More important—reverb tank or part values in a vintage Fender?

[eurekaiv]

A friend of mine just picked up a BF Super Reverb and he was telling me the reverb on it is crazy good sounding compared to just about any other Fender with built in reverb he's heard. So what I'm wondering is, how much does a tank play in the overall sound of the reverb circuit versus the variance of parts values in the circuit itself?

I've seen guts of the amp and so far as I can tell, the only mod it has is a cap across the tank input to ground that I assume is to filter out some high end/reduce noise—I guess this was stock on some later SF amps. In his case I worked out the .001uf cap would cut off around 10khz if the 15kΩ measurement for the reverb transformer I found is correct. Doesn't seem like that would have a dramatic effect on the tone of the reverb on its own.

[MWJB]

Reverb tanks (of the same spec) are hugely variable. May as well check that he has an original, 2 spring, style tank - "4AB3C1B". You can reduce the dwell by reducing the value of the 1Meg resistor at the 12AT7 grid if necessary. If the tank is original 1960s the springs may have stretched...if you have access to other 4AB3C1B tanks, substitute them until you find the best sounding one.

9AB2C1B, 3 spring, is also an option.

[eurekaiv]

How does a three spring sound compared to two? I may start looking around for other tanks to try. I've done a ton of work restoring my drip edge Deluxe Reverb and it's sounding great but the reverb is a bit noisy and a little anemic and tube swaps have done little to help it either.

[MWJB]

"How does a three spring sound compared to two?" Fuller, deeper. Don't go for the 9AB3C1B unless you fit a dwell control, 9AB2C1B compares best with the stock Fender tank. Some harp players have expressed a preference for the short decay 9AB1C1B. A good 2 spring sounds great too though.

the 4th digit denotes decay length - 1 short, 2 medium, 3 long.