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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There are some nice articles online which show how to interpret deviations in the waveform appearance and form some correlation with distortion.
ALTEC A Mono-block Tube Amps Stu Remington rebuild | Tube | Audiogon
PRMAug 2, As a matter of fact I altrc 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 Do you already have an account?
If you have, or can borrow, a copy of the Radiotron Designer’s Handbook it will give you everything you need to graph virtually anything. Compare that to the appearance of the input signal from your generator. These free programs can be found on this page: With this, however, I wouldn’t go beyond about 1 watt output keep your multimeter, set to an AC range, across the dummy load to monitor the voltage- keep it to 2.
I have have many other power amps that one would think would simply blow these out of the water and I really didn’t expect much with 15688a and was pleasantly surprised. Log in or Sign up. Az erosito reszet elegge macera szetszedni egyszer korabban mar nekiestemugyhogy ezert merult fel a kerdes, hogy a fentiek alapjan erdemes-e vele me’g tokoreszni, vagy kuka.
altec 1568a, hifi or PA amp?
And if the atlec 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.
Didn’t have time to study the schematics, but a quick glance suggests that your interpretation is correct.
I recently purchased a pair of Altec A EL34 based mono tube amps. In addition, some files are archived, so you need WinZip or WinRar to open that files.
Please post your results after doing the experimentation. Again, check out the aletc articles on that- it’s much easier to explain with pix than in words. But, if all is well with the volt bias, why mess with it?
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. These Altec amps were used in the finest movie theatres for multi-channel reproduction of Cinemascope magnetic soundtracks. It’s been my “bible” for longer than I can remember. They were intended for use in churches, bowling alleys, shopping malls, dance halls, high school auditoriums and, naturally, movie theaters.
It certainly is possible that they decided, at a later date, to run the tubes cooler to increase longevity. The amps I have were set at very close to volts bias and operate fine at this setting and sound absolutely astounding. That said, they sound good as they are. Post or PM if I can help any further. I agree with the low signal when feeding the input square waves as I wouldn’t want to fry the trannies or pwr sply.
You would then need to measure the transformer impedance easy to do with your signal generator to see which provides the closest match. You need to be a member in order to leave a comment.
Yes, my password is: In most amps, the clipping will not be symmetrical. In any event, you certainly have a good handle on what’s needed here to answer the bias question.
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. The difference in bias voltage between the 2 schematics remains a mystery.
Through Altec Voice of the Theatre speakers, of course. Sounds like you want to have some “fun” with this!
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. PalustrisAug 2, The chances are, even if it does increase the distortion a bit, you may not even notice a difference when playing music. Sign In Sign Up. Any comments would greatly be appreciated.
Your last name is definitely a credit to your interest in the subject!!! Considering that tube characteristics can change quite a bit as they age, a 7 volt bias variation could occur with normal use over time. Sziasztok, MX gyel van valakinek tapasztalata?
The only thing I can see would happen by changing the setting to volts altecc do would decrease the idle current through the EL34s and probably increase tube life, however, would lowering the plate current in alted manor change the sound that much as well? Of course, don’t leave it running like that for too long.
The power supply is good, but could use a choke and good caps. You certainly won’t hurt anything by running the tubes at a lower plate current.