Vox AC15C1 Reverb - seeking improvement

[hrod455]

Hello all, this is my first post.

I have a few old Fender and Fender style amps with fantastic reverb: SFDSR, BFSR, Allen amps.

I bought a Vox AC15C1 a couple years ago, and after sorting out a few cold solder joints, changing
the Greenback out for a Eminence Wizard, and a few tube changes the amp itself sounds great...all except
for the reverb. I've read several posts about swapping the pan which I did with a MOD 8EB2C1B but I'm still not happy with the sound. There is plenty of long hall like reverb, but it is completely undefined. I can only explain it as; it doesn't have enough of the primary 'dry' signal mixed in, it seems like it's all 'wet' signal from a mile away. Typically I don't turn the knob past '3', it becomes completely washy and unuseable.

I know that the Fender's are tube driven and the Vox isn't. People seem to be happy with the Vox Pathfinder 15r's reverb which is also not tube driven. Has anyone made improvements to the ac15's reverb circuit to mirror the 15r? Is this possible?

The Vox is never going to be a Fender reverb, but if there is some way to mix in some more 'dry' than 'wet' signal I think it would be a great improvement.

Thanks in advance,
-hrod

[hrod455]

Sorry, I should have posted this in the guitar amps section. Moderator, please move. Thanks

[Mick Bailey]

Welcome to the forum.

Would you post the schematic?

There are a couple of ways to do this - either reduce the gain of the reverb recovery stage, or to reduce the output level. Both of these are straightforward resistor changes, or replace either resistor with a trim pot. This won't alter the characteristics of the reverb, but you can adjust the point where the reverb gets overly wet, giving more control. So 3 can become 10, for example. Just need your particular schematic so that we're talking about the same component references.

The Pathfinder 15R is different enough to make converting your amp to that circuit difficult, unless you are experienced in such work.

BTW, Plenty of Fender amps have decent solid-state reverb.

[nickb]

What Mick said is quite correct.

The effect of the suggested changes would be to lower the reverb signal. But... this is just same as turning the reverb level down, which from what you said, isn't what you want.

So try this test. Turn the reverb level all the way to zero and you should only hear the dry signal. If that is true then the reverb level pot is working correctly and I can only conclude that it's the tone ( i.e. frequency balance) you don't like, especially as you say it's "undefined'. To me that means there is not enough upper mids and/or treble. There is a 560pF capacitor C21 on the reverb driver, try changing it to 270pF and see if it's more to your liking.

[hrod455]

Thank you for the replies. The reverb pot works as it should. If I turn it to zero or switch it off, it's all dry signal. I bought the amp new in either 2014 or 15. I'll see if the ref des C21 is in the driver circuit and the value is 560pf. Yes, adding more highs will help and I'll try lowering the value of that cap. Thanks!