Dumbleland Special 150w ser#009 Schematic

[talbany]

I have been reading this topic and was wondering if the preamp design as posted is correct. Like Erwin I can say that the video of the Dumbleland 009 sounds and works identical to the sss002 i build. I did use a much bigger 100W OT with extended low frequency range.

The difference in topology between #002 filter section and the Dumbleland schematic is that 002 has a DC coupled C.F mixer just after the Filter recovery,where the schematic does not. If you wanted it exactly like 002 then you can always use the unused 1/2 triode on V2b as a DC coupled C.F. feeding the pre amp out and Mstr Vol..Then you would basically have the same preamp section as 002. Classic stack ,feeding filters, feeding DC.C.C.F..off to the P.I

There are a lot of designs with a higher voltage on the screens than the maximum 400V in the data sheet that are working just fine. I use a pair in my own amp I build years ago on 470V (Va) and 468V (Vg2) wired like a regular pethode poweramp. It's been working for 14 years on the same tubes, nothing gets fried.

I've run higher voltages too, however, one question? do you own an amp company?
If so I would not recommend selling an amplifier to the general public that exceeds Max voltage ratings (that much) and try to stick to the advertised mfg data! if not you could open yourself up to some ugly lawsuits? Especially if someone gets injured or something catches fire. In the world of amp manufacturing we tend to lean more on the conservative side especially in regards to high Voltages I am pretty sure Dumble was aware of this .




Tony

[Richard1001]

The difference in topology between #002 filter section and the Dumbleland schematic is that (...)

Tony

sorry, I was not aware that the Dumbleland schematic is allready known.

[Max]

sorry, I was not aware that the Dumbleland schematic is allready known.

You may have a misunderstanding about this (?):

The schematic of the Dumbleland Special 150W #009 proposed by Aaron and talbany here in the first post is currently just a hypothesis that has not yet been substantiated by photographs of the actual circuitry of the Dumbleland Special 150W # 009:

… unfortunately no detailed gut shots of an actual specimen have yet to surface, so we are calling this version unverified for now …

And AFAIU this schematic of the SSS100W#002 https://ampgarage.com/forum/download/file.php?id=54132 is just a more legible copy of this handwritten schematic: https://ampgarage.com/forum/viewtopic.php?f=5&t=17827

So in contrast to, for example, this layout of ODS #0124 https://ampgarage.com/forum/download/fi ... &mode=view which is based on photographs of the actual circuitry of ODS #0124, this schematic of the SSS100W#002 https://ampgarage.com/forum/download/file.php?id=54132 is not based on photographs of the actual circuitry of SSS100W#002, but based on the not yet substantiated hypothesis, that this handwritten schematic of SSS#002 https://ampgarage.com/forum/viewtopic.php?f=5&t=17827 correctly represents the actual circuitry of SSS#002.

Best regards,

Max

[martin manning]

There are a lot of designs with a higher voltage on the screens than the maximum 400V in the datasheet that are working just fine. I use a pair in my own amp I build years ago on 470V (Va) and 468V (Vg2) wired like a regular pethode poweramp. It's been working for 14 years on the same tubes, nothing gets fried.

Which tube type, number, and primary impedance in this one?

Raa I measured close to 3450 ohm, tubes are Sylvania 6550A, screen resistors 510 ohm.

This would place the load line well below the Vg1=0 knee, which may cause problems when driven to full power. If the voltage is low enough, say around 400V, the load line will be well placed at 2k for a pair of 6550's, and deliver ~100W. When operating at higher voltages, it's better to use reduced screen voltage or UL.

[talbany]

The difference in topology between #002 filter section and the Dumbleland schematic is that (...)

Tony

sorry, I was not aware that the Dumbleland schematic is allready known.

I have been reading this topic

Go back and re-read the 1st paragraph of this discussion on page 1 of "Dumbleland Special 150W ser# 009 Schematic" on how the information was obtained and translated and lays out the case for our hypothesis...If you want to know more about the Filters/Driver U.L operation used in the schematic..Keep reading

BTW. If you have any other info to confirm or deny any circuits used in the schematic (preferably with some kind of proof)..Bring it! and I will update the schematic
Tony

[Richard1001]

sorry, I was not aware that the Dumbleland schematic is allready known.

