I am in the process of building this amp, one I have not done, getting ready to match some IRFP 240's and the way I see it is I do not need to match all 4 mosfets to each other but rather match Q5 and Q6 being they are the output ones and Q7 and Q8 being the Aleph constant current source matched to each other. I ordered 25 of the IRFP240's, which should be a tube from the same run and will not be far off to begin with, so matching all 4 would not be a problem but I am just being curious wanting info from more talented members than myself.
You are right, on both accounts. In my case, all 25 MOSFET's (Mouser) were perfectly matched.
My experience hasn't been that good, though getting 4 matched pairs from a
single rail was not a problem.
single rail was not a problem.
The last tube of 25 I bought were matched pretty good. I did match the ones I used in an amp I was building closer to each other. It could depend on method used in testing and how close you try to match but buying a tube of 25 from the same run is the way to buy these mosfets to get closer matches.
I already have the BA1 with the BA-3 front end and I am not sure there is going to be that big a difference in the sound with this Aleph J. The BA1 is one fine sounding amplifier. I just got the itch to build again since it has been a few months since I have built anything and this is one I have not built. My first FW clone was an Aleph 30 which did sound really good even with those IRF9610 mosfets. I also have plans to revisit the Aleph 30 and experiment with other front end mosfets just to play in the near future.
I already have the BA1 with the BA-3 front end and I am not sure there is going to be that big a difference in the sound with this Aleph J. The BA1 is one fine sounding amplifier. I just got the itch to build again since it has been a few months since I have built anything and this is one I have not built. My first FW clone was an Aleph 30 which did sound really good even with those IRF9610 mosfets. I also have plans to revisit the Aleph 30 and experiment with other front end mosfets just to play in the near future.
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AlephJ boards were back in stock "for a minute".
Hmmm, the other day I noticed AlephJ boards did not show sold out...I was ordering some of the DIYaudio store's new solder anyway, so I threw a set in the cart, hoping for the best. Checked back the next day as I thought I would post their arrival, but again "sold out" was posted over the AlephJ boards!
Hoping for the best, they indeed arrived today. Store still shows sold out today.
Guess I (and apparently a few others?) were lucky enough to score a set. Can you back order things from the store? This might also explain their quick sell out.
Well at least they are still coming in stock, I know I see people noting they are looking for them. They really went fast was just wondering why it only took one day...I do check sold out items regularly, but I suppose they could have been there a day or two before I saw them. It is a wonderful amp.
I have a few other projects to finish (Sissy sit and finishing touches on DC3G), and then another AlephJ will be added to the stable. I really like that amp.
Russellc
Hmmm, the other day I noticed AlephJ boards did not show sold out...I was ordering some of the DIYaudio store's new solder anyway, so I threw a set in the cart, hoping for the best. Checked back the next day as I thought I would post their arrival, but again "sold out" was posted over the AlephJ boards!
Hoping for the best, they indeed arrived today. Store still shows sold out today.
Guess I (and apparently a few others?) were lucky enough to score a set. Can you back order things from the store? This might also explain their quick sell out.
Well at least they are still coming in stock, I know I see people noting they are looking for them. They really went fast was just wondering why it only took one day...I do check sold out items regularly, but I suppose they could have been there a day or two before I saw them. It is a wonderful amp.
I have a few other projects to finish (Sissy sit and finishing touches on DC3G), and then another AlephJ will be added to the stable. I really like that amp.
Russellc
The solder is great! I'm finishing up an AJ board right now, and it's so darn easy using that solder that I'm almost tempted to desolder something just to see how easy that is.
I havent tried it yet, but when I do......could be problem, the Soldapullt I bought from Newark also arrived. Hope I dont get carried away and melt it on things just to have soldapullt suck it up!
Russellc
Very nice! I also bought some of that solder (and PP BA2 output stage boards
to 'practise' with. 🙂 )
to 'practise' with. 🙂 )
Is it going to have BA2 FE or BA3? I love the BA3...I never finished my BA2 boards, when BA3 came out I went that way.
Russellc
Russellc
It is a very nice amp, you will like it. Lots of potential, balanced etc., but I have always wondered about how the BA2 P-P amp would sound.
Russellc
Russellc
Few weeks ago i asked for help with the hiss in my Aleph J.
Output offset was jumping.
Now i can tell you, that one of the LSJ74 was guilty.
When i soldered them out and checked with transistor tester, i found out , that good one gives me the same measurment results in both orientation, the other one gives good measurements only in one position. When i rotate it for 180 degrees, it becomes fault.
So, i bought a matched quad 2sj74 from punkydawgs. Today i soldered two j-fets in faulty channel. Offset becomes excellent zero.
Question: should i replace good LSJ74 in the other channel with Toshiba or not?
Cheers
Output offset was jumping.
Now i can tell you, that one of the LSJ74 was guilty.
When i soldered them out and checked with transistor tester, i found out , that good one gives me the same measurment results in both orientation, the other one gives good measurements only in one position. When i rotate it for 180 degrees, it becomes fault.
So, i bought a matched quad 2sj74 from punkydawgs. Today i soldered two j-fets in faulty channel. Offset becomes excellent zero.
Question: should i replace good LSJ74 in the other channel with Toshiba or not?
Cheers
On our store boards there is a place for the R7 resistor along with the 2K pot. On the BOM there is not a listing for this resistor. The boards 6L6 used are not the same as these and he is talking about a jumper along with the pot. What goes in the R7 position on the store boards. I am not able to adjust offset or bias right now.
What did you put in R7? Both the 2K pot and the 1K fixed?
What do you have for R8? 1K fixed or a pot set at 1K?
What do you have for R8? 1K fixed or a pot set at 1K?
