Strange new vibrato circuit in DR Reissue

[Zouto]

Thanks Steve, I also swapped the lousy filter caps for some F&Ts, which reduced noise and hum quite a bit. The original first filter stage with 220uF/100V(C31) in series with 47uF/500V(C32) plus 100K/470K bleeders is quite weird. Using two 100µf/350V caps in series for a value of 50µf total with two 220K bleeders seems to me much better.

[potatofarmer]

Is there a schematic for this version of the amp?

Is there a reason to remove the grid stoppers- are the grid stoppers causing a problem, or is it just a nostalgia thing?

[Pedro Vecino]

I took the liberty of converting your post into a PDF file that I attached here so that people here can download it. Let me know if there are any edits that you would like.

Ok, Steve. Your page is great.
Thank you!

[Hal9999]

Thank You!

Here is a summary of the mods on my 68 Custom Deluxe Reverb:
All dB values was measured with an iPhone 6 running Audio tools SPL Pro, placed on top of the reverb tank (A Weigthed).
Problem 2 and 3 measured with all controls set down to 1.

Problem 1: Terrible hum when reverb is turned up.
Solution: Turned the reverb tank 180 degrees. The output side must be at the right, away from the transformers (seen from the back).
Result:
Clearer reverb with reduced noise.
At max reverb, amp noise is reduced by 5.5 dB!

Problem 2: Lots of noise when tremolo intensity is turned up.
From min to max intensity the noise level is raised by 11 dB!
Solution: Removed the ROHS tremolo circuit. Installed an optocoupler from TAD (FVIB Vibrato LDR for Fender).
Result:
No added noise at max intensity. Tremolo good.
Amp noise reduced with 2 dB.

Problem 3: Still some noise.
Solution: Removed the seven 10K grid resistors from V1,V2, V4 (pin 2 and 7) and V3 pin 7.
Result:
Amp noise reduced with 4.5 dB!

Total amp noise reduction after the ROHS tremolo and grid resistors removal is 6.5 dB!

Extra mod. 65/68 feedback Switch.
Replaced the never used ext speaker jack with a switch, who adds one 1.8K resistor in parallel with the 1.5K feedback resistor.
In 65 setting the amp noise is reduced with 1dB, and the amp is more tight/clean.
I prefer the 68 sound

Bias current 27 mA, not changed.

Regards.