The Amp Garage

Now I have moved all the grounding as suggested, but it did (next to) nothing with the hum at idle. The hum when gaining up is maybe a tiny bit better But wait... If I connect the negative feedback the hum pretty much disappears :) It's still present, but it's at a "normal" level for a tube amp I g...

Now I have moved all the grounding as suggested, but it did (next to) nothing with the hum at idle. The hum when gaining up is maybe a tiny bit better

bepone wrote: ↑Mon Aug 15, 2022 5:22 am not really,
this would be, lines in red added. you need to be very careful which capacitor to ground..here is grounded C2. you are trying to ground C1 which is the worst case...

Ok, thanks. While we're at it, what's the best place to ground the output jack?

Thanks @Stevem, @pdf64 and @bepone. Here's an updated layout, does this correspond with the tips you provided?

bepone wrote: ↑Sun Aug 14, 2022 7:30 am but wait, before all of that, do you have heaters grounded? 100R-200R from each heater line to the ground?

There's a center tap for the heaters on the PT..
(edit) and the CT is grounded

https://www.tube-town.net/info/datenbla ... -v2020.pdf

bepone wrote: ↑Sun Aug 14, 2022 7:21 am hi neighbour !
then fix the ground point close to input jack:

in this way you have 2 separate ground points, hi and low current, should be better,.. and best results noisewise are always when you have gnd point close to input jack..

Thanks, I'll give that a try later today

Yes, it's norwegian :) It's actually, well kind of, wired that way. The bottom/filter board ground is not grounded like that, it's connected to the same ground point as the ground bus. I think you can see it in the pictures. But I can try to wire the cathode bypass directly to the filter cap negativ...

Hello :) I have had this project this summer where I've built this Fender-ish amp from scratch. A friend of mine was interested in an amp with one good clean channel that looked like a Mesa. I figured I'd give it a go and I have spent lots of hours this summer bulding the headshell and the amp. Anyw...

I dont know if its relatable, but I had a similar issue a while back that turned out to be a faulty output transformer. https://ampgarage.com/forum/viewtopic.php?f=6&t=33621

I might be overthinking this whole project. But is the easiest solution to either skip the cathode follower and wire it as two individual normal gain stages (plate driven eq) or preferably add another tube and leave the marshall-ish pre amp and eq alone and make the fender-ish pre amp and eq like it...

I am currently re-building an amp that I have run into some issues with. I think there's a post around when I tried to sort out some issues with a Mesa DC-2 that I finally gave up on. The person owning it wanted me to rip out everything and build something new and a bit different in the chassis (and...

voltages at the supply are very low.. i never seen that in marshall.. something is missing in this story, 1R doesnt matter if is connected or bypassed.. where are those electrolytic caps and are you sure that you return all the connections ok? recheck all the grounds (- poles) and other what you to...

martin manning wrote: ↑Tue Apr 19, 2022 10:54 am BTW, it looks like the bias supply is connected directly to the PT secondary and not through the standby switch, so you have bias voltage when in standby, correct?

I did not see a couple of messages, sorry.
That seems to be correct (though, I dont have the amp at the moment)

Where are you grounding the cathode to make the noise go away? If you can short it to the chassis at the tube socket and stop it, the existing ground must be bad. I did not see a couple of messages, sorry. I dont ground to "ground" :lol: , I just short pin 1 to pin 8 (since the 1R is between 1 and ...

It's enough to bypass the resistor with a wire from pin 8 to 1 (as the resistors now hang between 8 and 1). That 1 ohm shouldn't make any difference. Maybe the socket is not making good contact with the tube pins? Have you cleaned and adjusted the socket tension? I cleaned but forgot to adjust tens...