Stage Centre Reverb tank impedance

[jrc4558]

Hey everybody! I would like to ask you, what would be an acceptable impedance for the reveb tank transducers to use it with Craig Anderton's Stage Centre reverb?
I've got a tank that I pulled out of old Traynor PA, input and output both measure just under 200 ohms. The unit (when I use that tank) sounds distorted and muddy, far from beautiful sparkling reverb. So before I go and spend money on recommended accutronics model, is there any way to adjust the cirquit to use with what I've got?
Thank you.

[brett]

Hi.
I built a centre stage a couple of years ago.
From memory, it uses an LM386, so it should drive anything (at least down to about 4 ohms).
Maybe you could try tapping the signal being sent to the tank, to ensure that the circuit is working ok ??
Are the springs in the tank properly supported and clean?
I guess that there's quite a few mechanical things that could be wrong with the tank.

good luck with it

[Aharon]

Hey everybody! I would like to ask you, what would be an acceptable impedance for the reveb tank transducers to use it with Craig Anderton's Stage Centre reverb?
I've got a tank that I pulled out of old Traynor PA, input and output both measure just under 200 ohms. The unit (when I use that tank) sounds distorted and muddy, far from beautiful sparkling reverb. So before I go and spend money on recommended accutronics model, is there any way to adjust the cirquit to use with what I've got?
Thank you.

Hi Constantin.
I used a 250 ohms model from an organ and it worked fine.You probably have to tweak the gain resistros in the Op's gain loop.I did.It's all explained in the notes.
Good luck
Aharon

[jrc4558]

Would buffering the input and output of the tank help? Just thinking out loud here.

[Aharon]

According to you it sounds distorted and muddy,you might be overdriving the tank.Tweak the gain and see,I think I lowered R7 to something like 220K.I have to go and check the notes I made (if i find them)
Aharon

[jrc4558]

Thanx, guys. After this thursday's midterm I'll try it.

[Mark Hammer]

Hi you two.  This would appear to be a largely Ontarian thread. :lol:

If you are considering use of a 386 to drive the low impedance load of the reverb tank, consider using the gain loop of the 386 reatively.  You are well aware that the gain is set by means of a resistor/cap comb in the feedback/compensation loop of the 386.  It can also be used to shape how the gain is distributed.  Normally, folks here tend to use a 10uf cap (as shown in the 386 appnotes) for full-bandwidth boost.  However, if you use smaller cap values, it can be configured as a sort of treble booster.  I suspect that parallel resistor/cap combos can also be used for some tonal shaping.

Not my idea.  I got it from a project article in Nuts and Volts a year ago (maybe 2) involving a 386-based "TV-booster" for hearing impaired seniors who wanted to be able to stick a speaker beside them on the Lazy-Boy and hear the top end a little more clearly when watching shows where they tend to mumble a lot (which would probably be every version of CSI).  The designer/author used a .05uf cap or something like that, instead of the standard 10uf one.  Clever idea.

Boosting the top end prior to the reverb springs is a great idea IMO.  Note that it can also serve as one half of a precomp-decomp noise-reduction circuit.  Crank the treble going into the springs, and cut back on the high end of the recovered (and bosted hissy) signal.

[Aharon]

Hi MArk!!!.With no NHL I suspect more canadians will resort to geeky hobbies like effect making now. 8^)

Hey Constantin,you can't go wrong with Mark Hammer's advice,we always learn something from him,I may go back and implement some of Marks suggestions.


I found those notes i made when I built the CSR and I lowered R7 to get rid of distortion and also changed R5 to 10K for unity gain output.
Now the value that you settle on largely depends on when you get rid of that distortion,I think i lended up with a 220K .
I wonder if a trimpot would be an advantage...........
That MAY cure the problem.
Aharon