#121 Todd Sharp's Dumble?

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fenderbender4
Posts: 37
Joined: Thu May 23, 2013 8:51 pm

#121 Todd Sharp's Dumble?

Post by fenderbender4 »

Anybody have info on this one? Played it? Been searching but haven't seen anything specific. I know it was/is for sale at Maverick music. Seems like a relatively unique dumble given the 150 watt rating, reverb, trem, AND the two concentric knobs on the overdrive circuit.

Whew, seems like a lot crammed in there.
marcos
Posts: 180
Joined: Tue Apr 07, 2009 12:04 pm
Location: Germany

Re: #121 Todd Sharp's Dumble?

Post by marcos »

#121 is basically a ODS preamp coupled with a SSS-style power section,
and some unique features, such as the 4 knob OD section , additional
pots for OD entrance trim and h.f. taper(tone control), and a 12 DW 7
tube in the OD circuit. Very versatile amp. There is a section in the Dumble
Book about this amp, including an interview with former owner Todd Sharpe, who had two these built by HAD, IIRC the other one was #120,
which got stolen. Hope this helps

Marcos
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M Fowler
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Location: Walcott ND

Re: #121 Todd Sharp's Dumble?

Post by M Fowler »

Here are the photos.
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fenderbender4
Posts: 37
Joined: Thu May 23, 2013 8:51 pm

Re: #121 Todd Sharp's Dumble?

Post by fenderbender4 »

marcos wrote:#121 is basically a ODS preamp coupled with a SSS-style power section,
and some unique features, such as the 4 knob OD section , additional
pots for OD entrance trim and h.f. taper(tone control), and a 12 DW 7
tube in the OD circuit. Very versatile amp. There is a section in the Dumble
Book about this amp, including an interview with former owner Todd Sharpe, who had two these built by HAD, IIRC the other one was #120,
which got stolen. Hope this helps

Marcos
Cool, thanks for the info. Has anyone seen the insides/guess what the values functions are of the additional concentric knobs?
Aaron
Posts: 641
Joined: Wed Feb 08, 2006 1:07 pm

Re: #121 Todd Sharp's Dumble?

Post by Aaron »

mojotom
Posts: 237
Joined: Wed Feb 01, 2006 12:47 am

Re: #121 Todd Sharp's Dumble?

Post by mojotom »

marcos wrote: Wed Mar 26, 2014 7:46 am #121 is basically a ODS preamp coupled with a SSS-style power section,
and some unique features, such as the 4 knob OD section , additional
pots for OD entrance trim and h.f. taper(tone control), and a 12 DW 7
tube in the OD circuit. Very versatile amp. There is a section in the Dumble
Book about this amp, including an interview with former owner Todd Sharpe, who had two these built by HAD, IIRC the other one was #120,
which got stolen. Hope this helps

Marcos
This is an old thread but I always been interested in that amp along with the silver alligator pentode amp.

I was thinking about the OD and what kind of controls those two concentric pots it could be (considering HF taper and OD trim are already on the back) but having a look at the pictures yesterday I noticed the two controls on the back are not actual potentiometers but seem to be just plugs to cover chassis holes while both HF taper and OD trim have been wired on the front.
OD trim/drive/level/HF taper.

Does it make sense to anyone else ?

ODS or SSS front end clean and ODS OD
Post 3 tube reverb
SSS or Dland or Odyssey PI (Dynamic and bias pots looked like an SVT type power amp)
Max
Posts: 1550
Joined: Wed May 31, 2006 6:08 pm

Re: #121 Todd Sharp's Dumble?

Post by Max »

"... Description

Dumble Overdrive Special 150 Watt which Mr. Dumble built for Todd Sharp in the second half of the eighties. Mr. Dumble made only very very few of these amplifiers. Indeed only this single specimen seems to be still in existence. The sisteramp #120, also made for Todd Sharp, has been stolen long ago and never reappeared up to now.

The overdrive section of the preamp is very sophisticated. The overdrive tube is a 7247 and not a 7025 as usual. This amplifier has four (staggered) pots to control the Overdrive: trigger (silver ring in the "level" location), taper (Marshall-like knob in the "level" location), level (silver ring in the "ratio" location), and ratio (Marshall-like knob in the "ratio" location).

Trigger adjusts how much of the scale of signal is fed into one triode of the overdrive tube. Level adjusts how much of the signal is fed into the other triode of the overdrive tube. Taper adjusts the scale of high frequencies in the overdrive section. Ratio adjusts how much of the overdrive circuit's signals is fed back into the preamp circuit.

Especially because the Overdrive tube is a 7247 (two different triodes with different characteristics in one tube) these four pots provide an extremely useful control of the harmonic content in order to fine-tune the overdrive circuit's voicing.

So you can adjust the overdrive section for a vast spectrum of tonal colors that by far exceeds the possibilities of a normal Overdrive Special. It's really amazing.

The reverb section is similar to the reverb section of a Steel String Singer. The send and return controls make possible the perfect blending of the reverb signal and the dry signal in a way that adds a warm singing tone to a huge clean or overdriven guitar tone.

The tremolo has a wide range of operation from very slow (the Ry Cooder tremolo) to very fast . It is extremely useful to achieve beautiful textures for all sorts of Blues and ballads together with the sophisticated reverb.

The power amp is similar to a 150 W Dumbleland (same transformers), but the phase inverter and driver tubes both are 7025s as in a Steel String Singer. The output power can be switched from 150 Watts to 75 Watts. The output impedance is switchable to 4, 8 and 16 Ohms. The original footswitch provides the possibility to switch on and off the overdrive, the preamp boost, the reverb, and the tremolo. Because this amplifier is heavy due to its giant transformers and the huge amount of electronic parts inside, the bias and the dynamic balance can be measured and adjusted the way an Ampeg SVT or V9 can be adjusted.

As you see this amplifier blends the qualities of a very sophisticated version of the Dumble overdrive circuit with the harmonically extremely rich, huge and mighty clean sounds of the Dumblelands and Steel String Singers. So maybe this is the ultimate and for sure the most versatile Dumble amp. You can't imagine a tonal color that cannot be achieved with this wonderful musical instrument. There is a signal path diagram of this amplifier on page 730 of the 4th edition of "The Tube Amp Book" by Aspen Pittman.

Preamp tubes specified by Mr. Dumble are 6 x 7025, 1 x 7247, 1 x 5751
Poweramp tubes specified by Mr. Dumble are 4 x 6550 or 4 x KT88 ..."

Source: http://thesubjectmatter.com/dumblearchi ... efault.htm

AFAIR Alexander Dumble once commented: If you turn off the OD, it's a SSS.

Cheers,

Max
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