Classic Kustom Amp Input Sensitivity

[Sowhat]

Does anyone happen to know the input sensitivity for a typical classic Kustom amplifier... not the preamp input sensitivity, the amplifier input sensitivity, I'm hoping it's near 750mv. Maybe one of you out there knows this piece of esoteric information and can save me from having to rig up and run tests with my poorly calibrated generator and scope.

[J M Fahey]

You needn't.
Just check feedback resistor ratio and remember output voltage is around 20V rms.
So if feedback is, say, 22K/1K, gain is around 20 and sensitivity becomes around 1V RMS.
And so on.

What will you drive it with?

[Sowhat]

Feedback resistor ratio... how cunning!

I have an old Kustom Kasino K424 which has two amps and 1 preamp board. I'm tossing the preamp board and put in a dual master volume preamp with reverb I made based on an Elliott Sound Products (ESP) P27B guitar preamp. This turns it into a Bi-amp. There's no crossover so it's not a died in the wool bi-amp but it is intended to match two musical instrument speaker cabinets of different SPL. This also gave me a chance to fiddle around with one of those Belton Digital reverb modules. The amp works good but I don't know how well it works just using my ear. I thought it was time to tweak things for optimum operation and one thing leads to another.

The P27B design has a 750mv output because of the diode clipping circuit. It does have a last unity gain stage however where I can adjust it's gain a bit to compensate.

Here's a few shots... it's a pretty radical redesign of a 40+ year old beast.





The painting I use for my avitar is a much younger me standing in front a few of my first rebuilds of this amp some 40 years ago which I made with a hacksaw and a soldering iron in my bedroom. No mods there however, just repackaged.

[J M Fahey]

**COOL** repackaging.
Very original.