DIY spring reverb out from an Marshall MS-4

[CaioAllures]

Hello boys and girls, after a sucessfully (and heavy modded hehehe) Green Ringer I'd decided upon making a springy thingie. Following this tutorial I've acquired some of the supplies listed, with the spotlight shining in the tiny Marshall MS-4



As you can see, if not familiarized with this fellow, it has 2 speakers, tone, gain and volume control. It's working like a charm. My goal is to read the guitar signal using the amp, pass it through a spring and coming back to electric signal using a piezo as a transducer. Pretty straightforward, but I want to add some stuff to it, so I could control it a little better:

1 - A mix potentiometer to control how much of the moisture I want to add in the original sound (I know it's related with a LM324, but not sure how to hook it)
2 - A spring in each speaker, meaning that I want to choose which one is on, with two kind of verbs at once, just one or the another. (sounds quite simple to me)
3 - Using a footswitch as the mix controller to make it snazzy and cool (this one is for the looks)

So, any tips from where to start?

Thanks in advance people!

[CaioAllures]

Idk if this allowed, but...

UP, no one can help me? I just need some simple solutions

[thomasha]

You will need another amp for the piezo, a lm386 will work.

I never tried it with a tl072, but I think you could just make two buffers, and mix the signal before them as in the rebote delay?

Or better, take the rebote delay schematic, remove the PT2399 and add the in and out. The 10k resistors would be the mix pot.

Using strings separately you will need to use different piezos, maybe only one lm386, and the switch between the piezo and the lm386.

Well, I never tried this, but sounds interesting.

Cheers,
Thomas

[CaioAllures]

You will need another amp for the piezo, a lm386 will work.

I never tried it with a tl072, but I think you could just make two buffers, and mix the signal before them as in the rebote delay?

Or better, take the rebote delay schematic, remove the PT2399 and add the in and out. The 10k resistors would be the mix pot.

Using strings separately you will need to use different piezos, maybe only one lm386, and the switch between the piezo and the lm386.

Well, I never tried this, but sounds interesting.

Cheers,
Thomas

Hey man, thanks for your answer! I don't want to write a lot but I'm kinda slow at it.

You suggested to 'take out the  PT2399 and add the in and out.' Then make it with some other op-amp?

Also could one use a 3-way lever after the piezo and before the chip, acting just like a pickup selector, but for the springs? Again, the two springs is a fancypants add-on, I was just planning to take advantage from the 2 buzzers that come with the Marshall unit. Thanks again!

[thomasha]

Hi,
the PT2399 is the delay chip, if you look to the schematic after the first opamp there is signal going direct to the second through a 24k resistor, and part of the signal to the PT2399 pin 15 and 16. When you remove the PT where pin 15 would be will be the input to the ms-4, and where the circuit returns to the second opamp would be the lm386 (after the springs);

This way the ms-4 and the lm386 will work like the wet side, while the resistor between opamps will be the dry side.
The mix control goes there also.

The 3 way switch thing will work, but is there an all on switch? like in the center position both sides are on, so you could switch between right, left, both.

I tried something like this with 2 piezos, lm386 to piezo - spring- piezo to lm386 but there was too much noise. the spring was an electric shower resistance...but it worked. Something you probably will see is that two strings are better than one, the reverb is more complex.

One thing I remember now, if you can find a better replacement for the lm386(lower noise) it would also be better. And maybe try a "preamp" between the piezo and the lm386
Cheers,
Thomas

[PRR]

Study ALL the reverb circuits you can find.

There is usually an input buffer, a reverb driver, the delay-line (springs, tubes, bits), a recovery amp (spring output is 1/1000th of what you put in), then a mixer to blend the dry and wet paths.

There are many differences in details. But they nearly all follow this overall plan. Study and steal.

BTW, guitar spring reverb is usually equivalent to *TWO* guitar amps. You have to get up from teeny guitar signal to a pretty large drive for the spring, nearly a whole low-power amp. Then the output from the spring is no larger than a guitar (maybe weaker) so you need another whole preamp and some kind of output stage, ultimately speaker-size.

[thomasha]

Found some ideias:

http://www.oberlin.edu/staff/thinders/reverb/reverb.html

http://www.diystompboxes.com/smfforum/index.php?topic=87780.0

http://www.diystompboxes.com/smfforum/index.php?topic=98139.0

http://www.instructables.com/id/DIY-Spring-Reverb/?ALLSTEPS

Cheers

[CaioAllures]

Hi,
the PT2399 is the delay chip, if you look to the schematic after the first opamp there is signal going direct to the second through a 24k resistor, and part of the signal to the PT2399 pin 15 and 16. When you remove the PT where pin 15 would be will be the input to the ms-4, and where the circuit returns to the second opamp would be the lm386 (after the springs);

This way the ms-4 and the lm386 will work like the wet side, while the resistor between opamps will be the dry side.
The mix control goes there also.

The 3 way switch thing will work, but is there an all on switch? like in the center position both sides are on, so you could switch between right, left, both.

I tried something like this with 2 piezos, lm386 to piezo - spring- piezo to lm386 but there was too much noise. the spring was an electric shower resistance...but it worked. Something you probably will see is that two strings are better than one, the reverb is more complex.

One thing I remember now, if you can find a better replacement for the lm386(lower noise) it would also be better. And maybe try a "preamp" between the piezo and the lm386
Cheers,
Thomas

Amazing, thanks a bunch!

Found some ideias:

http://www.oberlin.edu/staff/thinders/reverb/reverb.html

http://www.diystompboxes.com/smfforum/index.php?topic=87780.0

http://www.diystompboxes.com/smfforum/index.php?topic=98139.0

http://www.instructables.com/id/DIY-Spring-Reverb/?ALLSTEPS

Cheers

Study ALL the reverb circuits you can find.

There is usually an input buffer, a reverb driver, the delay-line (springs, tubes, bits), a recovery amp (spring output is 1/1000th of what you put in), then a mixer to blend the dry and wet paths.

There are many differences in details. But they nearly all follow this overall plan. Study and steal.

BTW, guitar spring reverb is usually equivalent to *TWO* guitar amps. You have to get up from teeny guitar signal to a pretty large drive for the spring, nearly a whole low-power amp. Then the output from the spring is no larger than a guitar (maybe weaker) so you need another whole preamp and some kind of output stage, ultimately speaker-size.

Woohoo gonna study a lot![ Ty guys@!

[CaioAllures]

Found some ideias:
SNIP
http://www.instructables.com/id/DIY-Spring-Reverb/?ALLSTEPS

Cheers

This instructable states that his spring out hasn't an amp hooked because he is using a line level signal. Guitar signal would be a mess up, even if driven for a proper guitar amp? Bear in mind that it's going to be modular attached into a monochord with pickup signal... I guess I was all hopeful and wrong hehehe.

http://www.diystompboxes.com/smfforum/index.php?topic=93871.msg808506#msg808506
might as well try this one, seems quite doable.

Thanks everyone

[thomasha]

I had to try it (again)

my build is basically what I said before:
Rebote delay input buffer->lm386 with bass boost->piezo->shower spring->piezo->lm386->rebote output buffer with mixer

the potentiometer mixes the clean and wet signal.

Still need to adjust the sound, it sounds too trebbly and not as loud as I wanted.
Maybe changing the first piezo for a small speaker, but my box has only 33 mm width.

Another issue is with the spring. As it's too short the reverb is fast, as a delay with a low time setting.

Thomas