Improving a Deluxe Reverb

[fiftynine]

What do you feel are the short comings of the originals and how did you address them? If you built a clone, what did you change that you stuck with and never looked back?

[RobBozic]

Hi,

1 - I'd definately put a negative feedback or as some call it a 'soul' control or even a switch to go from the original 820R to maybe 1500R,
2 - I'd put one of switches for the vibrato which disconnect it from the circuit thereby giving you more gain,
3 - Reduce the cathode bypass caps from 25uf to 10uf to slightly tighten up the bass.

There's tone of mods to Blackface amps but at the end of the day you don't want to stray too far from the original and the first two mods above are both switchable.

You should check out the Fender Diaz Vibroverb which has got some cool mods which switch in different mods for an overdriven tone.

Rob

[LooseChange]

A good set of tubes biased to taste and a good speaker and you are good to go.

[bluesbear]

If you want some clean headroom, you can lower the B+ resistors to raise the voltage to the PI and preamp. I try for SF numbers. That's just about right for me. I also add midrange, master, and presence on my builds. Of course, this stuff is all subjective. It just depends on what you're actually looking for.
Dave

[Dave]

Looking at the schematic, the two channels are almost identical except for a capacitor value and the reverb. It is very easy to run both channels thru the reverb circuit. Given that, there is no reason (IMHO) not to modify one of the channels as much as you like. That way you get a full on BFDR channel and the other you get whatever you inventive power allows for.

Dave

[eleventeen]

GREAT thread for me: I have a SF AB763 DR that I modded to 4 (yes 4) 6L6's about 30 years ago. I want to take it back to near-stock. Keep those cards & letters coming.

[sluckey]

Add a raw control to the tone stack. Wire it like a typical Fender mid control but use a 100K-250K pot.

Replace the .1µF coupling caps to the PA grids with .047µF.

[fiftynine]

Yes, please keep them coming. No one's mentioned trannies yet!

P.S. love this, LooseChange - "A good set of tubes biased to taste and a good speaker and you are good to go"

[FYL]

What do you feel are the short comings of the originals and how did you address them?

Great sounding in stock form, provided that you use good tubes and a great speaker. Even better when you use Doug's layo and build techniques. The only basic mod I can think of would be to halve coupling cap values in order to curb a slight tendency to boom.

[OldHouseScott]

you can lower the B+ resistors to raise the voltage to the PI and preamp

That's what I did on my DR build and it helped a bit. It broke up too early for my tastes with the stock values. It's funny, I see other posts suggesting ways to make one break up sooner/smoother.

[Fresh_Start]

First, Hoffman's AB763 with the bias vary tremolo.

Second, I jumpered the two channels between their respective coupling caps and the 3.3 meg reverb mix resistor.  Leave one channel stock and do whatever you want with the other.  I lowered the B+ voltage to the Normal channel to Brown/Tweed levels, put 220K plate resistor/2.7K cathode resistor on the first triode, used a Brown Vibroverb Treble pot (Doug sells them - thanks!), changed the Bright switch to a guitar/harp switch, etc.  But you could go Marshall with it too - change tone stack caps to .022 & slope resistor to 33k or 47K, use a MOSFET cathode follower, and stiffen power supply with a big filter cap.  Just 2 possible examples.

sluckey's right on the money - bigger, audio taper Mid pot plus smaller PI coupling caps.

I'd put no more than a 10uf cathode bypass cap on the first gain stage, but that's subject to taste.  Same for reverb recovery - don't need to boost thunder from reverb tank IMHO.

It's a fantastic circuit, but there's so much to play with too

Cheers,

Chip

[chocopower]

Here are some mods i have done to my Proreverb Clon. Close enought to the deluxe.

ignore the B+ swicht in the jtm45 preamp. After test, i quit it. No worth the time...

[phsyconoodler]

I don't mess too much with the circuit other than separating the shared cathode resistor/cap that V1 and V2 share.I really like the stock transformers.Speaker has to go;a Weber 12F150 goes in.Tubes are kind of personal.
  I don't like the sound with no negative feedback.I did one with a PPIMV in the low input of the reverb channel and it sounded pretty damn good,so that might be an option.I do like the raw control a lot.
  The Dumble mod to the first channel would be cool.Maybe a 5879 preamp tube for channel one would make it truly a versatile amp.Heck,divided by 13 did that.I like the idea of making channel one something totally different and using an A/B box to switch.

