Muzak 903A 6V6GT Tube Amplifier
Archived listing from the original vintage-amplifier.com. Prices, seller details and purchase links have been removed; this page is a reference record, and nothing here is for sale. About this archive.
Muzak 6V6 Tube Amplifier, Model 903A from the 1950’s. All the tubes are working and included.
Tubes: 1) 6V6GT | 1) 5Y3GT | 1) 6SL7GT –
The front panel knob controls the Volume and Power On/Off and a power light that doesn’t work so the bulb needs replacing. The back panel has a 6 screw terminal strip for output with user selectable voltages plus a 4 Ohm speaker terminal, and a 3 screw terminal strip for input. There are also 2 adjustments on top of the amp, one for Gain the other for Treble/On/Off.
We tested the input with a microphone using a 4 Ohm speaker for output and everything works nicely. All the tubes light up and all capacitors stayed nice and cool during our testing. The volume knob turns freely as it should with a little static in one spot during adjustment. This amp won’t blow out the windows and is best suited for small arenas, pubs, recording studios and practice.
The chassis and cage are in very nice condition with only minor age related scuffs as you can see in the pictures. A copy of the original schematic is also included on the inside of the bottom panel. It looks like it has all the original components to me except for the grounded power cord that was added at some point for safety. It measures approximately 8 1/4″ x 5 1/4″ x 6″ and weighs about 13 lbs. unpacked.
All tube amplifiers are brought up to full power slowly with a variac to avoid damage and to reform the capacitors. Although I test them to the best of my ability, I am not an expert!
About this model
Muzak supplied background music to shops, offices and restaurants, and amplifiers like this 903A drove the loudspeakers on site. It is a small single-ended unit with one 6V6GT output tube, a 6SL7GT and a 5Y3GT rectifier, a terminal strip for selectable line voltages plus a 4-ohm tap, and a copy of the schematic inside the bottom panel. The seller dated it to the 1950s.
One 6V6 gives about 5 watts. The seller tested it with a microphone into a 4-ohm speaker and suggested it for small rooms and practice.
Another amplifier that guitarists often convert is the Hammond AO-35, the reverb amplifier from the A-100 organ family.
| Maker | Muzak, USA |
|---|---|
| Model | 903A |
| Type | Background-music amplifier, single-ended |
| Tubes | 6V6GT, 6SL7GT, 5Y3GT (listing) |
| Outputs | Line-voltage taps and 4 Ω (listing) |
| Size and weight | About 8¼ × 5¼ × 6 in, 13 lb (listing) |
Questions collectors ask
How powerful is a single 6V6 amplifier?
About 5 watts, according to manufacturer data cited on Wikipedia.
What was Muzak equipment used for?
Playing background music in shops, offices and restaurants; amplifiers like the 903A drove the loudspeakers on site.
Sources: Wikipedia: 6V6.
