|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
73.181.211.24
In Reply to: RE: Attempting a simple 12AU7 preamp design. posted by gavinhaley on April 15, 2016 at 17:01:00
If all the 12AU7s are on a common winding, it's probably best to bias that winding halfway between the cathodes. Hopefully that's around 1/4 of the HV supply voltage, for best headroom.
If there are two heater windings available, then one can supply the voltage amp, and the other the cathode follower; they can then be biased separately.
For a preamp like this, linearity is not really an issue, since the output voltage has really enormous headroom. Using current sources greatly improves the circuit linearity, as well.
Follow Ups:
Hi Paul. Would the filaments on the CF stage need to be raised at all?
You can look up the data sheet, but most tubes are spec'd at +/-100v heater to cathode. You don't want to get too close to either end.
Paul
I found that !2AU7s should be run at about 8ma to be their most linear.What puzzles me is a 6CG7 and a 6SN7 are much more linear but the mass availability isn't there with the 6CG7 as it is for the 12AU7.
A friend you get for nothing,an enemy has to be bought
At what plate-cathode voltage did 8mA seem best?
About 300v as I recall.
A friend you get for nothing,an enemy has to be bought
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: