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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Log in or Sign up. It certainly is possible that they decided, at a later date, to run the tubes cooler to increase longevity.
Wanted: Peerless power transformer (for Altec A amplifier)
Please, do not make a copy of the downloaded manual and do not offer to sell it, altef use personally to repair defective appliance! I recently purchased a pair of Altec A EL34 based mono tube amps.
My major concern is why Altec printed two schematics with two very different bias levels and what they thought was correct. Post or PM if I can help any further. PhototoneAug 3, You could suffer a fatal electrical shock!
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Through Altec Voice of the Theatre speakers, of course. Is this a good assumption?
Altec 1568A Amplifier
As far as sound quality with the two bias voltages, why not reset it to and take a 15688a That said, they sound good as they are. 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.
PalustrisAug 2, It’s been my “bible” for longer than I can remember.
This, of course, will affect the required load impedance somewhat. You can try that for multiple frequencies to get some appreciation of what’s happening across the audio band. Tubes are all NOS and barely broken in with maybe 50 hours on them.
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. A guy named Tom Tutay does mods for them. Also, in case you are not familiar with it, check out www.
Altec A Amplifier | karltonkrill | Flickr
Sounds like you want to have some “fun” with this! And if the amp continues to sound great, they would never think to bring it altsc to a service tech I have a friend who has used his 1568w Research stuff for 20 years and has never had it looked at- he says it sounds just fine. They work excellent and I plan on keeping them all original as they just have too much vintage appeal to change them.
Already have an account? You would then need to measure the transformer impedance easy to do with your signal generator to see which provides the closest match.
Just off the shoulder of Orion. I assume doing this with a dummy load 1568aa also have at or near the maximum rated output level of 40 watts at say 1kHz would probably be a good place to start?
These free programs can be found on this page: Discussion in ‘ Tube Audio ‘ started by ke4mclAug 2, You can write in English language into the forum not only in Hungarian! As a matter of fact I do have a dual trace rather slow at 15Mhz but not a problem for audio stuff altef, 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 Also some files are djvu so you need djvu viewer to open them.
Register 1568 new account. 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 alttec me. I suspect that you’re not going to see a huge difference.
Any comments would greatly be appreciated.
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. Good luck to the repair! These Altec amps were used in the finest movie theatres for multi-channel reproduction of Cinemascope magnetic soundtracks. PRMAug 2, To open downloaded files you need acrobat reader or similar pdf reader program. 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.
Posted September 18, They were intended for use in churches, bowling alleys, shopping malls, dance halls, high school auditoriums and, naturally, movie theaters. Your name or 11568a address: Considering that tube characteristics can change quite a bit as they age, a 7 volt bias variation could occur with normal use over time. 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.
Most users of tube 1568x, unless they’re really into the technical side, never check tube bias anyway. It might be a fun experiment! The power supply is good, but could use a choke and good caps.
You certainly won’t hurt anything by running the tubes at a lower plate current.