Tube Amps / Music Electronics
For current discussions, please visit Music Electronics Forum. The sunn still shines online!

ampage archive

Vintage threads from the first ten years

Search for:  Mode:  

CC vs CFvs MF

7/26/2000 11:56 PM
CC vs CFvs MF
I did a test the other day with the rat I modded for bass(still on going). I had the rat turned up all the way with a J bass (cs60's pickups) I tend to like it with the front at about 8 and the bass full at this setting it starts to hum. I could change the "sound, tone" by blending in hum it caused a tone change. This makes me think clean amps might want some hum injection.  
I am not joking, has anyone done this?  
FWIW the amp is a modded 30 practice. I did not try this yet on the 1,500 watt amp, svt preamp setup.  
When an amp is up all the way and distorting could part of the tone be the mixing of the hum with the signal. If thats all it is one could inject hum.
7/27/2000 12:57 AM
Carl Z

I don't see why it wouldn't be plausable hypothesis. hook up a function generator and inject a nice clean 60 Hz signal at various points and see what happens. Couldn't hurt.  
Now, regarding the CC vs CF vs MF question, I've been knocking an idea around in my head. Here's the basic idea...MF resistors will undoubtedly develop a certain amount of electrostatic charge. This wouldn't be present in a CC or CF resistor. So I was thinking that there is a chance that there might be some capacitive coupling going on between these resistors that would affect the tone.  
Sound reasonable?  
Carl Z
7/27/2000 12:18 PM

I should have wrote that if hum can cause a tone change(IM, ear brain stuff)High gain and hiss might cause the same thing so maybe adding noise to a clean amp might be cool.  
Carl how would a MF pick up a charge?
7/27/2000 4:34 PM
fet Attn. Mr. Vex
I have always thought that there should be a guitar fuzztone that mixes a user-settable quantity of white/pink noise into the output. This noise addition would be gated by the guitar amplitude envelope. Possible?
7/27/2000 7:47 PM
Carl Z
Re: CC vs CFvs MF
I'm not completely sure. It seems logical that being a conductive metal that has some pretty healthy AC voltages developed across it, it might pick up some sort of charge or develop an electrostatic field. It's just a supposition as to why people would hear a difference between carbon and metal films.  
7/28/2000 2:26 PM

What we need to do (calling RG or Randall *laugh*)  
Is to take a few select values of CC/MF resistors, like 100k etc, ya konw, the more basic amp values ;)  
What we need to do is set them up and measure both resistance, inductance and capacitance of them, at various frequencies. THEN to throw some wrenches in the works, do this then float them at higher voltages, to see hwo that changes as the resistors heat. I think ***IF*** I mean really ****IF**** there are any difference in performance, this type of testing would bring it out. Any takers in the offer?
7/29/2000 7:45 AM
Re: CC vs CFvs MF/ Rambling
"What we need to do is set them up and measure both resistance, inductance and capacitance of them, at various frequencies."
No need. There will be no change in resistance or impedance with various frequencies applied if they are truly just resistors.  
I guess that's the real question though...  
are all these different resistors truly resistors and only resistors, or do the different construction techniques create variable capacitances and inductances in the actual resistor?  
Possibly some resistors could have slightly more or less distributed L and C based on how they are made or what they are made from.  
Measurable reactance of a singular resistor (at predetermimed frequencies) would be caused by these little distributed inductance and capacitances (IMO almost none in a small resistor), so it will be nearly zero Xl and Xc at most audible freqs... just the R.  
The capacitance or inductance shouldn't change by moving up and down in frequency though.  
The only thing that could change would be that lumped reactance value of the R, Xc and Xl at different frequencies and only if the C and L are large enough.  
Of course the higher in frequency you go, the more those small distributed capacitances and inductances (variable in different resistor constructions too) pop up and their reactance become a bigger part of the lumped LCR and subsequently there is a change in Zed and the Q of the circuit they are used in..  
But, a real resistor has virtually no reactance at audio frequencies.  
If Xl=0 and Xc=0 and R=1*X then it's 1*X ohms.  
Why some folks swear they can hear a difference in Carbon Comp, Carbon film, Mtl film or Mtl Oxide...  
I don't know.  

  Page 1 of 3 Next> Last Page>>