Dumbleland Special 150w ser#009 Schematic

[dorrisant]

Would it be a better idea to ditch the 12% taps for conventional screens with an extra filter node and a choke?

[didit]

Thanks Tony --

An interesting thread one might return to someday, though feel brief glimpses of at least a few angels ascending a pinhead.

Testing out UL/tapped-primaries to see if it's to your taste is recommended. Sunn & Magnatone both offered fine "existence proofs" of applicability to guitar/MI power amongst others. Would need to delve into specifics of Fender's designs before critiquing. I have heard of, though not actually heard, some questionable designs with sloppy interactions with the unique internal feedback of tapped-primaries. Leave whether UL is a marketing term for a specific design or an engineer's phrase with broad applicability to someone else.

Will again suggest it fits well within scope of Dumble's design aesthetics. Try it, you might like it---no magic, just physics.

Best .. Ian

[Max]

I have another question to (hopefully) better understand about the schematic proposed by Aaron and talbany:

Is its filter circuit possibly an RLC filter, or is an RLC filter part of the filter circuit suggested in this schematic?

By “RLC filter” I mean something like this: https://en.wikipedia.org/wiki/RLC_circuit#Filters

Best regards,

Max

[martin manning]

The filter stage in SSS amps is essentially two parallel RC filters, a low-pass and a high pass, with step-wise adjustable elements. There is an inductor included in some versions, but in the case of e.g. the 002, it does not affect frequencies in the audio range in any significant way.

[Max]

Thank you for your explanation.

In my question, however, I was less about how strong the respective influence of the three circuit elements R, L and C is on the overall filter effect, but about whether it is - based on its general structure (R/L/C) - an RLC filter like those explained here: https://en.wikipedia.org/wiki/RLC_circuit#Filters ?

So do I understand your explanation correctly to the effect that the filter of the DLS150W#009 (= filter of the SSS100W#002) is indeed an RLC filter in terms of its general structure, but an RLC filter in which the parameters of the circuit element L (in this case Triad SP-118) only have a very small influence on the overall filter effect?

Best regards,

Max

[martin manning]

So do I understand your explanation correctly to the effect that the filter of the DLS150W#009 (= filter of the SSS100W#002) is indeed an RLC filter in terms of its general structure, but an RLC filter in which the parameters of the circuit element L (in this case Triad SP-118) only have a very small influence on the overall filter effect?

At 300 mH the SP-118 inductor has virtually zero effect at the frequencies of interest, and so it might as well be replaced with a short piece of wire. In structure the step filter is a combination of R-C low pass and R-C high pass filters.

[Max]

Once again, thank you very much for your explanation.

Unfortunately, I am still not quite sure if I correctly understand what you mean:

Do you mean:

The filter circuit of DLS150W #009 is not an RLC filter due to its circuit structure alone, i.e. completely independent of the value for the inductance of the built-in inductor, and so it would not be an RLC filter even if L were not = 300mH, but for example = 30H?

Or do you mean:

If the inductance L were much larger than the 300mH of the Triad SP-118, for example 30H, then the filter circuit of DLS150W#009 could be called an RLC filter; but since the inductor involved in thís circuit only has such a small inductance, the filter circuit of DLS150W#009 cannot be called an RLC filter?

Thank you again and best regards,

Max

[talbany]

Would it be a better idea to ditch the 12% taps for conventional screens with an extra filter node and a choke?

It's your call?
IMO and in working with and converting my fair share of U.L Fenders (Popular in the 90's) The U.L taps do change the frequency response as well as the Dampening factor so both sound and feel with the operation. So for myself what would be my main inspiration behind building an #009 (style) amplifier?

Output Power.
An amp with that much current handling capability (@ those higher voltages)on demand power increases response time as well as touch sensitivity and wider bandwidth due mainly to the large plate 6550's the driver and sheer size of the output transformer. The amp just sounds huge even at lower volume levels
2 PI and driver
Driving the grids of the power tubes from the plates of the 12BH7 (AB2) is a different method of driving the grids than your standard LTP P.I .Little to none blocking distortion, increased sustain and plenty of punch, at any volume levels. There is also a kind of silkiness to the texture of the amp thats hard to describe, you just have to experience it
3.Filters
The filters in these amps offer a wide range of tonal options for any guitar. This along with the
R/J and deep switches gives you an over kill of options at any and all volume levels and speaker/cabinet combo's

For me these would be the main performance features and therefore the inspiration for wanting to build this kind of guitar amp.Others can determine which features best suit their needs and wants to fit their style and playing conditions or budget...4X 6L6's Standard Twin Showman Iron Non U.L (Lower voltage) standard P.S choke and a different tone stack? etc..

BTW Your pedals will take on a whole new dimension plugged into one of these amps especially an overdrive
Reverbs and delay's work just fine straight through the front end (no built in O.D)

Tony

[Richard1001]

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 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.

