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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Good luck to the repair! I have lived and breathed tubes for the past 50 years and still marvel at the amazing things that they can do! 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. My basic knowledge tells me that if the amp a,tec well, output tubes arent running at too high a plate zltec and the amp sounds great at the higher vdc bias plate current, go with that.

The power supply is good, but could use a choke and good caps.

Instead, contact your nearest service center! It might be a fun experiment! Through Altec Voice of the Theatre speakers, of course. There are some nice articles online which show how to interpret deviations in the waveform appearance and form some correlation with distortion.

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Fanatic, I do have a scope I could look at the change with. Share this post Link to post Share on other sites. In addition, some files are archived, so you need WinZip or WinRar to open that files.


This, of course, will affect the required load impedance somewhat. 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 for a new account in our community.

Altec 1568A Amplifier

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 was pleasantly surprised. By chance, is your ‘scope a dual trace type with which you can superimpose the waveforms?

I suspect that you’re not going to see a huge difference. You certainly won’t hurt anything by running the 1568 at a lower plate current. 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.

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. Who knows, you may find that the “correct” 168a voltage based on the graph is in between the two values printed!

Didn’t have time to study the schematics, but a quick glance suggests that your interpretation is correct. 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?

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To sum it up: Also some files are djvu so you need djvu viewer to open them. It certainly is possible that they decided, at altce later date, to run the tubes cooler to increase longevity. That said, they sound good as they are. I recently purchased a pair of Altec A EL34 based mono tube amps. Please, do not make a copy of the downloaded manual and do not offer to sell it, just use personally to repair defective appliance!

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Register a new account. My major concern is why Altec printed two schematics with two very different bias levels and what they thought was correct. These free programs can be found on this page: 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 The chances are, even if it does increase the distortion a bit, you may not even notice a difference when playing music.

Do you think they later changed the original bias spec of vdc to in an attempt to make the amp more bullet-proof and have longer tube life, or do you think they first chose volts and then they felt the plate current just needed to be higher for better operation and sound quality so they revised it to volts?

Sign in Already have an account? Compare that to the appearance of the input signal from your generator.