ODSR Clip

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Lousyatit
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ODSR Clip

Post by Lousyatit »

Found this today, for your approval a'78 ODSR running hard, enjoy.

https://www.youtube.com/watch?v=iIZB-x4_M3w
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Blackburn
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Re: ODSR Clip

Post by Blackburn »

Damn... :shock:
Charlie Wilson
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Re: ODSR Clip

Post by Charlie Wilson »

Wow, great rock crunch. AC/DC needs a wall of those.
:twisted: Any guesses at the circuit.
CW
groovtubin
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pics of 78 ODSR

Post by groovtubin »

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jelle
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Re: ODSR Clip

Post by jelle »

2nd gen voicing.
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dreric
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Re: ODSR Clip

Post by dreric »

Looks like #13 circuit. Interesting that he was going into the FET and the OD was dimed.
Eric
1949 Zenith, Zenith Toggle Recoil, Zenith 55 & 440
Lousyatit
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Re: ODSR Clip

Post by Lousyatit »

Interesting.

Antique Amplification has recently completed the full restoration of an impossibly scarce 1978 Dumble Overdrive Reverb Special (100 watt). The owner has requested that we assist in offering this fine specimen of Alexander “Howard” Dumble’s early work for sale. The ODRS is considered by many of the Dumble amplifier aficionados to be the “Holy Grail” of all Dumble amplifiers. The exact production of this model is unknown but has been estimated to be less than fifteen total units. The highest previously known serial number for an ODRS is #0078. This amp has a serial number in the #008X’s making it very likely the last of its kind produced by Mr. Dumble. The current owner is the original owner, a 67 year professional guitarist hailing from Ontario, Canada, by the name of Bobby Watson.

The Origins of this Amp
By the time the 1970’s had rolled around, Bobby Watson was already a seasoned professional musician. He was initially drawn to the Dumble sound while listening to Lowell George on a Little Feat recording. This prompted Bobby to research Lowell’s gear more closely and this is when he first became aware of the Dumble brand of amplification. In 1977, Bobby attended an Amos Garrett show at the El Macambo in Toronto. He thought that the sound of the amplifier Amos was using was familiar and but could not make out what exactly it was as the logo was too small to view from a distance and the cabinet style unfamiliar. As luck would have it, Bobby knew Bohdan Hluzco who was Amos Garrett’s drummer at that time. Bohdan introduced Bobby to Amos during a set break and they both discussed his amplifier which turned out to be a Dumble.

At this point in time Bobby made up his mind that he had to have a Dumble of his own. He contacted Howard Dumble, explaining how he was initially drawn to the Dumble sound by Lowell George and then shared with him his discussion with Amos Garrett. During the conversation, Dumble explained that the amp model that these musicians were using was called the “Overdrive Reverb Special”. Howard and Bobby also discussed enclosures, however, given the expense of the amplifier along with the reality that Bobby had plenty of decent enclosures to use, and he elected to purchase a head unit only. One part of the discussion that Bobby recalls clearly was mentioning that the logo on the amp was too small to read easily and that he suggested to Howard that he enlarge the graphic to solve this problem. Interestingly, when the amp did arrive, even though it is very obviously an Overdrive Reverb model, the graphic Howard used was the from the much larger “Overdrive Special” logo. No other known to exist ODRS has this unique feature.

Bobby placed the order for his own ODRS at the agreed upon price of $1,700 USD which was a very large sum of money for an amplifier in those days. This was the summer of 1977 and he would have to wait a year before it was completed. Considering the lead times that other Dumble customers contended with over the years, Bobby was actually quite fortunate to have to wait only one year.

In the late summer of 1978, the amplifier was completed and Bobby sent the final payment to Dumble. To avoid importation issues (duty), Bobby had Dumble ship the amplifier. The new Dumble amp was immediately pressed into service for a very busy, hardworking professional musician. Little did Bobby know at this time that his amplifier was one of the rarest models Dumble would ever produce and that judging from its serial number, his amplifier very likely was the last Overdrive Reverb Special Dumble ever produced.

The amplifier came appointed with what was standard for the model, black tolex vinyl covered cabinet with a walnut crossbar with the aluminum trim appropriate for the model/vintage. The front panel is covered in a medium brown suede and the black graphics silk screened directly onto the chassis with a protective clear coat was applied over the face and back panels of the chassis. The knobs and unique red colored slider switches are consistent with a 1970’s vintage, silver-face Dumble product. Being a 100 watt (advertised) amplifier, it uses 4 x 6L6GC tubes in the power section.

The amplifier also came with a chrome plated, stamped steel Fender style footswitch for turning on and off the reverb and overdrive features. A unique and cool feature of the switch is a hand cobbled aluminum placard showing the name “Rob Watson” that was hand fabricated and engraved by Howard Dumble himself. Since this is a late 70’s vintage amplifier, it was produced long before Dumble made prospective buyers sign legal contracts to protect his intellectual property and keep would be copycats from duplicating his designs. Additionally, there is no silicone “gooping” covering the pre-amp section as became a common practice by the time Dumble had transitioned into 1980’s produced amps.


Bobby used the amplifier religiously until 1987 when it failed. Bobby does not recall what exactly failed but he did take it to a local amplifier repair shop at this time since it was impractical for him, living in Toronto, to have Dumble repair the amplifier. At this time, both the power and output transformers (originally Woodward/Schumacher Fender parts) were replaced with 1960’s vintage Hammond iron and a new bias supply transformer added. Bobby had some problems getting the repair shop to complete the work and when it eventually was returned, it would power up but had a wicked oscillation and was unusable.

