The science of reverb springs

[Mark Amundson]

Most spring reverbs have input transducer impedances from 8 to over 30 ohms.
For solid state applications, generally a bipolar op-amp will drive the
spring if the input transducer is placed across the output and the inverting
input, much like a normal feedback resistor. In fact you should have another
feedback resistor across the spring anyways so that an open connection does
not rail out the the op-amp.

In most applications, the spring reverb drive and recovery circuits have a
fairly narrow (mid-range) audio pass-band as you do not the lows booming and
the highs sizzling. Also, the recovery circuit has to deal with the clanging
springs that occasionally happens (gun fire sounds).

This topic has been discussed extensively on the AMPAGE amp chatroom
recently for a tube driven circuit for the latest DIY guitar amp project
(for the AX84 website).

Mark Amundson,

-----Original Message-----
From: Rob & Heather Williams <will7370 at tao.sou.edu>
To: Synth Do-It-Yourselfers <synth-diy at mailhost.bpa.nl>
Date: Sunday, February 21, 1999 5:55 PM
Subject: The science of reverb springs


>Hi folks,
>
>Does anyone know if the impedance is the same for all reverb
>springs?  I've played around with them on the bench and I
>guess you cannot insert a signal into them without
>pre-amping it up fairly high, then when it comes out the
>other side it is ready for amplification again.  So I
>imagine it drops quite a bit going through the spring.
>
>Other than that, does anyone know of any information on the
>internet which discusses the science of reverb springs and
>what actually happens to create the reverb effect?
>
>Robert