Dear all,
I have al the parts, housing psu cooling etc to build the ajx amp.
The only thing I cannot find are 2 the two 2sj109bl dual jfets or 2 pairs of matched 2sj170 (also the different buy and sell forums didn't lead to any results yet)
Is there anyone that can help me out on this?? Or who knows a reliable source.
You would make a very happy person
René
I have al the parts, housing psu cooling etc to build the ajx amp.
The only thing I cannot find are 2 the two 2sj109bl dual jfets or 2 pairs of matched 2sj170 (also the different buy and sell forums didn't lead to any results yet)
Is there anyone that can help me out on this?? Or who knows a reliable source.
You would make a very happy person
René
Hi René,
if you get your hands on 2sj109bl you are a lucky guy. But there is also the possibility to buy 2 matched pairs of 2sj74. There trannies are also getting rare, so don't waste time and buy some. I don't know which the best source for originals is, perhaps some expert could help you. As a non-expert I chose h_a: http://www.diyaudio.com/forums/swap-meet/178558-matched-fets-your-f1-f4-f5-aleph-j.html
I wish you fun and good luck for your build! If you could document your steps in putting your AJ-X together for sure not only me would be very pleased!
Kind regards,
Matthias
if you get your hands on 2sj109bl you are a lucky guy. But there is also the possibility to buy 2 matched pairs of 2sj74. There trannies are also getting rare, so don't waste time and buy some. I don't know which the best source for originals is, perhaps some expert could help you. As a non-expert I chose h_a: http://www.diyaudio.com/forums/swap-meet/178558-matched-fets-your-f1-f4-f5-aleph-j.html
I wish you fun and good luck for your build! If you could document your steps in putting your AJ-X together for sure not only me would be very pleased!
Kind regards,
Matthias
not at all, i guess i just assumed because there is many references to j74; difficult to find agreed, i meant nothing by it.
nah look i hope he does, not enough people follow through and build this amp, even though it seems many buy pcbs, it just seems that too many underestimate the difficulty before deciding on it as a project.
an example is the amount of people that think there isnt a schematic, when it is literally the input schematic and 2 aleph js stuck together and deleting a couple of resistors at the join. the missing values are what throw people mainly i guess, a safe value could have been placed in the schematic, but i think its more truthful to not put one as the right value will change depending on the exact individual parts used and the load they are destined for
it is perhaps a little on the edge of stability and not quite as robust as the pass designs, but it seems its very rewarding. i'm in the middle of matching up my fets and resistors at the moment and waiting for the iron to show up. i'll try and take some pics as i go, but most pf the stuffing is already done and i'm a bit time poor, so it wont be a tutorial of any kind. i'm not knowledgeable enough to presume to do that anyway.
nah look i hope he does, not enough people follow through and build this amp, even though it seems many buy pcbs, it just seems that too many underestimate the difficulty before deciding on it as a project.
an example is the amount of people that think there isnt a schematic, when it is literally the input schematic and 2 aleph js stuck together and deleting a couple of resistors at the join. the missing values are what throw people mainly i guess, a safe value could have been placed in the schematic, but i think its more truthful to not put one as the right value will change depending on the exact individual parts used and the load they are destined for
it is perhaps a little on the edge of stability and not quite as robust as the pass designs, but it seems its very rewarding. i'm in the middle of matching up my fets and resistors at the moment and waiting for the iron to show up. i'll try and take some pics as i go, but most pf the stuffing is already done and i'm a bit time poor, so it wont be a tutorial of any kind. i'm not knowledgeable enough to presume to do that anyway.
Possibly on Ebay?
[QUOTE=Alettagla
Is there anyone that can help me out on this?? Or who knows a reliable source.
You would make a very happy person
Hi Alettagla,
I just found someone on Ebay from the UK for 16.29 GBP or make and offer. If you type just 2SJ109 it'll show up. In the picture it show the bl version but I would ask first.
I hope this helps.
