Quinn SDO-Reverb 183/102

[67plexi]

I love my #183 builds hard to believe it’s been a year.

I look at the ODS properly dialed in as a harmonic generator, TAG is 100% no Dumbelator needed.

[vibratoking]

I look at the ODS properly dialed in as a harmonic generator, TAG is 100% no Dumbelator needed.

I wish I could look at mine that way. Mine is a good amp, but has almost none of the transition into feedback (I'll refrain on calling it bloom) that I pointed to in Greg's clip.

[Structo]

Don't feel bad vibro.

It can be tough dialing in the PI on these amps.
You have to have the right tube and the right setting on the PI trimmer.

I haven't ever really gotten mine to do the bloom thing but then again, I haven't devoted a lot of time to it.

From what I understand, you need a very well balanced tube first of all, then making tiny adjustments to the trimmer and playing through it to find the right setting.

Unless you have a scope, then you can just balance the AC.

[CHIP]

I've always wondered, if you get everything set just right with the PI trimmer and the "right" tube and your amp is blooming into harmonic feedback. Then down the road a few years you have to change the PI tube, Do you start from scratch searching for the right tube again, and resetting the trimmer?
is this when the real Dumble owners call HAD for a tune-up?
I mean, as an owner you can't just start throwing any PI tube in the amp and expect the same results. Right?

[boldaslove6789]

I've always wondered, if you get everything set just right with the PI trimmer and the "right" tube and your amp is blooming into harmonic feedback. Then down the road a few years you have to change the PI tube, Do you start from scratch searching for the right tube again, and resetting the trimmer?
is this when the real Dumble owners call HAD for a tune-up?

Having a 12ax7 with matched triode's is key to balancing the PI right. Not having the right tube. Although I think a nice NOS tube will do this easier a new production tube will do it just as well. I have the PI set 7v apart (which varies from amp to amp) and the amp blooms into harmonic feedback with the middle pup combo on every guitar I own. If it will go into harmonic feedback with the Middle position it will do it even more with just the bridge pup.

[CHIP]

I know it's been discussed countless times, but
I have found over the last few years that certain tubes (NOS) really have a huge effect on my builds. If I put all new production tubes in, I lose the tone I want. Even if the PI tube has balanced triodes.
Just the way it's been working for me.

I really wanted to throw out the question to some of the guys that have been playing these amps for years or knows; When they or you change a PI tube do you reset trimmer? It's no prob for someone familiar with a Dumble type amp and knows what to do,but what about the player who has no amp tech background?

[Mr Dumble]

I know it's been discussed countless times, but
I have found over the last few years that certain tubes (NOS) really have a huge effect on my builds. If I put all new production tubes in, I lose the tone I want. Even if the PI tube has balanced triodes.
Just the way it's been working for me.

I really wanted to throw out the question to some of the guys that have been playing these amps for years or knows; When they or you change a PI tube do you reset trimmer? It's no prob for someone familiar with a Dumble type amp and knows what to do,but what about the player who has no amp tech background?

When changing tubes on the real 183 I found V1 made the biggest difference, and it liked GEs the most by FAR. (I have or had some clips with telefunkens posted for comparisons I believe) The other preamp tubes made minor differences, and when switching between GEs, (I have lots of them) I could not really tell any difference in any of the slots. With my Quinns, I naturally thought the GEs would be the best, but nope. I like the stock Chinese (russian?) tubes more than any of my NOS glass, including GEs, RCAs, telefunkens, Mullards, Bugle boys and others. Oh yea, one other point. This is for the overdrive channel only. The telefunkins had the best clean tones for what I like.

[Mr Dumble]

# 183 blooms at volumes so low, you have to put your ear up next to the speakers to even hear it.

That is exactly what I thought I remembered hearing. Thanks for that info. TAG, I have a question and this has probably been stated many times before, but I just want to keep it straight. When you say bloom, do you mean it turns into feedback or something else? I clearly hear notes with the Les Paul that bloom into feedback from 0:12s to 0:15s in this clip.

http://www.youtube.com/watch?v=kvFGgLHV ... e=youtu.be

Is that what you consider blooming? There was a long thread about blooming some time ago. I seem to remember that there was no single opinion about what blooming really is. Can we agree that that portion of Greg's clip is blooming?

Greg's amp does not appear to be cranked in that section of the clip, even though he says it is. I guess that's one of many reasons why clips can be deceiving.

