"Buzzing" sound behind the note

[dogears]

In my experience, a buzz like yours is not feedback or the CL preamp, but something in the power supply or some sort of lead dress issue... Just sayin'

lower resistor values means more neg feedback. Have you tried changing the leads of the ot to the plates?. I had an amp with that problem, and it turned out that i have some positive feedback...but don't know why it didn't scream as usual, but did the problem you have...if it goes away by going up on the feedback resistor...that might be the problem. also...try to identify if the problem is in the power section or the pre. do you have the grid resistors in the sockets?. what value?

I hadn't thought of the OT leads on the plates. It's not screamin', so I figured it was OK. I'll try swapping 'em. I do have the grid resistors on the sockets, 3.3k. I'll try the 5.7k seen on some schems. I thought the buzz problem was in the CL part of the preamp, but now think it might be in the power section. Will also try going down in value on the -f/b resistor (more -f/b), maybe 2.2k?
Thanx!
Ace!8-)>

[Icetech]

Ace, i had the same exact prob... on mine i used a 47pf cap across the PI like the old tweed bassman had (i believe thats what had it.. been like a year since i did it) and the prob went away..

[llemtt]

it seems like some sort of ringing in the output stage, try the 47pF across PI suggestion, if it goes away you have a stability problem in the power amp, maybe a bad OT or a power supply component or bad wire dressing as dogears suggest

my .02
teo

[jelle]

Hi,
In my 97 HRM amp the problem occurred when I cranked the normal channel's volume but when I turned the master up and played real gently on the guitar, I wouldn't hear the buzz. Only when there was high levels of signal in the preamp the buzz would happen. I rebuild it cos I figured it was bad lead dress. After that, the crosstalk was gone. I didn't touch the poweramp. I'd like to know what causes the buzz in your amp!

I'd also like to know which power supplycaps also can cause the buzz..

Good luck!
Jelle

[AcePepper]

Thank you all for all the tips!

I tried reversing the OT primarys, it screamed like hell, so I put 'em back.

Tried the 47pf across the PI plates, no change.

I'm fixin' to head out for the weekend (Arlington, TX Guitar Show!) I'll order some new filter caps and get back to it next week.
Thanx again!!
Ace

[drz400]

Thank you all for all the tips!

I tried reversing the OT primarys, it screamed like hell, so I put 'em back.

Tried the 47pf across the PI plates, no change.

I'm fixin' to head out for the weekend (Arlington, TX Guitar Show!) I'll order some new filter caps and get back to it next week.
Thanx again!!
Ace

Is the buzz in both modes clean and overdrive?
The description almost sounds like bleed

[novosibir]

I'm fixin' to head out for the weekend (Arlington, TX Guitar Show!) I'll order some new filter caps and get back to it next week.

Ace, just curious to hear, whether you've got your prob fixed meanwhile, or whether you gave up in building D-type amps at all, since it's already a while ago, that you've said to get back?

Larry

[AcePepper]

Hi All,
1st; Thanx for all the help and tips!!

I did get that amp to mellow out and it turned into a real sweetie. I wound up making some changes in the power supply resistor string. That tightened up the amp real nice and got rid of the ghost notes. Since then I've done 3 or 4 of these D-Type things and folks really dig 'em! The ones with higher plate voltages (B+ 490v or so) seem to be the happiest, but they all sing real well. I've even been introduced to/gotten to play a REAL ODS! Big Fun!! I'm not building them as a standard model, but they're in my bag 'o tricks for custom builds.

Thanx again! Y'all ROCK!!
Ace!8-)>