HI,
Following advice from various members, I am looking to build Aleph J amp. Not having had much knowledge or build experience, I am afraid I need some handholding and guidance.
I have been reading through various threads for almost 2-3 weeks but still no closer to seeking answers to a number of questions. I wanted to start a thread of my own to try and get some answers so I can order all the required parts in one go (and save on repeat shipping etc)..
Aleph J BOM
calls for 2SJ74-BL, I gather there is a limited stock of LSK170 at the diy store. Would these be the ones I need? Grade A, B or C? What is the likely hood of getting replacement parts? I am just a little worried about building an amp with "unobtanium" parts.
Universal PSU V3
what size caps do I need for this Amp?
Toroidal
What size would I need? Initially, I want to build a stereo config but later on I may move this to dual mono, with a Toroidal for each channel.
I read somewhere that there were a limited number of kits available? These may be the ideal starting point for me, anyone got any?
Thanks
Following advice from various members, I am looking to build Aleph J amp. Not having had much knowledge or build experience, I am afraid I need some handholding and guidance.
I have been reading through various threads for almost 2-3 weeks but still no closer to seeking answers to a number of questions. I wanted to start a thread of my own to try and get some answers so I can order all the required parts in one go (and save on repeat shipping etc)..
Aleph J BOM
calls for 2SJ74-BL, I gather there is a limited stock of LSK170 at the diy store. Would these be the ones I need? Grade A, B or C? What is the likely hood of getting replacement parts? I am just a little worried about building an amp with "unobtanium" parts.
Universal PSU V3
what size caps do I need for this Amp?
Toroidal
What size would I need? Initially, I want to build a stereo config but later on I may move this to dual mono, with a Toroidal for each channel.
I read somewhere that there were a limited number of kits available? These may be the ideal starting point for me, anyone got any?
Thanks
Dakku,
You might want to check with Jim (6L6) to see if he has any kits left over
(both power supply and Aleph J itself).
From the diyaudio store, the jfet you want is actually lsj74. Youb want Idss>8mA
so grade B or C I guess. Ideally they should be well-matched. Besides
the 2sj74, the 2sj108 would also be ok.
Capacitors: At least 120000 uF total for a stereo amp.
Transformer: The original uses a 300VA 2x18VAC. If you are in the US then
Antek ( Transformers - AnTek Products Corp ) would be a good source.
Cheers,
Dennis
You might want to check with Jim (6L6) to see if he has any kits left over
(both power supply and Aleph J itself).
From the diyaudio store, the jfet you want is actually lsj74. Youb want Idss>8mA
so grade B or C I guess. Ideally they should be well-matched. Besides
the 2sj74, the 2sj108 would also be ok.
Capacitors: At least 120000 uF total for a stereo amp.
Transformer: The original uses a 300VA 2x18VAC. If you are in the US then
Antek ( Transformers - AnTek Products Corp ) would be a good source.
Cheers,
Dennis
HI Dennis,
Thank you for the reply.. Good thing I didnt blindly purchase the parts then 🙂 I will check with 6L6, kit is most likely the easiest option for me.
I already have a 250VA 2X18VAC Transformer, do you think this would be sufficient?
I will post links here to the recommended parts for my own reference (Official BOM needs an update I guess).
JFETS
8 pieces of LSJ74 ULTRA LOW NOISE SINGLE P-CHANNEL JFET - Parts
Thank you for the reply.. Good thing I didnt blindly purchase the parts then 🙂 I will check with 6L6, kit is most likely the easiest option for me.
I already have a 250VA 2X18VAC Transformer, do you think this would be sufficient?
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I will post links here to the recommended parts for my own reference (Official BOM needs an update I guess).
JFETS
8 pieces of LSJ74 ULTRA LOW NOISE SINGLE P-CHANNEL JFET - Parts
250VA - good for starters
use no more then 120mF now , later add second xformer and bridges/cap bank
follow generic FW PSU schmtc , using split secondaries , each having own bridge
use no more then 120mF now , later add second xformer and bridges/cap bank
follow generic FW PSU schmtc , using split secondaries , each having own bridge
I have no first hand experience w/the Aleph J but unless Jim (6L6) has any kits left over here's what I would do:
A) Don't buy the Jfets from the diyaudio store. They are fine I am sure but not matched. Do you know how to match Jfets? If not then it will be easier to buy toshiba's from Spencer that are already matched. Ask him for a matched pair of 2SJ74. They are the real deal and you won't have to worry about matching or rating, etc. You need BL grade for the Toshiba parts. Here is his website FET Audio | Hi-End Audio Projects Don't buy jets from ebay.
B) 15,000uf or 22,000uf 35V capacitors. 8 total. Panasonic THSA are a popular choice. They are available from Mouser, Digikey, etc.
