🛠️ ReVox A77 Reel-To-Reel + DIY Varispeed Mod, Part 1: How-to, Tape Echo / Dub FX + Demos 🔊

A work in progress: Adding variable speed, AKA "Varispeed" / pitch control - to a ReVox A77 Mk IV reel to reel tape machine. See below for timeline links and more details!

UPDATE: August 9th, 2020: Part 2 is now live. https://youtu.be/acYfmASX-Y0

00:00 - Intro / quick demos
01:52 - DIY / how-to intro
02:33 - Experiment #1: 10KΩ Trimpot replacement
03:07 - Test: 10KΩ external potentiometer
04:15 - Experiment #2: DIY Varispeed Circuit
05:11 - A77 vs. B77 circuitry comparison
05:41 - ReVox B77 Variable Speed Control circuitry
05:55 - DIY Varispeed circuit build
06:34 - Wiring to 555 timer on ReVox A77 PCB
06:59 - Varispeed Test: it works!
08:00 - DEMOS: Tape echo / dub loop + Varispeed
08:18 - Demo: Real-time pitch shifting (±7?)
09:28 - Faster speeds increase frequency range
09:50 - Quick vs. gradual speed changes
10:26 - Double-time reggae dub effect
10:48 - Regular playback, pitch changes
11:42 - Telephone mic / voice echo silliness
12:29 - Cartoon-style sound effects
13:36 - Pitch deviation tone test (±7?) w/spectrum display
15:22 - Capstan motor running at different speeds, with sound
16:38 - Quick calibration of new 10KΩ pot

This is long, but may be of interest for those who have an A77 like this and want to try similar. If you aren't interested in the tech bits, you can skip to the demos.

I also happened to be watching a certain time travel movie series during the making of this, and found it inspiring. Sorry. ;)

This video covers two approaches: Trying a 10KΩ potentiometer (variable resistor), vs. building an "official" varispeed circuit based on the ReVox B77 remote varispeed control.

❇ DETAILS ❇

ReVox's B77 (Mk II?) and newer models have official varispeed features. With the B77 Mk II and the official ReVox varispeed remote control, you can get ±7 "deviation" in speed / pitch - which is a pretty great range.

The A77 model doesn't come with varispeed built-in, but it turns out you can add it if you have an A77 Mk IV model. These have what I'll call a "varispeed-compatible" circuit board (capstan motor speed control board) that uses a 555 timer IC to control motor speed. It looks very similar to the one used in later B77 models.

From what I've found, the A77 Mk IV 555 timer-based board can work with a circuit based on the official Varispeed remote control that ReVox makes for the B77.

❇ IN CLOSING ❇

I think this video took over 20 hours to edit and revise - maybe more time than was spent on the actual project. 😅

Thanks are due to various rights holders and artists whose work has been sourced and sampled, here. "No copyright intended." Please support your local musicians. And movie theaters. :P

Thanks are also due to the kind folks at tapeheads.net, an analog audio forum with some truly-knowledgeable and helpful people. Shout-out to user PierreO in particular, for tips on this project.

Thanks for watching.

Видео 🛠️ ReVox A77 Reel-To-Reel + DIY Varispeed Mod, Part 1: How-to, Tape Echo / Dub FX + Demos 🔊 канала Scott Schiller