aleph1.2 to AX100
Hi GL, I hope that your summer is going well! I got some jfets from Erno Borbely all matched and ready to go to begin a new board to install in my previous AX140 (based on measurements).
I have done a few upgrades to your original cirucuit and I would like to get an opinion from you on the input design.
I have upped the xformer to 2kva to reduce hum, this has helped as the tranny noise was reduced by half and now is not heard at the listening position but can be heard if you are standing near the amps. This is ok because a low noise plitron would cost more than my entire project to date. The amps have worked flawlessly driving my line array tweeters and if I did anything more to them I would play arround with the input offset on one amp (go through the matching mosfet ritual again).
This winter I want to try the j-fet inputs. The question I have is that you have ac coupled the inputs. My DEQX speaker correction, digital crossover, and room correction preamp has been modified/upgraded by the factory and now includes output balanced signal transformers. My entire system is dead quiet and no dc offset anywhere. My Pass 350.5 for the mid/bass only measures <3mv on the output. I also have 40uf caps in the +/- output lines to roll off the signal to protect the tweeters from the 50-100mv of dc output from the XA140's (rolls off the signal at 100hz, the DEQX digital crossover is set for 2700hz at 48db/octave.
My question would be with the DEQX having no dc offset at all will I need those expensive PP caps on the input? I know you made a comment somewhere in this thread that the circuit was more stable with the AC coupling. Did you ever come to a conclusion on that point or are you just enjoying the sounds. My hobby progects have been on hold since the Prime Minister at home has had me busy and I have been travelling a lot plus working out. Sometimes a beer in the yard on a hot day beats being inside.
Let me know what your opinion is? dave
Hi GL, I hope that your summer is going well! I got some jfets from Erno Borbely all matched and ready to go to begin a new board to install in my previous AX140 (based on measurements).
I have done a few upgrades to your original cirucuit and I would like to get an opinion from you on the input design.
I have upped the xformer to 2kva to reduce hum, this has helped as the tranny noise was reduced by half and now is not heard at the listening position but can be heard if you are standing near the amps. This is ok because a low noise plitron would cost more than my entire project to date. The amps have worked flawlessly driving my line array tweeters and if I did anything more to them I would play arround with the input offset on one amp (go through the matching mosfet ritual again).
This winter I want to try the j-fet inputs. The question I have is that you have ac coupled the inputs. My DEQX speaker correction, digital crossover, and room correction preamp has been modified/upgraded by the factory and now includes output balanced signal transformers. My entire system is dead quiet and no dc offset anywhere. My Pass 350.5 for the mid/bass only measures <3mv on the output. I also have 40uf caps in the +/- output lines to roll off the signal to protect the tweeters from the 50-100mv of dc output from the XA140's (rolls off the signal at 100hz, the DEQX digital crossover is set for 2700hz at 48db/octave.
My question would be with the DEQX having no dc offset at all will I need those expensive PP caps on the input? I know you made a comment somewhere in this thread that the circuit was more stable with the AC coupling. Did you ever come to a conclusion on that point or are you just enjoying the sounds. My hobby progects have been on hold since the Prime Minister at home has had me busy and I have been travelling a lot plus working out. Sometimes a beer in the yard on a hot day beats being inside.
Let me know what your opinion is? dave
Re: aleph1.2 to AX100
I think the caps are required. But if you'd like to leave them out, I suggest first putting in some cheap caps and measuring the voltage across them while the circuit is running. If you measure zero volts and it stays zero, I am wrong and the caps are probably unnecessary.
Jeremy
daly41k said:
I think the caps are required. But if you'd like to leave them out, I suggest first putting in some cheap caps and measuring the voltage across them while the circuit is running. If you measure zero volts and it stays zero, I am wrong and the caps are probably unnecessary.
Jeremy
Successfully build aleph-X.
Hi,
I have build aleph-x successfully. There was a distortion cause by the input wrong placement.
I need a bit help from you guys.
I just connected DVD output to Aleph-x (+in) and (GND). It is working fine with no distortion at all. But I am not sure is this correct.
