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.
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
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
)
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.
