previous: Mark Knapp Why do you think the input resistor... -- 2/12/2000 4:03 PM

Re: I learned this trick from Trace..So I have to agree! Works in my Marshall

2/13/2000 6:10 PM

Trace

Re: I learned this trick from Trace..So I have to agree! Works in my Marshall quote: "Why do you think the input resistor is a good place for carbon comps? Not trying to be adversarial, I just want to know your reasoning."     Mark, I'm not sure if there is any real reasoning to this to be honest with you. In some amps the Carbons a touch warmer (very small difference to perfectly honest with you) but some people can tell the difference. I also use metal film for the input resistors when I build amps (that's what I stock mostly now). I think both are fine to honest with you but all this boils down to my opinion.     quote: "I haven't experimented with this, but this is the point with the most gain in the amp. If you put carbon comp resisotrs there, you may have just created a noise problem."     I haven't noticed a big difference in the "noise factor" between the the carbons verses the metal films myself as far as teh input resistors are concerned. I also use sheilded wire on the input jacks and like to ground the jack to the same ground point as the cathode resistor on the first stage. On Fender's (and my amp's I build) I like to pull the input resistors off from the input jacks and solder them onto the actual grid pin of the tube socket. All this seems to help cut down noise but maybe I'm over analizing it a bit--ha,ha.     The input resistors do not "usually" go bad although it happens once in a great while (maybe someone else has seen it happen more often than I have).     I get a bunch of older amps in and out but as far the input resistors going off value goes, I haven't seen this happen nearly as much as plate resistors going off value (if at all) or being as noisey either. Now this is just from my experience and it certainly doesn't mean I'm right and everyone else is wrong. It's just my opinion based on my experiences, that's all.     In a different thread (Rick I think?) posted that the plate resistors in Marshalls are not as noisey as plate resistors in Fenders. I personally agree with that. Fenders have noiser plate resistors by far altought I can't really tell why that is but perhapes someone else here will be able to(?)     I've seen some older Marshalls (plexis & amps up to '76) where the "hiss" and or noise were reduced when replacing the plate resistors with metal films. To be honest (and I may get flagged for this...) I didn't notice any difference in actual "tone" of the amp after replacing the plate resistors over to metal films. Some say they are brighter sounding but in this section of the amp I don't hear any difference other it's being able to reduce some of the amp's hiss (if there is hiss there to begin with).     For what ever it's worth changing the plate resistors on the 1st preamp tube seems to make the most difference as far as reducing some of the amp's hiss is concerned. Typically I don't find there to by much difference when replacing the PI's plate resistors, again, for what it's worth.     Sorry for rambling;   Trace

 

Replies:

Mark Knapp Thank you. Do you also put the 1M r... -- 2/13/2000 8:39 PM Randall Aiken Trace, your empirical findings agre... -- 2/13/2000 9:20 PM Richie I have found a few bad input resist... -- 2/18/2000 11:48 PM