102 Feedback City

[talbany]

Hi Tony,

maybe it has already been discussed:

could you try to use a different filter cap + dropping resistor for V1. I could imagine that the 20uF V1 filter cap being so close to V1 could be responsible for the tendency to feedback.

You could just desolder the B+ wire to the filter and clip in a different cap (could you check the exact capacity of the orange TVA installed?).

Cheers,

Electron

Guy's Ive said this several times already.. Here are the caps I changed..
I too thought the B+ V1 coupling into grid of V1a due to the lead dress..I wrapped my alligator clip around b+ feeding V1 filter cap and attached to grid of V1a on my Music Man amp and heard no such change.. So been there!!

Screens 20uf
Phase inverter 20uf
V1 20uf

[talbany]

Alright..Let's strip this down to bare bones..Simple open strings first A&D strings.. Then bar chords on up the neck.. clean channel /no PAB.. Input vol on 6 Master set @ 2 1/2
I am standing about 6 ft from the amp..I am facing it..Pretty wild!!

What do you think!!

http://www.youtube.com/watch?v=Zx9eWMPAxZU

Tony

[ElectronAvalanche]

Guy's Ive said this several times already.. Here are the caps I changed..
I too thought the B+ V1 coupling into grid of V1a due to the lead dress..I wrapped my alligator clip around b+ feeding V1 filter cap and attached to grid of V1a on my Music Man amp and heard no such change.. So been there!!

Hi Tony,

sorry to disagree: you tried something very different from what I suggested if I understood you correctly.

It might be something with that SPECIFIC cap in your feedback "monster" amp. So you would need to swap out that specific cap, not trying to inject induced signal in a different amp.

Just my 2 cents....

It must be something on V1. It must have to do with the parts used (and I do not think that teh fact that their are NOS plays a role), so maybe the foil in one of the coupling caps is able to resonate very easily. So IMHO to really understand what is going on, you would have to replace each part one after the other to find out where the magic part is.

My 2 cents!

Electron

[LeftyStrat]

Alright..Let's strip this down to bare bones..Simple open strings first A&D strings.. Then bar chords on up the neck.. clean channel /no PAB.. Input vol on 6 Master set @ 2 1/2
I am standing about 6 ft from the amp..I am facing it..Pretty wild!!

What do you think!!

http://www.youtube.com/watch?v=Zx9eWMPAxZU

Tony

Okay, in this clip I can hear more clearly a compression effect. The initial attack kind of ducks, and then you hear it swell as it sustains. I'd be curious to see what kind of voltage sag is happening on the plate of each side of V1.

Also around 00:47 there seems to be some kind of pumping going on, where it sounds like it is going to die out and then hops on the pumping and starts sustaining.

[talbany]

Dominick

I don't buy the NOS theory either.. BUT wouldn't say a micro-phonic cap resonate at the same frequency or I would get more like a squealing effect..
Next time I get it out of the cab I will chop stick it and see..Thanks for your theory..

Okay, in this clip I can hear more clearly a compression effect.

I think what you are hearing there is the mic in the cheap camera compressing.. The amp does have a bit of compression to it but nothing I would consider unusual..Thanks again for helping out!!

Tony

[LeftyStrat]

I think what you are hearing there is the mic in the cheap camera compressing.. The amp does have a bit of compression to it but nothing I would consider unusual..Thanks again for helping out!!

Tony

Oh yeah, didn't think about that, probably the auto gain pumping.

[Dr d]

Just a thought....looking at the photo I see the caps associated with V1B aren't tied together with silicon. This might allow them vibrate sympathetically and aid the feedback. If they could be tempoarily stuck together and we find the feedback is dampened, then this could be the factor. What do you think?

[markr14850]

Do you have a long enough speaker cable to put the amp in another room?

This would rule out acoustic coupling between the speaker and some component in the amp.

If you don't have a long enough cable, maybe on the floor with some heavy blankets over it?

[CHIP]

Go to the bottom of page 8 of this thread. Tony explains.

[Max]

As far as I understand this discussion up to this point, many members here aperantly seem to think, that there's "something special" (some parts with unusual specifications, some kind of "magic", some kind of a special combination of special parts, magic, some special layout details, NOS parts and everything etc.) going on in Tony's "Feedback City" amp.

But other members here aperantly seem to think that what's demonstrated in Tony's clips is rather usual:

Greg (boldaslove6789) https://tubeamparchive.com/viewtopic.ph ... 725#200725 :

"I've built and tweaked a few straight #183 (& #102 clones), and owned a Quinn #183 Preamp, all of which generated that Feedback easily. Since there is no LNFB on V1 on #183 to load the signal down it actually can feedback more than #102."

