Gaussmarkov spring reverb build

[MKD]

Hey all,

Planning on building this reverb http://gaussmarkov.net/wordpress/circuits/spring-reverb/

And wondering if i can sub out the specified 8ab2a1b accutonics/mod reverb tank for one of the accutonics blue reverb tanks??

Original tank - https://www.amplifiedparts.com/products/reverb-tank-mod-8ab2a1b
New tank - https://www.amplifiedparts.com/products/reverb-tank-accutronics-amc-2bf2

Input/output impendence on the original is 10ohms/2575ohms, the blue reverb is 150ohms/1500ohms

reason is purely down to size of the tank. Id like to put it into a pedal and it not be as huge as the van amps one (large version..)

So....can i use the blue reverb tank, or what do i need to do to the circuit to make it so i can use the blue reverb tank...


Thanks!!

[Strategy]

Accutronics make all their tanks (including those little blue ones) in a variety of impedances, so you could actually order a single one direct here if it's something that a place like Amplifiedparts doesn't stock:

http://www.accutronicsreverb.com/

This page also contains the table which explains the part codes, which indicate enclosure type, input impedance, output impedance, and several other aspects of the spec. So you can use that table to figure out the part code for what you want!

[MKD]

So you can do custom tanks from accutronics? The values listed are the ones they have for each tank. Id rather keep it cheaper than custom tank runs etc...

Is there a way to raise the corcuits required impedence to 150ohm and output dropped to 1500 ohm? How do i go about doing that?

[antonis]

<Is there a way to raise the corcuits required impedence to 150ohm and output dropped to 1500 ohm?>

On which circuits points are you refered on..??

[reddesert]

The schematic for the original project at http://www.solorb.com/elect/musiccirc/reverb2/ uses a small transformer in front of the reverb tank for impedance matching. This transformer presents a moderate impedance to the circuit driving it, and transforms that to the very low impedance to drive the reverb tank's input. The original schematic suggests a 500 ohm/8 ohm transformer; the 8 ohm secondary is close enough to the 10 ohm input impedance of the reverb tank.

I don't know why gaussmarkov's schematic has a 42TM018 transformer, which is 10K to 10K. Perhaps he meant a 42TM013, which is 1K to 8 ohms. (Someone suggests this change in the comments on his webpage.)

To drive your tank input of 150 ohms, you would need a transformer that has a moderate impedance primary to be driven by the op-amp (probably not critical, but somewhere around 500-1K ohms or more), and a secondary that matches the input of the tank, so roughly 150 ohms.

The difference in output impedances is probably less critical since those go into a tone stack and recovery amplifier right away.

[MKD]

Thanks reddesert, thats more what im after.

The only transformer i can find locally is the 1k-8ohm so ill look for one with the specs you mention.

Awesome. Thanks!

[MKD]

Again, hard to find one locally with those specs, any idea where to find a suitable transformer?

[MKD]

Or failing that, can i use resistors to increase the input impedence on the 1k 8ohm transformer output to make it 150ohm, and then use resistors after the tank output to raise the output impedence to suit the original tank specs?

Effectively making the blue reverb tank the same impedence as the original large accutronics one.
What are the dissadvantages in doing this?

[idiot savant]

I recommend reading Rod Elliott's excellent reverb article:

http://sound.whsites.net/articles/reverb.htm

For a 150R input tank, you really don't need to mess with transformers at all. You should be able to drive it directly with a suitable circuit.

[printer2]

First off, you say you want to make a pedal unit, I take that as keeping it on the floor. I would be hesitant in using a spring reverb on the floor as it will pick up, well floor noise. At 150 ohms you could probably drive it directly from a pair of opamps depending on the supply voltage.

[MKD]

Interstng article and very informative.

But im not going to redesign the circuit, just after a transformer option or resistor option to use a different tank....

Point taken about floor noise etc etc, spaceman orion / van amps reverb is what im going for. Proper isolation and suspension of the tank seems to work well for the orion.

Back to the resistor option though...the tank would recieve 8ohms from transformer + (resistor load) to equal 150 ohm specified input for the blue reverb tank. Tank output of 1500 ohm + ( resistor load) to equal the specified output load of the original tank which would mean the same load going back into the circuit...

So effectively between the transformer output and the post-tank input to the circuit would be the same resistance as the original tank, and the blue reverb would be fed the correct resistance...

Does that make sense? Logically it seems it would work?

[reddesert]

Putting a resistor in series with the tank isn't likely to do anything that you want.

A transformer turns a source of some voltage and current into a different pair of voltage and current (like a 10:1 transformer that takes 120 V wall voltage, drawing a small current, and outputs 12 VAC with about 10x as much current). Rod Elliott's article describes the voltage and current demands of the reverb tank in more detail than I knew. If you use a different transformer and put a resistor in series with it, you'll just limit the current that can be delivered to the tank, dissipating most of the driving power in the resistor.

[Ben N]

What a seasonally appropriate project.

(My kids: "Daaaad, you didn't.")