Altec 432B Amplifier questions

[radiolee]

Hello all-

Anybody familiar with this amp? It's a mono PA amp running 7027A's for outputs. I have two of them and have used them in the past to power A-7's and they sound great.

My question is on the microphone transformers. Not being a live performance kind of guy, I'm wondering as to their specific function. Do they match a low impedance mike to a high impedance input or vice versa? I was thinking of selling them off to someone who might use them, but maybe I should hang on to them.

Also, can anyone tell me a likely cause why the output on one is significantly lower on one than the other? Were there different circuits on different versions or is there an internal problem? Cranked, they sound the same. It seems like the only difference is the position of the volume control.

Thanks!

Lee

[radiolee]

Sorry, the model # is 342B--

Did you hear about the dyslexic atheist?
He didn't believe in dogs.

Peace

Lee

[AL-TEC]

Hi radiolee. The mono tube-type PA amplifiers you have is a very good one if it is in good shape, and works with no hum....ect. It is a circa mid 60's model that was rated at 35 watts at less than 2% distortion @ 1khz. Four input channels/bass/treble/master.
I have utilyzed these mono PA amplifiers very much in the past. They were VERY consistant and could be left "on" all day , all night, and keep going like the "Energiser Bunny"! By now tough your units may need a "tune-up" so they will be "up to par". New filter caps would be a good idea to start. Pots to be cleaned with "Tech-spray".
These amps were great "work-horses" as most all old Altec tube amps were. They need the input transformers model 4722 (green ones) to match the low Z microphones to the HI Z circuitry of the tube inputs. Some audio engineers STILL believe that transformer matched mic inputs are BEST, rather than the newest IC chip "direct" mic inputs to match low Z mics. I feel that this is not necessarily a big hang-up either way. Direct inputs without transformers give a wider bandwith/frequency response, and less distortion. Enough about that.
Your amps have similar circuitry in the pre-amp section as the Altec 1567 tube pre-amp/mixer. But the tube output of your 342's have higher inherent distorion than many pro tube, or solid state units. :confused This does not mean anything bad. Some audio persons might not worry about the higher distotion ratings, and may actually want to run the front end, or output into distortion for certain reasons such as a musical instrument source such as guitar
The output tube pairs could be a source of the different level sound between your units. A good tube checker might be needed. They may be weak.

Thanks, AL-TEC

[radiolee]

Hi Al-
Thanks for the great info. Maybe if we had the 342B's back when I was hangin' with the band, we wouldn't have had to use the Shure Vocalmaster and I might still have hearing in my right ear(!)

Great info. I love these amps, they're a perfect match for my A-7's.Didn't know their reputation as workhorses, that's good to know.

I think I swapped the tube pairs between the two amps and same story on the volume control. Hmmm.

I would recommend these amps to anyone and I paid a total of 125 for both. They're on eBay all the time.

Thanks again!

Lee

[Todd W. White]

The Altec 342B was a "souped up" version of the 342A - the "A" was a 20-watt unit, the "B" boasted 30 watts.

The problem was that the "A" sounded better, but Altec wanted a 30-watt unit to compete in the marketplace, so they cranked up the critter 'till you could really burn yourself if you stuck your hand int the wrong place while it was running!

The "B", as a result, DOES have higher output distortion than the "A" - but at lower wattages, it still sounds pretty good.

[radiolee]

Todd-

I never knew there was an "A" version. Did it look the same as the "B"?

Output tubes?

Thanks!

Lee

[Fitts]

I can suggest a possible cause for the problem you describe. You might have two pots with different tapers.

If one is an audio taper and the other is linear then they will sound the same at full volume but not match in between.

Just a thought,