Dumbleland Special 150w ser#009 Schematic

[Richard1001]

Since the Ebb2 is fed into the power amp in the 012 diagram, that says it is conventional pentode operation. At 500V Va, Raa has to be around 2k to avoid over dissipation on the plates, which puts the load line well below the Vg1=0 knee. It could be that large screen resistors are used to keep the screen current under control as in the examples cited above. I don't think these amps would be designed to operate in a way that would make them unreliable at high power. Indeed the choke in the 012 power supply schematic would need to have a high current rating, something like 2A. There is what looks like a choke between the PT and OT in the photos. It doesn't look to be very large physically.

How did you come to the conclusion for a rating of 2A for the choke Martin?

[Max]

Some more pictures of ODS 150W #0121: https://www.vintageguitar.com/31567/dum ... -od150-wr/

Best regards,

Max

[martin manning]

How did you come to the conclusion for a rating of 2A for the choke Martin?

6550 data sheet, but i should have said 1A since the data sheet gives values for two tubes. At 450V max signal current for plate plus screen for four tubes would be 666.

[talbany]

... Are you saying that Brandon was reffering to one of those as 121? ...

AFAIR Brandon‘s referring to:

"the other it was around 495" = SSS150W Eric Johnson (many pictures online)

"525 on the plates" = SSS150W Colin James/Kirk Hammett = copy of SSS150W SRV (special order by Colin James)

Colin James/Kirk Hammett:


SSS 150W Colin James.png
Thanks for the clarification!



SRV:


SSS 150W SRV.png


The two transformers in this SRV SSS look quite similar to the transformers in ODS # 0121 (in my personal impression).

Best regards,

Max

Max
So a question still remains IMO is?...... When did he discontinue with U.L operation after the Winterland or after the D-land and when he went with the SSS? (in 80's) he changed the driver/Pi and ran them at lower voltages (accept for Pentode) We also know that most SSS's did not have OPT equipped with taps and had the D.C.C driver and was designed for lead guitar so it's safe to assume he was going for a different sound and feel with his comment about D-Land being too silky clean (given the added dampening factor provided by the taps) I am certainly more inclined to believe he would go Non U.L at 500Vdc than 550 or higher.
Although 121/122 were a one of it's kind had the D-land transformers it had the SSS PI/Driver setup making the output section more SSS like than a Dumbleland than the advertisement suggests..This would make sense since Todd S was also lead guitar player.

If this is true then this quote by Dumble make sense?
..

I actually started making a series of amplifiers called the Dumbleland in about '66, and I still make them. That was the forerunner of the Steel-String Singer. I didn't change a whole lot about that; it was a design way ahead of its time. It was too much power and too silky clean for people. It's perfect for Stevie Ray, though. ... " https://ampgarage.com/forum/viewtopic.php?f=4&t=22012

.
Stevies output section is more D-land than SSS and has the same transformers as 009 Dumbleland has and IMO why Dumble refers to it as a Dumbleland
BTW.Ditching the taps is a big deal and will IMO noticeably alter the sound and something you would normally do when changing models..Custom amps (like SRV) all bets are off!
Does this make sense?
Tony

[martin manning]

I am certainly more inclined to believe he would go Non U.L at 500Vdc than 550 or higher.
Although 121/122 were a one of it's kind had the D-land transformers it had the SSS PI/Driver setup making the output section more SSS like than a Dumbleland than the advertisement suggests...

For sure running higher plate voltage increases the need to either use UL or drop significant screen voltage somehow. Normal pentode operation is just fine at 400V plate and screen, with 1k Raa, but at 450V you need to increase the load to limit dissipation, and then you need to start reducing screen voltage one way or another to stay out of trouble there. At around 450V is where you get 150W (see 6550 data sheet, where the suggested screen voltage for 450V plates is 310V with 3k5 Raa). Going to UL or increasing the screen resistors are different ways of applying negative feedback at the screens, and I believe there will be some difference in the sound and feel between these options, since the variation in screen voltage vs. signal level will be different.

[talbany]

I am certainly more inclined to believe he would go Non U.L at 500Vdc than 550 or higher.
Although 121/122 were a one of it's kind had the D-land transformers it had the SSS PI/Driver setup making the output section more SSS like than a Dumbleland than the advertisement suggests...

