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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The chances are, even if it does increase the distortion a bit, you may not even notice a difference when playing music. Again, check out the online articles on that- it’s much easier to explain with pix than in words.

It certainly is possible that they decided, 15668a a later date, to run the tubes cooler to increase longevity. In addition, some files are archived, so you need WinZip or 1658a to open that files.

These amps were designed to be “bullet proof” and idiot proof. 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. Yes, my password is: But, in any event, you can connect your 8 or 4 ohm resistive load assuming it’s rated for the power needed and look at the sine wave appearance at the point just before the onset of visible clipping a flattening of either the top or bottom rounded portion of the waveform.

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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? 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. PhototoneAug 3, 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 alrec registration.


There are some nice articles online which show how to interpret deviations in the waveform appearance and form some correlation with distortion. I recently purchased a pair of Altec A EL34 based mono tube amps. Just off the shoulder of Orion. Share This Page Tweet. The basic circuit topology is very similar to a standard Williamson, so as a first draft you could try converting 158a to straight Williamson.

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. Posted September 18, If you know someone with a CAD program it sure will save you a bunch of time. PalustrisAug 2, It’s been my “bible” for longer than I can remember. The only thing I can see would happen by changing the setting to volts would do would decrease the idle current through altef EL34s and probably increase tube life, however, would lowering the plate current in this manor change the sound that much as well?

This file is downloadable free of charge: Any comments would greatly be appreciated. You could always put a ‘scope on the output with a proper load connected and see what effect the altered bias has You can write in English language into the forum not only in Hungarian!

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 156a8.

I agree with the low signal when feeding the input square waves as I wouldn’t want to fry the trannies or pwr sply.

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. Posted September 19, My major concern is why Altec printed two schematics with two very different bias levels and what they thought was correct. Your name 15688a email address: PhototoneAug 2, You certainly won’t hurt anything by running the tubes at a lower plate current.

If you have, or can borrow, a copy of the Radiotron Designer’s Handbook it will altsc you everything you need to graph virtually anything. Log in or Sign up.


Tube DIY Asylum

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

You could suffer a fatal electrical shock! 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.

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.

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 If you are not familiar with electronics, do not attempt to repair!

Also some files are djvu so you need djvu viewer to open them. Sounds like you want to have some “fun” with this!

altec a, hifi or PA amp? | Audiokarma Home Audio Stereo Discussion Forums

I have lived and breathed tubes for the past 50 years and still marvel at the amazing things that they can do! Already have an account? But, if all is well with the volt bias, why mess with it? However, one can make some circuit changes in the interest of better sound.

Tubes are all NOS and barely broken in with maybe 50 hours on them. Of course, don’t leave it running like that for too long.