egnater hiss

[banjoze]

To those of you that built the seminar amp (or anyone else who would like to comment for that matter):

how much hiss does your amp have? Mine is pretty quiet on the cln input, but the low and high have more than I care for... with the amp master on halfway and the gain on halfway, there's quite a bit of hiss. Or, with either of them cranked beyond half-way and the other not.. still quite a lot of hiss.... put both on 2 o'clock and it's obnoxious.. anything above that, unbearable...

i'm wondering if something is not grounded well??

Or, is this typical?

I also get a lot of noise artifacts when I move the presence knob around... almost like a scratching / scraping sound as I move it than stops when I stop turning the knob...

[tmac]

Ok, since no one has responded yet...I haven't built an Egnater amp but I've built a JCM800 style amp (from a trashed Bassman head) and I'm pretty sure these Egnater seminar amps are pretty close to that circuit (somebody please correct if I'm off here).

The noise in presence control when you rotate it is normal if it's the old style presence circuit and is caused by voltage being on the pot (What does ZFEX call it the "Crackle Ok" knob?)

On the hiss - You may want to swap in some different preamp tubes to see if that helps. But a bit of hissssss is fairly normal for these, especially if these amps have more gain built in than a regular JCM800 which is pretty popular these days & I believe you have the option to do that while you build your seminar amp, or maybe they get modded later. Also, with the gain & master at halfway you're talking about a very loud volume level so you're bound to notice some hiss (especially if the circuit has been modded for MORE gain). Or maybe the plate resistors got a little too hot during install and may have become noisey. I don't know if they use carbon comp here or not but they can be noisey sometimes. Or maybe grid wires are a touch too long and are closer to something they shouldn't be(but I believe Bruce keeps a watchful eye on every build during these classes, and inspects every one). Maybe he'll see your post and respond.

It shouldn't be a grounding issue though. Different kind of noise. Hummmmmm rather than hissssssss.