So I wonder, what may be the reason/s for these (IMO) large discrepancies concerning the question, if what Tony demonstrates here is completely usual or -on the contrary - rather special? Do you think, that these large discrepancies concerning "rather special or completely usual" are just caused by differences in the way different members here perceive Tony's clips? Or what do you think are the reason's for these (IMO) large discrepancies concerning the question, if what Tony demonstrates here is rather usual or rather special?

What I wonder about is this e.g.:

Why do aperantly many members here seem to think that it's necessary or at least helpfull in some way to find this special reason, this special magic part etc. that enables Tony's "Feedback City" to provide a player with this kind of feedback, but aperantly no one here seems to feel the need to find out what special kind of magic part etc. enables #0183 and its clones e.g. (or perhaps other Dumble ODS amps, too?) to provide a player with "that Feedback"?

Cheers,

Max

[boldaslove6789]

I do agree that Tony's amp has something special going on.

My Quinn SDO-R does this harmonic Feedback easily and only the v1 and V2 preamp tubes have Dumble ODS style lead dress, other that that the amp is not a 1:1 clone of any Dumble ODS by any means.

The Harmonic Feedback can certainly be achieved with New Production parts (especially ones with 1% tolerances), but there has to be something that the NOS resistors and NOS Bassman trafo add. Maybe it's just the changing of the molecular structure of the carbon over a period of 40 years that makes this Harmonic Feedback much more "Musical" with NOS parts/transformer.

IMO Tony's amp sounds so damn good because of the combination of NOS tubes, NOS parts, 1:1 Dumble ODS lead dress, and a 40 year old Bassman 100 trafo, not just any one thing.

[Max]

I do agree that Tony's amp has something special going on. My Quinn SDO-R does this harmonic Feedback easily and only the v1 and V2 preamp tubes have Dumble ODS style lead dress, other that that the amp is not a 1:1 clone of any Dumble ODS by any means.

Greg, to avoid misunderstandings:

Do I get you right now, that you think that the original #0183 and the "straight #0183 clones" you built are not able to provide a player with "that Feedback", which Tony demonstrates in his clips here?

Cheers,

Max

[boldaslove6789]

It's soo hard to tell and say "For Sure" without physically having the amps next to each but yes, as far as my experience has been all the amps I've been around, built and/or tweaked were able to produce a very musical Harmonic Feedback that I liked.

The differences are these:

Tony's "Feedback City" amp seems to take off into a very "Musical feedback" on every note on the guitar neck, it blooms as the notes reach the uppermost harmonic.

Some of the amps I've been around that closely resembled Tony's "Feedback City" amp also Fed Back just not on every single note on the neck. Some notes would take off into feedback while others did not.

My Quinn SDO-R being the only exception as it does take off into that very Musical harmonic feedback on every single note but doesn't have that same "Bloom" and I think that this is where the use of NOS parts factors in..

i just think some amps do it better than others and that using NOS materials helps make this phenomenon happen more easily and more musical.

I'm going to change out as many of the new prod. parts in my Quinn to the same NOS stuff Dumble used (Q-lines, Beyshlags, etc.) so it will be more definitive and I can say for sure that the use of NOS parts makes this phenomenon happen.

Hope that helps...

[erwin_ve]

...but aperantly no one here seems to feel the need to find out what special kind of magic part etc. enables #0183 and its clones e.g. (or perhaps other Dumble ODS amps, too?) to provide a player with "that Feedback"?

Cheers,

Max

Check the 12 pages before this one; plenty members asked about specific things, me included...
Edit: and many players like playing on the edge of feedback. Playing extremely loud was/is necessary to be on the edge. Tony's clips are not loud. But his system acts like it is played loud. I don't know Max how it works out for you, but for me that is like a dream.

[CHIP]

[/quote]Why do aperantly many members here seem to think that it's necessary or at least helpfull in some way to find this special reason, this special magic part etc. that enables Tony's "Feedback City" to provide a player with this kind of feedback, but aperantly no one here seems to feel the need to find out what special kind of magic part etc. enables #0183 and its clones e.g. (or perhaps other Dumble ODS amps, too?) to provide a player with "that Feedback"?

Max,
IMHO if any member here built an amp that does what Tony's is doing.
and would be willing to share, and that's the important word here, share,
whether it be #183, #102 , #124 ect. I think there would be just as much interest to what's going on in the amp, among members here.