At this point, Bobby became frustrated with the entire situation and he ended up putting the amp into storage in his home for more than two decades. Meanwhile, he continued his career, eventually moving to Memphis, Tennessee for a number of years while actively employing his craft as a guitarist/singer/songwriter. During the next 25 years, the Dumble sat broken in Bobby’s Peterborough home until a close friend convinced him to allow a qualified repair shop bring it back to life.

This is where Antique Amplification enters the story. We agreed to repair the amplifier for Bobby back in January of 2014. What arrived was a neglected but mostly complete and original Dumble Overdrive Reverb Special. Unlike many other Dumble amplifiers, it had never been sent back to Dumble for upgrades or modifications. We set about diagnosing the various issues the amplifier had including the improperly installed, incorrect transformers. We quickly brought it to life after determining and correcting the polarity hook-up problem with the output transformer caused by the previous repair shop.

It took some time to source correctly date coded original Woodward/Schumacher power and output transformers, identical to what the amplifier would have left Dumble’s workbench with in 1978. In fact, we managed to locate a “New Old Stock” or NOS Power transformer! A few other components were a challenge to source as well. We elected to replace the electrolytic capacitors for obvious reasons. A considerable amount of time and effort went into the disassembly, assembly and the very involved cleaning process required given the conditions the amplifier was subjected to while stored for those 25 years. The amp is, circuit-wise, identical to the way Mr. Dumble conceived the amp in 1978. No modifications were made to deviate from the original circuit design.

Today, we are proud to point out that Bobby’s amp has been restored to its former glory. The sine wave is pristine, every control works as designed and the amp now pumps out a very healthy 90 watts RMS (Into 4 ohms). We have included many high resolution images detailing this seldom seen rarity of Howard Dumble’s highly regarded and highly sought after amplifier production.

We have also included a variety of audio/video examples for your perusal.

*Note*
Antique Amplification will not provide schematics, circuit layout, circuit details, component values or any images describing or depicting the internal features of this amplifier.
hitchcaster
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Re: ODSR Clip

Post by hitchcaster »

intersting 87' botched repair job...... :shock:
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dreric
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Re: ODSR Clip

Post by dreric »

How close to #13?
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Eric
1949 Zenith, Zenith Toggle Recoil, Zenith 55 & 440
Charlie Wilson
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Re: ODSR Clip

Post by Charlie Wilson »

Hello, I may be new to learning about Dumble amplifiers but I have repaired a lot of amplifiers and I have a hard time believing that the output AND power transformer went bad in the amplifier. Then to install new ones and not know to reverse the primary leads on the power tube plates to solve the oscillation issue. That is a drag the original owner had to deal with that. I curious though, the description says that they installed a new "bias supply" transformer. Do they mean relay supply and why did they replace it?
CW
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Blackburn
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Re: ODSR Clip

Post by Blackburn »

Wow, that's a great story (Despite the butchery) and so glad to hear that the amp was returned to it's former glory, or close enough. The work looks very well done. I'm curious why the amp wasn't simply returned to HAD, though. :?
Last edited by Blackburn on Tue Aug 19, 2014 4:29 pm, edited 2 times in total.
vibratoking
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Re: ODSR Clip

Post by vibratoking »

The amp is, circuit-wise, identical to the way Mr. Dumble conceived the amp in 1978. No modifications were made to deviate from the original circuit design.
Kind of a silly statement considering the amp has been worked on at least once by guys that didn't know what they were doing. There is no way to make that statement and be sure that it is true IMO.

That thing has lost big value due to being seriously hacked at least one time. These guys are really trying to do a hard sales job to created a buzz about a hacked unit. Be interesting to see just how much someone will pay for that.
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jelle
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Re: ODSR Clip

Post by jelle »

Allright,

It is my understanding that the Hammond transformer used did not have a bias tab, so instead of using the HV winding of the PT to generate bias voltage, a separate transformer was added.

Also, the person who fixed this one up went through great lenghts to ensure that everything was period correct, and left no stone unturned, and in the process many experts were consulted.

This is a great project excecuted by one very thorough individual. And in my opinion, that is one lucky amp. 8)

As such I fully disagree with the opinion that it is currently in a butchered condition.

This is without doubt one of the cleanest 70s Dumbles in existence. The fact that it is a rare model to begin with, will only add to the value.

Jelle
Last edited by jelle on Tue Aug 19, 2014 6:35 pm, edited 1 time in total.
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ToneMerc
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Re: ODSR Clip

Post by ToneMerc »

jelle wrote:
As such I fully disagree with the opinion that it is currently it is currently in a butchered condition.

This is without doubt one of the cleanest 70s Dumbles in existence. The fact that it is a rare model to begin with, will only add to the value.

Jelle
I concur Jelle.

TM
Charlie Wilson
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Re: ODSR Clip

Post by Charlie Wilson »

Ok, fair enough as far as the bias transformer goes. A couple extra holes in the chassis that didn't need to be there. I think it does matter that it does not have the original transformers that HAD installed but it does look like they did a nice job with the amp. I hope the owner gets a lot of money to make up for all of the headache of trying to get this thing fixed.
CW
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