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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altec 1568a, hifi or PA amp?

Again, check out the online articles on that- it’s much easier to explain with pix than in words. The difference in bias voltage between the 2 schematics remains a mystery. Share This Page Tweet. 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. Sign in Already have an account? PhototoneAug 2, The amps I have were set at very close to volts bias and operate fine at this setting and sound absolutely astounding.

As far as sound quality with the two bias voltages, why not reset it to and take a listen? So, I hope this helps you a little bit. I assume doing this 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? It certainly is possible that they decided, at a later date, to run the tubes cooler to increase longevity. I suspect that you’re not going to see a huge difference.

Most users of tube equipment, unless they’re really into the technical side, never check tube bias anyway. You would then need to measure the transformer impedance easy to do with your signal generator to see which provides the closest match. 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.


You can try that for multiple frequencies to get some appreciation of what’s happening across the audio band. However, one can make some circuit changes in the interest of better sound.

They were intended for use in churches, bowling alleys, shopping malls, dance halls, high school auditoriums and, naturally, movie theaters. Posted September 19, Also, in case you are not familiar with it, check out www.

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.

Used altec a for Sale |

I have lived and breathed tubes for the past 50 years and still marvel at the amazing things that they can do! That said, they sound good as they are.

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 Share this post Link to post Share on other sites. Good luck to the repair! Your altwc or email address: My major concern is why Altec printed two schematics with two very different bias levels and what they thought was correct.

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A guy named Tom Tutay does mods for them. 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. The chances are, even if it does increase the distortion a bit, you may not even notice a difference when playing music.

PRMAug 3, 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 these and alhec pleasantly surprised. Already have an account? This, of course, will affect the required load impedance somewhat. Considering that tube characteristics can change quite a bit as they age, a 7 volt bias variation could occur with normal use over time.


Instead, contact your nearest service center! PalustrisAug 2, Fanatic, I do have a scope I could look at the change with. Looking for other manual? 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 aletc.

Sziasztok, MX gyel van valakinek tapasztalata? Also some files are djvu so you need djvu viewer to open 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 change the sound that much as well? Posted September 18, Sounds like you want to have some “fun” with this! 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.

Please, do not make a copy of the downloaded manual and do not offer to sell it, just use personally to repair defective appliance! It would have been helpful if they printed a serial range for each one, and even more helpful if they specified the plate voltages of the el34s.

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