Selmer Truvoice Echo Units
Echo 200, Echo 300 and Echo 400
LETHAL VOLTAGES PRESENT THROUGHOUT THE CHASSIS
After someone mentioned these old echo units (thanks for the email Nick) I tried to find some schematics on the web, but could only come up with two hand drawn circuits which crop up everywhere. I don't know who drew them or wether they were factory drawings but they do have drawing and part numbers.
These are cleaned up versions using the same circuits and component values.
If anyone could provide any more information or lend me a unit to draw up (I know they're gold dust) I would be extremely grateful and we could get some more information out there. Alternatively, if you've got one for sale I'd be interested.
These are the three main sites to visit in connection with these units.
http://www.amp-fix.com/ John doesn't accept repairs anymore but has years of experience with echos and everything else you can think of.
http://www.chambonino.com/ Lots of interesting repair write ups and photographs by John Chambers.
To hear Bert Weedon (the man who got me interested in guitars, bless him) demonstrating an Echo 400 go to
1. Selmer Truvoice Echo 200
This is from a hand drawn diagram marked "Drg No. 2096/2" and "Part No. D32". Left click on the image to enlarge it.
I don't know what happened to the Echo 100 but the 200 was cheap (hopefully) and cheerful. If the original schematic is correct, you can use EITHER the Mic or Instrument channel. That doesn't sound very useful so the jack switching connections may not be right. There's no dry signal level control and the four way head selector switch gives only three fixed echo effects plus "Off".
Nov 2020: Thanks to Philip Ramage for correcting the connection from SW3c to V2b. Drawing up-issued to 'c'. There's also something odd about R28 and R29 around S3c.
All contributions welcome.
2. Selmer Truvoice Echo 300 MkI
Many thanks to John Beer for coming up with the original circuit details of the MkI and for help with the other Watkins schematics on the site. This is a re-draw of Drawing No. 2160/5. Part No. D62. Left click to enlarge the image.
The 300 now has four push button head selectors instead of the 200's rotary switch and the three inputs have individual volume controls. Very useful.
3. Selmer Truvoice Echo 300 MkII
This is from a hand drawn diagram marked "Drg No. 2229" and "Part No. D69". It shows the bias oscillator as an EL84 (odd) whereas the earlier versions used an ECF82.
Left click to enlarge the image.
4. Selmer Truvoice Echo 400
I don't have a schematic for the 400, but I do have a copy of Bert Weedon's demonstration record with a picture of one on the label. There's no mention of which version the recording was made with so we'll just have to assume it was a 400. I'll put a sound file on when I get a minute but you can already hear both sides on YouTube:
https://youtu.be/_9mdysaDSsg (side 1)
https://youtu.be/av4y23marGw (side 2)
More details as they become available.
I'm too old to see it properly, but the guitar looks like a Hofner Colorama or 172.
(EDIT: I'm told it's a V2, the UK version of the 172. Thanks John)
It's surprising how many of these records are still about. They were dealer sales aids and, as it says on side 2, "Not For Sale To The Public".
The commentator, David Gell, was a well known radio presenter on Luxembourg and the BBC.