Reverb mods made

[Bob-I]

I think I'll start a new thread on my 3 channel amp....

I tried Gary's reverb ckt today with some jumpers. I disconnected the 3.3/10pF reverb mixer and jumperd in a 100k direct from the reverb input to the PI input to mix directly at the PI as Gary suggested. The results are dramatic.

1) The reverb is wet an smooth, Dick Dale look out.
2) The clipping at the PI is gone, plus I can run the clean preamps much hotter and get a more rounded tone from them
3) The ODS, where it's still in need of work is far better.

I narrowed down my hum problem to the reverb return tube. It's a pretty basic ckt so I don't know what this issue is. Maybe it's simply too close to the speaker jacks. Back to work now that lunch is over so I'll have to look into it later.

[Icetech]

I use the same reverb circuit and was suprised how well it works with 1 tube:) and the fact it doesn't sound bad on the OD circuit....

[Bob-I]

I use the same reverb circuit and was suprised how well it works with 1 tube:) and the fact it doesn't sound bad on the OD circuit....

Slight correction... I used the mods Gary suggested, not the entire ckt. I'm still using the parallel 12AT7 on the drive, and 2 stages of return with a 12AX7.

[glasman]

I use the same reverb circuit and was suprised how well it works with 1 tube:) and the fact it doesn't sound bad on the OD circuit....

Slight correction... I used the mods Gary suggested, not the entire ckt. I'm still using the parallel 12AT7 on the drive, and 2 stages of return with a 12AX7.

Glad to hear the ideas helped. I would love to have the extra tubes for the driver and recovery. Someday.....

Gary

[ElectronAvalanche]

Hi Bob,

could you please elaborate a bit more on the circuit you used?

I tried to find the mods by Gary to no avail.

I have one 12AT7 as a driver tube and one half 12AX7a.

Thanks in advance,

Electron

[glasman]

Hi Bob,

could you please elaborate a bit more on the circuit you used?

I tried to find the mods by Gary to no avail.

I have one 12AT7 as a driver tube and one half 12AX7a.

Thanks in advance,

Electron

Check out this thread. It is towards the bottom of page one.

http://maximoaudio.com/forum/viewtopic.php?t=481

[ElectronAvalanche]

Hi Gary,

thanks for the help! Now I see it!

I will go this route and report back!

Thanks again,

Electron

[Bob-I]

I've just completed the updated schematic.

I'm still having hum issues with the return ckt, plus there appears to be more gain in this than necessary. Reverb return above about 3 is simply too much reverb.

Another change I'll make later too. In moving the dry signal I eleminated the 10pF cap across the 3.3M mixer resistor. This leaves the Dumble channel much more Dumble'y but the Fender channel is a tad dull. I'll add a bypass cap to the mixer resistor at the exit of the Fender channel. I'll have to do some calculations to get the same bypass frequency, but my initial guess is that a .001uF will be approx. the same.

Damn the hum man.....

[glasman]

I've just completed the updated schematic.

I'm still having hum issues with the return ckt, plus there appears to be more gain in this than necessary. Reverb return above about 3 is simply too much reverb.

Another change I'll make later too. In moving the dry signal I eleminated the 10pF cap across the 3.3M mixer resistor. This leaves the Dumble channel much more Dumble'y but the Fender channel is a tad dull. I'll add a bypass cap to the mixer resistor at the exit of the Fender channel. I'll have to do some calculations to get the same bypass frequency, but my initial guess is that a .001uF will be approx. the same.

Damn the hum man.....

You could try reducing the gain of the first recovery amp. This is a trick that Matchless did in their amps. See the Chieftain schematic at schematicheaven.com

Also increasing the size of the 470K before the last recovery amp would do the same thing. Although it may darken the reverb tone.

On the fender side of the preamp. You might try reducing the mix resistors a bit. This will brighten things and your idea of a parallel cap will also help. I just wonder if you would be better served to switch the preamps via a relay and eliminate the interaction between the D and F preamps trhough the mix resistors.

Gary

[glasman]

One other question. I notice there is no blocking cap on the second reverb recovery amp. As drawn, you have the plate tied directly to the mix resistor that goes to a 1M to ground. I think I would add a .001 to .01uf and 100K in series on the output of the recovery amp to the summing point.


Gary

[Bob-I]

quote]


You could try reducing the gain of the first recovery amp. This is a trick that Matchless did in their amps. See the Chieftain schematic at schematicheaven.com

Also increasing the size of the 470K before the last recovery amp would do the same thing. Although it may darken the reverb tone.

The Matchless schematic is a tad blurry, did I see a 22K load resistor on the first recovery amp?

On the fender side of the preamp. You might try reducing the mix resistors a bit. This will brighten things and your idea of a parallel cap will also help. I just wonder if you would be better served to switch the preamps via a relay and eliminate the interaction between the D and F preamps trhough the mix resistors.

Gary

I thought about relay switching the output of the preamps, but I'm trying to keep the relay system as simple as possible and still achieve the 3 channel switching. I'll keep that in mind if I can't get the results I'm looking for.

I'll piddle with the mixer for now.

Thx Gary, you're a wealth of information

[glasman]

Yes I think it is a 22K

Here would be my change to the output of the reverb.

Gary

[Bob-I]

Actually, I decided to try reducing the gain first. The 2 extra components, the coupling cap and series resistor look good, but it would require I change my layout. I'll try lowering the first return load resistor to 22K, then the second to maybe 47K. I believe that should address the reverb balance.

[MarkB]

Bob

Have you seen the TUT reverb? K. O'C. talks about ways of dealing with reverb noise.

[Bob-I]

Bob

Have you seen the TUT reverb? K. O'C. talks about ways of dealing with reverb noise.

No I haven't. I'd like to