[eleventeen]

Maybe a 5879 preamp tube for channel one would make it truly a versatile amp. Heck, divided by 13 did that. I like the idea of making channel one something totally different and using an A/B box to switch.

Boy, that's a cool idea. Mmmm, mmmm, mmmm.

[bigdaddy]

First lower the B+ so you can use any 6V6 tube. JJ can live but NOS tubes don't sound good to me with those higher voltages. Plates on a 6V6 sound best at 350v-380v no higher, once you get higher the sweetness of the 6V6 is lost and you might as well go with the JJs or even move to a 6L6GC.

Second use a good speaker like an original Jensen C12N. Another really good speaker is the Celestion Gold and the old Naylor 12s which sound like a mix of a C12N and Greenback. Some use a Celestion vintage 30, but I did not like it at all.

Third as for transformers, at the higher voltages it seems like an 8K primary OT sounds better then the 6.6K for the 6V6.

Fourth a switch or switched pot to remove the trem, gives you more gain. The 2 channels already sound different the reverb channel has extra gain and cutting the trem gives a higher gain amp.

Anything else to me isn't a BFDR anymore. Although making the normal channel into something with a 5879 or EF86 sounds interesting.

[phsyconoodler]

There sure are some variation in people's speaker preferences.To me a Celestion Gold has no bottom end to speak of compared to a Weber or Jensen.A greenback is kind of nice but too midrangy for my tastes,but it has some nice sweet spots.
  I like a Jensen P12N quite a bit in a DR.The P12Q is nice too.
Depends on what you like I guess.
  I find the only real difference between the two channels now is the lack of reverb in one.A slight gain difference.Big deal.Two same-tone channels bores me to tears.Lets face it; the normal channels seldom get used on a DR.What better way to mod the crap out of and truly make the DR more versatile?
  Frankly I like the way a pedal sounds rather than the amp overdrive as it is and usually if it's that loud it's too loud for the rest of the band anyway.I have a Custom Vibrolux that's going under the knife soon.The normal channel getting the 'morph' treatment for sure.
  Maybe a Tweed channel with a raw control?Hmmmm....Maybe a 5879 ,I will know when I start doing it.Either way it's going to be different.
Volume,tone raw.Something like that.I like using an A/B box rather than add a relay.Less 'stuff' inside the amp.
  I really dig the AB763 circuit overall,just want that edge for leads with no pedals.
 

[mresistor]

I've been using Celestion made Carvin GS12-75-8's in my DR's and love them. They have actually been preferred over the Weber 12F150 when compared. They're alot like a G12T-75 but sadly they're not available anymore.  I also like making the normal channel in to something a little different like Mike Thompson describes in his book (page 36 in the link) some would call this Marshallizing the normal channel. I've also added a mid pot on the Vibrato channel and mounted it in the back where the ground switch was and put a chickenhead knob on it so the position could be "felt".

what one can do to a DR normal channel

My two centavos.

[tommytornado]

I used a bigger OT/the 30-35W 4K one that goes in a BF Pro/Vibrolux & Tweed Pro/Super/Bandmaster.  The bass notes are bigger and more defined/clear/hifi and it gives it up a little later OD wise.  I like it. 

As has been suggested, I make the reverb/trem work on the normal channel..  And I modify it's tone stack to match up with humbuckers better than the stock Fender circuit.  V1A lower the bypass cap to 5uF, tone stack = 250pF/.022uF/.022uF w/ 56k or 82K slope resistor. 

.047uF PI coupling caps.
25KA mid pots for each channel added on the back panel. 
At lower volumes I like the NFB disengaged.

I am using the $29 Carvin British style speaker.. 

[bigdaddy]

I just remove the second input and use a mid control there. You can go 10K or 25K, even 50K. The small fender knobs fit well there and do not get in the way of the input, they come in cream or brown, they make black now too.

The bigger OT at 4K@4ohms works out to 8K@8ohms. So a bandmaster/tremolux/vibrolux OT works out fine. David Allen has one that I used before and sounded better then a mercury magnetic one.

I hate pedals and just turn the amp to 10.

[alerich]

Change the reverb intensity pot from 1M linear taper to 1M audio taper. I did that mod on my 1972 Super Reverb. It makes the reverb so much more user friendly. No more "on/off" effect when you get to 3 on the control.