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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Fanatic, I do have a scope I could look at the change with. Post or PM if I can help any further.

Vintage Altec Lansing A Mono Block Tube Amplifier | eBay

I understand that if I were altecc run the bias voltage to volts it would lower the plate current but what effect on sound quality and output capacity would result in this change is a mystery to me. The basic circuit topology is very similar to a standard Williamson, so as 5168a first draft you could try alted it to straight Williamson. Again, check out the online articles on that- it’s much easier to explain with pix than in words.

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 altrc sine and square, variac, Audio Control SA RTA, various Fluke multi-meters 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.

Who knows, you may find that the “correct” bias voltage based on the graph is in between the two values printed! As far as output power, measure it at 1 kHz at the onset of clipping on the ‘scope and compare with the 1568x bias values.


Both appear to be unaltered printings on Altec released manuals and other than this one change they appear identical. The amps I have were set at very close to volts bias and operate fine at this setting and sound absolutely astounding.

You would then need to measure the transformer impedance easy to do with your signal generator to see which provides the closest match. You certainly won’t hurt anything by running the tubes at a lower plate current. Discussion in ‘ Tube Audio ‘ started by ke4mclAug 2, If you know someone with a CAD program it sure will save you a bunch of time.

PhototoneAug 3, Most users of tube equipment, unless they’re really into the technical alteec, never check tube bias anyway. My major concern is why Altec printed two schematics with two very different 1568z levels and what they thought was correct.

It certainly is possible that they decided, at a later date, to run the tubes cooler to increase longevity. You can write in English language into the forum not only in Hungarian!

I assume doing atec with a dummy load I also have at or near the maximum rated output level of 40 watts at say 1kHz would probably be a good place to start? Do you already have an account? This file is downloadable free of charge: By chance, is your ‘scope a dual trace type with which you can superimpose the waveforms? These free programs can be found on this page: Since Altec used the same output xfmr in both units, it apparently isn’t of much concern. Tubes are all NOS and barely broken in with maybe 50 hours on them.

Sounds like you want to have some “fun” with this!


No, create an account now. Through Altec Voice of the Theatre speakers, of course.

Altec 1568A Amplifier

Posted September 18, PRMAug 2, Your name or email address: The chances are, even if it does increase the distortion a bit, you may not even notice a difference when playing music. As such, they are designed with certain technical features that would make them immune to most of the common mistakes a non technical operator might make such as running them with no load.

That said, they sound good as they are. My basic knowledge tells me that if the amp performs well, output tubes arent running at too high a plate altfc and the amp sounds great at the higher vdc bias plate current, go with that.

It might be a fun experiment! Please, do not make a copy of the downloaded manual and do not offer to sell it, just use personally to repair defective appliance! To sum it up: They were intended for use in churches, bowling alleys, shopping malls, dance halls, high school auditoriums and, naturally, movie theaters.

ALTEC A Mono-block Tube Amps Stu Remington rebuild | Tube | Audiogon

Posted September 19, In addition, some files are archived, so you need WinZip or WinRar to open that files. Is this a good assumption? These Altec amps were used in the finest movie theatres for multi-channel reproduction of Cinemascope magnetic soundtracks.

So, I hope this helps you a little bit. In any event, you certainly have a good handle on what’s needed here to answer the bias question. Your last name 1658a definitely a credit to your interest in the subject!!! Log in or Aaltec up.