I don't know from which point the Dumblelend amps are featured with reverb, but it could be helpfull to have a timeline to see how the amps developed.
If the Dumbleland amps only feature reverb after the introducion of the SSS, it could be that the first SSS amps where build close to a Dumbleland. It would be possible someone bought a Dumbleland amp, liked it for guitar and asked Dumble to build a similar amp for guitar with adition of reverb which became the SSS. And when the SSS evolved (different preamp more suited for guitar, no CF driver) the Dumbleland amps became available with reverb for players who still wanted that sound.

Maybe my thoughts are not right, and I also don't know for sure when the Dumbleland amp became available with reverb so I am just guessing. But it is a fact that the SSS002 sounds realy close to the video of the Dumbleland 009. So if I had to guess the preamp design of that amp i would copy the SSS002, lose the 3 tubes for reverb, but keep the V2 with cathode follower. Maybe use a higher plate resistor for V2a to have a little more gain, making up for the lower gain 12AU7 PI.

For the poweramp the oddessey design could be close as allready stated. I read in an old posts on this forum someone say that he had only seen Dumbleland poweramps with AC coupling to the powertube grids.

For the wiring of the powertubes there are realy 3 options. UL, non UL with lowered supply for the screens, or just wired as regular penthodes. 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.

[Max]

... it could be helpfull to have a timeline to see how the amps developed....

Alexander Dumble 1985: “ …I actually started making a series of amplifiers called the Dumbleland in about '66, and I still make them. ..." https://ampgarage.com/forum/viewtopic.php?f=4&t=22012

With regard to the reasons for introducing the “Steel String Singer” model, Alexander Dumble wrote that people found the Dumbleland Special 150W to be too powerful and “too silky clean”:

“ … it was a design way ahead of its time. It was too much power and too silky clean for people. …” https://ampgarage.com/forum/viewtopic.php?f=4&t=22012

As far as I know, Alexander Dumble offered the model called "Steel String Singer" for the first time in his price list from 1978 and in this price list exclusively as a 100W combo with reverb and with either a 12 "or a 15" speaker. The price for this 100W combo with reverb in 1978 was $ 2,490.00 with a 12" speaker and $ 2,500.00 with a 15" speaker. Here's a front view of SSS100W #001 with a 12” speaker (JBL): http://web.archive.org/web/200604270130 ... /sss1f.jpg

In this price list from 1978 the model "Dumbleland Special" is only offered as a 150W head, either without reverb or with reverb. The price for the version without reverb was $ 1,482.00 and for the version with reverb it was $ 1,760.00.

BTW: These prices correspond exactly to the prices at that time for the model "OD (Overdrive) - 150W": without reverb $ 1,482.00 and with reverb $ 1,760.00. Here you can find some pictures of such an “OD-150W” without reverb:
https://ampgarage.com/forum/viewtopic.php?f=4&t=19847
http://www.amparchives.com/folder/2568/

From the mid-80s at the latest, Alexander Dumble also offered the models "Dumbleland Bass 150W" and "Dumbleland Special 300SL" (see prices here in talbany's first post).

The "Dumbleland Bass 150W" and the "Dumbleland Special 150W" models then are no longer listed in the 1990 price list.

Best regards,

Max

[Richard1001]

With regard to the reasons for introducing the “Steel String Singer” model, Alexander Dumble wrote that people found the Dumbleland Special 150W to be too powerful and “too silky clean”:

“ … it was a design way ahead of its time. It was too much power and too silky clean for people. …” https://ampgarage.com/forum/viewtopic.php?f=4&t=22012

Interesting. The first SSS amps have a PI/DC coupled 12ax7 driver and lower power 100W 6l6 output, with more harmonic content and compression. This could mean the main difference between the two is the power amplifier and the Dumbleland could be build with the less compressing 12au7 / 12bh7 driver, indirect coupling to the power tubes and UL powertube wiring, making it too silky clean for people. Which could mean too little harmonic content and compression.
I am just guessing ofcourse...

[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?

[martin manning]

Do you mean:

[1] The filter circuit of DLS150W #009 is not an RLC filter due to its circuit structure alone, i.e. completely independent of the value for the inductance of the built-in inductor, and so it would not be an RLC filter even if L were not = 300mH, but for example = 30H?

Or do you mean:

[2] If the inductance L were much larger than the 300mH of the Triad SP-118, for example 30H, then the filter circuit of DLS150W#009 could be called an RLC filter; but since the inductor involved in thís circuit only has such a small inductance, the filter circuit of DLS150W#009 cannot be called an RLC filter?

I think the circuit is fundamentally two parallel RC filters, so my meaning is closest to [1] above, and I have no idea why the inductor is there. However, the response is not completely independent of the inductor value, and if you increase its value by 10x or so there will be some effect on the high frequencies in the audible range. That is a moot point in my opinion, since the filter as-built does not include such a large value inductor.

[Richard1001]

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.

[Max]

I think the circuit is fundamentally two parallel RC filters, so my meaning is closest to [1] above, and I have no idea why the inductor is there. However, the response is not completely independent of the inductor value, and if you increase its value by 10x or so there will be some effect on the high frequencies in the audible range.

Thanks for the clarifiation and best regards,

Max