|
Tubes Asylum Questions about tubes and gear that glows. FAQ |
|
|
|
Tubes Asylum Questions about tubes and gear that glows. FAQ |
|
In Reply to: Re: Dynaco ST-70: upgrading using mod kits or replacing existing parts? posted by John H on July 24, 2002 at 18:11:17:
Just a bit of an overview, a larger resistor between the output transformer and driver cathode will reduce the feedback, smaller will increase.The small pf cap many amps use across that resistor may also need tweaking for optimum square wave response and/or stability from HF oscillation if you change radically.
You can remove the resistor entirely, but with less feedback you get a narrower frequency range and more output impedance, generally considered a bad thing.
You can remove it and really like it better with an UL or triode amp like the ST70 because the damping factor should still be somewhat reasonable. This is generally not the case with pentode connected output stages, the output impedance just becomes too high, but YMMV.
If you want to experiment, try doubling the size of the resistor. If you hate it I would leave it where it was stock. If you like it try removing it all and see what you think. You can't hurt anything by removing it, although you head towards instability increasing the feedback. Some amps probably run more of a ragged edge in this regard than others with the parameters their designers settled on.
-jd
This post is made possible by the generous support of people like you and our sponsors:
Follow Ups
- Re: Dynaco ST-70: upgrading using mod kits or replacing existing parts? - jdarg 11:43:51 07/25/02 (0)
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2024, Audio Asylum, all rights reserved ]
