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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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Again, check out the online articles on that- it’s much easier to explain with pix than in words. In any event, you certainly have a good handle on what’s needed here to answer the bias question. The power supply is good, but could use a choke and good caps.

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Is this a good assumption? 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. Good luck to the repair! My basic knowledge tells me that if the amp performs well, output tubes arent running at too high a plate current and the amp sounds great at the higher vdc bias plate current, go with that.

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?


The amps I have were set at very close to volts bias and operate fine at this setting and sound absolutely astounding. Compare that to the appearance of the input signal from your generator.

This, of course, will affect the required load impedance somewhat. No, create an account now.

Post or PM if I can help any further. Please, do not make a copy of the downloaded manual and do not offer to sell it, just use personally to repair defective appliance!

You would then need to measure the transformer impedance easy to do with your signal generator to see which provides the closest match. They work excellent and I plan on keeping them all original as they just have too much vintage appeal to change 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? They were intended for use in churches, bowling alleys, shopping malls, dance halls, high school auditoriums and, naturally, movie theaters.

altec 1568a, hifi or PA amp?

Do you already have an account? To open downloaded files you need acrobat reader or similar pdf reader program. Fanatic, I do have a scope I could look at the change with.

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.

Posted September 19, Yes, my password is: PRMAug 2, In addition, some files are archived, so you need WinZip or WinRar to open that files. I have lived and breathed tubes for the past 50 years and still marvel at the amazing things that they can do! 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. Any comments would greatly be appreciated. Share this post Link to post Share on other sites. The difference in bias voltage between the 2 schematics remains a mystery.


Vintage Altec Lansing A Mono Block Tube Amplifier | eBay

Also some files are djvu so you need djvu viewer to open them. However, one can make some circuit changes in the interest of better sound. You could always put a ‘scope on the output with a proper load connected and see what effect the altered bias has It’s been my “bible” for longer than I can remember. You certainly won’t hurt anything by running the tubes at a lower plate current. Just off the shoulder of Orion.

Wanted: Peerless power transformer (for Altec A amplifier)

I recently purchased a pair of Altec A EL34 based mono tube amps. Looking for other manual? I agree altex the low signal when feeding the input square waves as I wouldn’t want to fry the trannies or pwr sply.

Sign in Already have an account? By chance, is your ‘scope a dual trace type with which you can superimpose the waveforms?

If you know someone with a CAD program it sure will save you a bunch of time.