Silvertone 1333 - Tremolo - How to slow down

[eman-blues]

Hello Amp Repair Gurus,
Any suggestions on how to modify the Silvertone 1333 Tremolo circuit to make it slower and deeper? (Schematic attached)

1. Would chaning the 68K resistor (R26) below the speed pot impact the speed? Or do some of the capacitors need to change?
2. For the depth, would changin

1. g the 1M resistor (R32) above the strength/depth pot change the depth range of the tremolo?
2. Any other suggestions?

Many Thanks!!
-E

[loudthud]

Speed: R26 won't have much effect on the slow end of the pot. Change R27 to 1Meg. If not slow enough, change caps to higher value or add caps in parallel with C13, C14, C15, .01 or .02 uF.

Depth: Lower R32. Change R24 to 250 Ohm 5W. If you are losing depth at slower speeds, increase C17

[Helmholtz]

If depth at slow speed is still not enough increase C12 to 250µ.

[eman-blues]

I lowered R32 and got a very deep cool sound. But there is a popping sound at idle.
would tweaking R24 and C17 help reduce the popping sound?

[loudthud]

I'm not sure what you mean by popping sound, but there is a limit on how deep tremolo can go with the "bias wiggle" circuit.

It usually helps to lower the bias current on the output tubes, that's why I recommended the 250 for R24. You might even go one step higher at 270.

I like Helmholtz' idea of increasing C12.

If it pops with no guitar, the Tremolo signal is probably too big for the 6V6s to handle. Try changing R24 first, then try lowering R32 a little at a time.

[Helmholtz]

It's essential that power tubes are balanced to avoid LF popping or kind of motorboating.
Only balanced tubes will reject the common mode LF modulation..

[eman-blues]

Hey folks,
Thanks for all the suggestions. I wanted to follow back up witht he results. I got the tremolo slowed down and much deeper to make it very cool and swampy. There are the mods I did:

• Increased R27 (from original value of 560K) to 1Mohm
• Lowered R32 (from original value of 1M) to 270K
  • Also experiemented with reducing R32 to 68K.

Thanks for all the help!