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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Your last name is definitely a credit to your interest in the subject!!! Any comments would greatly be appreciated.

Through Altec Voice of the Theatre speakers, of course. These amps were designed to be “bullet proof” and idiot proof.

PRMAug 2, Just off the shoulder of Orion. I recently purchased a pair of Altec A EL34 based mono tube amps. In most amps, the 156a8 will not be symmetrical. It certainly is possible that they decided, at a later date, to run the tubes cooler to increase longevity.

You can try that for multiple frequencies to get some appreciation of what’s happening across the audio band.

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The power supply is good, but could use a choke and good caps. 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. Good luck to the repair! Tubes are all NOS and barely broken in with maybe 50 hours on them. 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.


PRMAug 3, 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 Do you already have an account?

Fanatic, I do have a scope I could look at the change with.

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. You can write in English language into the forum not only in Hungarian! 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. Most users of tube equipment, unless they’re really into the technical side, never check tube bias anyway.

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.

You could suffer a fatal electrical shock! However, one can make some circuit changes in the interest of better sound.


That said, they sound good as they are. 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 Mono-block Tube Amps Stu Remington rebuild [Expired]

There are some nice articles online which show how to interpret deviations in the waveform appearance and form some correlation with distortion.

Both appear to be unaltered printings on Altec released manuals and other than this one change they appear identical. 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. Who knows, you may find that the “correct” bias voltage based on the graph is in between the two values printed!

By chance, is your ‘scope a dual trace type with which you can superimpose the waveforms? Posted September 18, The basic circuit topology is very similar to a standard Williamson, so as a first draft you could try converting it to straight Williamson.

Wanted: Peerless power transformer (for Altec A amplifier)

So, I hope this helps you a little bit. Yes, my password is: Please, do not make a copy of the downloaded manual and do not offer to sell it, just use personally to repair defective appliance! Sign up for a new account in our community. PalustrisAug 2,