Universal high impedance reverb ckt design and pcb art

[ivey]

I designed and developed this ckt to be used in solid state and tube amps using only two transistors and a number of other parts, to be a cheap and easy to build and use ckt.

It will allow tube amp builders to use spring reverb units without having to use extra tubes or a matching/coupling transformer. It can be powered by using the 12volt dc filament voltage.

[ivey]

Here is the schematic of the ckt

I use CircuitMaker 2000 and Quickroute 3.6 for schematic and layout

[ivey]

I updated the schematic. This the final version

Updated schematic.

[Chuck H]

Have you tested this circuit? A pn3566 looks to be rated 100mA @ 1V. That doesn't seem like enough to drive a reverb pan.

[ivey]

Have you tested this circuit? A pn3566 looks to be rated 100mA @ 1V. That doesn't seem like enough to drive a reverb pan.

Yes Chuck, I used this circuit for forty three years. I recently stopped pref boarding the design and put it on a pcb.

I and Joseph Retinivia designed it in 1967. Least it to Teaselco that same year, to use in cheap Japanese guitar amps during that period.

The PN3566 is a stuff little bugger, that has 500ma of output current. If you cut out a half inch square of alco, and glued it on he back, you can get 1 amp out of it. And it is very high gain.

Check out the PDF

[ivey]

The right schematic with updates

Sorry for the error

[Chuck H]

Huh... I must have accidentally looked at the wrong spec sheet then. And thank you for sharing.

[J M Fahey]

Dear ivey, thanks for sharing.
Please delete earlier wrong schematics, it may be confusing.
And Rev14.pdf still does not match the PCB.
On the PCB R2 goes to Q1's collector (which I think is right), on the schematic it goes straight to +24V.
Recheck it and post the final version.
And that transistor isn't asked to pass more than around 20mA anyway.

[Chuck H]

I didn't diagnose the circuit as you did JM. So how do we get good tank drive from 20mA @ some low voltage?

[J M Fahey]

I didn't build this one, but it should work with high impedance tanks. The design looks reasonable.
There were similar circuits in the old days and they worked, one example is Traynor SS PA heads.
No Twin Reverb class, but then nobody else is
Anyway the ubiquitous TL072/LM1458 used by everybody and his brother does not (easily) supply much more than around 6mA, that's why many parallel 2 or 3 of them.
A few wise guys use NE553x which are beefier.
PHATT (Philip Abbott of Nambour, Australia), a cool fellow at SSGuitar has designed and built a killer reverb circuit, with an OpAmp driving a couple TO220 complementary transistors and feeding them around 45V (or was it +/-45V?).
Talk about strong, clean reverb !!
But to each his own, this simple reverb circuit is easier to build and debug by a regular guitar player with *some* building experience.

EDIT: where did I get the 20mA number from?: 680 ohms load with around 12V dc across it gives about that.

[R.G.]

Along those lines, the internal reverb circuit from the old Thomas Vox amplifiers used what amounts to a discrete power amp with the same complementary transistors for outputs for driving its reverb. Works, reliable, deep reverb. It ran on 28Vdc, but like all feedback circuits, was kind of immune to power supply levels as long as it survives.

Craig Anderton designed a very good sounding reverb driver/recovery setup using a packaged power amp chip, LM2877 (?) or similar in 14 pin DIP. I think it can be found by searching "Stage Center Reverb".

And many older reverbs simply drove the tank with a tap off of the speaker output.

[ivey]

O.K. guys I will delete/remove the incorrect schematics . Thank you for your support. It helps a great deal