Synth Spring Reverb circuit

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tardishead

Well-known member
Joined
Aug 11, 2004
Messages
623
Anyone out there familiar with the wireless world synth reverb schematic. I built this with a spring tank I found and it does work but I think I have a slightly different input inpedance on my tank which results not enough gain. The output is fine and loud as can be heard when tapping the tank. Basically I need more gain into the tank.

how do I get more gain out of TR3 and TR4?

schematic can be found at

any help greatly appreciated

Mike
http://www.physicsenterprises.andrews.edu/diy_archive/schematics/synths/index.html
 
normal_MMreverb.gif

here's the schemo.

looks like trimmer r6 could be adjusted for more gain?
not sure if thats gain or bias set. need someone more expert than me to tell you for sure.
r10 should be matched to the reverb tank impedence.
maybe the feedback r15 could be changed for more gain.
Kelly
 
Hello Kelly,
The signal to noise ratio is pretty high on that schematic. Any chance of sending me a larger one? When i try to print this one it comes out pixalized.
TIA,
Nek


Sleeper said:
normal_MMreverb.gif

here's the schemo.

looks like trimmer r6 could be adjusted for more gain?
not sure if thats gain or bias set. need someone more expert than me to tell you for sure.
r10 should be matched to the reverb tank impedence.
maybe the feedback r15 could be changed for more gain.
Kelly
 
> trimmer r6 could be adjusted for more gain?

No.... R6 sets the idle current in TR3 TR4, and turning it all the way will probably smoke them.

It's not a "slight impedance" issue.

The driver is unity gain. No easy change. Unity gain into the spring needs a BIG signal into the driver. From more normal signals we use gains of 5 to 50.

Mike: you already built this? Arg. There are better plans around.

Here's the simplest fix. Yank the first transistor. Cobble a sub-board with an opamp and two resistors. It will need to connect to +15V , -15V, ground, TR1 Base-hole, TR1 Emitter-hole, to-spring resistor. Start with new "R2" as 5K (4K7, 6K8, whatever). When wired right, the wire to the spring will be zero V DC (+/-50mV). It should now be many times louder. If you need more, take "R2" higher.
 

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