C) I would get a new transformer. 250VA will work but you will always wonder if bigger would be better....Also, it may run hot depending on how much capacitance you are running. I'd get a 400VA or 600VA from Antek inc. They are reasonably priced. In a dual mono situation 250VA would be good. But can you find another one of that same transformer?
Also, that chassis looks awfully small compared to the transformer. Is that the chassis you plan to use? You better make sure you have enough heat sink.
Be sure to read Jim's guide over and over again:
http://www.diyaudio.com/forums/pass-labs/241729-aleph-j-illustrated-build-guide.html
Also, C1 1UF capacitor will have a influence on the sound. It's wise to spend some money here.
A) Don't buy the Jfets from the diyaudio store. They are fine I am sure but not matched. Do you know how to match Jfets? If not then it will be easier to buy toshiba's from Spencer that are already matched. Ask him for a matched pair of 2SJ74. They are the real deal and you won't have to worry about matching or rating, etc. You need BL grade for the Toshiba parts. Here is his website FET Audio | Hi-End Audio Projects Don't buy jets from ebay.
B) 15,000uf or 22,000uf 35V capacitors. 8 total. Panasonic THSA are a popular choice. They are available from Mouser, Digikey, etc.
C) I would get a new transformer. 250VA will work but you will always wonder if bigger would be better....Also, it may run hot depending on how much capacitance you are running. I'd get a 400VA or 600VA from Antek inc. They are reasonably priced. In a dual mono situation 250VA would be good. But can you find another one of that same transformer?
Also, that chassis looks awfully small compared to the transformer. Is that the chassis you plan to use? You better make sure you have enough heat sink.
Be sure to read Jim's guide over and over again:
http://www.diyaudio.com/forums/pass-labs/241729-aleph-j-illustrated-build-guide.html
Also, C1 1UF capacitor will have a influence on the sound. It's wise to spend some money here.
JFETS is exactly what is causing me to not press the trigger.
So the original part is now no longer and old-new stock is difficult to get hold of; diyaudio's LSJ74 have some concerns.
Should I be worried about sinking some hard earned money into something for which I may no longer be able to repair should something go wrong in a year?
So the original part is now no longer and old-new stock is difficult to get hold of; diyaudio's LSJ74 have some concerns.
Should I be worried about sinking some hard earned money into something for which I may no longer be able to repair should something go wrong in a year?
Buy Jfets from the store and match yourself, or buy matches from spencer and don't worry about it.
Perhaps Hannes (member name " h_a " ) has full transistor kits - he may. That would be the easiest.
There are no concerns with the LSJ74 from the store. They work fine, you just need two matched pair, and that's going to require more than 10...
Get a new transformer, 300-400VA. The 250 will be running too close to rated power in the AJ.
PSU caps need to be 10mm lead spacing, 'snap-in', 35V and no bigger than 35mm diameter.
What chassis do you intend to use?
Look at this page and read ALL the links in it. Aleph J (2 PCBs included, which makes 2 channels) - Circuit Boards Most of the information you are looking for is already here. 🙂 🙂
Perhaps Hannes (member name " h_a " ) has full transistor kits - he may. That would be the easiest.
There are no concerns with the LSJ74 from the store. They work fine, you just need two matched pair, and that's going to require more than 10...
Get a new transformer, 300-400VA. The 250 will be running too close to rated power in the AJ.
PSU caps need to be 10mm lead spacing, 'snap-in', 35V and no bigger than 35mm diameter.
What chassis do you intend to use?
Look at this page and read ALL the links in it. Aleph J (2 PCBs included, which makes 2 channels) - Circuit Boards Most of the information you are looking for is already here. 🙂 🙂
Dakku,
If you are worried about availability of the toshiba jfets then you wont be able to build any of the pass designs. I think the jfets will be available in the future...either new production or nos at a greater cost. You priced good tubes lately? If you are going to do pass designed diy you will be using these jfets. Period. If you want something as futureproof as posopaml.ible you better get out your magnifying glass....its gonna be all smd and opamps.
The aleph j is a good choice. Follow what people have said here, read the guides, study up on the basics and you will be fine. If this all seems really daunting its because it is. But after you build one it will open doors to other stuff, the knowledge learned is the real payoff.
Thanks guys, I will try to read up some more and post any questions here..
re chassis, I am not entirely sure. I was thinking of building some wood + aluminium hybrid if time permits. I am quite drawn to those exotic wood fronted cases. Lets see. Failing that I may have to get the recommended 4U chassis.
re chassis, I am not entirely sure. I was thinking of building some wood + aluminium hybrid if time permits. I am quite drawn to those exotic wood fronted cases. Lets see. Failing that I may have to get the recommended 4U chassis.
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