Aleph J Schematic

[hayenc]

Did you ever come up with this change sheet? I have the BrianGT boards also and thinking I'd do the J if I could find enough info to pull it off correctly.

Thanks!

No, work and life got in the way. I will see how much I can get done this weekend.

Craig

 

[eboz]

No, work and life got in the way. I will see how much I can get done this weekend.

Craig

Alright cool! I'd very much like to see the result. Have you built the -J using the BrianGT board already?

 

[JimT]

I have compared the Aleph J schematic to the BrianGT Mini Aleph schematic and boards. I think I have all the changes figured out but could use a second set of eyes to check this.

Here is a spreadsheet of the comparision

Thanks
Jim

 

[eboz]

I have compared the Aleph J schematic to the BrianGT Mini Aleph schematic and boards. I think I have all the changes figured out but could use a second set of eyes to check this.

Here is a spreadsheet of the comparision

Thanks
Jim

Jim,

I took a look and it looks good, but seems to be missing the zeners. Thanks for the work you've done on this.

 

[JimT]

Thanks for checking. . I will add the zeners to the file and post it later. Until then, Z1 on the Aleph J schematic is 9.1V and is labeled Z5 on the BrianGT boards. The other zeners on the BrianGT boards are left open. I have to check the connections to the output board and add them as well.


Jim

 

[Bengali]

Hi,

I am interested too in using the brian gt boards for an aleph J.

so are you using front end of the brian gt board in place of the aleph J's?

I have not compared schematic between the mini-A or the J.
is it the front end that make the difference?

thanks.

 

[eboz]

Hi,

I am interested too in using the brian gt boards for an aleph J.

so are you using front end of the brian gt board in place of the aleph J's?

I have not compared schematic between the mini-A or the J.
is it the front end that make the difference?

thanks.

I think you can use all of the boards, including the power supply boards. On the output boards I think it will be required to change the pin orientation of the mosfets. I think the number of output devices changes as well.

 

[Bengali]

Hi Eboz,

so those who have built aleph J's. what are you using as a replacement for the 2SJ109's? I thought it's this JFET that
makes it an aleph J.

btw, I bought your preamp chassis very nice to work with.

thx

 

[Zen Mod]

Hi Eboz,

so those who have built aleph J's. what are you using as a replacement for the 2SJ109's? I thought it's this JFET that
makes it an aleph J.

btw, I bought your preamp chassis very nice to work with.

thx

2SJ109BL is matched pair of 2SJ74BL , in one package ;

Spencer and Ruach are your friends ......... if you are looking for these little critters ...

 

[audiodan]

Im sure I read somewhere that Pass Labs was selling 2SJ109BL

 

[Nelson Pass]

Im sure I read somewhere that Pass Labs was selling 2SJ109BL

We are not. Rumor has it that Linear Systems is preparing a
complement to the LSK389.

 

[samoloko]

how Aleph J compare to F5

 

[Zen Mod]

how Aleph J compare to F5

easy ........




to my ears - J is still better , when adequate spks are used ;
if spks needs more current ( not necessarily just watts ) , it's probably better to use F5

 

[der_yeti]

Hi,

finally my casing arrived the day before yesterday and I hope that my AJ will be finished in the next couple of days.

 

[massimo]

I think that some of the new features intruduced in the BA1 front end schematics colud be applied in the Aleph J too.
I'm referring to the RC filter (R210 + C205 and R211 + C206 on BA1) useful to isolated and clean the PS a bit and to drop a Volt or so to keep the input fets well within their safe voltage range and to the CCS made by a 2SK170 instead of the ZTX550 (Q2 on A-J) plus the (noisy) zener, capacitor (C4) and dropping resistor (R5).
Also R7 could be replaced by a pot as in BA1.
Can we get rid of the IN- coupling cap (C1)?

 

[Vigo]

I am thinking about maby building some of this myself.
But i dont have the possibilty to make my own PCB's.

Is there anyone here that can sell me some boards or point me to a place to purcase them.

 

[eboz]

I am thinking about maby building some of this myself.
But i dont have the possibilty to make my own PCB's.

Is there anyone here that can sell me some boards or point me to a place to purcase them.

Vigo,

We are discussing the possibility of using pcb's from BrianGT of chipamp.com which were designed to be build as the Mini Aleph, Alelph 5 or Aleph 30. You can still purchase them from this order form, looks like he ships international.
http://www.chipamp.com/orders.shtml

If you are interested and want to save a few dollars, I would send my boards to you for the price of shipping (read free). I have two amp boards and two power supply boards.

 

[Vigo]

Thanks alot

I whould like that very much.

 

[Bill Fuss]

This thread's been quiet for a while, even though there is a GB for boards for the "J" now.
I just finished a build using the BrianGT boards and am very pleased with the outcome. Quite a bit more detail and depth than the A5 I,ve had for a couple years now.
I'm not able to bias it up to full bias due to my heatsinks so a new chassis is in order, and I would actually like to add a couple of output devices for more current into 4 ohms. Is there a consensus on the number of devices the jfets can drive successfully with the available current? My jfet's Idss is around 10ma so I could increase the front end bias somewhat if that would help.
Any and all opinions are appreciated. Thanks in advance.

Bill

 

[h_a]

Additional fets don't give you more power into 4R, they just share the heat. 4R power is solely limited by the bias current.

Also increasing current in the differential pair is really limited, as they run already more or less full steam. 4mA limits the number of output pairs pretty much.

If you really want to go that way, you could however start paralleling jfets (matched) and upping the tail current. Then you could add more fets - but power in 4R will still be the same.

Have fun, Hannes