AB763 Deluxe Reverb with 6v6

[moonbird]

Hello all -

My first post here --

Couple years back I bought a pre-built Hoffman-style turret AB763 - built as a Deluxe Reverb with the powertube bias tremelo. I am gearing up to put this beast together.

One of the things I have thought about is using 6v6s instead of 6L6s which the board was build for (I think). Can someone please help me think through ALL of the potential changes - I will need to consider. Why 6v6s?? I like the sound of them better - plus I was able to purchase a quad of old RCA Jan 6v6g's (shouldered) that I am itching to try.

I have NOT purchased any iron for this task -- so NO suggestions are off the table. In fact I NEED iron recommendations. Don't have any idea on the PT. Considering an Onetics Model F OT - could use some recommendation on the wattage to buy based on the suggested operating point.  Speakers will be two 10" 16 ohm tone tubbys (one alnico and one 40/40 ceramic). Will be housing this beast in a custom solid walnut combo cab that I was lucky enough to find on EBAY a while back. Music style - vintage blues, some rockabilly, SURF!! I have built a couple amps at this point - but this is the biggest task I have taken on to date.

Please do not hold back -- if reducing the power with 6V6s spoils this design IYHO -- make your case. Thanks much.

 -- moonbird

[phsyconoodler]

Well for starters a Deluxe Reverb was made with 6V6's originally.Whether yours had 6L6's or not is irrelevant.The amp will likely work with both tube types.Obviously I don't know who built the amp;you said you bought it already built?
  The bias of the output tubes is the only thing to be concerned about.6V6's take less current than 6L6's.
The AB763 circuit is virtually identical with very minor changes from the Deluxe Reverb(6V6's) all the way to the Twin Reverb.(6L6's)

[sluckey]

If it's a standard Hoffman AB763 board, you don't need to change anything on it, except maybe the feedback resistor. Some AB763s use a 820/100 ohm feedback divider and some use 820/47 ohm divider depending on the speaker impedance you choose.  It's really a very minor change and will work either way.

The differences between the different AB763 models are the transformers and speakers. The circuit remains the same. Hoffman has all the transformers (other parts too) to build as a Deluxe Reverb. Just look at the links at the top of this page.

Welcome aboard... Steve

[OldHouseScott]

One other slight change is the bias range resistor on the DR is 10k, whereas amps with the 6L6s used 27k.

[sluckey]

They just keep coming... The B+ dropping resistors are 10K and 10K for the DR, rather than 1K and 4.7K.

[moonbird]

Great -- this what I need. Is there a tube voltage chart somewhere. What is the loaded HV at the PT? thx again!

[moonbird]

some AB763s use a 820/100 ohm feedback divider and some use 820/47 ohm divider depending on the speaker impedance.

It is a standard I believe -- built by an "authorized" builder (charles@revolveramps.com) or so he said. I will be using two 16 ohm paralleled 10" for an 8 ohm load -- which divider should I use - thx.

[moonbird]

One other thing I forgot --

The cab I have will not accommodate the 11 or so knobs required -- so I thought I would leave off the "Normal" channel. Seems pretty straight forward to do -- but I was not sure about the 220K mix resistor(s) that go into pin 2 on the 12AT7 PI tube. If I have only one channel -- is the 22K resistor still needed or recommended?? Figger it is -- but I thought I would ask. thx again to all.

[moonbird]

Its all coming back now -- I did buy a PT -- it is a hammond 290BX (Fender replacement) for the DR 330VAC CT, -50V bias tap, 5V=3A, 6.3V=3A. Does this one work ok for the hoffman design with 6V6?? thx.

[sluckey]

which divider should I use

820/47Ω for 8Ω spkr load

I did buy a PT -- it is a hammond 290BX

That's fine.