Capacitor coupled reverb tank impedance?

[Dingleberry]

Hi.

Last week when servicing my friends Ampeg VT-22 I felt in love with that reverb and now I really need to build one myself as a stand alone unit.

I have one tank that might be suitable for that build.
It is from a Italian late 60's amp, Steelphon Pioneer that I gutted for projects sometime ago. The reverb was capacitive coupled with triode strapped ecl86 driver. There is schematic attached below.
There is no markings on the tank despite a sticker which says it's a Hammond reverberation unit and below that there stands only lots of patent numbers. No model number or other codes/markings in the tank.

The Ampeg style reverb tank is supposed to be 4fb3... type, in-Z=1475ohms and out-Z=2250ohms. I found a dc-resistance/impedance conversion chart
and it's also attached below. My measurements with fluke are a bit on the low side comparing to the chart, but of course the chart not 100% accurate.

I got input dcR 168.82 ohms and output dcR 170.00 ohms.
It's in the neighbourhood and way closer to 4FB-type that any other if looking at the chart.
There is a difference in Z-out with 6cg7 and triode strapped ecl86 but is there really a reason not to try it? It shouldn't explode.

My question is: Would that tank perform ok in Ampeg-style 6cg7 driven reverb? How the lower input impedance affects the sound? How forgiving those kind of reverb circuits are?

Thank you already. Just want to be sure before I place an order for new tank.

-T

[Dingleberry]

Anyone?

Member Luthierwnc has built one "Ampeg"-style stand alone unit and he kindly posted a schematic named "Reverbalope" here on forum also. I'll think I follow that as a basis. Got to try that my existing tank and see how it behaves.

-T

[Phil_S]

Find the schematic for the Gibson GA15-RVT. It has a cap driven tank and it looks to me like a very similar design. You should be able to cross reference for the tank used in that amp. It was a Gibbs tank (later Accutronics) which I think is now owned by Belton. Write to them and they will tell you what tank was used in that amp, which is from the 1960's. If you search this forum, you might find it, too.

[Luthierwnc]

Dingleberry remembered the post but it was on the music electronics forum:

http://music-electronics-forum.com/t11544/

It is a pretty simple build. You may want to change some values to dumb it down because it is way too much at the end of the sweep. I always thought the Fender standalone was too so ya picks yer poison. Use stout supply and cathode resistors on the back half of the 6CG7. The Ampeg cathode resistors were worked pretty hard. All the ones I've seen had a nice mocha-latte tan sh

[chief mushroom cloud]

Sano cao coupled reverb was best I ever heard in a guitar amp.....

[ampdoc1]

I had the same problem a few months back with my Silvertone 1474. This had that cheezy piezo tube that is the worst ever!!! Did a lot of digging, asked questions, and tried a few pans, all to no avail.

But by happenstance, I found an easy fix that will probably work for you. Basically the reverb driver and return on these amps work well as an effect loop. Just hook up the cables to your favorite reverb effect unit, set the in and out levels and you're good to go.