrams, there's lots to look at, happy hunting.

kind regards

bill

SY · 6th September 2005, 10:49 AM

100-130V is a bit low for that tube. It will be happier with more like 150-180V on the plate. The linearity improves at currents of 8mA or higher.

amperex · 6th September 2005, 02:58 PM

A list of preamp tubes that performs well at lower plate voltages are the 27, 37, 56, 76 & 6P5GT. I would guess the 6P5GT is the least microphonic of the lot.

Sch3mat1c · 6th September 2005, 05:05 PM

If it's doing only 10V, it's not going to make any difference for any tube.

Tim

amperex · 6th September 2005, 05:41 PM

The post did state 100-130 volts plate.

jacquesF77 · 6th September 2005, 08:24 PM

For a nice 8 to 10mA plate current, 160 to 180V is better as SJ told

jacques

andyjevans · 6th September 2005, 09:13 PM

A list of preamp tubes that performs well at lower plate voltages are the 27, 37, 56, 76 & 6P5GT.>>

How about a SRPP with say 76 below and 6J5GT above? This is on my 'must try building it' list. I'm wondering if such a SRPP would drive a 2a3 or 6B4G? Andy

AudioGeek · 6th September 2005, 10:47 PM

ok i can change it around...

for 250-260v supply voltage with the 6SN7 resistor loaded with NO cathode bypass cap..

what would be a good RL and bias point?

actually given that the 6B4G's need about 60v grid and the 6BX7's gain is about 10 then 6v output of the 6SN7 is all is needed.

Thanks for any info!

SY · 6th September 2005, 11:58 PM

At that voltage, you'd probably want to use an active current source as a plate load- a typical value of 47K as a plate load will require something like 500V as a supply if you want to run the tube in its linear range.

6th September 2005, 03:55 AM	#1
AudioGeek diyAudio Member Join Date: Jan 2004 Location: Minnesota	6sn7 operating points whats a good operating point for an input stage? probably not bypass cathode resistor. will be cap coupling to 6BX7 into a 1:1/1 phase splitter tranny. power supply voltage is around 260v. Is 100-130v too low for plate voltage on 6SN7? voltage output will be very low so does it really matter? will be for a 6SN7 cap coupled to 6BX7 to drive PP 6B4G's. any help would be appreciated as I don't know that much about 6SN7's and 6BX7's except what is said about how they sound. __________________ Richard C Jones "The wannabe AudioGeek"

6th September 2005, 10:49 AM	#3
SY Tetsujin diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX	100-130V is a bit low for that tube. It will be happier with more like 150-180V on the plate. The linearity improves at currents of 8mA or higher. __________________ "We all feel like that, Reggie, now and then, especially when Spring is upon us, but few of us would care to put it on our cards." — Sir Archibald Clerk-Kerr

6th September 2005, 05:05 PM	#5
Sch3mat1c diyAudio Member Join Date: Jan 2003 Location: Milwaukee, WI	If it's doing only 10V, it's not going to make any difference for any tube. 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!"

6th September 2005, 10:47 PM	#9
AudioGeek diyAudio Member Join Date: Jan 2004 Location: Minnesota	what do you suggest? ok i can change it around... for 250-260v supply voltage with the 6SN7 resistor loaded with NO cathode bypass cap.. what would be a good RL and bias point? actually given that the 6B4G's need about 60v grid and the 6BX7's gain is about 10 then 6v output of the 6SN7 is all is needed. Thanks for any info! __________________ Richard C Jones "The wannabe AudioGeek"

6th September 2005, 11:58 PM	#10
SY Tetsujin diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX	At that voltage, you'd probably want to use an active current source as a plate load- a typical value of 47K as a plate load will require something like 500V as a supply if you want to run the tube in its linear range. __________________ "We all feel like that, Reggie, now and then, especially when Spring is upon us, but few of us would care to put it on our cards." — Sir Archibald Clerk-Kerr


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6th September 2005, 10:12 AM	#2
billr diyAudio Member Join Date: Dec 2003 Location: new zealand	hi, like they say, it all depends here's a URL to a site that has typical bias points for the 6sn7. this is taken from the RCA handbook. you may find it useful. http://www.triodeel.com/rca_c13.gif another way to do this is to look at circuit diagrams that use this valve. also look at the triodeel main page on tube diagrams, there's lots to look at, happy hunting. kind regards bill

6th September 2005, 02:58 PM	#4
amperex diyAudio Member Join Date: Feb 2005 Location: MI	A list of preamp tubes that performs well at lower plate voltages are the 27, 37, 56, 76 & 6P5GT. I would guess the 6P5GT is the least microphonic of the lot.

6th September 2005, 05:41 PM	#6
amperex diyAudio Member Join Date: Feb 2005 Location: MI	The post did state 100-130 volts plate.

6th September 2005, 08:24 PM	#7
jacquesF77 diyAudio Member Join Date: Aug 2004 Location: France	For a nice 8 to 10mA plate current, 160 to 180V is better as SJ told jacques

6th September 2005, 09:13 PM	#8
andyjevans diyAudio Member Join Date: Sep 2003 Location: London	A list of preamp tubes that performs well at lower plate voltages are the 27, 37, 56, 76 & 6P5GT.>> How about a SRPP with say 76 below and 6J5GT above? This is on my 'must try building it' list. I'm wondering if such a SRPP would drive a 2a3 or 6B4G? Andy

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