Spring reverb carvin sx-100 guitar amp

Thread Starter

Adam Monarch

Joined Mar 17, 2019
59
I was doing some potentiometor contact cleaning. And I removed and reconnected the spring reverb.
The were sme rubber washers that were hardened and were falling apart.

I removed the rubber washers and applied a little bit of glue on each side of the spring reverb 90 degrees to the screws on the opposing sides.
I did this so I can remove the spring reverb if I had to. I also used some opposing friction to the head of the screws so they would not move.

My question is, is the chassis of the spring reverb suppose to be grounded to the inner and outer of the main chassis of the amp. I am using a continuity meter to check the connections. So far the spring reverb is connected to the inner chasis of the amp and the outer chassis of the amp is not connected to anything.

I think I connected everything correctly but I just want some feedback to double check my solution.
 

billnow

Joined Aug 4, 2010
18
I believe that the purpose of the rubber washers is to mechanically isolate the reverb tank from the vibrations caused by the speaker. The reverb tanks I'm familiar with are connected to ground via the input or output connectors of the tank.
 

Wolframore

Joined Jan 21, 2019
2,317
Basic operation of spring or plate reverb is transducer on one end and a pickup/microphone on the other end. This signal is mixed with audio to add the reverb sounds from the mechanical device. The spring and plate is suspended from the chassis and requires mechanical isolation. The lack of mechanical isolation could induce resonance and feedback at higher levels. Since the spring or plate is not part of the circuit no electrical isolation is required.
 

KL7AJ

Joined Nov 4, 2008
2,229
Basic operation of spring or plate reverb is transducer on one end and a pickup/microphone on the other end. This signal is mixed with audio to add the reverb sounds from the mechanical device. The spring and plate is suspended from the chassis and requires mechanical isolation. The lack of mechanical isolation could induce resonance and feedback at higher levels. Since the spring or plate is not part of the circuit no electrical isolation is required.
It shouldn't matter if the frame is electrically grounded to the chassis...but it probably wouldn't hurt. The rubber grommets ARE sort of important, however. They should be replaced with equivalent or even "mushier" ones.
 

MisterBill2

Joined Jan 23, 2018
8,990
If you find that there is hum in the reverb channel then possibly the frame should be connected to the chassis. If not, then there is no need. Most reverb spring assemblies were fairly low impedance devices and so hum was usually not a problem. But vibration pickup was a problem on many occasions. Mounting the reverb springs on foam sponges might be a handy way to go.
 

MisterBill2

Joined Jan 23, 2018
8,990
Probably the most effective way to mechanicaly isolate the reverb spring assembly would be wit a spring suspension. Low spring-rate extension springs with a bit of silicone sealer applied to provide damping. McMaster-Carr would have the springs but other places would be cheaper.
 
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