123 Schematic

[talbany]

Max
Here is the pic Gregor posted on the bay..Perhaps yourself or others can clearly see a green stripe on the slope..I cant..gregor did say he would post some better shots but I never got any!!If in fact the schematic was taken from these shots..I don't know..This is all I am saying..

As far as the needles go this is an insane method that was used to find these values..
To find the plate values all you would need to do is find the output to V1's filter node then measure the resistance at the plate of the tube socket..V1a pin 1 V1b pin 6.. Then measure pin 3 to ground would give you the Resistance value of the cathode,same with pin 8..You don't need the needles to find these values.. As for the slope you can take the same filter point node and if you were using the needles find either lead of the bass or mid cap that connects to the slope and calculate the series resistance, since you would already know the plate values ..If one knew approx where these leads were it would only take a couple stabs to find it.. There is only 1 resistor in that general area.. Is there a chance he got it wrong, sure..But I would trust the needle method to find the slope value over this pic I posted..

Have a great weekend!!

Tony

[Max]

Have a great weekend!!

Same to you and thanks for explaining!

Max

[bluesfendermanblues]

Hi guys, I copied all Gregor Hildens pics from the Ebay add. Here ya go

[bluesfendermanblues]

and a few more....

[Structo]

I wish I had some software to enhance colors but here is a close up of the Slope Resistor in #094.

Then there is a picture of the OD2 output resistor which I believe is a 150K.

They look similar, I would say brown, green, yellow, red.

[Dr d]

I would agree with you Tom. Looks like a green stripe to me making it a 150K slope.

[stevlech]

Just thinking out loud:
Maybe the decision to raise the slope to 150k was to compensate for the extra low end from higher plate loads?

Has anyone seen a Dumble with high plates and 100k slope?

[marcos]

My 2 (Euro) cents:
I cannot comment on the accuracy of the schematic, but I have seen 2
Dumbles of the same era that have the classic tone stack with the 150k slope
resistors. BTW I used this variation in a number of my own amp mods,
eventually changing the mid cap to .01, I felt the tonestack discussed here
was a little too thin overall, although I was able to produce some nice tones.
IMHO the 150k slope produces very glassy but smooth highs.

Marcos

[talbany]

., I felt the tonestack discussed here
was a little too thin overall,

Marcos
Thanks for jumping in
Max has stated that this 123 amp (with presumably) a150k slope and .047/100k mid set up was voiced for a particular 56 Strat. Since (for me) humbuckers have a tendency to be a bit more bass heavy due to their design and output I am wondering why he went to this setup?..Can you comment on possibly why he did this in your opinion..

Thanks and have a good one!!

Tony

[marcos]

Tony,
I don´t really feel qualified to talk about #123, as I have never
seen or played the amp. I spoke to about 6 players who did meet #123,
they all agreed that it was almost impossible produce distortion when in clean mode, probably the result of the combination of the high plate design, LNFB on V1b and the "Modified Classic" tonestack.
I don´t see why this circuit would be voiced particularly for
a certain guitar, it should perform well with humbuckers, too.
I did spend a lot of time with this type of tonestack, though,
I used it for a couple of years in my personal amp.
Generally I would use higher settings of the bass and mid controls
and reduce the treble, as compared to the Skyliner.
The tonal difference is mostly in the lower mids, the Skyliner has
more of a vocal quality to my ears, but is not as versatile IMO.
My theory is that HAD used the 150k slope at a time when the Classic stack was evolving into the Skyliner.

Marcos

[Max]

I don´t see why this circuit would be voiced particularly for
a certain guitar, it should perform well with humbuckers, too.

AFAIR what the first owner of #0123 once told, he visited Alexander Dumble two or three times after the delivery for tweaking the amp to be in best accord with his personal taste and playing style. But I don’t know which technical details of this amp might be a result of these tweaking procedures.

When discussing these transition generation and 4th generation low plate and high plate ODS amps with such a "classic" tone stack and such a "pre precision power supply", IMO one should keep in mind that AFAIK somewhere between 60 and 80 ODS amps have originally been built with such a "classic" tone stack and this kind of power supply in the serial # range between around #0070 and #0150.

And AFAIK all these transition generation and 4th generation low plate and high plate classic amps have been used in the 80ies by IMO rather individual players like Robben Ford, Larry Carlton, Steve Farris, Ry Cooder, Brian Wilson, Dean Parks, Carlos Rios, David Williams, Christopher Cross, Stevie Ray Vaughn, Tom Verlaine, Terry Haggerty and many others for countless studio and live recordings. And all these countless 80ies recordings of players with IMO rather different musical approaches and playing styles (and AFAIK rather different guitars, too) are IMO good demonstrations of the versatility of these transition generation and 4th generation ODS amps with such a "classic" tone stack.

BTW: AFAIR #0123 is one of the ODS amps with a "preamp boost" middle postion of the rock / jazz switch.

Cheers,

Max

[talbany]

Marcos/Max

Thanks for your comments!!

And AFAIK all these transition generation and 4th generation low plate and high plate classic amps have been used in the 80ies by IMO rather individual players like Robben Ford, Larry Carlton, Steve Farris, Ry Cooder, Brian Wilson, Dean Parks, Carlos Rios, David Williams, Christopher Cross, Stevie Ray Vaughn, Tom Verlaine, Terry Haggerty and many others for countless studio and live recordings. And all these countless 80ies recordings of players with IMO rather different musical approaches and playing styles (and AFAIK rather different guitars, too) are IMO good demonstrations of the versatility of these transition generation and 4th generation ODS amps with such a "classic" tone stack.

Although I have never played an ODS transition generation classic, I have built/modified around 20 amps with this classic stack (using 100k slope) in both high and low plates..One of our earlier 2.2 (22 watt) Earthquakes (low plate) lunch box amps had this stack and thought it was extremely versatile..I can get Fendery type clean tones with a Strat much easier from a low plate classic..Walter Becker has one of our 2.2's and loves it's versatility..If I were going into a studio unknowing I would grab my 2 KT88 classic over my Skyliners..
On my high plate Skyliners... I find I hardly ever get my bass above 4 and have to run my treble up to around 7 to find a balanced transparent clean tone..This modified (150k)classic sounds intriguing..
Btw..I also think the power transformer w/ euro taps and 7581's helps with the amps ability to stay clean on up as well as the things Marcos mentioned..I also find if the clean channel is tight and clean, the OD side always sounds better..Balance/Balance..FWIW

Thanks Again!!

Tony

[ER]

Off topic; I used to live a couple houses down from Walter Becker, I never wanted to bug him but I wish in hindsight that I at least tried once, he's probably just a regular dude (or a major one anyways).

[ic-racer]

With respect to the #094 schematic, same as you have done, I enlarged the picture and played with it in Photoshop. Looked like 150K to me at the time.

I'm a little surprised after these few years there was not much discussion or fine-tuning of that schematic such as I have seen with some of the others.

[Max]

I'm a little surprised after these few years there was not much discussion or fine-tuning of that schematic such as I have seen with some of the others.

BTW: IMO just the same happened in regard to the schematic of the #0123 preamp you posted already in 2008 in the same thread http://ampgarage.com/forum/viewtopic.php?p=56782#56782. I always thought this to be rather surprising, too, because the general structure of the power supply and the power amp of these transition generation and 4th generation "classic" ODS 100W amps was already well documented then by Gil's pictures of #0124 (4th generation "classic" updated to skyline specs) and Gregor's pictures of #0094 (transition generation "classic").

But for whatever reasons up to now there seemed to be not that much interest in discussing the circuit versions of the "Talk To Your Daughter" (Robben Ford) and "Last Nite" (Larry Carlton) etc. ODS generations (transition and 4th) with a "classic" tone stack and still without a precision power supply.

Cheers,

Max