Aleph J cascoded three incarnations

[Zen Mod]

yup

 

[tonimxp]

Are you talking about c4? You could try 7pf or 10pf.

Just tryed 7pf Is ok... thanks.

 

[gary s]

Very nice work Antonio, can I ask - do you have a BOM or parts list for the files as shown in your post #37?

 

[tonimxp]

Hi Gary and company...here there is all that you need updated.
between few days hope to able to post also THD , THD vs FR , FR and others measure with Arta Software that at moment is KO.

 

[Zen Mod]

and, got the music flows?

 

[tonimxp]

Hi Alex! Naturally I've already listened to it and I think I'm already quite satisfied with it...I have to say that I already come from F5...and maybe I need to metabolize the new character of Aleph j.
For this reason I prefer to do a review in a few days....
Also I would like to play a bit with the bias and ac gain.
Stay tuned...
P.s. what do you think about 2sj74 source resistors degeneration optional?
What they can introduce in term of sound?

 

[Zen Mod]

degeneration will decrease OLG, thus decreasing amount of NFB, thus increasing THD

how much, depends of source resistors value

better not doing that

 

[Mikerodrig27]

You may like different music with the Aleph J as opposed to the F5. Try some simpler music with great vocals and then take it from there.

 

[Zen Mod]

F5 is for Sissies

but, then, Aleph J is for Sissies, too

 

[gary s]

Thanks Antonio for the further documentation.

 

[tonimxp]

Hey ragazzi!
Eccomi tornato...
Vi racconto le mie impressioni su Aleph j zen modded...
Premetto che ho portato l'aleph a 1A per dispositivo (470mV su R25 e 470mV su R29).
Il cabinet è 3U/400 e la temperatura è ok.
Poi ho giocato con P3 (500r) ottenendo così due condizioni:
1) Senso antiorario P3 (0r) + R19= 680r
2) Tempo P3(500r) + R19= 1180r (questo valore serve per ottenere AC Gain di circa il 50% @ 8 Ohm di carico.
Beh voglio essere breve..
1) In senso antiorario garantisce Thd inferiore rispetto a quello orario.
2) L'andamento della FFT è ottimo in entrambi i casi (scala dalla seconda alla terza, quarta, ecc.).
Ma... non chiedetemi perché...
Le mie orecchie preferivano P3 ruotato in senso orario (R ac gain Total=1180r.
Perché?
Perché il suono acquisisce un senso di tridimensionalità drammaticamente superiore!
Sembrano creare "virtualmente" delle diagonali che partono da sinistra verso destra dietro e viceversa!
Ma c'è di più... anche a me è capitato di sentire qualcosa di mai sentito prima.... cosa?
Suoni provenienti anche dalle mie spalle!
Ragazzi...vi garantisco che non fumo erba!
Non a caso il progetto di Mr. Pass prevede 1200r in quel luogo.
Il mio unico dubbio ora rimane su come gestire eventualmente P3 su carichi a 4 Ohm (lo proverò nei prossimi giorni).
Antonio
Grazie ad Alex.

 

[Zen Mod]

Your ears are only one you need to please

 

[Mikerodrig27]

Is it possible to add a 4ohm/8ohm switch for AC gain? I don't believe the bias and the DC offset changes much with AC gain. I could be wrong. I didn't pay much attention to it when I was changing the settings on the Alephs I built recently

I'm glad you were enjoying your Aleph J

So I have a question regarding the cascode again, is there any Sonic benefit to having cascoded JFETs on a low voltage circuit That is well within the JFETs range? I understand it is needed at higher voltages.

Thanks

 

[Zen Mod]

do whatever you want, but avoid obsession

I mean, keep it pointed at new builds, not endless gilding the lily

cascodes, if you're chicken as ZM is, your JFets will never see more than 15V

 

[Zen Mod]

I don't believe the bias and the DC offset changes much with AC gain.

no change at all

 

[Mikerodrig27]

do whatever you want, but avoid obsession

I mean, keep it pointed at new builds, not endless gilding the lily

cascodes, if you're chicken as ZM is, your JFets will never see more than 15V

I agree. Your and Antonio's AJ cascode board design is great.

Okay. I understand only purpose of cascode is voltage. That makes sense. Thank you.

 

[tonimxp]

Thank you mike...but believe me..the credit is all to Alex...i just put things together with a little salt in the pumpkin...

 

[tonimxp]

Sorry for the Italian post above... unfortunately I wrote with my mobile phone and something went wrong...

Please read down


Hey guys!
Here I am back...
I'll tell you my impressions on Aleph j zen modded...
I state that I brought the aleph to 1A per device (470mV on R25 and 470mV on R29).
The cabinet is 3U/400 and the temperature is ok.
Then I played with P3 (500r) thus obtaining two conditions:
1) Counterclockwise P3 (0r) + R19= 680r
2) Time P3(500r) + R19= 1180r (this value is used to obtain AC Gain of about 50% @ 8 Ohm load.
Well I want to be brief..
1) Counterclockwise guarantees lower Thd than clockwise.
2) The trend of the FFT is excellent in both cases (scale from second to third, fourth, etc.).
But...don't ask me why...
My ears preferred P3 rotated clockwise (R ac gain Total=1180r.
Why?
Because the sound acquires a dramatically superior sense of three-dimensionality!
They seem to "virtually" create diagonals that start from left to right behind and vice versa!
But there's more... it happened to me too to hear something never heard before.... what?
Sounds coming from my shoulders too!
Guys...I guarantee you I don't smoke weed!
It is no coincidence that Mr. Pass's project provides for 1200r in that place.
My only doubt now remains on how to possibly manage P3 on 4 Ohm loads (I'll try it in the next few days).
Anthony
Thanks to Alex.

 

[Zen Mod]

only purpose of cascode is voltage

first glance on it is voltage
second glance on it is dissipation

anyhow, all roads are leading to Rome ( again those damn 'Talians), I did chose my own - keeping those puny JFets on moderate temperature

some other guys like to keep them hot, and on verge of Idss

try it in as much many ways you can think of, choose a way closest to your heart, keep doing that way

 

[Zen Mod]

Sorry for the Italian post above

what?
I remember reading #51 and understanding what's written, thus replying
as I'm pretty much illiterate in Italian, conclusion is - it was in English

Gremlins?