You may have a misunderstanding about this (?):

The schematic of the Dumbleland Special 150W #009 proposed by Aaron and talbany here in the first post is currently just a hypothesis that has not yet been substantiated by photographs of the actual circuitry of the Dumbleland Special 150W # 009:

… unfortunately no detailed gut shots of an actual specimen have yet to surface, so we are calling this version unverified for now …

And AFAIU this schematic of the SSS100W#002 https://ampgarage.com/forum/download/file.php?id=54132 is just a more legible copy of this handwritten schematic: https://ampgarage.com/forum/viewtopic.php?f=5&t=17827

So in contrast to, for example, this layout of ODS #0124 https://ampgarage.com/forum/download/fi ... &mode=view which is based on photographs of the actual circuit of ODS #0124, this schematic of the SSS100W#002 https://ampgarage.com/forum/download/file.php?id=54132 is just based on the not yet substantiated hypothesis, that this handwritten schematic of SSS#002 https://ampgarage.com/forum/viewtopic.php?f=5&t=17827 correctly represents the actual circuit of SSS#002.

Best regards,

Max

The schematic of the sss002 you posted is outdated. Since then there have been updates. Erwin and Ryan did a ton of research on this and updates on the schematic accordingly. Before and after building my own SSS002 i top did a lot of research and found some additional 'errors' either misdrawn on the japanese schematic or mis interpreted by someone who had redrawn the schematic. I posted everything i did but maybe it would be nice to have an updated schematic.

The last thing i did was a lot of measuring when i finished the amp. That's when i found the first local feedback loop was doing next to nothing with a 1 Meg feedback resistor. So my conclusion was it had to be 100k like the SSS001 to have the same kind of ratio as the other loops in the amp.

I also looked at the effect of the second feedback loop, which is essentialy feeding the signal from the output of the filter switches back to the input of the filter switches. I found that this loop plays a role in the sound of the filter switches and their different settings.

Just to copy these filter switches in a different schematic without the context of what makes it sound the way they do, does not realy work well i think.

I have no doubt that you are right in saying that there are different kind of filters Dumble used in various amps. Either slight variations or something completely different , i would not know. Without gutshots there is no way knowing exactly how the Dumbleland 009 is wired.

[talbany]

Just to copy these filter switches in a different schematic without the context of what makes it sound the way they do, does not realy work well i think.

A few pages back I already posted Ryans Spice sim plots from #002" schematic.
https://ampgarage.com/forum/viewtopic.p ... 41#p411041

https://ampgarage.com/forum/viewtopic.p ... 44#p426944

Complaints around here about the filters on #002 are legendary..This is why I suggested using Martins Filters

Filter values were taken from SSS# 002 from this hand drawn schematic https://ampgarage.com/forum/viewtopic.php?f=5&t=17827, #002 also used a Triad SP-118 inductor to feed the filters. This is considered optional Read here: https://ampgarage.com/forum/viewtopic.p ... r&start=15

The filters in 002 have been known to cause complaints by several builders that has used the same values. Because of these complaints a different filter array was developed better suited for the frequency range for guitar, by member Martin Manning..Thank you MM

http://ampgarage.com/forum/viewtopic.ph ... 57#p378857

Tony

[Richard1001]

Which tube type, number, and primary impedance in this one?

Raa I measured close to 3450 ohm, tubes are Sylvania 6550A, screen resistors 510 ohm.

This would place the load line well below the Vg1=0 knee, which may cause problems when driven to full power. If the voltage is low enough, say around 400V, the load line will be well placed at 2k for a pair of 6550's, and deliver ~100W. When operating at higher voltages, it's better to use reduced screen voltage or UL.

Well i suppose it is a good thing then that Marshall and Mesa users are known to play their amplifiers at bedroom levels.

[Richard1001]

Just to copy these filter switches in a different schematic without the context of what makes it sound the way they do, does not realy work well i think.

