GENERAL DESCRIPTION. The A Amplifier is a rack mounted, AC operated power amplifier intended for use in sound reinforcing, paging, music distribution. Hi there, up for sale is a Vintage Altec A Tube Amplifier. It is in EXCELLENT condition and sounds fantastic and works as it should. This would be perfect. i’ve read mixed reviews on these online. some say they arent all that special and basically PA amps. i saw some stuff that claims they are good.

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Posted September 18, Fanatic, I do have a scope I could look at the change with. These amps were designed to be “bullet proof” and idiot proof. There are some nice articles online which show how to interpret deviations in the waveform appearance and form some correlation with distortion. Since Altec used the same output xfmr in qltec units, it apparently isn’t of much concern.

To sum it up: Is this a good assumption? Also some files are djvu so you need djvu viewer to open them.

altec a, hifi or PA amp? | Audiokarma Home Audio Stereo Discussion Forums

If you want to join us and get repairing help please sign in or sign up by altecc a simple electrical test or write your question to the Message board without registration. Just off the shoulder of Orion. The basic circuit topology is very similar to a standard Williamson, so as a first draft you could try converting it to straight Williamson.

Compare that to the appearance of the input signal from your generator. Who knows, you may find that the “correct” bias voltage based altecc the graph is in between the two values printed! To open downloaded files you need acrobat reader or similar pdf reader program. You certainly won’t hurt anything by running the tubes at a lower plate current. As a matter of fact I do have a dual trace rather slow at 15Mhz but not a problem for audio stuff scope, also have two 8 ohm watt Dale power resistors, signal generator for both sine and square, variac, Audio Control SA RTA, various Fluke multi-meters Of course, don’t leave it running like that for too long.


Altec 1568A Amplifier

PalustrisAug 2, It certainly is possible that they decided, at aotec later date, to run the tubes cooler to increase longevity. You could always put a ‘scope on the output with a proper load connected and see what effect the altered aotec has This, of course, will affect the required load impedance somewhat. It’s been my “bible” for longer than I can remember. Post or PM if I can help any further.

And if the amp continues to sound great, they would never think to bring it in to a service tech I have a friend who has used his Audio Research stuff for 20 years and has never had it looked at- he says it sounds just fine. A guy named Tom Tutay does mods for them. One thing I have noticed is there are two versions of factory released schematics running around the web that appear to be identical except for one has a volt bias level and the other has a volt bias level.

In any event, you certainly have a good sltec on what’s needed here to answer the bias question. PRMAug 3, Considering that tube characteristics can change quite a bit as they age, a 7 volt bias variation could occur with normal use over time.


They work excellent and I plan on keeping them all original as they just have too much vintage appeal to change them. The only thing I can see would happen by changing the setting to volts would do would decrease the idle current through the EL34s and probably increase tube life, however, would lowering the plate current in this manor altce the sound that much as well?

Please post your results after doing the experimentation.

These Altec amps were used in the finest movie theatres for multi-channel reproduction of Cinemascope magnetic soundtracks.

You would then need to measure the transformer impedance easy to do with your signal generator to see which provides the closest match.

These free programs can be found on this page: My major concern is why Altec printed two schematics with two very different bias levels and what they thought was aletc. They were intended for use in churches, bowling alleys, shopping malls, dance halls, high school auditoriums and, naturally, movie theaters.

I agree with the low signal when feeding the input square waves as I wouldn’t want to fry the trannies or pwr sply. That said, they sound good as they are. Share This Page Tweet.