"70ies circuit Bludodrive"

[Max]

3rd generation "pre-classic" ODS pictures

[Structo]

Thanks for the information Max.

But the Dumble stacks aren't really a true Baxendall tone stack.
The Baxendall also does not have a mid control but rather a fixed resistor.

I would agree that Alexander based his tone stack on the Baxendall originally but they are modified and not true to the design any longer.

As you can see the two are quite different.

Baxendall Tone Stack
[img:273:266]http://lh4.ggpht.com/_MHnI-B0pJ8k/TKSg3 ... 0Stack.JPG[/img]

#40 Tone Stack
[img:355:364]http://lh6.ggpht.com/_MHnI-B0pJ8k/TKSg3 ... 0Stack.JPG[/img]

[Guitarman18]

Hi Max,

Thanks for posting the chronology with pics. It really helps to have it set out like that. Ultimately it would be great to have a separate thread started, with sound clips (choice examples from the real Dumble clips thread) included and then put up as a sticky.

Cheers,

Paul.

[Max]

Thanks for the information Max.

But the Dumble stacks aren't really a true Baxendall tone stack.
The Baxendall also does not have a mid control but rather a fixed resistor.

I would agree that Alexander based his tone stack on the Baxendall originally but they are modified and not true to the design any longer.

As you can see the two are quite different.

Baxendall Tone Stack
[img:273:266]http://lh4.ggpht.com/_MHnI-B0pJ8k/TKSg3 ... 0Stack.JPG[/img]

#40 Tone Stack
[img:355:364]http://lh6.ggpht.com/_MHnI-B0pJ8k/TKSg3 ... 0Stack.JPG[/img]

Hi Tom,

the #40 tone stack you've posted is not correct. The tonestack of #40 is a typical 2nd generation tone stack and has these values:

Treble: 500KL pot / 510pF treble cap
100k slope resistor
Mid: 250KA pot / .01 mid cap
Bass: 1 MA pot / .1 bass cap / .002 soldered between the terminals 2 and 3 of the bass pot and .02 cap soldered between terminals 1 and 2 of the bass pot / 10K tail:

"James configuration" at the 2nd generation bass pot:

Maybe I did not use ideal semantics and it is just a misunderstanding. Here's again what Tony posted here https://tubeamparchive.com/viewtopic.ph ... 141#130141 concerning this topic:

Marcos/Max
As Max puts it the bass pot configuration is indeed James inspired.. In a passive stack all these caps attached to the bass pot as well as the R/J .005 are used to dump certain frequency's.. In the case of the James (concentrating on 100Hz - 1K depending on the caps value)..
The cool thing about the James configuration is it doesn't effect the amount of sweep it's directed more at certain frequency so you can really shape those frequency's you want to cut and yet not effect the total sweep..If you want to lift all frequency's (or pot) you can just lift the 10k resistor..So as you can see the James is perfect for shaping the frequency response of the bass control..Dumble obviously used this to his advantage either to shape the low/ low mid freq to a customers taste or guitar or speakers etc..Or to try and keep the amps consistent..

You can run it through the Tone stack calculator and see what I mean if you like..Click James stack..It's not identical but you get the idea..

Hope this helps!!

Tony

All the best, Tom,

Max

[Structo]

You know I was wondering about that schematic, it is the only one I have for #40 and there are a lot of wrong values and best guesses.


Are you sure the bass pot was 1M?

Both the schematic and Tony's layout has that as 500K.

I was also wondering about the correctness of the layout as the caps on the bass pot do not agree with the James stack or the schematics of the amps.

[img:400:241]http://lh4.ggpht.com/_MHnI-B0pJ8k/TKS4j ... Layout.JPG[/img]

[Max]

You know I was wondering about that schematic, it is the only one I have for #40 and there are a lot of wrong values and best guesses.


Are you sure the bass pot was 1M?

Both the schematic and Tony's layout has that as 500K.

I was also wondering about the correctness of the layout as the caps on the bass pot do not agree with the James stack or the schematics of the amps.

http://picasaweb.google.com/lh/photo/Za ... directlink

Hi Tom,

Yes, I am sure about the 1MA bass pot for 2nd generation. And you are right, the James configuration at the bass pot is wrong too in the layout. And there are some more faults. But this is no big surprise IMO because you don't see many values on the gut pics clear enough. But perhaps Tony (talbany) can chime in and comment himmself on his layout.

All the best,

Max

[marcos]

Hi guys,
I love this thread, but most of this has been discussed in earlier threads,
the last time in the "Pre-Classic Tonestacks" thread in the files section.
One thing to consider: A batch of about ten amps were (SrNrs. 30s/40s)
were made for the german importer at the time, Applied Acoustics in Bochum
Germany, the guys who later on manufactured Kitty Hawk amps:These amps
were very similar, made for sale in their shop, not voiced to the player
or tweaked or anything.#40 may well be one of them.One typical feature of these amps is the export power transformer.
There are many inaccuracies in the #40 schematic, which has never been updated so far.Most of the corrections can be found in Tony´s 70s layout.
How do I know? My personal amp is from that batch, but there are slight variations from amp to amp, I´ll send some more info on this soon.

