Semisouth Aleph J?

[manniraj]

Thanks to @Ylab for sharing pair of boards laid out by @RainfallSky, progress so far as plan is to build per the original with IRFP150 mosfets.

 

[TungstenAudio]

I recommend installing a 10 Ohm resistor at the HBR location. I believe this is important with the proximity of the Speaker Rtn to the board GND.

 

[manniraj]

I found few of these Semisouths 120R100 can we use these fets?

 

[Zen Mod]

yes

 

[Zen Mod]

no, no good!!

send them to OPLDF

 

[william2001]

Are we positive that's a real McCoy?

 

[manniraj]

Are we positive that's a real McCoy?

Yes they are genuine I got them couple of years back from Mouser when @EUVL posted about these FETs and grabbed few pieces
But I think not exact equivalent to Semisouth R100 I guess if I remember that post from Patrick. Here is the part - https://www.mouser.com/ProductDetail/726-IJW120R100T1

 

[manniraj]

I found few of these Semisouths 120R100 can we use these fets?

Sorry they are not Semisouth but Infineon

 

[Zen Mod]

I replied for semisouths ....100

pic said "100" to my brain, while not seeing "I"

sorry, no have experience with Infineons

but - even if I don't have, glance at datasheet sez - no Go - Normally On (like SJDP) but stratospheric -14-ish volts

 

[Zen Mod]

verdict - OPLDF!

 

[TungstenAudio]

I can offer that these boards sound excellent with other FETs in the output locations. I wrote about my build a while ago.
The IRFP150 would still be fine in the upper (Q8) position and something like an IXTQ36N30P or IXTQ75N10P in the lower position. The higher Vgs at Q9 may be accommodated readily if the J74 JFets are on the higher end of the 'BL' grade.

The high transconductance FETs will be different than the SS, but have a unique sound that is worth a build.

 

[mbrennwa]

I have some SemiSouth parts in my stash. If someone needs them really badly, shoot me a PM.

 

[mordikai]

Can somebody point me to the gerbers for these boards or if anybody has a pair they are willing to part with I would be grateful.

 

[RainfallSky]

I will upload 2 versions when I am at home.

P.S.: A few spice tests with SemiSouth SJEP120R100 and IRFP240. (I don't have a good model for IRFP150)

1. R12,R13 - 0.22 Ohm, Q8 - SJEP120R100. Q9 - SJEP120R100 = R21 need 5K to reach 2A bias.
Good pot value would be 5K preset to 3K before solder.

2. R12,R13 - 0.22 Ohm, Q8 - IRFP240. Q9 - SJEP120R100 = R21 need 22K to reach 2A bias.
At 20K it reach 1.92A bias.
Good pot value would be 20K or 25K preset to 14K before solder.

3. R12,R13 - 0.22 Ohm, Q8 - IRFP240. Q9 - IRFP240 = R21 need 33K to reach 2A bias.
At 25K it reach 1.87A bias.
Good pot value would be 25K or 50K preset to 16K before solder.

50K
https://www.mouser.com/ProductDetail/652-3299Y-1-503LF

25K
https://www.mouser.com/ProductDetail/652-3299Y-1-253LF

20K
https://www.mouser.com/ProductDetail/652-3299Y-1-203LF

5K
https://www.mouser.com/ProductDetail/652-3299Y-1-502LF

 

[manniraj]

A few more steps all of the parts from my bin so far and only missing the 5pf Mica cap and then the IRFP150 mosfets. Missed setting the trimmers with the preset values before soldering so let’s see if I can measure the resistance now on the board.

 

[TungstenAudio]

If you have 10pF caps, those will work just fine in place of 5pF.
I would recommend simply giving the potentiometers two full turns clockwise (like turning off a faucet). They are difficult to measure once soldered into the board.

 

[manniraj]

Yes @TungstenAudio I am exploring the idea of using a pair of 10pf TDK ceramic caps I have in series to get the 5pf value if I do not intend to place a new order but anyway I have to get the IRFP150 as I have only matched quads of IRFP240/9240 for original Aleph but this board was more interesting for me to try out.

 

[RainfallSky]

Can somebody point me to the gerbers for these boards or if anybody has a pair they are willing to part with I would be grateful.

Here is the gerbers file and schematic.

I will upload another version tomorow.
I was asked if I could add option to change pots with a fixed resistors.
Attempt was made but I left it on another PC.

 

[RainfallSky]

I will upload another version tomorow.
I was asked if I could add option to change pots with a fixed resistors.
Attempt was made but I left it on another PC.

Here it is. May be not perfect but you deside.. )

 

[manniraj]

Almost done except the jfets and mosfets. Tested the Antek AN6218 with the LT4320 crc psu getting around +/-26vdc without load.