Eric
[QUOTE=Alettagla
Is there anyone that can help me out on this?? Or who knows a reliable source.
You would make a very happy person
Hi Alettagla,
I just found someone on Ebay from the UK for 16.29 GBP or make and offer. If you type just 2SJ109 it'll show up. In the picture it show the bl version but I would ask first.
I hope this helps.
Eric
Question about speaker protection
Hi guys,
I have a question about reliability in components for these boards. When, after one of these MOSFET beasts is running, are you willing to 'commit' and hook up your best speakers? I have spent considerable effort tweaking* the cones/domes on my reference midrange and tweeter drivers and it would be a crying shame should a component failure send them some DC. Any thoughts on DC blocking circuits?
Frank
*http://www.diyaudio.com/forums/mult...ng-impressions-techniques-62.html#post2525428
Hi guys,
I have a question about reliability in components for these boards. When, after one of these MOSFET beasts is running, are you willing to 'commit' and hook up your best speakers? I have spent considerable effort tweaking* the cones/domes on my reference midrange and tweeter drivers and it would be a crying shame should a component failure send them some DC. Any thoughts on DC blocking circuits?
Frank
*http://www.diyaudio.com/forums/mult...ng-impressions-techniques-62.html#post2525428
when you have done the final setup and adjusted to recommended dc levels and its stable at that level, run overnight and if still all good in the morning i think you are safe. if you need protection there will be several ccts here on the forum, but i dont know one offhand. preferably no caps though for my taste
Right - bi-amped. The tweeters have caps but the midranges have no such protection. From having a temporary (stupid) input contact fault in my DIY balanced preamp, I know just how fast one of these voice coils melts down. That was before careful tweaking. Now, the price of a re-cone would be the least of my disappointments.
Cheers,
Frank
I've seen Mr Pass say that he doesn't bother with protection circuits on X amps because most faults will just drag both outputs to one rail or the other. I'm sorry, I looked and couldn't track down where I saw him say it, but I can link you to the first time I told someone else about seeing him say it ;P
Thanks for that. My build is for midrange (150Hz up) so I'm using PD's JX board but building it up as a 'plain vanilla' J. ...but I'm with qusp in objecting to added capacitors...
F.
A protection circuit with built in delay would protect against turn on/off transients, but usually are not considered to be very good fault protection devices. They are usually just too slow, but I would bet someone has come up with one. I just haven't heard about it.
The Alephs are about as dependable as Class A amps can get, depending on the heat sinking and construction of course.
Best, Bill
The Alephs are about as dependable as Class A amps can get, depending on the heat sinking and construction of course.
Best, Bill
I've seen two.
Velleman Inc.
and
http://www.diyaudio.com/forums/parts/91146-simple-speaker-protection-circuit-4.html#post1077498
I'm what you would call an 'end user' - not qualified to develop circuits on my own. I have no idea what became of Russ White's circuit...
Thanks Bill, that's what I want to hear! My construction will ultimately be built into a rack, so it will have active cooling with heatsink thermostats to cut out transformer supplies if a 'slow' thermal overload takes place. I chose 75C (167F) based on charts in the MOSFET data sheet. I thought that would be clearly between normal Aleph operating temps and the threshold for thermal damage. Beyond that, I'm putting an LCD readout of heatsink temp on the chassis front panel and we'll just have to see how much air needs to be moved to approach the '5 second touch' target. Seem reasonable?
Frank
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Search for NTE7100
al similar chips work the same
I made one for my F5 and it works realy well
Manuals are Japan standard (wery litle information)
Also have a look at Amplimo speaker relay it has special contacts just for this aplication.
I can not post drawings at present (Need a DFX converter) but let me know if you are stuck
al similar chips work the same
I made one for my F5 and it works realy well
Manuals are Japan standard (wery litle information)
Also have a look at Amplimo speaker relay it has special contacts just for this aplication.
I can not post drawings at present (Need a DFX converter) but let me know if you are stuck