Electro-Harmonix vintage stereo pulse modulator

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"This stereo pulse modulator surely is one of the earliest pedals EH ever made, even down to the Dymo labeling on the back. It's like a weird kind of vibrato or tremolo - modulates the input volume and adds beats or pulses to it. The timing of these is adjusted using the dials. It has RCA jacks (and will come with four 3' long cables), which suggests it was meant for home use almost as if you'd plug it into your stereo system, however this would result in very bizarre outcomes indeed. As it is you'd need a stereo guitar or keyboard rig to experience all of its functions. The beats are irregular and don't line up in an orderly array as you'd expect with a modern tremolo or vibrato device. While I don't know for sure I suspect this is an intrinsic feature of the unit. The internal electronics are clean and show no sign of modification. So here's the bottom line: this is a peculiar unit with potentially few practical applications. If you're intrigued by what it does, or if you're an EH completist, or into sonic experimentation, then you should consider it. If you're looking for something that you can use immediately as a modern tremolo or vibrato effect, then I would get something else."