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Old 6th September 2005, 03:55 AM   #1
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Default 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.
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Old 6th September 2005, 10:12 AM   #2
billr is offline billr  New Zealand
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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
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Old 6th September 2005, 10:49 AM   #3
SY is offline SY  United States
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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.
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Old 6th September 2005, 02:58 PM   #4
amperex is offline amperex  United States
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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.
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Old 6th September 2005, 05:05 PM   #5
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If it's doing only 10V, it's not going to make any difference for any tube.

Tim
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Old 6th September 2005, 05:41 PM   #6
amperex is offline amperex  United States
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The post did state 100-130 volts plate.
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Old 6th September 2005, 08:24 PM   #7
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For a nice 8 to 10mA plate current, 160 to 180V is better as SJ told

jacques
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Old 6th September 2005, 09:13 PM   #8
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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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Old 6th September 2005, 10:47 PM   #9
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Default 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!
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Old 6th September 2005, 11:58 PM   #10
SY is offline SY  United States
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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.
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