Selmer Treble 'N' Bass 50 MkIII
The MKIIIs turn up in 1967, losing the GZ34 of the old MKIIs in favour of solid state rectifiers but gaining an extra ECC83 for the new Echo In/Out facilities
It's a shame that they also lose the attractive woven grill cloth in favour of a rather ugly, flat aluminium panel. The controls are now set back in a new, bevelled cabinet design.
It looks as though the slide into the design catastrophe of the 70s has started.
There seem to have been several wiring colour schemes (that's why colours aren't shown in the layout drawings) and a variation in the layout around the Echo In/Out circuit. Early examples may have C11 mounted on the board through an extra eyelet, while on later versions it sits between the board and the Echo In socket. Makes no difference. The circuit is the same.
After sixty years, like most things, a lot of them will have been dropped, repaired, modified or hacked about. Watch out for dubious mains cable connections. Very nice amps and well worth bringing back to life.
Corrections / comments welcomed.
NEW TREBLE 'N' BASS 50 MARK III
A new and improved version of one of the most successful amps ever produced. 50 watts with such a wide tonal range that the amp is ideal for every use from Bass to P.A. Twin channel, four inputs and separate volume, bass and treble controls for each channel. Very smooth frequency response throughout the tonal range and superb performance without distortion at high volume levels.
Designed and manufactured by Selmer.
No. 7085. Complete with waterproof cover. 59 gns.
SPECIFICATION – TREBLE 'N' BASS 50 Mk III
Two channels (bass channel, normal channel).
Two inputs per channel (high impedance)
Volume, treble and bass controls on each channel.
Two sockets at rear for connection to echo unit between preamplifier and power amplifier.
Power output: 50 watts r.m.s.
Mains input: 115V, 125V, 205V, 225V, 245V, 50 – 60 c.p.s.
Output impedance: 7.5 ohms and 15 ohms by means of locking-type jack to prevent accidental disconnection of speaker lead.
Valves: 2 – EL34, 4 – ECC83.
Rectifiers: 2 – BY128, 1 – BY105
Separate mains and H.T. fuses.
Neon pilot light.
Cabinet finish: Black, black panel and white lettering, Black and satin chrome trim.
IMPORTANT: These drawings and notes are provided for interest only and are not guaranteed to be accurate. Use at your own risk and discretion. The equipment shown contains lethal voltages and should only be worked on by people with suitable training and experience. Schematics and layouts are typical but will vary.
PRINTING
Wix (bless 'em 😖) have changed their image format - again - to avif just to make them awkward to print. Unless you want to buy a converter, the easiest way to make a hard copy is:
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Left click when the magnifying glass icon appears and wait for the picture to clear.
(On a touch screen, tap on the image). This will display a higher res file. -
Right click and 'save image as' to somewhere as an avif file.
(On a touch screen, touch and hold down to view the menu) -
Upload the saved file to your Google Drive.
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Open the file and use the print menu to make a hard copy or save as a pdf.
Selmer Treble 'N' Bass 50 MkIII Schematic
Component ID numbers are for convenience only. No factory numbers available at the time.
Selmer Treble 'N' Bass 50 MkIII. Component Layout and Wiring Diagram (Early)
Selmer Treble 'N' Bass 50 MkIII. Component Layout and Wiring Diagram (Late)
Selmer Treble 'N' Bass 50 MkIII. Chassis and Rear Panel Layout
