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Old 4th September 2008, 10:50 AM   #551
Matt63 is offline Matt63  Canada
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Default AX-100 PCB

Hi everyone,
Can anyone can tell me where to buy the PCB now.
Thanks
Matt
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Old 4th September 2008, 04:37 PM   #552
gl is offline gl  United States
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There never was a PCB for the AX100 or AX100J. They were both built with perf board. Macka may have done a PCB. I can't remember.

Your best bet is to look for one of the group buy Aleph-X PCB's if you really, really have to have one. But frankly, perfboard will do fine. There isn't that much front end stuff to wire up. And 99% of the build time goes into the chassis, power supplies and output/heatsink assemblies anyway.

Graeme
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Old 23rd October 2008, 06:09 PM   #553
gl is offline gl  United States
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The AX100J amplifiers were taken to the BAF last Sunday. Here is great photo of the underside of one unit taken by member Wavebourn:

http://www.diyaudio.com/forums/showt...80#post1637180

The photo in the previous post has yours truly sharing a laugh with Vladimir (AR2). We were scheduled to have a joint listening session and presentation at 6:30 comparing his Aleph 3's to the AX100J's but the schedule kind of fell apart by about mid-afternoon. Maybe next year.

It was a wonderful time and I really enjoyed talking to all the people who came by to look at the amps and ask questions.

Cheers,
Graeme
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Old 1st November 2008, 06:37 AM   #554
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At Burning Amp this year,I was admiring the old black-style power transformers on these amps made by Signal Transformers. When I was going to school so very long ago, they were the guys to go to for quality power transformers for power amps. At the time, they were at 1 Junius Street in Brooklyn, NY. They moved to Long Island, and have since (I think) been bought up by somene else. Their signature style was the black varnish they used on their transformers.
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Old 21st November 2008, 11:33 PM   #555
gl is offline gl  United States
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Hi wrenchone,

I purchased those transformers from Signal at that address in 1979 I believe. They were used to build two stereo A40's. The transformers were removed from those amps in 1982 and used to build two Threshold R4000 clone monoblocks. Then the R4000's were converted to Stasis 2 clones. There is a photo of one of those somewhere on this site. They were then scavenged to build the AX100's in 2005.

These transformers have performed yeoman service for a long, long time. I have definitely gotten my moneys worth out of them.

Graeme
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Old 8th December 2008, 05:27 PM   #556
daly41k is offline daly41k  United States
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Default living with the AX100

GL, I have had my AX140's (6 fets per quad at 550ma) running for a year or more with out any issues. They run as advertised; extremely hot as the heat sinks can be touched only for a few seconds. I think that is 3.3 amps of bias.

I have pulled them out of service to do a winter mod by upgrading to balanced and matched jfets. In reading your comments, I am wondering if you are still ac coupling your amps to your preamp? My preamp is the DEQX room/speaker measurement system that has balanced line transformers on its outputs. No DC at all and a dead quiet system. Are the coupling caps required because the input circuit has some residual dc on it or are you just protecting the amp/speaker etc. ?

I am going to turn down the bias a bit since I don't need more than 50w/ch to run my ribbon tweeters in my line array and the amp will only see signals above 2500khz. However, I want to design it full range for versitilaty. Perhaps I will reconfigure it at 115w/ch.

I also am going to do some housekeeping and shorten wires etc. and I am still bothered by some transformer mechanical hum so reducing the bias a bit should help with that. Hope you have a good holiday season. dave
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Old 8th December 2008, 09:16 PM   #557
daly41k is offline daly41k  United States
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Default ax100

Gl-sorry as I have 12 outputs avergaing about 550ma which gives a total of about 6.6 amps. I am going to scale it back to 5amps like yours since I don't need all the class A power. dave
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Old 9th December 2008, 06:47 PM   #558
gl is offline gl  United States
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Hi Dave,

I am currently running the amps AC coupled at the inputs. This was due to DC balance problems not speaker protection.

I now run the amps with balanced inputs but I haven't tried removing the input caps.

I don't think that the input caps degrade the sound that much compared to a lot of other things.

My recommendation in your case would be to experiment on the bench without speakers attached.

And holiday greetings back to you. It sounds like you have some serious winter project stuff going.

Graeme
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Old 15th December 2008, 06:03 PM   #559
daly41k is offline daly41k  United States
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Default ax100

GL, I was looking at your revised schematic and I noticed that you added source resistors 15ohms to the input fets. Why did yo do this as I am just curious? Also I have some extra Jfets and could I use them in place of your cascoded transistors on the Input? I may have some signal transistors from other projects lying around but I would have to dig them up. I am just getting started and it is hard or modify something that isn't broke and working well but it is a nice winter project. dave
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Old 18th December 2008, 12:34 PM   #560
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Gl, When you get some time could you possible make a small list of substitute jfets which would perform well in this amp. The 109 series is becoming harder to source. Thanks Tad and Good Hollidays to all.
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