Spring Reverb Options

[Rigormortis]

In my Traynor YCV20WR, I have an Accutronics reverb. My only problem with the reverb is that it adds a very high frequency, almost a tinny ringing echo. If the reverb knob is all the way down, that sound isn't there. I'm trying to get away from tinny sounds with my Strat.

Other reviewers of this amp almost universally mention the reverb is too harsh. Some can't describe what's wrong, but just say don't turn the reverb up or you'll be sorry.

I was wondering about adding a capacitor and maybe a tone pot to put some of those higher frequencies to ground. I was thinking of placing it in the wire going to the tank, and mounting it inside the open back, somewhere out of the way. I also have a push/pull 500k pot that might be able to replace the main reverb control, adding a tone control.

Would this be worth doing? I guess I could solder one in pretty fast and see. But could these wires actually carry significant currant? I haven't tested them yet to see, and if so, this tone pot idea could be a bad one.

The other idea I had was to get a different kind of reverb that sounds better, or modify the actual springs in this one--like spray painting them or something.

[52 Bill]

I'm not at all familiar with the design of your amp, but what you propose is possible.

Most amp designers limit the frequencies that are sent into the tank to intentionally give the reverb a specific tonal response. Some players think that built-in Fender reverbs are too bright and will switch the 500pf input cap with a larger value to give the reverb a fuller tone.

If you clip in a small value cap from hot to ground across the reverb return wire, you can roll off some of the high frequencies coming from the tank. This may or may not be what you are looking for, but it will not hurt anything to try it. If you find a value that you like, then adding a pot in series with the cap will give you a reverb tone control.

I would stay away from adding anything to the tank input as the driver chip will probably not like the added capacitance.

[Rigormortis]

OK. I've got caps of different values I can put in the return line.

I still haven't checked those wires to see what kind of power flows through.

[Enzo]

No power involved, the pan out is just a tiny signal not much different from a guitar signal. I would not try rolling off the input.

The reverb drive typically has a small input cap since bottom end in a reverb makes lots of mud and little nice tone. You can add a little more bottom, but you don't want a lot. If the return is too tinny, you can roll off some highs, but I wouldn't prefer to do it right at the pan signal.

I might add some rolloff parts to the reverb level control itself. I would not want to add a rolloff cap right to the pan out because it may add noise. Let the recovery stage amplify the pan signal and THEN roll off the highs or otherwise massage the tone.

Look, the same Accutronics pans sound just fine elsewhere, so it is not the pan that sounds bad. Your return circuit is just too shrill for you.

[Rigormortis]

I've wondered about that Accutronics and why so many of the reviews of this amp have noticed the same thing--the tinny sound of the reverb. It's like playing inside a tin building if you turn the reverb up past 5.

I can also hear hints that high pitched sound at lower reverb levels. It's closest to the kind of squeal you get if you unplug and turn the gain way up and volume way up--the pitch that makes dogs sit up and take notice.

So what can I do to make the return circuit less shrill? Would adding a cap to the main reverb pot do it? Or maybe there's already one there.

[Enzo]

Find the schematic for the thing and start looking. Recovery stages are all fairly similar anyway, a typical voltage amp stage feeding a level control with its output. DEpending on what you want to do, think of how you would make a gain stage less shrill in the amp itself. You can add bottom to make the overall balance less shrill, but iof it has a shrill overtone, then it might sound shrill with more bottom. SO then rolling off the top might be the ticket.

You can add some bypass cap around the plate resistor, you can add RC to ground from the signal path, for example as suggested right at the reverb control. Add a cap and resistor in series across that pot. Make the resistor variable and you have th eclassic tone knob from a guitar. You can also slap a cap all by itself acros the signal path to ground. Experiment with values.

[Rigormortis]

I'll open it and take a peek.

It's a 2005 Traynor YCV20WR.

What cap and resistor values are normal in that position? Would it be a lot like the values for a guitar?

[Mark Black]

The service manual with schematic is available on the Traynor site (I love that about those guys).

Looks like reverb recovery is via a TL072 Op Amp (U2). You might try some larger values for C34 (shown as 100p/100V) in the negative feedback portion of the circuit.

Good luck!

[Enzo]

Oh I was thinking it was tube, sorry, same strategies apply though.

[Rigormortis]

OK. Thanks.

Today, I figured out a little more about the high pitched tinny sound coming from the reverb. I can turn the reverb up past 5 and turn the main volume and gain up past 5 and get the reverb to feedback that sound without any guitar cable input. That's not good.

[Rigormortis]

OK. I found the cap. C34. (Here's the address for the schematic: http://www.traynoramps.com/downloads...an/smycv20.pdf.)

There are lots of caps in that reverb circuit, and resistors. I guess that's the likely one in the recovery stage.

In your experience, do spring reverbs have that kind of feedback? And would toning down the highs likely fix it?

[Rigormortis]

I just noticed some of the changes they made in subsequent versions. (Mine is apparently 2003, version 2.0 or maybe 3.0--I'll have to look at the resistor changes for 3.0 and see if I have them.) I definitely don't have the speaker and headphone out options--just the FX loop.

I see they changed C35 cap value upward. It's positioned near to C34.Do you see any other changes they made that might be relevant to the reverb?

[Steve Conner]

Well, spring reverbs can feed back under some circumstances. Fender put the reverb tank inside a kind of vinyl sack on their combo amps, and that seems to help damp the vibrations that cause feedback. Also, the actual spring line dangles inside the case on other springs, to help keep vibrations out. If the tank is mounted the wrong way up, or the amp is tilted a lot or set on its side, it can bottom out on the case and negate the effect of the springs. (BTW, that's why an amp with spring reverb goes Spanggggggg! when you kick it.)

The Accutronics type 4 reverb tanks are their best models. They are supposed to be the biggest, fullest sounding spring reverb you can get, so it shouldn't really sound tinny or trashy. I bought one a while back for a homebuilt project that I just finished, and when I heard it for the first time, it was deep and ghostly like a cathedral, not trashy or surfy at all. I bought one of those vinyl bags too, and had no problems with feedback.

C59 will be adding a lot of treble boost to the reverb return at lower knob settings, so you could try removing this capacitor to mellow it out. If you're feeling really brave, you could also remove D5 and D6 to increase the reverb drive level and remove trashy clipping from it, at the slight risk of burning out Q9 and Q10, trashing U2 and generally voiding your warranty even more.

If that doesn't work, I'd blame those silicooties infesting the thing, and chalk it up as another excuse to buy a better amp...

[Rigormortis]

Steve, you're too funny!

I might take out that C59. Just remove it? Or can I put in a cap of a different value? I can't gt my head around what it's doing--should it go lower or higher to make less treble?

I imagine the warranty is long gone anyway. This is probably a 2003, a version 2 or 3--which makes me wonder whether I should try to do some of the revisions they recorded for later versions, particularly the changes to the reverb circuit. For example, C35 and R88.

[52 Bill]

C59 is a treble bypass cap or shunt cap. High frequencies pass thru the cap, around the resistance of the pot, allowing for a boost in treble response at any intermediate settings of the pot. At either end of the pot rotation, the cap has no effect.

It basically acts just like the cap that Fender used for the bright switch on their amps. You can remove it completely or adjust the value (smaller values allow less boost). If you remove it and then the reverb is too dark sounding, then try a 220pf cap.

As for upgrading to the newest circuit version, it may be more trouble than it's worth, but if there are specific reverb circuit changes, try them and see if they address your problems with the sound. Later, you can always go back in and modify the circuit to taste. Do you know anyone with the newer version? Does the new version reverb sound better?