Biggest source of noise

[misterwhizzy]

I get quite a bit of noise out of my amp when the gain is anywhere above 5. What caps or resistors in general contribute to noise? I'm willing to mod the amp to reduce it. I hear "tone caps" as a general term, but are these the caps in the tone stack? Bypass caps in the gain stages? Something else entirely?

[Chris of Arabia]

Re: Biggest source of noise

If the caps smoothing the power are out of kilter, you'll get mains hum, so I guess that counts as noise.

[glassman]

Re: Biggest source of noise

Hiss and high gain go hand in hand...you can't reduce it without sacrificing something. You can reduce the treble response slightly at the early stages of the amp using very low value caps (5pF to 10pF) across the plate resistors BUT it will alter the overall tone of the amp. This works great in a really treble heavy amp but if the tone of the amp is already well balanced, it may not be a great outcome.

Another trick is to add a couple of diodes (parallel, opposed polarity) at the input to the master volume; this cuts off any signal below 0.6 volts (which your noise should be below; if not, you can add more diode sets in series) at the expense of a little added crossover distortion. Most people don't hear the crossover distortion but you may hear the cutoff when the signal drops below that level.

[Bludave]

Re: Biggest source of noise

Once the drums kick in you won't hear it


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[Agileguy_101]

Re: Biggest source of noise

Once the drums kick in you won't hear it


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There's more to music than playing live (like recording)

[Bludave]

Re: Biggest source of noise

There's more to music than playing live (like recording)

True and when in the studio i leave the sound to the engineer. Generally they know more about that then I. When playing live its a bit different. I just try to get a good balance to it all and be able to hear everything


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[misterwhizzy]

Re: Biggest source of noise

Another trick is to add a couple of diodes (parallel, opposed polarity) at the input to the master volume; this cuts off any signal below 0.6 volts (which your noise should be below; if not, you can add more diode sets in series) at the expense of a little added crossover distortion. Most people don't hear the crossover distortion but you may hear the cutoff when the signal drops below that level.

That's an interesting and easily reversible mod. I may give that a shot while I'm swapping out the filter cap. Thanks, Jerry.