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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I’m thinking I should just measure the plate current at either setting and see what value fits the EL34’s recommended plate current curves the best.
There are some nice articles online which 1568q how to interpret deviations in the waveform appearance and form some correlation with distortion. As a matter of fact I do have a dual trace rather slow at 15Mhz but not a problem for altev 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 If you want to join us and get repairing help please sign in or sign up by completing a simple electrical test or write your question to the Message board without registration.
These amps were designed to be “bullet proof” and idiot proof. Please post your results after doing the experimentation.
altec 1568a, hifi or PA amp?
The amps are large enough and easy enough to work on that you can do almost anything you want with respect to refining the circuit for your own use. Sign in Already have an account? To open downloaded files you need acrobat reader or similar pdf reader program.
PhototoneAug 2, Most users of tube equipment, unless they’re really into the technical side, never check tube bias anyway. It’s been my “bible” for longer than I can remember. I agree with the low signal when feeding the input square waves as I wouldn’t want to fry the trannies or pwr sply.
Sign up for a new account in our community. Looking for other manual? So, I hope this helps you a little bit.
Altec A Proper Bias Level – Technical/Modifications – The Klipsch Audio Community
Create an account or sign in to comment You need to be a member in order to leave a comment Create an account Sign up atec a new account in our community. My major 15688a is why Altec printed two schematics with two very different bias levels and what they thought was correct.
These Altec amps were used in the finest movie theatres for multi-channel reproduction of Cinemascope magnetic soundtracks. Through Altec Voice of the Theatre speakers, of course. Already have an account?
But, if all is well with alyec volt bias, why mess with it? They work excellent and I plan on keeping them all original as they just have too much vintage appeal to change them.
I suspect that you’re not going to see a huge difference. Also some files are djvu so you need djvu viewer a,tec open them. They were intended for use in churches, bowling alleys, shopping malls, dance halls, high school auditoriums and, naturally, movie theaters.
ALTEC 1568A Mono-block Tube Amps Stu Remington rebuild [Expired]
I understand that if I were to 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. In any event, you certainly have a good handle on what’s needed here to answer the bias question. Who knows, you may find that the “correct” bias voltage based on the graph is in between the two values printed!
PalustrisAug 2, If you have, or can borrow, a copy of qltec Radiotron Designer’s Handbook it will give you everything you need to graph virtually anything. Sign In Sign Up. No, create an account now. If you are not familiar with electronics, do not attempt to repair! You would then need to measure the transformer impedance easy to do with your signal generator to see which provides the closest match.
PRMAug 2, You certainly won’t hurt anything by running the tubes at a lower plate current. Of course, don’t leave it running like that for too long. Any comments would greatly be appreciated. If you know someone with a CAD program it sure will save you a bunch of time. You need to be a member in order to leave a comment.
As far as output power, measure it at 1 kHz at the onset of clipping on the ‘scope and compare with the two bias values. PRMAug 3, Yes, my altce is: These free programs can be found on this page: Just off the shoulder of Orion. 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 change the sound that much as well? 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.
The amps I have were set at very alec to volts bias and operate fine at this setting and sound absolutely astounding. It certainly is possible that they decided, at a later date, to run the tubes cooler to increase longevity.
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