Feedback

[greiswig]

I remember hearing a clip of one of Normster's builds...a non-HRM D'Lite IIRC. He would fret a note, and the note would blossom from a near-clean tone to nice feedback within a few seconds. He did this across the fretboard, going string to string, at "bedroom levels."

I've got my D'Lite now, and I am not getting that kind of feedback. In fact, I really am not getting anything to feedback. What's the secret? Is it all the guitar and how resonant it is?

[skyboltone]

Norm's built a million amps greiswig. Post gut shots and ask for guidance. It takes time. You'll get there.

[Structo]

Hmmm, I doubt that it was at bedroom levels especially on a clean setting.
I'm not saying that what you remember isn't correct, it just hasn't been my experience with this amp.
Having the gain up considerably will get this effect on clean or OD.
The amp is pretty rich in harmonics and is something I like.
But you have to get the strings vibrating with the amp to get that kind of feedback.
Just my 2¢.
YMMV

[greiswig]

Norm's built a million amps greiswig. Post gut shots and ask for guidance. It takes time. You'll get there.

Thanks much. I understand that Norm's built a lot, and I haven't. In fact, to try to get this one right, I had someone else do the initial build who had built quite a few. (Not a million!)

I'd be ashamed to post gut shots at this stage: I'm in mid tweak, trying out the Skyliner stack, Bluesmaster PI, etc. to see how they sound. I'll try to get some up later, though.

Part of what I'm trying to do with questions like this one is to get theoretical knowledge as well as guidance. On this one, I'm trying to find out what causes that to happen. As my Salem neighbor noted, ordinarily feedback comes acoustically; the speaker has to move some air and excite the strings. In my experience, that typically happens only at certain frequencies where the guitar resonance is just right. In the clip, Norm seemed to indicate that it wasn't very loud, and it was happening across notes. That seems distinctly different.

[Bob-I]

Hopefully Norm will jump in here, but I spoke to him about that and he said it was a surprise, not at all planned. It takes 15-20 minutes of running for it to start then it happens at will, even at lower gain levels.

I wish there was some magic formula, but apparently it's a combination of many factors.

BTW, lead dress has a huge effect on the amp. For example the plate and cathode leads to V2 should run parallel for best bloom and bottom end tightness, go figure. HAD knows something we don't know.

[Structo]

Huh, I hadn't noticed you were from Oregon Greiswig.
Portland?
BTW, I agree about the resonant frequencies.
Probably a combination of a lot of things coming together just right.
Guitar, amp circuit, etc.

I can't wait to dig into my D44 and tweak some values.
I'm still in the research and learning mode before I fire up the iron.
For the most part I am happy with it.
I would like to tame a little of the harshness or sizzle.
But on some songs, I like it the way it is.....
Too many choices and too little knowledge on my part to decide what to do about it right now.

[Normster]

OK, this is gonna sound like mojo BS, but here goes...

1. The amp MUST be fully warmed up, at least 20-30 minutes.
2. Set input volume at 2:00 (o'clock)
3. Set OD gain anywhere above 10:00
4. Engage PAB
5. Bring master volume up until the amp starts to feed back

Here's the strange part, once the amp begins to feed back, you can bring the master volume down pretty low and it will still get harmonic feedback. In fact, you can even bring down the gain levels. I have no idea why the amp will continue to get nice harmonics after being played at louder volumes, but it does!

BTW, a semi-hollowbody will feed back at lower volumes, especially if you get the distance and angle correct. If I sit about 3-4 feet from the amp with my Artcore AS-83 (Gibson Classic 57 pickups) and angle the guitar at 45 degrees from the amp, it will get feedback at conversation levels.

[Structo]

Cool!
Thanks for straightening me out on that Norm!

[greiswig]

OK, this is gonna sound like mojo BS, but here goes...

1. The amp MUST be fully warmed up, at least 20-30 minutes.
2. Set input volume at 2:00 (o'clock)
3. Set OD gain anywhere above 10:00
4. Engage PAB
5. Bring master volume up until the amp starts to feed back

Here's the strange part, once the amp begins to feed back, you can bring the master volume down pretty low and it will still get harmonic feedback. In fact, you can even bring down the gain levels. I have no idea why the amp will continue to get nice harmonics after being played at louder volumes, but it does!

BTW, a semi-hollowbody will feed back at lower volumes, especially if you get the distance and angle correct. If I sit about 3-4 feet from the amp with my Artcore AS-83 (Gibson Classic 57 pickups) and angle the guitar at 45 degrees from the amp, it will get feedback at conversation levels.

Hee hee! Yep...sounds like mojo. It'd be interesting to see if others can replicate this effect. I'll give it a go, too.

[groovtubin]

OK, this is gonna sound like mojo BS, but here goes...

1. The amp MUST be fully warmed up, at least 20-30 minutes.
2. Set input volume at 2:00 (o'clock)
3. Set OD gain anywhere above 10:00
4. Engage PAB
5. Bring master volume up until the amp starts to feed back

Here's the strange part, once the amp begins to feed back, you can bring the master volume down pretty low and it will still get harmonic feedback. In fact, you can even bring down the gain levels. I have no idea why the amp will continue to get nice harmonics after being played at louder volumes, but it does!

BTW, a semi-hollowbody will feed back at lower volumes, especially if you get the distance and angle correct. If I sit about 3-4 feet from the amp with my Artcore AS-83 (Gibson Classic 57 pickups) and angle the guitar at 45 degrees from the amp, it will get feedback at conversation levels.

http://www.myspace.com/omegaamps

cool! mine does same thing, it was feeding back at ""3"" on OD pre and master!! The lead dress is truly important

[Structo]

So are you talking about v1, v2 cathode and plate wires run touching each other?

[brownnote]

So are you talking about v1, v2 cathode and plate wires run touching each other?

yes....right next to each other...although the first prototypes were not wired to this convention and still produce harmonic feedback at low volumes, the lead dress is very important.

I think it has a lot to do with the amp being warm and the voltages your preamp tubes are settling into...different tubes will give you a range of voltages on V1 & V2...as a broad rule of thumb, you should try to get as close to 200v as you can, V2 will be a little higher in the 210v range.

poor connections will kill the tone...the amp works and sounds OK but doesn't respond as it should.

Mechanical connections are recommended on every solder possible.

In other words, wrap your leads...don't rely on solder to hold your connections together.

[greiswig]

(SNIP)

poor connections will kill the tone...the amp works and sounds OK but doesn't respond as it should.

Mechanical connections are recommended on every solder possible.

In other words, wrap your leads...don't rely on solder to hold your connections together.

Okay...but I'm trying to understand what wrapped leads would look like on a eyelet board? And how does one make this good mechanical connection on "tweaks." where you're subbing a component on an already-assembled eyelet board? Any pix? Illustrations? Carefully-crafted descriptions ablaze with clarity?

[Structo]

Heheheh, I was wondering the same thing.
I'm new to eyelet boards and the only way I've seen them done is to bend the leads flat to the underside of the board, then snip close to eyelet.
Not very mechanical IMO.

[brownnote]

carefully twist the bare wire end to the component lead end in a over-under-over-under-under-over-under-under-over-over fashion.
Then insert it into the eyelet.




























JUST KIDDING!!