[Phil Allison[_4_]]

Les Cargill wrote:

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There seem to be two common configurations, one with an input
impedance of around 10 ohms that can be driven by the speaker
output of an amplifier, and the other with an input impedance of
around 2.5 k Ohms, which can be driven by practically anything.
They all have a pretty low output impedance so they can drive
anything.


** Not quite true.

The input and output coils of reverb tanks are inductors, so the
impedance rises with frequency right across the audio band. The
numbers quoted in the published data are for 1kHz only PLUS the
normal input power level is less than 10 milliwatts.

The 8ohm input types cannot be driven direct from an audio amp, it
would massively over power them. Output impedance values vary from
a few hundred ohms to a few thousand at 1kHz.

By directly, he means that they use the same power amp that drives
the speakers in order to drive the reverb tank. There _is_ a
resistive attenuator in there.


Most[1] guitar amps have a drop somewhere about the input of the power
amp/PI with a separate driver. Having the power amp itself drive it
would be a feedback loop.


** Exactly, reverb units need an independent drive amp - which is often just an op-amp.

I know of onlyy one guitar amp where speaker signal was tapped off and fed to a reverb tank. However that amp had TWO power channels and the output of the reverb connected to the input of the spare channel.


..... Phil