AB763 Single Channel Reverb Only has no headroom.

[3choplex]

I’d love any input as to why I don’t have any headroom.
I’m building a single channel AB763 Deluxe Reverb using Hoffman’s board and schematic for the most part. Because I am using a princeton chassis (which has one fewer preamp tube), I removed the vibrato circuit. I just connected the bias supply to the power tube grid leak resistors.
I’m using magnetic components iron–the deluxe reverb standard parts. In retrospect, I think the power transformer is overpowered.

The amp works, and it sounds really good, but it has basically no clean headroom. I am assuming it’s because when I pulled the vibe circuit I didn’t adjust any of the other voltages to account for the reduced current load, and because it doesn’t have the normal channel.
Are the high voltages the likely culprit? If so, I suppose I’ll opt for zeners in the B+. Ultimately, I’d be happy if I could get a bit of clean headroom, but less than a stock DR—I wanted a clean amp in the first place, but this sounds so good I don’t want to lose the grind altogether when I turn up.
v1   12ax7   
1   Plate 2   204
2   Grid 2   0
3   Cath 2   1
4   H   2.8
5   H   2.8
6   Plate 1   201
7   Grid 1   0
8   Cath 1   1
9   H   2.8

v2   12at7   verb send
1   Plate 2   455
2   Grid 2   0
3   Cath 2   8
4   H   2.8
5   H   2.8
6   Plate 1   455
7   Grid 1   0
8   Cath 1   8
9   H   2.8

v3   12ax7    verb recover
1   Plate 2   196
2   Grid 2   0
3   Cath 2   1
4   H   2.8
5   H   2.8
6   Plate 1   199
7   Grid 1   0
8   Cath 1   1
9   H   2.8

v4 (Tremolo circuit--did not include)

v5   12at7   PI
1   Plate 2   215
2   Grid 2   25
3   Cath 2   81
4   H   2.8
5   H   2.8
6   Plate 1   210
7   Grid 1   28
8   Cath 1   81
9   H   2.8

v6   6V6   
1   NC   
2   h   2.8
3   Plate   465
4   Screen   463
5   Control   -31
6   NC   
7   H   2.8
8   Cathode   0

v7   6V6   
1   NC   
2   h   
3   Plate   462
4   Screen   462
5   Control   -31
6   NC   
7   H   
8   Cathode   0

Power   5Y3   
1   NC   
2   465
3   NC   
4   350ac
5   NC   
6   350ac
7   NC   
8   465

[sluckey]

I’m building a single channel AB763 Deluxe Reverb using Hoffman’s board and schematic for the most part.

How closely did you follow Hoffman's plan? Refer to Hoffman's preamp schematic. Did you include that 47K resistor just prior to the phase inverter?

[3choplex]

I followed it exactly except for 2 changes--the trem circuit, and the first two dropping resistors are 10k.

I have the 47k resistor there.

[3choplex]

The 47k is to replace the 50k intensity pot from the original vibrato circuit, right? Can I just replace it with a 50k pot to use as a master volume and solve most of my problem? (My chassis has holes for 2 more pots anyway.) My thought (which may be wrong) is that a smaller value would allow more signal to ground before the phase inverter, thus the 50k pot?

I saw that you used a 100k pot plus a 220k resistor in your schematic. I assume that the 220k would attenuate the signal as well? 

(I also have an older Hoffman layout and schematic that is exactly what I did (I don't see that it's on the website anymore) where the schematic just has the 47k.)

[3choplex]

It looks like the schem I used eliminated the 220k mixing resistor. I'll try that next.

[3choplex]

I installed a 250k pot where the mixing resistor would normally be. For the record, 120k seems to be the magic spot for me, but I like the flexibility. It seems like it fixed my problem, but I'm going to live with a few days to make sure.

Thanks, Sluckey, your question about the 47k resistor kind of sent me down the rabbit hole to the solution.

[3choplex]

So on to my next question--the voltages are too high and I'm worried its going to eat 6V6s for breakfast.

My understanding is that if I put a zener on the CT, it's going to cause problems with the bias supply. Is my next best option a zener on the B+, or a mosfet follies kind of arrangement on the CT?