# David Allen Brown Sugar



## Wootang (Oct 6, 2020)

I just picked this up. Good sounds coming out of it. 

My issue is that I really like the reverb tank it has. However, I can't use it because of the noise it generates. Anything passed 3 and it introduces a static hum to the noise floor that just makes it so I don't want to use it ever. As a result I leave it at 0 and use reverb from my pedalboard to much less desirable effect. 

Anyone familiar with the issue? must be a fairly common one. 

Specs below:











Output Power30W with 6L6s, 15W with 6V6s.Tube Compliment(4) 12AX7s, (2) 6L6s or (2) EL34s or (2) 6V6s and (1) GZ34 (5Y3 with 6V6s).ClassAB push-pull with with cathode bias.EqualizationBass, Middle, Treble, presence, and RAW controls plus BRIGHT switch.ReverbAll-tube driven, 3-spring medium delay Accutronics tank in a padded reverb bag with shielded cables and TONE control.ChassisNow featuring an 18-gauge non magnetic *stainless-steel* chassis with TIG welded corners.CircuitryHand-wired point-to-point with tinned solid-core PVC wiring, G-10 glass epoxy circuit board with brass eyelets. Carbon film resistors, Mallory M150 and CDM silver mica tone capacitors, Switchcraft jacks, Carling switches, and high-quality molded type sockets.TransformersCool and quiet running Allen TP40D 180ma power transformer, TO35MT upgrade paper bobbin interleaved winding output transformer, TR reverb transformer and TRCH large choke are all U.S. made. See the TRANSFORMERS page for details.TopologyA unique blend of a brown-era preamp (tone controls, phase inverter and presence control) with a tweed-era cathode-biased output section and wonderful blackface-era reverb. Enhanced with a bright switch, middle and RAW controls, reverb TONE control, impedance switch and the ability to use 6V6, 6L6 or EL34 power tubes for a truly unique and versatile amp with the best qualities of each era in one handsome package.CabinetFinger-jointed pine with custom brown Tolex and grill cloths. Brushed brass logo, brown/ivory faceplate and black or cream barrel knobs.Speaker(s)Eminence Red, White and Blues 12" speaker, Eminence Legend 151 15", or (2) Eminence Copperheads 10".Special FeaturesRAW mid/gain boost control, presence control, impedance switch, extension speaker jack, and TONE control for the reverb. Brown era tone controls and phase inverter with cathode bias. Blackface era reverb.Size and Weight1x15 Combo - 22"W x 20"H x 10"D, 53 lbs.
1x12 Combo - 22"W x 18"H x 10"D, 51 lbs.
2x10 Combo - 22"W x 20"H x 10"D, 53 lbs.
Head - 22"W x 10"H x 10"D, 32 lbs.


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## cboutilier (Jan 12, 2016)

I had this issue with a vintage amp once before, and it was simply a bad reverb control pot.


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## Latole (Aug 11, 2020)

These amp can be bought as a kit : 
A beginner can do some building "mystake. 

Check for bad lead dress ; show pictures from inside the amp
Any mod by previous owner ?


Check for a noisy 12AX7 tube
Check Reverb cables, you can use standard stereo RCA cables.


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## DaddyDog (Apr 21, 2017)

Wootang said:


> Anything passed 3 and it introduces a static hum to the noise floor that just makes it so I don't want to use it ever.


This happened to me once when I bought a chassis, tank, and cab separately, and had to put them together myself. There's a right way, and a wrong way, for the reverb tank. Try spinning it 180 degrees. The idea is to have the transducer (?) as far away from the power transformer as possible. Or maybe it was the output transformer. Regardless, spin it and try.

You can also try moving the tank out of the head, just for testing. It that completely removes the hum, you could possibly install the tank in your speaker cab, and connect with long RCA cables. I almost did that.


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## nonreverb (Sep 19, 2006)

DaddyDog said:


> This happened to me once when I bought a chassis, tank, and cab separately, and had to put them together myself. There's a right way, and a wrong way, for the reverb tank. Try spinning it 180 degrees. The idea is to have the transducer (?) as far away from the power transformer as possible. Or maybe it was the output transformer. Regardless, spin it and try.
> 
> You can also try moving the tank out of the head, just for testing. It that completely removes the hum, you could possibly install the tank in your speaker cab, and connect with long RCA cables. I almost did that.


Yup...+1, send coil needs to be as far from the power transformer as possible as the 60 cycle radiation can be picked up by the coil...even though it's surrounded by the grounded reveb tank shell.


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## AnthonyZ (Dec 9, 2020)

I assume that you purchased the Allen head used? Why not just call David Allen?


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## Latole (Aug 11, 2020)

AnthonyZ said:


> I assume that you purchased the Allen head used? Why not just call David Allen?