A few pages back I already posted Ryans Spice sim plots from #002" schematic.
https://ampgarage.com/forum/viewtopic.p ... 41#p411041

https://ampgarage.com/forum/viewtopic.p ... 44#p426944

Complaints around here about the filters on #002 are legendary..This is why I suggested using Martins Filters

Filter values were taken from SSS# 002 from this hand drawn schematic https://ampgarage.com/forum/viewtopic.php?f=5&t=17827, #002 also used a Triad SP-118 inductor to feed the filters. This is considered optional Read here: https://ampgarage.com/forum/viewtopic.p ... r&start=15

The filters in 002 have been known to cause complaints by several builders that has used the same values. Because of these complaints a different filter array was developed better suited for the frequency range for guitar, by member Martin Manning..Thank you MM

http://ampgarage.com/forum/viewtopic.ph ... 57#p378857

Tony

My appologies if i misunderstood, but i thought the goal was to together come up with the most likely accurate schematic of the Dumbleland 009.

[talbany]

My appologies if i misunderstood, but i thought the goal was to together come up with the most likely accurate schematic of the Dumbleland 009.

My apologies if i misunderstood back are you referring to the filters not being "accurate"?

Tony

[rccolgan]

The preamp design of the sss002 (and 001) to me is very ingenious, and i can't imagine this design was only used for these two amps. The two feedback loops give (when used with 100k and 470k feedbaback resistors) a very nice compression effect. For use with a bass guitar this would give a very nice effect.

This is good info and I just updated my #002 drawings (now pushed to GitHub) I am rushing through my weekend chores so I can make the LNFB change from 1M to 100k! Looking back at the gut shots of SSS #002 it appears the color bands are indeed brown-black-yellow

[martin manning]

Raa I measured close to 3450 ohm, tubes are Sylvania 6550A, screen resistors 510 ohm.

This would place the load line well below the Vg1=0 knee, which may cause problems when driven to full power. If the voltage is low enough, say around 400V, the load line will be well placed at 2k for a pair of 6550's, and deliver ~100W. When operating at higher voltages, it's better to use reduced screen voltage or UL.

Well i suppose it is a good thing then that Marshall and Mesa users are known to play their amplifiers at bedroom levels. :wink:

Can you point me to some Marshall or MESA amps that are running 6550 or KT88 that way?

[Richard1001]

Yes, that is what i mean, together with the role the local feedback loops play in the sound and workings of the tonestack and filters.

A lot of people used the 1M as the first feedback resistor as shown on the Japanse schematic, but changing to 100k not only made a diffrence to the tonestack, but also to the sound of the filters. I look at these loops as being in series, and essential to the way this whole preamp sounds.

[Max]

... Looking back at the gut shots of SSS #002 it appears the color bands are indeed brown-black-yellow.

Could you please post a link to these gut shots so that this 100K hypothesis can be checked against these?

Thanks and best regards,

Max

[Richard1001]

This would place the load line well below the Vg1=0 knee, which may cause problems when driven to full power. If the voltage is low enough, say around 400V, the load line will be well placed at 2k for a pair of 6550's, and deliver ~100W. When operating at higher voltages, it's better to use reduced screen voltage or UL.

Well i suppose it is a good thing then that Marshall and Mesa users are known to play their amplifiers at bedroom levels.

Can you point me to some Marshall or MESA amps that are running 6550 or KT88 that way?

The marshall 100w 1959 jcm800 MK II is an EL34 amp that was converted for 6550's simply by changing one resistor in the bias supply. As i understand this was done because shipping the amps overseas a lot of the EL34 powertubes did not survive, so they where shipped without tubes and could take 6550's that where plenty in the USA. Don't know if the story is thrue, but the 6550 work with 450V the screens.

The Mesa Boogie bass 400 schematic shows 540V for the plates and 535V for the screens and can be used with either 6l6GC or 6550 tubes. They use 2700 ohm current limiting screen resistors.

Marshall also produced bass amplifiers in the 80's with 6550's with the screens on high voltage. There where two models i believe one with 4 power tubes an one with 8 6550's producing 375W RMS .