The Amp Garage

Oh sorry you mean the other end, that all gets grounded back at the input jack along with the rest of the preamp. PI and outputs have their own ground and the AC ground has its own. Its not the best grounding scheme ever but in this case it happens to be very quiet. Yeah, I just don't happen to have...

Did you power the heaters from a battery supply as an initial test item, to cross-check that the noise wasn't significantly ingressing by other pathways (such as B+ or ...). No but the common mode filtering knocked out the noise so well and the B+ lines where very clean that I didn't feel it was ne...

Installed the 20mH CMC this weekend and took some pics of the results: IMG_5956.JPG Pin 4/5 of V1 on blue and output of second stage on yellow with all controls dimed. This was with the 20mH CMC and 22uF non-polarized caps to ground. Unfortunately I was tired and in a rush when I ordered them and wa...

I feel kinda stupid for not just thinking to check it from the get-go, just one of those things that's so ever-present you kinda just take it for granted. Anyways I think one of the biggest takeaways from all this is that heater elevation does basically nothing to prevent this sort of noise from get...

Nworbetan, RG, I unfortunately ran out of time tonight and didn't have a chance to get the pictures I promised. I did however manage to fix the grounding and subsequently found the source of the noise. Turned out to be the fluorescent shop light hanging overhead. Explains why that noise was always p...

<r><QUOTE><s>[quote]</s>Interesting. It would be revealing to see a second trace with the filament voltage, to be able to spot the relative positions of the peaks and valleys of the noise and the AC mains waveform. It seems like the noise magnitude envelopes are similar to full wave rectified sine(i...

I did take some pics of the noise today: IMG_5927.JPG This is the filament waveform without any filtering. I forgot to take one of the line all by itself but they're practically identical. The line being obviously just scaled up from what you see here. IMG_5929.JPG This is the output of the second g...

The noise is just present on the power line without the amp hooked up. Its pretty much always there and I'm not really sure whats causing it. Can you post a pic of how noisy the wall voltage is without the amp plugged in? You might've missed the bullseye when you described it, but it could still be...

Thanks for all the replies, I'll try to address everyone's points in order: -Electrostatic shield would definitely be effective in combating this issue. Unfortunately I don't know of anyone making off the shelf PT's with them included. I'm at the point now where I could fairly easily design my own b...

So as promised in my other thread here is a technique seldom seen for the reduction of heater noise. While working on my little 6v6 Express this weekend I found that a fair bit of noise was coupling into the preamp from the filaments. In this particular case it was the result of a rather large amoun...

That's certainly possible. However in the 3 2203 style amps I've done I can dime everything and not have a problem. I've never included any of the additional stability caps either. At least that's what I remember, should go back and verify that. I think it'd be interesting to see how the express beh...

Hey everyone, haven't been around much these past few years, been busy learning and designing power electronics so I haven't had much time for guitar amp stuff. Work has slowed down (for the time being) so I've been spending some time screwing around with that 6v6 express I built a while back. Its o...

Can you post a schematic? If the diode you're referring to is the one I'm thinking of then its there for over current protection and is not strictly speaking necessary. Its connected from one side of the current limiting/sense resistor to the gate of the mosfet. The way it works is, under zero load ...

Think I'd rather have the one made out of colored pencils:

https://www.youtube.com/watch?v=NmnVYSsE8NU

You might also find this helpful: https://masteryourtest.com/study/ Here's some relevant youtube channels that I subscribe to you may find helpful, some technical, some just about general music/recording: https://www.youtube.com/channel/UCU9SoQxJewrWb_3GxeteQPA https://www.youtube.com/channel/UCS0N5...