For sure running higher plate voltage increases the need to either use UL or drop significant screen voltage somehow. Normal pentode operation is just fine at 400V plate and screen, with 1k Raa, but at 450V you need to increase the load, and then you need to start reducing screen voltage one way or another to stay out of trouble. Around 450V is where you get 150W (see 6550 data sheet, where the suggested screen voltage for 450V plates is 310V). Going to UL or increasing the screen resistors are different ways of applying negative feedback at the screens, and I believe there will be some difference in the sound and feel between these options, since the variation in screen voltage vs. signal level will be different.

Thanks Martin!
So your'e looking at 450V Max being the spot. I agree with the higher screen resistors offering some regulation (But increases Sag) Here Dumble kept the screens low with 47R with the taps connected on the Winterland.

Winterland.jpg

Tony

[Richard1001]

I am certainly more inclined to believe he would go Non U.L at 500Vdc than 550 or higher.
Although 121/122 were a one of it's kind had the D-land transformers it had the SSS PI/Driver setup making the output section more SSS like than a Dumbleland than the advertisement suggests...

For sure running higher plate voltage increases the need to either use UL or drop significant screen voltage somehow. Normal pentode operation is just fine at 400V plate and screen, with 1k Raa, but at 450V you need to increase the load to limit dissipation, and then you need to start reducing screen voltage one way or another to stay out of trouble there. At around 450V is where you get 150W (see 6550 data sheet, where the suggested screen voltage for 450V plates is 310V with 3k5 Raa). Going to UL or increasing the screen resistors are different ways of applying negative feedback at the screens, and I believe there will be some difference in the sound and feel between these options, since the variation in screen voltage vs. signal level will be different.

If the datasheet is leading and you want to stay below the maximum screen voltages given in the dstasheet, the GE 6550A datasheet shows 440V max on the screens wired as penthode, and 450V max on the screens with UL wiring. So to me the difference is not that much
Since the Dumbleland 009 amp supposetly delivers 137W of continuous output power, I would think there has to be some sag. If there wasn't i would expect the output power to be higher with a 500 or 550V anode supply voltage.

[Max]

... When did he discontinue with U.L operation after the Winterland or after the D-land ...

With all of Alexander Dumble's amplifiers that don't fall under the categories ODS 50W or ODS 100W, there is IMO almost no systematic and consistent and therefore predictable relationship between the respective model designation and/or the respective external appearance on the one hand and the respective circuit details on the other.

Perhaps one of the most glaring examples of these inconsistencies between model designations on the one hand and circuit details on the other may be the "DL-" model designation on the back of this Dumble amp: https://www.gbase.com/powered/overland- ... -crocodile

So, for example, from the fact that Winterland #003 has a UL circuit, in my opinion it cannot necessarily be concluded that "Winterland" #XYZ also has one.

And, for example, with regard to the “Dumbleland” Overdrive Special 150W #006 and the Dumbleland Special 150W #009 in my opinion it cannot necessarily be concluded that they have a similar OT wiring, just because their OTs look similar.

And, for example, with regard to Dumbleland Special 150W #009 and some other Dumbleland Special 150W #XYZ in my opinion it couldn’t necessarily be concluded without comparing pictures of their circuitries that they have e.g. the same local FB and filter circuits just because both are named “Dumbleland Special”.

And if, for example, it should turn out - be it in two weeks or two years based on pictures that may have become known by then - that DLS#009 has an UL circuit, in my opinion the conclusion could not be drawn from this that some other DLS#XYZ also has an UL circuit - vice versa.

And just because the transformers and maybe(?) even the PI/Driver tubes of an SRV SSS150W may look similar to the transformers and PI/Driver tubes of DLS150W #009, IMO one cannot conclude that their output stages have the same circuitry without comparing pictures of their circuitries.

And, for example, if Brandon writes that he has not yet seen an SSS with an UL circuit, then in my opinion it cannot be concluded that there is no UL circuit in some SSS that he has not yet seen.

etc.

So with regard to the circuit of DLS#009 IMO, from a practical point of view, the most sensible thing may be a personal assumption which one personally considers the most likely based on the facts known so far and based on the knowledge in the field of electronic engineering. And this personal assumption could then perhaps be subjected to practical testing in the personal practice as a builder and as a musician. And IMO this forum would be an ideal place to then discuss the results of practical testing with one another.

...and when he went with the SSS? ...

