Spring Reverb - electronics question..

grappagreen

Hi all,

Posting this in the amp forum as it's more a question around design than FX per se..

I've searched for a long time for a spring reverb pedal/unit that gives me the sound I have in my head. Lush, diffuse, warm etc.. Having been through loads of digital pedals I gave up on these and ended up buying a Carl Martin Headroom.Ultimately I'm dissatisfied with this as it's cold, harsh and somewhat metallic..

Having done some more research it seems to me that the spring tank is one of the most significant contributors to the quality of the verb and that the fact that the Martin has a very short, 2 spring tank is perhaps the reason I don't like the sound.

Is it possible to disconnect this and plumb it into another external tank? I'm totally comfortable with the mechanical/electrical work in actually doing this but I have no idea about electronic design.. looking at Accutronics tanks they have various tanks but with differing input/output impedance and I can't see the specs for the tank in the Martin (haven't opened it up yet to take a look). 

Just in case it makes any difference I am running the reverb in the loop of a dumbelator type circuit (Ceriatone C-Lator).. If this leads to the desired outcome I would probably envisage taking the Martin circuit out, popping it into a smaller format enclosure and mounting this and the tank in the rack holding my C-Lator..

Appreciate any insights..

Regards,

Simon

ICBM

If you can find the spec of the tank then there’s no reason a larger one of similar spec won’t work. The chances are it’s probably fairly standard, but as you’ve already found there is quite a lot of variation. It also might not sound quite how you expect if the circuit is tuned for the small unit.

Or just buy a Boss FRV-1 before the prices get truly ridiculous... they really do sound almost identical to an original Fender 6G15 reverb unit.

grappagreen

Thanks @ICBM ;

FRV-1 now purchased!  

There are few things worse than an itch you can't scratch! Hopefully this will get me to where I want to be..

Si

musteatbrain

I have a Fender 6G15 unit.
there’s lots of good pedals these days, the only thing they don’t do as well is respond to picking dynamics, although lots of them do have algorithms to mimic that element.

As yet, none of the pedals I have tried react the same when you hit the strings harder. 
I think the FRV-1 sounds great too though.
It’s certainly a lot more convenient and less fragile!

grappagreen

musteatbrain said:

I have a Fender 6G15 unit.
there’s lots of good pedals these days, the only thing they don’t do as well is respond to picking dynamics, although lots of them do have algorithms to mimic that element.

As yet, none of the pedals I have tried react the same when you hit the strings harder. 
I think the FRV-1 sounds great too though.
It’s certainly a lot more convenient and less fragile!

I get the feeling at some point I will just have to bite the bullet and grab the real thing..

To be honest my experience with pedals has been disappointing - not sure why but nothing I've tried with a spring emu seems to hit the mark. As for the CM again I was left wanting again..

I'm hoping the FRV-1 will fill the void for a while and offers some convenience into the bargain.. 

Si

kizzer

Try a SurfyBear pedal or you can build one like I did here.

grappagreen

kizzer said:

Try a SurfyBear pedal or you can build one like I did here.

@kizzer - Thanks. I'll check this out!

ICBM

grappagreen said:

I get the feeling at some point I will just have to bite the bullet and grab the real thing..

The Fender reissue one isn't at all bad - provided you go to the trouble of getting a real 6K6 valve, which the originals used. These aren't available new now, so Fender substituted a 6V6, which is the nearest currently-produced equivalent - but doesn't bias the same, so the result is that the reverb sounds thin and trashy. Oddly, they didn't alter the circuit (one resistor change is all it would need) to compensate, but that does at least mean that if you simply replace the valve, you then have the correct original circuit and sound. The 6K6 is not ridiculously rare or expensive yet.

And remember to undo the shipping lock! A friend of mine bought one and thought it wasn't working properly until I showed him that .

grappagreen

ICBM said:

grappagreen said:

I get the feeling at some point I will just have to bite the bullet and grab the real thing..

The Fender reissue one isn't at all bad - provided you go to the trouble of getting a real 6K6 valve, which the originals used. These aren't available new now, so Fender substituted a 6V6, which is the nearest currently-produced equivalent - but doesn't bias the same, so the result is that the reverb sounds thin and trashy. Oddly, they didn't alter the circuit (one resistor change is all it would need) to compensate, but that does at least mean that if you simply replace the valve, you then have the correct original circuit and sound. The 6K6 is not ridiculously rare or expensive yet.

