Tube Amps / Music Electronics
For current discussions, please visit Music Electronics Forum.

ampage archive

Vintage threads from the first ten years

Search for:  Mode:  

Re: CC vs CFvs MF

7/28/2000 11:39 AM
Re: CC vs CFvs MF
Some tube amps have a poor filtered supply on the power section, but are hum-less because the push-pull connection will cancel the hum. However when you drive the output stage into distortion you can generate some intermodulation products that do not get cancelled. Pritchard of Pritchard Amps (who also designed the PRS ss amps) has a patent on a solid state emulation of this (he calls it "FAT" injection) - hum purposedly injected (as a common mode voltage) to a diff amp driven into distortion. That's on my "to-try" list. The diff amp would allow the noise changing the tone without you have to hear the noise...
And now, a word from our sponsors:

7/28/2000 12:24 PM

GFR I own a PRS head maybe I trace it
7/28/2000 4:06 PM

Goto get the list of patents and download them all! All the patents have some interesting schematics and great text on tube power stage distortion... It should be in a book!!!  
I don't know if the PRS has the hum injection trick as it's a newer patent but it may have some nice tricks. If you trace it I would like to see it, please.
7/30/2000 5:53 PM
Danny Rawlins

The 60Hz mains frequency would be producing beat frequencies with the note also harmonics of 60Hz range up in tone including white noise (thermal noise) in the gain of the amp turned up contains heaps of frequencies. when a amp is cliping it generates heaps of frequencies from the squarewave as a squarewave signal is made up of sinewaves with diferent 2nd and 3rd order harmonics.  
About the resistors, the amount of inductance and capactance in a resistor is so small that it won't affect audio frequencies only rf. wire round resistors contain more inductance because of the way the wire is wround there are wire wround resistors that have two windings in antiphase to compinsate the inductance. wire wround resistors can affect the sound slightly but carbon and metal resistors don't differ much in inductance and capactance, the resistors that have a spiral resistance element will contain more inductance and capactance but not enouth to upset the circuit, the lead length can affect the inductance also. corbon composite resistors contain more thermal noise than metal film resistors also metal films offer less temperature drift and a tighter tolerance than carbon resistors.  
capacitors have more or less inductance depends on the type like electroyic caps have more inductance and monolithic caps contain the least amount of inductance because of the diferen't way they are made rolled up and sandwitched respectfully.

<<First Page<PrevPage 3 of 3