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Old 30th April 2011, 05:25 PM   #1
yero is offline yero  United States
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Default Franks 6sn7 line stage question

I built a pas-3 line stage but the gain was to high. When connecting the pas to a solid state amp, It is at full volume with the volume control at 9'clock. Some members tried to help me but sy said start with a new line stage. So my question is what is the gain of franks line stage. Sy said no more than 10 db of gain. So does Franks circuit have less gain than the pas circuit. Can any one recommend a line circuit with low gain. thanks to all.
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Old 30th April 2011, 05:34 PM   #2
SY is offline SY  United States
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Frank's stage has a gain of about 20dB, which is rather high for modern sources. It has a lower source impedance and is less sensitive to loading compared to the PAS; it's not the best line stage out there, but it's very good if you need that amount of gain, and it's good enough to be audibly transparent in most applications (which, really, is all you can ask of a line stage).
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Old 30th April 2011, 07:32 PM   #3
yero is offline yero  United States
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The gain is to high. Si what about the 12au7 that has the first stage as a amplifier and the other section a cathhode follower. Some one said that it was from the RCA manual. will that have lower gain. What about the Impass preamp. Can it be used minus the transformers?
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Old 30th April 2011, 07:58 PM   #4
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12AU7 will give you the same gain, and higher distortion. oops. ImPasse will give you higher performance but even more gain (I just use a unity gain buffer in my system). I'd check out the 12B4 circuits that have been discussed here; low gain, good performance.
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Old 30th April 2011, 08:13 PM   #5
yero is offline yero  United States
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Si I obtained a large collection of tubes from my father who worked at bell aircraft. most of the tubes were hand selected and matched pairs, JAN NOS. The 12b4 is the only tube I do not have. What about the Norman Koren 12au7 design
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Old 30th April 2011, 08:19 PM   #6
SY is offline SY  United States
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Tubes are cheap, especially compared to all the components around them. 12B4 are available for $10-ish.

Once you've seen the linearity data on 12AU7, you may choose something different. Gain is still the same as 6SN7, so you get nothing in the trade other than higher distortion.
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Old 30th April 2011, 09:22 PM   #7
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Hello,
Short of or before you scrap your line stage take a look at the Goldpoint link below and scroll down to -"It gets loud too soon".
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My preference is a buffer line stage with a gain of near zero db’s (as SY said in a previous post)
DT
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