And remember to undo the shipping lock! A friend of mine bought one and thought it wasn't working properly until I showed him that .

Thanks @ICBM ;

Gonna take a look now..

Si

musteatbrain

grappagreen said:

I get the feeling at some point I will just have to bite the bullet and grab the real thing..

Si

That’s the process I went through. Mine’s an early 90s reissue.
They are expensive, but if you have an old amp with great cleans they go together really well.

oh, and don’t forget about the shipping lock or you will look like an idiot in front of an amp tech like I did.

grappagreen

musteatbrain said:

oh, and don’t forget about the shipping lock or you will look like an idiot in front of an amp tech like I did.

I'm seeing a trend here...

@ICBM - is the 6K6 a straight swap? You don't have to mess with the BIAS etc?

Thanks,

Si

ICBM

grappagreen said:

@ICBM - is the 6K6 a straight swap? You don't have to mess with the BIAS etc?

Yes, that's the whole point - the circuit is the exact same as the original, which was designed for a 6K6. Fender didn't modify it to take the 6V6, so the bias is then wrong - too cold, so the sound is thin and harsh. Simply replace the 6V6 with a 6K6 and it's good to go.

grappagreen

ICBM said:

grappagreen said:

@ICBM - is the 6K6 a straight swap? You don't have to mess with the BIAS etc?

Yes, that's the whole point - the circuit is the exact same as the original, which was designed for a 6K6. Fender didn't modify it to take the 6V6, so the bias is then wrong - too cold, so the sound is thin and harsh. Simply replace the 6V6 with a 6K6 and it's good to go.

Got it! Thanks...

ecc83

Some years ago when son was home playing and recording I thought of getting a stand alone spring reverb unit. Until I saw the price! I then looked at tanks, not too bad, and I then roughed out a drive/recovery circuit. 

Would have used valve drive back then but now I would go for an 8 Ohm tank send transducer and drive it with a TDA3050 or similar IC amp. Recovery would be the ubiquitous NE5532 or maybe pus the boat out for the even lower noise LM4562.

Nice little project now winter is acoming in?

Dave.

thermionic

Take the transducers out of the tank and rig up a couple of Slinkys stretched across the room. Cavernous!

grappagreen

kizzer said:

Try a SurfyBear pedal or you can build one like I did here.

@kizzer - Thanks. I'll check this out!

Funkfingers

musteatbrain said:

none of the pedals I have tried reacts the same when you hit the strings harder. 

I'll wager that none of the pedals you tried had valves in it.

Gassage

Just buy a Twin or a Deluxe and be done with it!

musteatbrain

Funkfingers said:

musteatbrain said:

none of the pedals I have tried reacts the same when you hit the strings harder. 

I'll wager that none of the pedals you tried had valves in it.

Correctomundo @ ;
What witchcraft is this of which you speak?

jpfamps

ecc83 said:

Some years ago when son was home playing and recording I thought of getting a stand alone spring reverb unit. Until I saw the price! I then looked at tanks, not too bad, and I then roughed out a drive/recovery circuit. 

Would have used valve drive back then but now I would go for an 8 Ohm tank send transducer and drive it with a TDA3050 or similar IC amp. Recovery would be the ubiquitous NE5532 or maybe pus the boat out for the even lower noise LM4562.

Nice little project now winter is acoming in?

Dave.

You don't want to drive the tank with a voltage source, ie the TDA3050; this is because the input transducer of the tank is (almost) a pure inductance so you will be have a low pass filter. 

Reverb tanks should be driven, ideally, from a current source.

You could configure a TDA3050 for constant current operation (although this is not recommended with these chips), but this would be overkill. A couple of cheap BJTs would be all that's required to drive a medium impedance tank.

There are plenty of circuits on the web for this. An excellent article on this can be found here:

http://sound.whsites.net/project34.htm

re the recovery amp, an NE5534 is likely to be lowest noise of the usual suspects, however as the output impedance of the tank rises with frequency and is not insignificant, you can't discount current noise, so the LM4562 may in fact be noisier than an NE5532/4. 

Another option would be a low noise discrete JFET (very low current noise) combined with an op-amp in a hybrid configuration.

Oddly I am in the process of prototyping something like this at the moment, but for another application.

grappagreen

Received the FRV-1 tonight.. closest I’ve got to the ‘sound’ I’ve been looking for so thanks @ICBM ;

Time to hunt for a real one now methinks..

Si