Marcos

[talbany]

#40 Layout
At the time of the layout there was very little here and elsewhere on the 70's era amps.. I spent some time investigating the stack of the now known 2nd generation as in #40 and 13 and I found no such evidence at the time and through those sources a standard stack was ever implemented// Marcos mentioned his amp (and suspected 40) used the same Centralab 500K treble pot (same era) .. As written here.. https://tubeamparchive.com/viewtopic.ph ... 13&start=0

the Treble pot was 250 KL (CTS type) while my amp had 500 KL (big Centralab pot, clearly visible on the #40 pix)

The hand drawn layout I have of #13 clearly shows a 1M treble pot..

Maybe these were customs or one offs or maybe the ODSR's were different..Don't have clue..

If we label the 40 layout as 40 then we should perhaps find the exact values of 40..(Like 124) Without an accurate schematic or the amp in front of us or more detailed pics like 124 doing a layout from those pictures alone can easily yield these mistakes in the cross referencing of other amps to determine certain unknown values..(I can hear it now.. Hey man I was just in #40 and your layout is wrong Treble pot is 500K..)..

We should do a revision of the layout to represent a more standard/popular version and call it 2nd generation ODS 50w layout perhaps thats the best way to go.

So you kinda see my confusion here.. I don't doubt Max's statement and am grateful he is here to clarify this and will no doubt update the layout/layout's the best and most accurate way possible just know others could be slightly different..

Tom
The wiring on the layout is indeed wrong obviously.. I'll address this in the updates.. Thanks for pointing it out.. You can run those cap values in the TSC just know that it really only apply's in Jazz mode ..it's is shorted in Rock mode.I know you don't care for jazz mode so thought I would mention..

Hey Marcos glad you chimed in

Tony

[Structo]

Thanks you guys.
I'm just trying to wrap my head around the various tone stacks as they are so important to the overall function and tonality of an amp.

Obviously Mr. Dumble took cues from the Baxendall tone stack but later on decided to change it. Perhaps it caused too much signal loss, not sure.

To me the Skyline stack seems pretty subtle in it's adjustments unless you go crazy and really give the knobs a twist.

At louder volumes the difference is more apparent.

One thing is for sure, the tone that Brandon is getting out of his silverface amp, whatever anybody wants to call it, is pretty cool sounding.
More raw in your face than the smooth overdrive of the later year amps.

[Max]

These amps
were very similar, made for sale in their shop, not voiced to the player
or tweaked or anything.#40 may well be one of them.One typical feature of these amps is the export power transformer.

Hi marcos,

hope you are well!

I don't think that the variable PT is some kind of proof that this is one of the amps that have been exported to Europe. I know others with this kind of PT that have not been exported but have been built for US residents who ordered them like this because they have been touring musicians.

BTW: Of course the exported amps have not been tuned to a special player. But AFAIK it is not correct that they have not been tweaked. AFAIK Alexander did never ever let an amp leave his shop without being completely satisfied with his performance. So "not voiced to the player", yes, but "not tweaked", no, at least AFAIK.

All the best,

Max

[Max]

The hand drawn layout I have of #13 clearly shows a 1M treble pot..

Maybe these were customs or one offs or maybe the ODSR's were different..Don't have clue..

Hi Tony,

This confusion arises IMO because people think about an ODR as some kind of ODS with added reverb. But this is not the case. Both 2nd generation ODR (like #13) I had my own nose in, did indeed have a 1M treble pot, but not a single 2nd generation ODS. And these ODR are very special amps with a reverb mix before the OD entrance AFAIR. And of course Alexander has chosen all the values in an ODR in a special way as these are special amps and not an ODS with added reverb. So I would not recommend to use ODR specs to build an ODS replica. And 2nd generation ODR amps sound rather different than 2nd generation ODS amps.

The tone stack of at least 90% of all the 2nd generation ODS I had my own nose in (at least 6) or that I have seen on gut pics (at least 4) - and that have not been already updated or modified! - is the one I have posted here already.

But I admit - the around ten 2nd generation amps I have seen in person or on gut pics are indeed still less than 20% of all 2nd generation ODS.
But on the other hand: #124 is probably less than 5% of all 4th generation "classic" amps that have been updated to "skyline" specs.

All the best,

Max

[Billion81]

But on the other hand I will for sure continue to post here what is my opinion about this kind of "cocktail" approach. And IMO this is complete nonsense.

Why? Because every single Dumble amp has been built by Alexander Dumble as a kind of individual "tone generator system":

Are you implying that by deviating from the given Dumble circuit (let's use #40) by adding or modding with ideas from a different era or circuit is less of a tone generator than a carbon copy build piece for piece?

I think a more accurate thought to your second statement would be that every single Dumble amp has been built by HAD for an individual as a tone generator system?

In fact aren't successive builds by HAD considered cocktails of previous builds or is only he allowed to mod his circuits?

humbly,

ted

[dr. who]

What effect do the soldered cap(s) have on the bass? Same for the 1.8k vs 10k tails.

[jelle]

What effect do the soldered cap(s) have on the bass? Same for the 1.8k vs 10k tails.

Please read the contributions by Max in this tread.

[groovtubin]

100 Watt 70's.. Boing!!

Reminds me of the late great John Candy in Uncle Buck where he's flipping the 20 lb pancake and mumbles.."Yep this is where you seperate the men from the boys"..

Tony

Tony there are a FEW more MEN here than most you guys w/goods are lead ta blv! lol!

jim@Omegaamps