Technik / Equipment / Instrumente

Hallo Bluesgitarreros,

schaut mal, was es bei Ebay gab.

Aktuelles Gebot: US $75.300,00
(ca. EUR 50.792,58) Mindestpreis nicht erreicht.

General Information

During the last months some reputable tradespeople in the United States have been asked for appraisals for this amp, because the insurance company had asked for an update. As there seems to be only this single specimen of a 150 W Dumble Overdrive Special still in existence, some of these salespeople said some collectors might be willing to pay up to 150,000 US$ for this unique combination of Steel-String-Singer-like and Dumbleland-like clean sounds with an additional, especially sophisticated overdrive channel, reverb and tremolo. (When this amp was sent to Germany it’s price was nearly thrice the price that was prevailing at this time for a normal Overdrive Special 100 Watt.)

For such a high value instrument the insurance company now asks 5 % of its value each year to insure the taking of this amplifier to gigs or on tour. And to pay around 600 $ a month to use this amp on live gigs or tours doesn’t seem to make sense anymore, and to leave the amp alone without using it doesn’t seem to make sense either. (Perhaps Carlos or John or Larry or Robben or anyone else can get a better deal with their insurance companies) So it is for sale now.

Please don’t hesitate to bid any price you think is appropriate and above the starting price. Let’s get in contact and see which price is realistic. There is no hurry and the amp is going to be offered again if no offer meets the reserve price.

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

Condition

The amplifier is in excellent condition according to the standards of the "Vintage Guitar Magazine Price Guide". Electronics are 100 % original, and the preamp isn't covered with silicone. So service would be easy, if ever necessary.

The amplifier was used on at least a weekly base, so all capacitors are still working fine and you can hardly see any AC-ripple on a scope.

Gruß und schönen Sonntag
Heinz