The "Steel String Singer" model was introduced around 1978 (1978 price schedule: SSS 100W combo). AFAIR SRV got his first SSS 150W in 1983. The Steel String Singer 150W is still listed in the 1986 and 1990 price schedules. AFAIR about 10 to 15 years ago was the last time I heard about Alexander Dumble offering a customer to make an SSS 150W. But of course, that doesn't necessarily mean that he no longer offers an SSS 150W today.

Best regards,

Max

[talbany]

I appreciate everyones input into the discussion and putting forth their arguments. Fun Huh?

So setting the engineering aspect aside for a moment and think about the business/ Manufacturing logistics side, perhaps see if this leads to any clues here?(Having run a dinky amp company for 5 years ) here is what I am considering

When would Dumble make the change from U.L with Winterland and Non U.L with SSS?
1. U.L amps started to generate a bad reputation amongst guitarists somewhere early/mid 80's for being too clean too sterile (I believe was the word De jure) for the times I was there Thanks Fender
2. How would one go by ditching an amp you make that has a feature that has a bad reputation?
3. Offer up a brand new model and separate yourself from that design feature ASAP!
4. In comes the SSS (mid 80's) no longer U.L has a new Driver/ reverb or Tremolo (whatever players want)..Anything to further separate the 2 amp designs
Problem?....He still has transformers left over for the Dumbleland model?
1. For the 100W versions use the Twin since it's already spec'd out for these features gives me typical Twin voltages and already have them for my ODS Models and drop the taps.
2.For the 150W versions if I load the old ones from the Dumbleland down with the added accessories OD or Reverb or Tremolo new driver use big screen (or dropping) resistors to regulate the screens (which was unlabeled on the block diagram ) enough to get away with ditching the U.L and still use the transformers I have .. Dumble built only several of these.
Here comes SRV??
1. We know Stevie used Jackson's Dumbleland on the recordings of Texas Flood and more than likely told him to make him one just like it but for advertisement purposes Dumble would much rather have Stevie sport the newer SSS logo to help promote the new amp.
2. Still having the D-Land transformers, he designed his more similar to a Dumbland with the old output section BH7/12AU7 and possibly still wired in the taps (For that silky clean/sterile quality ) Perfect for Stevie.We know his has taps on the Sunn OPT?

Both Winterland and Dumbleland ran about the same voltages 550V, that along with his added comment about Dumbleland being too clean/silky I still believe he used the taps in #009 and ditched them for the SSS,
Oh BTW.Max I disagree with your hypothesis that Dumble would use the taps occasionally and or indiscriminately. If there is one thing i've learned about Dumble is he is very methodical and fairly consistent in his approach to amp building and how his amps generate it's sound!! (ditching the taps is IMO a drastic change) as well as wanted to separate himself from the U.L designs for reason he has already publicly stated.

It was too much power and too silky clean for people. It's perfect for Stevie Ray, though. ..

AFAIK Brandon has only seen the insides of 2 SSS's (in 08) No D-Lands I do however agree that we should let the musician decide!

At the end of the day, Dumble ran a small 1 man operation with probably not a lot of capitol and would still have to deal with certain logistical and financial hurdles when adding new models to the line for whatever reasons/problems that may arise during the shift in sentiment (or change in sound) within the musical community. I am sure other amp companies that went U.L had to deal with the same issues as Dumble in the early 80's...For me this makes some sense..Any claims to refute my argument??...Bring it

Again thanks to all who participated keep em coming!

[talbany]

Hello Richard
Just wondering? Do you happen to know what that transformer is doing feeding Ebb1(plates) on the block diagram?

121.jpeg

Thanks?
Tony

[Richard1001]

Hello Richard
Just wondering? Do you happen to know what that transformer is doing feeding Ebb1(plates) on the block diagram?
121.jpeg
Thanks?
Tony

I don't know exactly which transformer you mean. The output transformer and power transformer are quite obvious in their function so i can't Imagine you would have questions about that, and the coil after the standby switch is a choke, but that's obvious too.

Can you explain what you would like to know?

[Richard1001]

I appreciate everyones input into the discussion and putting forth their arguments. Fun Huh?

