reverb tank mods

[ac15]

Has anyone on this forum ever swapped their "regular" reverb tank in their non-Fender tube amp and put in a Fender reverb tank? I've got a Vox amp which has an "OK" reverb, but it doesn't sound nearly as spacious and lush as Fender reverbs are known for. I'm thinking of making this change, but am wondering if there are other factors besides the reverb tank itself that account for how great the Fender verb usually sounds. Are there factors that would make this mod impossible or cause problems? The amp I'm referring to is a Vox AC15 (the Korg?Marshall "reissue," not the original from ther 60's. Thanks.

Steve

[Guest Mike Lee]

If you want to try it I have two Fender-spec Accutronics reverb tanks. One is a long two-spring long delay, and the other is a long 3-spring long delay. Both were used in a Vibro King, but I think they will also work in Fender outboard reverbs and Blackface amps.

The two-spring is the classic splashy Fender sound, and the three-spring is less springy and more lush.

There are issues of impedance matching between the amp and the tank in the case of tube & transformer driven reverb circuits.

[tralfax19645]

Hi,

The VOX reverb is an entirely different beast, there is nothing you can do to it to make it sound like a fender.

The main difference is the way fender drops the dry signal way down, adds the reverb and reamplifies it again before hitting the power amp. The VOX never reamplifies the mixed signal. The dry goes to one side of the phase inverter, the reverb to the other.

rob

[ac15]

Mike,

Thanks for the info. I may possibly be interested.

Rob,

Are you saying this mod is not possible with this amp? If I'm understanding correctly, you're saying the tank itself isn't even the issue, but rather, the way the tank is placed in the circuit etc.

Thanks for your replies.

Steve

[belgian]

Hi,

The VOX reverb is an entirely different beast, there is nothing you can do to it to make it sound like a fender.

The main difference is the way fender drops the dry signal way down, adds the reverb and reamplifies it again before hitting the power amp. The VOX never reamplifies the mixed signal. The dry goes to one side of the phase inverter, the reverb to the other.

rob

Rob,

The reverb is the only thing I am not complety happy with on my amp (remember the VAC 2X12 shipped to Belgium). What are the suggestions for other tanks ?

[tralfax19645]

Hi Belgian,

I remeber that tweed 2 12,that was a nice looker.

You can replace the 12AT7 with a 5751,thats a nice mod. I would not use a 12AX7, it will feedback too much.

You can use the following reverb tanks, 4ab3c1b,(long 2 spring)9ab2a1b/9ab2c1b (long 3 spring) or 8ab2a1b (short 3 spring). The amp came with a 8ab2a1b.

rob

[BCR Greg]

The 5751 outta do it.

[tralfax19645]

Hi AC 15,

Yes, the reverb circuits are very different between a fender and vox.

the only way I know of to keep the stock VOX sound and get fender reverb is to use the stand alone fender reverb unit. The fender amplifies the mixed signal and VOX does not. thats the biggest difference, (there are other too )

rob

[belgian]

Hi Belgian,

I remeber that tweed 2 12,that was a nice looker.

You can replace the 12AT7 with a 5751,thats a nice mod. I would not use a 12AX7, it will feedback too much.

You can use the following reverb tanks, 4ab3c1b,(long 2 spring)9ab2a1b/9ab2c1b (long 3 spring) or 8ab2a1b (short 3 spring). The amp came with a 8ab2a1b.

rob

What will be the effect of a replacement with the 5751 ? And is it just a simple tube swap or does it needs another socket or adjustments too ?

[ac15]

Rob,

Looks like the reverb tank would be the answer then. Maybe that's best because I can use it with my other "non-reverb" amps as well. Thanks.

Steve