For input connection of aleph-x as I am driving from DVD player to aleph-x.
Pls tell me is this correct way.
(DVD player + out) goes to (+ in Aleph-x)
(DVD player GND out) goes to ( GND Aleph-x)
How about aleph-x (– input)? Should I keep just open?
Thank you for your help. very clean sound.
Best regards
michael
Hi,
I have build aleph-x successfully. There was a distortion cause by the input wrong placement.
I need a bit help from you guys.
I just connected DVD output to Aleph-x (+in) and (GND). It is working fine with no distortion at all. But I am not sure is this correct.
For input connection of aleph-x as I am driving from DVD player to aleph-x.
Pls tell me is this correct way.
(DVD player + out) goes to (+ in Aleph-x)
(DVD player GND out) goes to ( GND Aleph-x)
How about aleph-x (– input)? Should I keep just open?
Thank you for your help. very clean sound.
Best regards
michael
macka said:
hi, Ian
what value for this input capacitors..
now im using 100uf bipolar is this ok?
and.. is it possible to have - (minus) Diff DC offset?
when i measure diff DC offset on my aleph X with no input signal sometimes DC offset showing 40mv to -15 for the + side.
and 60-100mv for the - side..
is it normal? and do they have bad effect?
abs DC offset are about 30mv for left and 100mv right channell
thank you
Hi Dave,
Wow! I go away to Toronto for a week and suddenly this thread roars back to life after weeks of dormancy!
As you guessed, I have been listening to music for the most part. I have not been doing any experiments on the AX100J since my last posts on the subject. My experiments have been confined to a UGS based line amp which is coming along well and sounds very nice. I have talked about that earlier as well.
I read only one question in your post and that is in regard to the input coupling caps. My recommendation is to include them. I recall one or more people stating that they could be removed if you were using balanced inputs where the driving device had equal impedances on both legs. I have not tried this even though I now have the new line amp driving the AX100J's in balanced mode.
So far my summer has been consumed with travel and home repairs too - snow damage to the deck, and next month a new roof goes on. So audio is taking a back seat here too.
Regards,
Graeme
Wow! I go away to Toronto for a week and suddenly this thread roars back to life after weeks of dormancy!
As you guessed, I have been listening to music for the most part. I have not been doing any experiments on the AX100J since my last posts on the subject. My experiments have been confined to a UGS based line amp which is coming along well and sounds very nice. I have talked about that earlier as well.
I read only one question in your post and that is in regard to the input coupling caps. My recommendation is to include them. I recall one or more people stating that they could be removed if you were using balanced inputs where the driving device had equal impedances on both legs. I have not tried this even though I now have the new line amp driving the AX100J's in balanced mode.
So far my summer has been consumed with travel and home repairs too - snow damage to the deck, and next month a new roof goes on. So audio is taking a back seat here too.
Regards,
Graeme
aleph 1.2 to xa100
GL, thanks, I will try it first with some caps in place and take the suggestion of measuring across the caps and if no dc is present then I will try the circuit with out. I am also going t dress up the chasis so these beauties will be welcome in the house. I have been listening to them for about a year now with no problems.
One mono unit runs slightly hotter than the other but I have been too lazy to drag it back to the test bench and readjust the bias on the hotter unit. I will keep in touch with you as I proceed.
Have a great summer and don't fall through the roof. dave
GL, thanks, I will try it first with some caps in place and take the suggestion of measuring across the caps and if no dc is present then I will try the circuit with out. I am also going t dress up the chasis so these beauties will be welcome in the house. I have been listening to them for about a year now with no problems.
One mono unit runs slightly hotter than the other but I have been too lazy to drag it back to the test bench and readjust the bias on the hotter unit. I will keep in touch with you as I proceed.
Have a great summer and don't fall through the roof. dave
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
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
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/showthread.php?postid=1637180#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
http://www.diyaudio.com/forums/showthread.php?postid=1637180#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
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.
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
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
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
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
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
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
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
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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