|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
76.90.39.24
In Reply to: RE: Circuit rev 2.2 posted by Paul Joppa on December 14, 2014 at 11:00:57
"First change would inject any hum at the cathode of the driver, instead of at the plate and attenuated by the plate choke impedance - so I would expect a lot more hum. It's a fairly easy experiment though ..."
Ultrapath requires a very quiet PS.
"The second change is unclear; you appear to describe moving the 2A3 bypass cap to parallel the existing ultrapath cap?"
The ultrapath cap goes from the output of the PS to the cathode of the 2a3, not ground.
What I am proposing is to remove the 2a3 cathode bypass cap (it's not needed, the ultrapath cap bypasses the cathode resistor) and use it as a cap from B+ to ground in order to reduce the ripple of the PS.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Follow Ups:
Yes, I am not following the ultrapath design exactly. The cap from cathode to ground does have an influence on the bass, I believe. In any case, ultrapath relies on the power supply impedance being large, i.e. the last element being a choke, so a cap to ground at the B+ is out unless you add in another choke.
"...ultrapath relies on the power supply impedance being large,..."
Ultrapath takes advantage of the power supply "path" impedance being large.
The impedance of the power supply path, even when the last element of the PS is a cap, is large (compared to the reactance of the ultrapath cap) because it includes the value of the cathode resistor.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
I can't locate an example, but I think in the original circuit there was a resistor between the power supply and the top of the output transformer. However there seem to be a great many variations all going under the Ultrapath name.
I'll change the name of the capacitor in the schematic, and edit my text to refer to "cathode-coupled" output, which I believe is a more widely accepted term.
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: