Dumbleland Special Schematic

[erwin_ve]

Mcintosh was a pioneer in its era. How mr Dumble borrowed from those designs?
Looking at the old 1954-1962(!) tube version of a MC-30 it has almost the same last stage 12ax7 cf driver before the powertubes as a sss002.

From a historic perspective it interesting to look at those McIntosh designs and how Mr Dumble implemented those in the Odyssey, Dumbleland and Sss designs.

[Max]

I see. From a historical perspektive I understand to some extent what Bombacaototal and you are pointing at. I've always thought that what they call their "untity coupled circuit" is something rather unique and not present in other amps (including Dumble amps): "The patented Mclntosh Unity Coupled circuit and output transformer have established Mclntosh amplifiers as the unchallenged leaders in the audio field." https://manualzz.com/doc/3316623/mcinto ... r-s-manual

But this might be a different (here: off?) topic anyway.

All the best,

Max

[erwin_ve]

I see. From a historical perspektive I understand to some extent what Bombacaototal and you are pointing at. I've always thought that what they call their "untity coupled circuit" is something rather unique and not present in other amps (including Dumble amps): "The patented Mclntosh Unity Coupled circuit and output transformer have established Mclntosh amplifiers as the unchallenged leaders in the audio field." https://manualzz.com/doc/3316623/mcinto ... r-s-manual

But this might be a different (here: off?) topic anyway.

All the best,

Max

Off topic? Off course not! What can you tell about the unity coupled circuit?
Understanding historical milestones give a better understanding for following designs. We all stand on the shoulders of the ones before us.

[Max]

"McIntosh Unity Coupled circuit":

Technical Description: https://manualzz.com/doc/3316623/mcinto ... r-s-manual

Service Manual: https://www.manualslib.com/manual/94906 ... tml#manual

Cheers,

Max

[erwin_ve]

"McIntosh Unity Coupled circuit":

Technical Description: https://manualzz.com/doc/3316623/mcinto ... r-s-manual

Service Manual: https://www.manualslib.com/manual/94906 ... tml#manual

Cheers,

Max

So if I understand correctly: a kind of negative feedback through opposing transformer windings?

[Max]

Here you can drink at the source :



All the best,

Max

[rootz]

"McIntosh Unity Coupled circuit":

Technical Description: https://manualzz.com/doc/3316623/mcinto ... r-s-manual

Service Manual: https://www.manualslib.com/manual/94906 ... tml#manual

Cheers,

Max

So if I understand correctly: a kind of negative feedback through opposing transformer windings?

Yes, and in many places. Look at the winding for the power tube cathodes. Or at the winding for the cf drivers. Much more elaborate than HAD ever did. I seriously doubt the mcintosh amps were his main source of inspiration. CF and transformers driving the output tubes used to more common practice when output triodes were still the main power tubes. Also 807 tubes greatly benefitted from class ab2 long before the mcintosh amps. More info here: https://lilienthalengineering.com/100-a ... -2-1945-54

[talbany]

Here is the phase inverter used in the Williamson another
kit style Audio amp popular in the 50's

Amp-Williamson-2 (1).gif

The 6SN7 was a popular driver at the time for HiFi use. https://www.angelfire.com/electronic/fu ... Heart.html https://www.effectrode.com/knowledge-ba ... al-triode/

"Winterland"

Winterland.jpeg

Dumble AC coupled the 1st gain stage (for GNFB) adjusted the Plate resistors (plate voltage/impedance) for the 12AX load lines along with the coupling capacitors for desired frequency response (which was the same .22 couplers to feed the driver.) Same "split Load" Phase inverter

The Williamson amplifier was pioneered in 1947 just after the WWII

http://www.r-type.org/pdfs/dtnw-amp.pdf
https://en.wikipedia.org/wiki/Williamson_amplifier


Btw.Where Dumble added for GNFB Marshall installed their tonestack. Again feeding a split load/Driver
Marshall Major 200W

Marshall Major 200w.gif

Tony

[jfs322]

IMO one should take into account the possibility, that at the time when #009 lost its original knobs, its original circuit perhaps was altered, too. If so, the historically correct circuit of #009 may differ from the circuit that the people of Two Rock met on their bench. E. G.: As is visible on some pictures of #009 its chassis was signed in 1978. Now ask yourself based on the ODS generations: Do you really think that a “classic” tone stack is very likely in an amp built in ’78?

Are you suggesting that simply because knobs where changed that the circuit itself was probably changed too? That's a bit of a leap, in my opinion. Lots of people change the cosmetics of their amps without touching the circuit. For example, the current knobs on SSS #002 are not the original knobs (it came with stock chickenhead knobs); is it also your contention that #002 circuit has been updated as well, based simply on the fact that it has new knobs? Also, SSS #004 is currently in a completely different headshell than it originally came with -- are you also therefore suggesting that it's circuit too must have been updated? Is your standard here simply whether it's possible? In other words, if the standard is simply whether "it's possible that the circuit has changed," well that's a low bar to meet. Anything is possible, but I think this group is more interested in what is likely, i.e. based on something more than speculation derived from "what's possible."

However, I do agree with you re: your tonestack point. If we are going back on time-period, an amp built in '78 falls closer in the 2nd Gen era than the Classic stack period, so if we are making assumptions on the which tonestack is in #009 based solely on time period, it would more likely be a 2nd Gen tonestack. But again, that's based solely on the manufacture date of the amp and nothing more.

[pompeiisneaks]

IMO one should take into account the possibility, that at the time when #009 lost its original knobs, its original circuit perhaps was altered, too. If so, the historically correct circuit of #009 may differ from the circuit that the people of Two Rock met on their bench. E. G.: As is visible on some pictures of #009 its chassis was signed in 1978. Now ask yourself based on the ODS generations: Do you really think that a “classic” tone stack is very likely in an amp built in ’78?

Are you suggesting that simply because knobs where changed that the circuit itself was probably changed too? That's a bit of a leap, in my opinion. Lots of people change the cosmetics of their amps without touching the circuit. For example, the current knobs on SSS #002 are not the original knobs (it came with stock chickenhead knobs); is it also your contention that #002 circuit has been updated as well, based simply on the fact that it has new knobs? Also, SSS #004 is currently in a completely different headshell than it originally came with -- are you also therefore suggesting that it's circuit too must have been updated? Is your standard here simply whether it's possible? In other words, if the standard is simply whether "it's possible that the circuit has changed," well that's a low bar to meet. Anything is possible, but I think this group is more interested in what is likely, i.e. based on something more than speculation derived from "what's possible."

However, I do agree with you re: your tonestack point. If we are going back on time-period, an amp built in '78 falls closer in the 2nd Gen era than the Classic stack period, so if we are making assumptions on the which tonestack is in #009 based solely on time period, it would more likely be a 2nd Gen tonestack. But again, that's based solely on the manufacture date of the amp and nothing more.

My 2c on the tone stack, going to your point, is that hey, maybe this amp was his first experiment with a later style tone stack and he liked it so much all amps ended up using it, but only after he had some time to listen and feel how they all worked/interacted etc. i.e. even though all tone stacks were 2nd Gen at that 'time' when did he come up with the tone stack he used later? some time 'before' he started actually using them.

This falls yet again into that whole point you make that I agree with fully... guessing is something that can be fun and is rarely useful real data beats guessing every time. While forever guessing, someone can play devils advocate and guess something slightly or massively different from the first idea...

Edit: last sentence was poorly written and made no sense... fixed (For ever guess, became While forever guessing)

~Phil

[Max]

... I think this group is more interested in what is likely, i.e. based on something more than speculation derived from "what's possible". ...

Of course.

... real data beats guessing every time. ...

Exactly.

So @jfs322: What kind of tone stack is in your DL #009 clone?

All the best,

Max

[talbany]

My 2c on the tone stack, going to your point, is that hey, maybe this amp was his first experiment with a later style tone stack and he liked it so much all amps ended up using it, but only after he had some time to listen and feel how they all worked/interacted etc. i.e. even though all tone stacks were 2nd Gen at that 'time' when did he come up with the tone stack he used later? some time 'before' he started actually using them.

However, I do agree with you re: your tonestack point. If we are going back on time-period, an amp built in '78 falls closer in the 2nd Gen era than the Classic stack period, so if we are making assumptions on the which tonestack is in #009 based solely on time period, it would more likely be a 2nd Gen tonestack. But again, that's based solely on the manufacture date of the amp and nothing more.

Not only that but there were several different versions of the 2nd and 3rd generation tone stacks.
This includes different value pots and caps used across the bass pot (James configuration). So without actually being inside the amp or have very detailed shots it's virtually impossible..These tone stacks also come with their problems and don't function like your typical tonestack either if we do confirm it to be either a 2nd or 3rd generation I will update the schematic for historical purposes but would keep the Classic stack as the one I would recommend going with instead of a 2nd or 3rd generation. This is why I went with a "Classic"

For those of you that would like to read more about the different 2nd/3rd generation stacks Dumble used? it"s discussed here
https://ampgarage.com/forum/viewtopic.p ... is#p129794

Tony

[jfs322]

So @jfs322: What kind of tone stack is in your DL #009 clone?

All the best,

Max

I wish I knew, I would definitely share if I knew the specifics, but my amp is not a part-for-part, value-for-value clone of a Dumbleland, but rather an "inspired-by" amp that used the PI/Driver configuration of a Dumbleland as the foundation and improved upon the amp from there. I wasn't really interested in an exact clone, but rather an Dumbleland "inspired" amp that is better suited to my playing needs. So the PI/Driver is taken from their experience with Dumblelands, and the tonestack we settled on was a few tweaks on a low-plate skyliner. I'm not a huge stickler for historical accuracy, so I don't need a value-for-value clone, but I imagine most on there are looking to clone the exact circuit. I'd advise people to just have fun with it and experiment -- take the basic PI/Driver topology from the Odyssey, and try different front end tonestacks and tweak PI/Driver values to taste. I know the stated goal of this thread is to uncover the exact #009 circuit, and that's a nice goal, but I don't think we're ever going to find that information out. So until we do, I'd advise people to take what we have thus far and experiment.

[Max]

,,, my amp is not a part-for-part, value-for-value clone of a Dumbleland, but rather an "inspired-by" amp ...

I see. Thanks for the clarification.

So this schematic https://ampgarage.com/forum/download/fi ... &mode=view isn't "BASED ON DUMBLELAND #009" (as it's written on this schematic) but it's based on some more general infos jfs322 posted here in regard to the PI/Driver configuration of his "inspired-by" amp and - apart from this exception - otherwise on pure speculation:

- DL#009 tone stack might be a "classic" because talbany recommends this
- DL#009 filters might be those shown in some schematic of SSS100W #002
- DL#009 filter recovery might be the one shown in some schematic of SSS100W #002, but imagined without reverb
- DL#009 power amp and DL#009 power supply might be similar to an Odyssey amp

But - without a reliable database: of course - it might be different: https://ampgarage.com/forum/viewtopic.p ... 52#p426452

... I know the stated goal of this thread is to uncover the exact #009 circuit, and that's a nice goal, but I don't think we're ever going to find that information out. ...

As pictures of the interior of DL#009 aren’t available and my personal memory after now around 25 years is rather vague, too: Most likely

So until we do, I'd advise people to take what we have thus far and experiment. ...

IMO this advice makes a lot of sense.

All the best,

Max

[talbany]

I would like to thank Aaron and JFS322 and Bombacaototal for their contributions to the effort
Just like with the Overdrive Special line..Someone starts the ball rolling on a particular amp or schematic shares it with the community and the world so others can join in and help us verify what we do not know about #009 or any other Dumbleland and collectively put the pieces of the puzzle together
The best thing about the Garage is we can document everything in full view on the www. In the weeks,months, years ahead I will continue to collect more data as new pictures and info comes to the light. Feel free to PM me if you wish to be discreet


P.S Hey Phil?
Since we have nothing about the Dumbleland documented so far perhaps you would be so kind as to add a Dumbleland sticky in the files section. I will be happy to do a quick description of the schematic and either Aaron or myself can update if needed, keep up with the thread and answer any questions for those interested in building one of these great amps from what we know so far . This will hopefully get some attention who wish to contribute.. Let me know if I can help further!!
Thanks!!
Tony