+1 

And was it a kit ? I ask before with no aswer


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## Wootang (Oct 6, 2020)

Latole said:


> +1
> 
> And was it a kit ? I ask before with no aswer


Appreciate the response. Amp sounds absolutely amazing. Great tone. Just got the time today. Its a kit. Guy with 28 years experience did the kit. Today I took out amp from chassis to see if the reverb noise was from an insulation/proximity thing. Same problem and no difference, reverb knob still making noise . I also used different RCA cables and that did not change it.here are some photos. Hopefully you can see a bit of what is going on.

Thanks


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## Latole (Aug 11, 2020)

The problem could come from the location of the wires. All wires must run along the metal frame otherwise these wires could act as an antenna and pick up noise as is currently the case.

The wires which must cross must do so in 90 degrees.
The wires should avoid being in parallel with each other too close to each other.

These are the most obvious problems.There can be something else too .
Do you have the schematic ?

I was the only one who mentioned that it could be a kit because the problem looked too much like a neglected assembly in detail. This guy doesn't have a lot of amp experience because he neglected this aspect.

This is what it should look like


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## Wootang (Oct 6, 2020)

Looks nice and neat.
I understand what you’re saying however there is no noise from any of the other knobs that are also wired this way.. raw, presence etc. Amp is very quiet and sounds great... just the reverb...


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## jb welder (Sep 14, 2010)

What it looks like inside has nothing to do with what it sounds like. Sometimes what looks neat is not the best practice as far as the sonic and noise performance goes.


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## Paul Running (Apr 12, 2020)

I won't say I practice neat routing however, it produces the sound I desire.


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## Latole (Aug 11, 2020)

Paul Running said:


> I won't say I practice neat routing however, it produces the sound I desire.


I tis a rat nest but all wire look short.
Doing a bad job may work sometimes, doing a good job always work and sound better


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## Paul Running (Apr 12, 2020)

True point-to-point wiring.


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## Latole (Aug 11, 2020)

Paul Running said:


> True point-to-point wiring.


Yes and ?


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## Paul Running (Apr 12, 2020)

Point-to-point construction, uses the leads of components such as resistors and capacitors to bridge as much of the distance between connections as possible, often removing the need to add additional wire between the components.


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## Latole (Aug 11, 2020)

I know. Did not help to OP issue


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## Paul Running (Apr 12, 2020)

No, it was an example of jb welder's comment...the trouble-shooter may fall down a rabbit hole chasing neat wiring.


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## Latole (Aug 11, 2020)

I would be able to fix this problem by having the amp in front of me. 
To do it remotely, I do not see how it is possible.


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## jb welder (Sep 14, 2010)

The worst thing here is that you don't know if the reverb hum is a new problem or something that has been there since it was built. If the builder had 28yrs. experience, you would think he would have noticed the hum, but you can never be sure.

A quick thing to try would be cleaning the reverb connectors at both the tank and the chassis (if you haven't already done this).

Another thing I noticed is from the description, there is a reverb tone pot as well as level? If so that's another place for hum to get in.


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## Wootang (Oct 6, 2020)

Been sent off to the best to get a clean bill of health!!


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## Latole (Aug 11, 2020)

" Anything passed 3 and it introduces a static hum to the noise floor"
-Wootang

Reverb is another pre-amp stage, it bring more gain. That is why you turn the pot you reach noise if amp is not well built. 


Amp is play mode; 
Look for microphonic 12AX7 tube, Not V1, this tube sound always microphonic 
Tap tube's glass gently with a screwdriver handle . 
Do same on wires and parts, mostly on to the reverb circuit. 
If you here "pop", something wrong there

Are 12AX7 tubes are standard in this amp ? 12AT7 is often use for Reverb Driver with gain of 47% ( less noise ) 
12AX7 have 100% gain

Best is to bring back the amp to the seller to fix this issue.

Nos schematic as I ask 2 days ago ?


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## nonreverb (Sep 19, 2006)

One thing I would like to ask if I may: Have you done a continuity test on the tank shield itself? If the tank's shield ground is not attached to the cable ground reference, the tank will be very noisy. You could do a resistance check from the ground from the amp chassis to the tank shell. If it's not a dead short you might need to check for a ground fault.
*Update edit* Also, I forgot to mention. Some tanks have isolated grounds on either the input or output connections. If the tank has either on of these and is not the spec. type for that amp, it will definitely cause a ground lift condition and conesquently, lots of noise.


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## Wootang (Oct 6, 2020)

Update all fixed up. Added master volume and clean bill of health


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## nonreverb (Sep 19, 2006)

Wootang said:


> Update all fixed up. Added master volume and clean bill of health


What was the prognosis?


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