Aleph J Schematic

[Nelson Pass]

So it should be possible to tweak the limiter by looking at clipping figures.

You can tweak it by removing it altogether - the feedback
loop will pretty much shut it down when you get enough
asymmetry in the output due to the + current source running
out of poop.

 

[bobodioulasso]

I should have bet you wouldn't rely on a limiter to make the amp work.

 

[Nelson Pass]

Belt and suspenders.

 

[Zen Mod]

Belt and suspenders.

old trick - to prevent hydraulic absorber to go in two pieces ....... when axle is going away from chassis

beat me if I can remember where I saw that ...... leather belt & spiral spring .... probably some old army vehicle on junkyard

 

[eyoung]

Pre-IRS Corvettes '61 and earlier...pre sway bar.

El

 

[Zen Mod]

tnx .

that's called torsion stabilizer axle on this side of big splash

in any case - good thing to have in amplifier ..... to prevent you of sideways headbanging

 

[jacco vermeulen]

Not torsion bar, aka stabiliser bar, or just sway bar ?

 

[Zen Mod]

Dutchlalaland is above my experience , so you are not count in equation

you're above big splash ........

" .......we are not going to sell our precious weed to strangers !! "

xenofobs !

 

[Fcrawley]

Well,
Which PCB are we going to use. BrianGT, NP, Balanced or what? All these different choices and which BOM's to use.
I know that it should be easy but the parts and the boards don't track one another. Another Easter Egg hunt.

I want to build a quad stereo amp 4 channels and balanced output. Who has a board and who has the BOM?

Fred

 

[anilva]

Starting my Aleph-J build

I am about to start my Aleph-j build. I am going to use Peter Daniel's boards. Couple of doubts I wanted to clear before I start the assembly.

a. Is a 500va toroid enough?

b. I am planning to use Pass general power supply like the one suggested for F5. Should I change anything in that?

c. Can I put in a presets in series with R8 and R27 to adjust the bias and offset as suggested in one of the earlier threads.

d. Some of the resistor values are very precise in the schematic like 4.75k, 392 ohms, 221k etc. Should I add smaller resistors to make precise values?

Thanks in advance.

 

[d to the g]

assuming an aleph-j, and not j-x or jQ or some other version, then...

1) yes
2) i'd double the size of at least the first capacitor. download psudII and simulate!
3) no idea
4) no. just get 1% resistors and you'll be set.

 

[Bill Fuss]

a. 500va is enough

b. that's fine, but ground the case directly and put the cl60 between the case and the PS neutral

c. don't put anything in series with them, but they can be replaced with trimmers

d. you should be using 1% resistors. the values on the schematic are standard RN55 values, the precise values are not imperative, just stay close

You're welcome.

 

[anilva]

assuming an aleph-j, and not j-x or jQ or some other version, then...

1) yes
2) i'd double the size of at least the first capacitor. download psudII and simulate!
3) no idea
4) no. just get 1% resistors and you'll be set.

a. 500va is enough

b. that's fine, but ground the case directly and put the cl60 between the case and the PS neutral

c. don't put anything in series with them, but they can be replaced with trimmers

d. you should be using 1% resistors. the values on the schematic are standard RN55 values, the precise values are not imperative, just stay close

You're welcome.

Thanks to both of you. I built F5, but some how not confident of Aleph-J due to lack of any adjustments (via presets) of bias and offsets. All seems to depend on how good a matching pair of 2SJ74BLs I get for the frontend.

Cheers.

 

[Bill Fuss]

A decently matched pair of J74s is not difficult to find, and the offset feedback will keep you very close to zero offset.
Don't worry.
The J runs quite a bit more bias than the F5 so it will get hotter.

 

[anilva]

A decently matched pair of J74s is not difficult to find, and the offset feedback will keep you very close to zero offset.
Don't worry.
The J runs quite a bit more bias than the F5 so it will get hotter.

Thanks. I ordered few matched pairs from Blues. I will go ahead with the build. I already got the Matched IRFPs from Tech-DIY.

Another aside. I found these JFETs on ebay 20 X 2SJ74BL (10 Matched pairs) - HIGH IDSS - eBay (item 230565979823 end time Dec-24-10 19:52:28 PST)

and bought them. Are they of any use? These are very high IDSS 2SJ74BLs matched pairs.

Cheers.

 

[Zen Mod]

they're absolutely useful in any schematic where biased with CCS

or in any schematic where biased with source resistor , but gain and output resistance of stage isn't critical

edit : so - use them in Aleph amp input LTP , without worry

 

[anilva]

they're absolutely useful in any schematic where biased with CCS

or in any schematic where biased with source resistor , but gain and output resistance of stage isn't critical

edit : so - use them in Aleph amp input LTP , without worry

Thanks Zen Mod. I will go ahead and use 2 each in place of 2SJ109 in the Aleph J build.

Merry Christmas.

 

[Bill Fuss]

I also bought some of those, but after testing them I returned them. The seller admitted to me that they are counterfeits but still claims they are very good jfets. Their parameters aren't even close to j74s.

Happy Holidays Everyone!

 

[Zen Mod]

I also bought some of those, but after testing them I returned them. The seller admitted to me that they are counterfeits but still claims they are very good jfets. Their parameters aren't even close to j74s.

Happy Holidays Everyone!

you're right ;

only curve tracer will reveal what they are

either that or manual curve tracing

 

[Bill Fuss]

Every time I try to manually trace them the pencil moves them and I have to start over.