DIY effects loop with blend (deacy project).

Steenamaroo

Steenamaroo

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Hi all,
I'm just thinking out loud at this stage, but I'm tempted to add one of those little 9" reverb tanks to my deacy amp.
For those who don't know, the deacy consists of this circuit with this treble booster before it, all contained in one cabinet.

I'm thinking the reverb has to go right at the beginning of the path because sometimes I disengage the treble booster.

I've seen plenty of schematics for this kind of thing but they've all been bi-polar psu.
I'd rather build something which operates on 9V DC, as that's the power supply the amp is using.

I'm thinking I can use an lm386 to boost instrument level and drive a reverb tank, but I'd need something to set the output back around instrument level, right?

Also, I'm open to the idea of putting the reverb unit after the main amp if that saves the need for a dedicated drive unit.
I'm not sure how that would sound, though.

I'm a little out of my depth, but with some help it's seems like it might be doable.

To be clear, this'll be a permanent reverb tank install : There wont be any jacks and I wont be using any other effects in this loop.
Any info is much appreciated.
 
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Lots of ways to skin this moggy Steen old chap!

Many, quite well thought of guitar amps drive a reverb tank from a TL072. IMO that IC does not have the OP current capability especially when you consider that tanks used to be driven from a 2watt valve stage!

Half an NE5532 would be better in my view but even better would be an NE and pair of complimentary transistors, as used for headphone outs on many a modest mixer. The other 1/2 of the chip will then make a fine low noise recovery amp.

The LM386 is a great idea and 9V should give you about a watt. I suggested the 5532 for economy but 386 and NE5534, single chip would do fine.

Dave.
 
Dave,
Thanks for the info and for taking the time. That's all encouraging.
I'm confident that I could set up drive and recovery with a bit of googling/tweaking, but I'm less confident about how I'm summing/blending the dry and wet signals.

I've browsed a lot of schemos and some seems very complicated - Others not so much.
 
Probably best to look at the original classic Fender 6G15 ?...
https://www.google.co.uk/search?q=f...ectronics%2Fschemview.php%3Fid%3D837;1080;629

(wow! din't know it would do that!) Anyway, you can see that there is a thru path to a passive mixer for wet and dry at the output. Note that the bottom valve is a cathode follower, presumably to keep the mixed signals in phase.

I reckon that breaks down to a 386 driver and an NE5532 for the recovery and other stage. OR you could just have a summing amp there. The pots can be 10k, NEs will drive 600Ohms. Do you want a footswitch? If so I suggest a J112 FET shorting the tank output. You will need to "breadboard" this! Lots of tweaks needed I bet. Have you thought of "regeneration"? That is feeding some output back, of course, too much and it will take off.

Dave.
 
Ok, that sounds like a plan forming. Thanks again. :)

I don't want a footswitch so that simplifies things slightly, and the fact that it's all before the amp+tb means it's very easy to breadboard and test the thing as I go without causing any problems.

I haven't thought about regeneration.
I figured I need a drive amp, recovery amp, and something to stop feedback along the dry path, right?


EDIT: I've heard of guys using an aux send and returning to a preamp in the studio, in a pinch.
That prompted me to look for basic ne5532 preamp schematics as a starting point.

I'll pick up a tank and try to sort out 386 drive + 5532 recovery, then we'll see what's what. :)
Thanks for your help.
 
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Steenamaroo said:
Ok, that sounds like a plan forming. Thanks again. :)

I don't want a footswitch so that simplifies things slightly, and the fact that it's all before the amp+tb means it's very easy to breadboard and test the thing as I go without causing any problems.

I haven't thought about regeneration.
I figured I need a drive amp, recovery amp, and something to stop feedback along the dry path, right?


EDIT: I've heard of guys using an aux send and returning to a preamp in the studio, in a pinch.
That prompted me to look for basic ne5532 preamp schematics as a starting point.

I'll pick up a tank and try to sort out 386 drive + 5532 recovery, then we'll see what's what. :)
Thanks for your help.
Click to expand...

Regeneration. Well "reverb" tank is a bit of a misnomer. They are really just a very badly damped delay line! In digital delays to get a reverb effect you have feed the output back into the input (same for tape) . Most guitar spring verbs don't bother but it might be worth a dabble?

I see you are UK? Do look at Maplin and the Velleman projects mainly their "ONE Watt amp kit(386) and "Low noise Pre amp" . The resistors will need reducing in the latter to lower the noise but they give you a PCB and all the bits to kick off with.

The pre amp is stereo and uses a TL072 but if you find that too noisy or low in drive a 3352 is a drop in.

Dave.
 
ecc83 said:
Most guitar spring verbs don't bother but it might be worth a dabble?

I see you are UK? Do look at Maplin and the Velleman projects
Click to expand...

Ah, ok. Good to know, and thanks for the tip on the maplin kits.
I'd like to keep it DIY if possible, but at least I know where to look if I'm having difficulties.

I'll post back next week when I've gathered all the bits.

Cheers, Dave!
 
Well I've built a little 386 circuit and a 5532 curcuit on the same board.
386 side works fine. Doesn't have much power, of course, but I don't know what's required yet so I'll leave it alone for now.
The 5532 chip is in the post - I used a socket on the circuit board so I can drop the chip in and test when it arrives.

I'm thinking of using a little speaker and a microphone in place of the verb tank just to test the thing out.
I figure if I can drive a small speaker via 386, point it at a mic (through 5532) and get vaguely close to an instrument level final output, I'm probably along the right lines.
I'll worry about blend after that.

I was thinking, rather than blend between wet and dry, it might be preferable to have both wet and dry full bore and use a pot to ground the reverb signal, probably before the 5532 circuit, I guess.
That means the main amp level never dips. Just a thought.

I've put a bid on a verb tank too, so hopefully I'll have one of those in a few days.

I'll post back soon with my findings and pics.
 
Right! First thing to do when you get that tank is check the continuity of the two transducer coils. The tanks seem to fail O/C on the input side mostly very commonly these days according to a guitaramp tech I know.
The top name of course is Accutronics and they seem to be the worse offenders!

Dave.
 
Popped the 5532 in and the two circuits work.
I have guitar -> 386 -> speaker -> mic -> 5532 -> amp and it's coming in at roughly the same level as guitar -> amp would.
It's noisy as hell but this is a pretty high gain amplifier (the deacy). I guess most of that's coming from unbalanced mic.

If I reverse the thing, ie
mic -> 5532 -> lm386 -> passive speaker
and speak into the mic, it's clean and clear.

Didn't know what to expect but the 5532 circuit drives a headphone at a comfortable listening volume.

So, this is encouraging I suppose. I missed out on that tank so I'll have to look for another one.
Until then.....
 
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