The Kool-Verb

This is a simple but nice sounding reverb based on the FV-1 dsp chip. Lots of low pass filtering gives a nice washy sound. You can adjust from a small room to a large hall.  The unit provides about a 75/25(dry) max reverb. Anything more than that is useless. Check out the stomp amp demo for how it sounds…same reverb, but just with just one fixed room setting.

The switch mode power supply keeps the current down to 30mA so you can use a battery if desired. You can use a linear regulator and it will work great, but then the current consumption doubles.

The schematic:


built into a 1590b case:

kool verb



2 thoughts on “The Kool-Verb

  1. Hello Ray. Why do you use inverted op-amp in the end? it should make a inverted phase signal for output, or not? I think we should have same phase on input and output. What do you think about it too? Thank you.

    • The output being inverted is not an issue unless….you are going to combine two independent signal chains one of which is non inverted. I never do this so it does not concern me. The rationale behind this configuration choice is that I can scale the dry and wet gains independently and when adjusting the mix and I get a greater range of reverb level. Also the FV-1 doesn’t have a large signal headroom, so I need unity gain in the first stage, low impedance feedback in the output stage, and a very quiet op amp. The simple RC filtering also attenuates the reverb output a little bit so I account for that with the gain adjustment in the output summing stage. Finally, my mix pot is configured in an unusual way providing an even distribution of reverb level over the span of the control. This is because the signal is applied to the wiper instead of taken from the wiper. This approach works well with the traditional inverted summing amp.

Leave a Reply to Aleksey Cancel reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s