102 Feedback City

[martin manning]

Another test for Tony...
what if you connect a "silicon" buffer stage between guitar and amp input such as a clean booster or something equivalent? does the feedback improve? does it lessen?

Easy... That's the FET input.

[llemtt]

@Martin
Yes, that's what I though in first place, but if I remember correctly Tony's amp don't have the fet circuit..

@Tony
I'm trying to understand if the interaction of the pickup (mainly inductance) with the tube input stage is part of the feedback behavior. Putting some circuit between guitar and amp should break any direct interaction.

Thinking about components instead I'm currently pointing my finger toward those big grid resistors on V1, I don't see them frequently on other tube amps and such a feedback either...

cheers
Teo

[ToneMerc]

Thinking about components instead I'm currently pointing my finger toward those big grid resistors on V1, I don't see them frequently on other tube amps and such a feedback either...

cheers
Teo

If it was as easy as simply a 1W Piher on V1's grid then my last 3 builds would sing like Tony's

TM

[llemtt]

behavior belongs to the system as a whole but some parts maybe come into play more then others

bigger grid (and leak, and plate, and...) resistors means more signal coupling...

cheers
Teo

[JHP]

Tony that amp sounds amazing! Love the corners on the new cab.

I have a Bludo 102. It does the feedback on command thing pretty well.



http://soundcloud.com/peterdjp/bludo-feedbackbloom

[martin manning]

Tony, et al, I've been reading around in the TW forum and learned that the tonstack wiring (lead dress) can have a big effect on harmonic feedback in the Express circuit. I scanned through this thread quickly for pictures of that area, but I don't see any (sorry if I missed a link somewhere). Is it possible that the tonestack wiring layout in this amp is somehow different than you and others have used previously?

[CHIP]

There's some pictures in this thread;
http://ampgarage.com/forum/viewtopic.php?t=17211

[Structo]

Not sure if this is partly why but the plate and cathode wires are not as usual, no LNFB, no snubbers on V2 and a 68pf bright cap on the master.

[llemtt]

Tom, why do you say cathode wires are unusual?

[Structo]

Because the three wires that run on the left side of the socket are not all grouped together in parallel.
This creates a bit of crosstalk between those wires.

This is thought to be part of the mojo of Dumble amps.

[vibratoking]

Not sure if this is partly why but the plate and cathode wires are not as usual, no LNFB, no snubbers on V2 and a 68pf bright cap on the master.

The plate and cathode wires look like the layout of 183. Mine is just like this as well and I don't have the feedback phenomenon.

I removed the V2 snubbers on mine. It sounds harsh and nasty without the snubbers. I have to put them back in.

68pF bright cap is too harsh to my ears.

[sergio]

I also removed the 68Pf cap and now sounds much better, less fuzzy , more smooth and definite overdrive!

Abuot the feedback , none idea sorry!

[amplifiednation]

This is my 102 doing some controlled feedback with just a tele bridge pickup. This isn't the same as Tonys but it seems to me the #102 loves to take off! The harmonics rise with every note.

Here are my settings...Fuchs reverb/series loop

[wokkel]

Bump


Maybe everybody is busy building SSS and borderlines.
But I still wonder what the recipy for feedback is.

Tony, you mentioned your next build would be a 123 with same components.

Any news? At all?

Harald

[talbany]

Bump


Maybe everybody is busy building SSS and borderlines.
But I still wonder what the recipy for feedback is.

Tony, you mentioned your next build would be a 123 with same components.

Any news? At all?

Harald

Harold
I am actually in the process of rebuilding the preamp of another amp I have using the exact same layout and parts as my 102..It's going slow and tedious..Will keep you posted..

Tony