Other Amps

Reverb tank grounding…

1

I’m looking for a particular reverb tank for my Ampeg GVT15-112. The stock tank is the common 8EB2C1B, but I’m looking for a two-spring replacement to tame it a little bit. So, from what I can tell, I need a 1EB2C1B, which I don’t think exists – or if it did, it is no longer made. As an alternative, I’m considering the 1AB2B1B from AES. From what I can tell, everything would seem to work except for the grounding configuration (input grounded, output insulated). The 8EB2C1B is the opposite (input insulated, output grounded). Will this be an issue? Thanks!

2

That first A is 8 ohm input, you need E, 600 or 800 ohm.

You could probably modify the grounding.

I wonder if you could just clip one of the springs out?

There's an 8EB1C1B that should be a short decay.

5

Yeah, just dampen one of the springs! Duct tape! Some of the tanks have a lock on them and people go nuts wondering what happened.

I have a RealTube RT-921 that I bought on the internet when the internet was all new and shiny. It got to me with a broken spring and no way to fix it. I taped the spring down, you can tell the channels are slightly different, but they both sound fine.

The tanks are cheap, go experiment!

You could probably also find an 800 to 8 ohm transformer with a high enough voltage rating.

6

It was forever and a day ago, but I do remember trying the damper thing.

I used "soft blonde cushion foam" cut to shape surrounding each spring, then to fit the inside of the enclosure, ... placed it dead center.

Important to make it stable so the effect stays the same.

Way, way back memory...

7

Thanks for the tips, gentlemen. I think I'll just buy a couple and see what works!

8

Do you know what brand pan came in the amp? Belton tanks generally have longer decays. You might want to consider a two spring 17" pan if it will fit. According to the Ampeg GVT15-112 manual the amp is 18" wide so a 17" pan would probably fit. The proper 17" two spring pan would be a 4EB21CB. I prefer MOD brand tanks (they sound more like the vintage USA tanks and are made better than the current Accutronic imports which also tend to sound a bit metallic). The MOD 4EB21CB also has a shorter decay time (1.5 to 2.75) than the short 3 spring units (1.75 to 3.0).

9

If the reverb is tube driven you could try using a lower gain tube driver to tame the reverb as well. Can't find a schematic myself to go further with this advice

10

My experience with a 5751 versus an AX7 as the Reverb Return is that it is quieter, inherent noise level went down. Doesn't change the decay.

I have alway used an AT7 or equivalent for the Send.

Might be easier to weaken the Reverb by changing the Capacitor in the circuit, and leave the tank alone...I went the other way on my CVR with the cap change, boosting up to the much more Fendery Reverb sound.

Took a while to find a downloadable schematic for the Ampeg, need to compare to what I did on my Fender.

In my case I went up from 500pF to 3300pF. In your case, my inclination is to go lower...

Ampeg circuit probably is a bit different, but the intent should still be there.

11

I don't believe the reverb in the Ampeg GVT15-112 is tube driven but I could be wrong.

12

Transistor driven, C20 seems to be the target 330pF/630V cap, sinusoidal +6 dB from 1kHz to 48kHz.

13

Y'all have officially gone over my head! I draw the line Hz's and pF's and what not.

14

Ha!

I did so such that an Amp Tech might have a starting point...Worked great on my Fender boosting Reverb.

I also read something since about tieing a rubber band around the springs, ... A 70's trick which may be where I figured to use foam. Too long ago, cannot remember.

http://www.diystompboxes.co...

This new entity which owns the Ampeg name may or may not be copying some of the older circuit schemes. Ampeg always a different thing regarding "Echo", some might say it was in-between Reverb and Tremelo.

15

I think you could put an external, in-line volume control before the reverb tank, a dwell control.


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