Bogen MX6A Tube Mixer, Lear Siegler Era
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.
Vintage Bogen MX6A Amplifier. All of the tubes light up and are included……
2) 12AX7
1) 12AT7
There are 4 control knobs on the front for Mic-1, Mic-2, Mic-3 and Mic-4. The back panel has four 1/4″ MIC Inputs and two 1/4″ Phono Inputs, plus a shielded wire with an RCA plug for the speaker output. We tested all inputs on this amp with a microphone using an 8 Ohm speaker for output. All the tubes light up and all capacitors stayed nice and cool during our testing. All the knobs turn freely as they should but we just barely got a tiny bit of static sound out of this one. So it will need some work or possibly new tubes to bring it back up to its full potential. It looks like it still has all the original components underneath. The chassis and cage are in good cosmetic condition as can be seen in the photos so it’s a good candidate for a rebuild. It measures approximately 8″ x 5 3/8″ x 4 7/8″ and weighs about 8 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
The MX6A is the later version of the MX6 mixer. The title's mention of Lear Siegler (spelled "Sieglar" on the original page) dates it: Siegler Corporation bought Bogen's parent in 1957, and after the 1962 merger that created Lear Siegler, Bogen became that group's Bogen Communications division. The layout matches the earlier unit: four microphone level controls, four quarter-inch microphone inputs and two phono inputs, with two 12AX7s and a 12AT7 inside.
The seller heard only a little static from it and offered it as a rebuild candidate with original components. Before replacing tubes on a mixer like this, check the coupling capacitors and the power supply; a silent channel is more often a capacitor than a tube.
| Maker | David Bogen Company, USA |
|---|---|
| Owner at the time | Lear Siegler (Bogen division from 1962) |
| Type | Four-channel microphone mixer / preamplifier |
| Tubes | 2 × 12AX7, 1 × 12AT7 (listing) |
| Inputs | 4 × ¼-inch microphone, 2 × ¼-inch phono (listing) |
| Size and weight | About 8 × 5⅜ × 4⅞ in, 8 lb (listing) |
Questions collectors ask
How does the MX6A differ from the MX6?
From the two archived listings, very little: the same inputs and tube complement. The MX6 listing mentions a separate power knob, while the MX6A has four level controls on the front.
What should be checked first on a silent tube mixer?
The power supply and coupling capacitors, then the tubes. Old capacitors fail far more often than small-signal tubes.
Sources: Wikipedia: 12AX7; FundingUniverse: Bogen Communications history.
