Deluxe Reverb too clean

[rutledj]

I built a deluxe reverb clone based on the schematics found here at hoffmanamps.com.  It uses the output tube bias tremolo circuit rather than the original deluxe circuit.


My amp sounds great. My only issue is that it never breaks up or distorts.  I thought deluxe reverbs usually started breaking up around 11:00 on the volume dial. Am I wrong on this?

Thanks,
Rut

[tubenit]

What tubes and speaker do you have in it?  What is it biased at?  Can you provide a little more information.

With respect, Tubenit

[rutledj]

Sorry but I don't have a good way to upload a schematic with voltages. But They appear to be normal based on other readings I've seen. I'm using tung-sol preamp tubes and EHX output tubes. The speaker is a Warehouse ET65.

[bnwitt]

You could just list the voltages:

Tube     Pin 1      Pin2     Pin3    Pin4       Pin5       Pin6     Pin7     Pin8      Pin9
V1        180          -        1.3     3.1AC    3.1AC     180       0        1.3       3.1AC
V2        170          -        1.3     3.1AC    3.1AC     170       0        1.3       3.1AC
V3        410          -        8.7     3.1AC    3.1AC     410       0        1.3       3.1AC
V4        170          -        1.3     3.1AC    3.1AC     180       0        1.3       3.1AC
V5        270          -        2.1     3.1AC    3.1AC     180       0        17.0     3.1AC
V6        170          -        77.0   3.1AC    3.1AC     180       0        77.0     3.1AC
V7         -          3.1AC    415     415       -35        -35     3.1AC     -           X
V8         -          3.1AC    415     415       -35        -35     3.1AC     -           X
V9         -          330AC     -      330AC      -           -          -         420        X

I've attached a PDF file of a voltage chart for you convenience.

[bnwitt]

One question, which value of negative feedback resistor did you use, the 47 ohm or the 100 ohm?

[bmccowan]

Hello,
I wanted to add some ideas here based on my experience with the blackface amps. Fender went to a lot of trouble to make them clean, and one of the ways they did that was to boost the B+ voltage up to 400 +. I have had some limited luck dropping the voltage with a different rectifier tube and/or larger dropping resistors. 5V4 and 5R4 rectifiers will drop the voltage some.
Also, last year I built a 6G3 deluxe and love the tone of that amp. More midrange, less headroom. So perhaps adopt some of the circuitry from that amp in addition to trying the rectifier swap. 6G3s have about 50v less B+
I also have tried eliminating or limiting the neg feedback. But it seems to me that the bass gets flabby.
B Mac

[Joel]

In the Hoffman Deluxe Reverb there is a 47k resistor to ground just before the PI.  I swapped that out for a 1Meg volume pot.  Massive volume/gain increase!  I tamed it by swapping the 12AX7's in V1 and V2 to 5751's.  Amp sounds stellar!  I also use a WGS ET65 speaker - it's a magic speaker.

TLDR: swap the 47k to a higher value for more signal into the PI.

[Ed_Chambley]

Certainly lowering the voltages would reduce headroom, but the AB763 and 6G3 Deluxe have a bit if tonal differences.  IOW, Billy Gibbons used the Brown Deluxe and it did grind.  One thing is the Blackface "should" be cleaner.


Things that get a Deluxe to breakup earlier.  Make your NFB adjustable.  Sure, it will change the bass response, but so will the temperature change or when the room you are playing fills with more people the tone changes.  Put a 12Ax7 in the PI.  Increase the plate resistor on V1.  Lower the bypass cap on V1 to 4.7uf/25v  which simply removes Bass below what is needed.  Then replace the 6.8K resistor that is the mid with a pot.  Some use 25K, I use a 250K generally.  With the 250K you will have a raw control which reduces the losses in the tonestack and also brings mids up a lot.  The upper mids is where you want you breakup and the AB763 tonestack is designed to be a Blackface.


A low watt speaker.


If you are using the JJ 6V6S, which a lot do now, this tube is capable of handling higher voltages but will also provide more clean headroom. 


And of course, Humbuckers.

[rutledj]

Here are my voltage readings. Thanks for the PDF file.

[bnwitt]

I assume the 691VAC readings on pins 2 and 4 of the rectifier are between pins and not each pin to ground right?

[rutledj]

Correct.

[Toxophilite]

I think the original designers would be proud of you! As this is what they would hope to achieve
It's only recently that amps have been designed to distort.


Mine tend to start distorting around halfway up and are only fully distorted almost dimed
i actually wish they were more like yours!



Your B+ voltages look a little on the high side for a Deluxe +20V or so(not necessarily for an AB763 in general)
Are you using a GZ34? Can you try a 5U4G rectifier ?

[rutledj]

Well, I guess I built it correctly. By all accounts it is behaving as normal. I just always thought they started breaking up with volume about half way up, but since I've never owned a real one I had nothing to compare it to.  I'll use pedals for overdrive and be content. The clean sound is pristine. 


Thanks for your input.

[bnwitt]

Frankly the DR is the most recorded amp in history and most of it's professional users have multiple pedals in front to achieve their different killer tones.  The only difference in the Hoffman version and the original is the awesome sounding 6G16 bias vary Tremolo.  That being said, we do have higher voltages today compared to when the amp was built originally so there may be slightly more clean headroom then back in the day.  One way to achieve the lower voltages and check it out would be with a variac.  I don't think there will be much difference but who knows.

I would suggest you put an overdrive pedal in front of it.  And I can't recommend the Klon type OD enough.  I posted a thread with some Youtube clips of the deluxe and "Klone" OD combination in this forum but one of the moderators saw fit to move it to the effects forum so look for it there.  Great pedals can make this amp sing and the Klon is one of the best overdrive circuits out there.  I know that many players today want an amp that does everything without external devices but I've never played one that claims to do it all that sounds as good as the old Holy grail amps with a good pedal board.  You've got yourself and awesome tube amp there and it just needs some quality pedals to complete your tonal quest.  Have fun with it and congratulations on a successful build.
Barry