Overdrive and Reverb

[luthierwnc]

Hi All,

A friend has been on me to make him another amp. He wants both a spring reverb and a switchable additional gain stage. I enjoy a challenge but all of my experiments and most of what I have read over 15 years of messing with these things tells me reverb and OD don't like each other. We're in the design stage but recent shoulder surgery has given me a lot of spare time noodling in front of the TV. This should probably be two different amps on an A/B stomper but right now it is just pencil on paper.

A couple years ago there were some designs floated at the Ampgarage on single tube verbs inserted just before the PI. Most of those guys have since recanted and said a digital unit into a buffered loop was a much better solution. That's what I did but much more because of the active loop sound than the verb.

Have any of you either made or played an amp that successfully combined a clean reverb and overdrive? This doesn't have to be done on the cheap or in any terrible hurry.

Other design leanings: Figure a pair of 5881's or 7591's. Head and cab driving two ceramic 10's. Diode rectifier. Discrete 12v switching relays with their own power supply. Switchable fixed or cathode bias. Plate volts will depend on where the sweet spot is for the cleans. It is has to be a tube reverb, I've gotten fond of the ECL82 design used in the 18 watt Marshall.

Thanks for looking and I hope to hear from you,

Skip

[chipaudette]

Why not build off the Mesa Boogie Mark IIC -> Mark IV schematics? They all have high gain overdrive in the front and a tube driven reverb after.

I think that the key is to control the volume before the reverb (ie, a post-distortion master volume). If your master volumes are after the reverb, then the super-hot overdrive signal is just going to cream your reverb input. Ick. So, put the master volumes before the reverb.

With two channels, you need both a master volume for the clean channel and another for the overdrive channel. If your overdrive shares much of the signal path with your clean channel (as is done in the Mesa Amps), you'll need some relays or LDRs to switch in your overdrive elements AND to switch in your lead channel's master volume.

Good luck!

Chip

[txstrat]

You might have a look at two schematics:
1. Fender Champ II
2. Fender Deluxe Reverb II

both are Rivera designed circuits from the early 80s.

1. is basically a standard Fender preamp with an added third gain stage and a mid boost for a tweed like sound. You could add a mid pot (25K) for extra mid boost (great boogie like sounds).
2. is a double channel amp and the reverb sounds good in both channels.

At least you could adapt the reverb section for an amp with switchable third gain stage.

I prefer a cathode biased power amp for these amps since it adds a more singin' character.

Perhaps what you're looking for.

[tubeswell]

Further to what chip said PV put their reverb circuits after the first 4 pre-amp gain stages but before the PI in some of their amps. A nice sustainy lead can sound better with verb (however as you say, if its too rough you wouldn't notice what else's going on)

[luthierwnc]

Thanks guys,

The situation called for practice management.

We had a nice long talk about the differences between ideal, electronically possible and budget. Plus the difference between dirt and gain. The tube count is starting to drop. I'll post the eventual schematic after I fire it up.

Cheers, Skip