Ah! Glad you brought that up. Great point! That is NOT what I call blooming. That is feedback. I could not stand an amp that did that on every note, it would ruin your phrasing. Most amps will do that given enough gain. My 72 50 Watt Marshall did that all over the place. Great for ONE kind of music, and thats it. I went nuts trying to play blues and mellower music with it, as I had to choke every note or it started feedintg back like that. The note bloom I refer to is what I call the unique Dumble note "phasing" or note "flipping" type of thing. There is a clear example of it that I posted in that thread you refer to. It is NOT the same thing as feedback, which is clear in the times you posted above.

[boldaslove6789]

I really wanted to throw out the question to some of the guys that have been playing these amps for years or knows; When they or you change a PI tube do you reset trimmer? It's no prob for someone familiar with a Dumble type amp and knows what to do,but what about the player who has no amp tech background?

I adjust the PI trimmer every time I change the PI tube. I also adjust the trigger control (OD trim) every time I change the V2 OD2 tube. Although not everybody should do this if you don't know how (knowing regular tube amp safety).

When HAD sold an ODS to an original owner he would often give them documentation on how to set the internal trim pots as well as how to Bias the Pwr tubes correctly, sometimes even a picture.

For the PI tube HAD would also often refer to the Ampeg way of adjusting the PI trim to customers.

[CHIP]

Thanks for the responses guys.
TAG great to hear your Quinn likes the new production glass (Ruby?).
It bothers me to think of the day when NOS supplies finally dry up.
And what scant supply that is left is only affordable to the rich and famous. (I guess we might already be to that point!)

[greiswig]

I have an externally-accessible 10-turn PI trimmer on my amp. I got some white heatshrink, opened up the amp, got a few likely PI tubes and adjusted the multiturn trimmer for AC balance. Then I marked the heatshrink for # of turns to balance point and #DC volts off the tube is. Then put that on te tube. That helps me get it at least in the ballpark without opening the amp.

However, I recently checked the Sovtek LPS I've had in there for a couple months and it had drifted on the # of turns.

[Mr Dumble]

Thanks for the responses guys.
TAG great to hear your Quinn likes the new production glass (Ruby?).
It bothers me to think of the day when NOS supplies finally dry up.
And what scant supply that is left is only affordable to the rich and famous. (I guess we might already be to that point!)

hey Chip,
I bought most of the glass long ago when it was not that expensive, but in any case, i am glad they like the cheap stuff as well! Oddly, my old Emerald Pros HATED new tubes, and GEs, Teles or RCAs were a must. On the other hand, my old plain TwoRock Customs (Which I still love) loved the new stuff as well, and did not need vintage tubes. It really seems to be an amp to amp thing.

[lovetone]

I've always wondered, if you get everything set just right with the PI trimmer and the "right" tube and your amp is blooming into harmonic feedback. Then down the road a few years you have to change the PI tube, Do you start from scratch searching for the right tube again, and resetting the trimmer?
is this when the real Dumble owners call HAD for a tune-up?

Having a 12ax7 with matched triode's is key to balancing the PI right. Not having the right tube. Although I think a nice NOS tube will do this easier a new production tube will do it just as well. I have the PI set 7v apart (which varies from amp to amp) and the amp blooms into harmonic feedback with the middle pup combo on every guitar I own. If it will go into harmonic feedback with the Middle position it will do it even more with just the bridge pup.

When you set the PI 7v apart is that ac or dc?

As some mention ac balance.

Thanks Geoff

[talbany]

When you set the PI 7v apart is that ac or dc?

As some mention ac balance.

We set for AC Balance/ Signal

If the AC balance is off in a symetrical circuit, you get some even harmonic distortion products.

If the DC balance is off a little bit, you may get better microdynamics (linearity at very small signal levels) because the transformer core will be biased into a more linear region at quiesence.
FWIW..The only time I believe DC balance is critical would be in the operation of say a toroidal style OPT or something with greater sensitivity to core saturation

've always wondered, if you get everything set just right with the PI trimmer and the "right" tube and your amp is blooming into harmonic feedback. Then down the road a few years you have to change the PI tube, Do you start from scratch searching for the right tube again, and resetting the trimmer?
is this when the real Dumble owners call HAD for a tune-up?
I mean, as an owner you can't just start throwing any PI tube in the amp and expect the same results. Right?

Chip
Yes calibration is need after you change the PI tube as well as output tubes..Also as both tubes age, a given designed imbalance will drift so you never stay perfect for very long or years as you say..
Re-calibrate after changing or altering
PI Tube
Output tubes
Output transformer
Changing or modifying of the global NFB
_________________

Tony

[CHIP]

Tony, thanks for the clarification.