So setting the engineering aspect aside for a moment and think about the business/ Manufacturing logistics side, perhaps see if this leads to any clues here?(Having run a dinky amp company for 5 years ) here is what I am considering

When would Dumble make the change from U.L with Winterland and Non U.L with SSS?
1. U.L amps started to generate a bad reputation amongst guitarists somewhere early/mid 80's for being too clean too sterile (I believe was the word De jure) for the times I was there Thanks Fender
2. How would one go by ditching an amp you make that has a feature that has a bad reputation?
3. Offer up a brand new model and separate yourself from that design feature ASAP!
4. In comes the SSS (mid 80's) no longer U.L has a new Driver/ reverb or Tremolo (whatever players want)..Anything to further separate the 2 amp designs
Problem?....He still has transformers left over for the Dumbleland model?
1. For the 100W versions use the Twin since it's already spec'd out for these features gives me typical Twin voltages and already have them for my ODS Models and drop the taps.
2.For the 150W versions if I load the old ones from the Dumbleland down with the added accessories OD or Reverb or Tremolo new driver use big screen (or dropping) resistors to regulate the screens (which was unlabeled on the block diagram ) enough to get away with ditching the U.L and still use the transformers I have .. Dumble built only several of these.
Here comes SRV??
1. We know Stevie used Jackson's Dumbleland on the recordings of Texas Flood and more than likely told him to make him one just like it but for advertisement purposes Dumble would much rather have Stevie sport the newer SSS logo to help promote the new amp.
2. Still having the D-Land transformers, he designed his more similar to a Dumbland with the old output section BH7/12AU7 and possibly still wired in the taps (For that silky clean/sterile quality ) Perfect for Stevie.We know his has taps on the Sunn OPT?

Both Winterland and Dumbleland ran about the same voltages 550V, that along with his added comment about Dumbleland being too clean/silky I still believe he used the taps in #009 and ditched them for the SSS,
Oh BTW.Max I disagree with your hypothesis that Dumble would use the taps occasionally and or indiscriminately. If there is one thing i've learned about Dumble is he is very methodical and fairly consistent in his approach to amp building and how his amps generate it's sound!! (ditching the taps is IMO a drastic change) as well as wanted to separate himself from the U.L designs for reason he has already publicly stated.

It was too much power and too silky clean for people. It's perfect for Stevie Ray, though. ..

AFAIK Brandon has only seen the insides of 2 SSS's (in 08) No D-Lands I do however agree that we should let the musician decide!

At the end of the day, Dumble ran a small 1 man operation with probably not a lot of capitol and would still have to deal with certain logistical and financial hurdles when adding new models to the line for whatever reasons/problems that may arise during the shift in sentiment (or change in sound) within the musical community. I am sure other amp companies that went U.L had to deal with the same issues as Dumble in the early 80's...For me this makes some sense..Any claims to refute my argument??...Bring it

Again thanks to all who participated keep em coming!

You are right, it is fun!

Without a doubt i don't know as much about Mr. Dumble as you probably do but from what i read about him, he does not exactly strike me as someone who would choose convenience and money over his standard for quality. And as i understand it he harvested transformers from other amplifiers he bought. Also not a very economical way to obtain parts. So if there is some truth in the assumption that he decided to go non UL as a result of the bad reputation this type of poweramp got with guitarplayers, the reason for him to keep using the same output transformers would be for the sound he was looking for, and not economical. But that's my opinion. As i mentioned before, having a bigger iron core with a larger bandwith and less saturation realy makes a big difference in sound and dynamic.

As for using an UL transformer without the taps, it is realy no big deal at all. And i also know that 6550 tubes can take more abuse than the datasheet would have you believe. It is a bit like the 12ax7 CF driver working on more than 470V. Sure, according to the datasheet this is way past the maximum voltage rating. But meanwhile McIntosh amps are playing for decades without a problem.

[martin manning]

What doesn't quite make sense to me is 550V plates. To get down to the advertised output power of 150W would require 100V of sag, and then the screens would really like to drop another 100V, down to 350 or so.

[Max]

... The output transformer and power transformer are quite obvious in their function ...

In this block diagram, published by Aspen Pittman in the 4th edition of his book "The Tube Amp Book" on page 730 - and which, by the way, has been known in this forum for years now - the output transformer and its three primary connections (BLU/RED/GRN) are quite obvious indeed. So I also have some difficulties to understand talbany's question about the function of connecting the primary center tap (RED) to +Ebb1. Is this connection somehow unusual?

Best regards,

Max

[Roe]

Wiring up a UL/pentode switch shouldn't be that difficult or? Finding proper transformers seems more difficult (the a451s are few and far between for example)