AlephJ Mimi! (Mini)

[lykkedk]

Hi all here.

First off merry christmas and soon a happy newyear 🙂

While rebuilding my poweramp (F5 at moment, F6 at desk)... i was feeling that it might be a way better idea to lower the power, and going for smaller heatsinks; also i would like a smaller chassis to be honest.
I think i can get along fine with ~15Watt with my current speakers/preamp. (Speakers 90dB, Preamp DCG3 with gain X 2).

The heatsinks i have now, can "easily" blow away 200W (F5, AlephJ etc.) for a stereo setup. If i split them, i will end up with half of that approx.

So an Mini Aleph, uses around 100W for a two channel setup, which would be fine. -But when i was surfing around i also read about a mini alephJ, and mini Babelfish, -soo this could be very interessting to build i think. -I just cant seem to find good information regarding those?, also the Mini aleph is difficult to find right information about. So i would be pleased if someone here has some schematic, links, whatever about such mini amp.'s 🙂

I prefer something like mini aleph, but maybee a newer version with jfet's.
Also the babelfish mini i am very currius about!

Jesper.

EDIT : Name of thread!

 

[grimberg]

Follow the link below to the original thread:

http://www.diyaudio.com/forums/pass-labs/2001-mini.html

 

[lykkedk]

Thanks... i read allready a lot in this thread!

Jesper.

 

[Dennis Hui]

Hi Jesper,

I think you can modify a mini-a to use a jfet front end using the same
modification for the Aleph 3. The latter modification is shown in the
first schematics in this post:

http://www.diyaudio.com/forums/pass-labs/267857-aleph-design-reloaded.html#post4184920

Cheers,
Dennis

 

[Zen Mod]

lykk

read this

 

[lykkedk]

Thanks.. all!

So this schm. Babelfish it's possible to run this at lower rail's?

Jesper.

 

[Zen Mod]

as said zillion times , for any mosfet based output stage - do not use lower PSU rails than +/-15V , or you're having trouble due to increased nonlinearity of inherent mosfet capacitances

then use whatever Iq you want , but I wouldn't go lower than 1A

yes , this schmtc can be used for Mini , in which case you can skip cascodes for input JFets ...... or leave them , but with necessary change in voltage biasing

few other resistor values need to be optimized , strictly for rails and Iq one intend to use .....

 

[didiet78]

Thanks.. all!

So this schm. Babelfish it's possible to run this at lower rail's?

Jesper.

Anything to change if i use j176 or j103 to replace j271?

 

[res07njc]

In one of the Zen articles Nelson said he liked the sound of a mosfet running 40 watts (current times volts).

 

[Zen Mod]

Anything to change if i use j176 or j103 to replace j271?

there is ancient pdf I made (almost 10 yrs ago) , floating as attachment in several posts here

anyway , here it is again

I remember I included J176 on list because few boyz tried it and they were satisfied ; however - I remember also funny listening tests revealing (sound) difference between various parts used in CCS above input LTP ...... where I can understand difference betewwn bad CCS and good (enough ) CCS ...... but frankly I cant grasp differene between two good (enough) ones

so , I didn't tried J176 and I have reserve about other ppl experience (see above)

disclaimer - my ZMengrish isn't much better now ,than it was then

however ,comparing to Toshibas and even to J271 , J176 is somewhat wimpy in one of most important parameters - xconductance (read-gain)

if you must use it , double it - use 2+2 in input LTP ..... all 4 matched of course at , say , 2.5mA

J103 (you asked for) was , I believe typo - you probably meant on 2SJ103 ; answer is no - xconductance is waaaay too low

 

[grimberg]

disclaimer - my ZMengrish isn't much better now ,than it was then

Considering that every now and then you have something interesting to say, I would rather read it in ZMengrish than not at all.

 

[lykkedk]

as said zillion times , for any mosfet based output stage - do not use lower PSU rails than +/-15V , or you're having trouble due to increased nonlinearity of inherent mosfet capacitances

then use whatever Iq you want , but I wouldn't go lower than 1A

yes , this schmtc can be used for Mini , in which case you can skip cascodes for input JFets ...... or leave them , but with necessary change in voltage biasing

few other resistor values need to be optimized , strictly for rails and Iq one intend to use .....

Also what's written, due to cascoding rail can be lower.

Anyway, if used with 2 pcs. irfp240's running with normal Pass rails 😀 (2x23vdc).. how much dissapation must i expect?

Jesper.

 

[lykkedk]

I found this.

Maybee with 17v rails it could be good?
Looks interessting i think!

Jesper.

 

[Zen Mod]

Also what's written, due to cascoding rail can be lower.

Anyway, if used with 2 pcs. irfp240's running with normal Pass rails 😀 (2x23vdc).. how much dissapation must i expect?

Jesper.

due to cascoding , rail voltage can be higher
that was at least one reason why cascoding at all

dissipation , P=U x I

I found this.

Maybee with 17v rails it could be good?
Looks interessting i think!

Jesper.

sch is incomplete (missing values)
as I said - take any Aleph schematic , change few resistor values (decrease Iq and rails accommodation) and that's it

 

[lykkedk]

due to cascoding , rail voltage can be higher
that was at least one reason why cascoding at all

dissipation , P=U x I




sch is incomplete (missing values)
as I said - take any Aleph schematic , change few resistor values (decrease Iq and rails accommodation) and that's it

Yep; I kindoff understand this, but if we compare the attachment i posted before i see that there is only two mosfets, instead of four which exsist in original AlephJ sch. (attached here)

So i throught (also what i read) that an "mini" Aleph, is both lower voltage rail,s and less output devices?
Am i right ?

Jesper.

 

[Zen Mod]

pretty simple and effective logic was used in making entire Aleph series - starting from lower rails and dissipation , going to higher rails and dissipation , resulting in broad span of power figures

taking in account that there is sane limit for dissipation per mosfet , it's logical to multiply pairs as needed for particular amp

anyway , as i remember , idea for Mini Aleph came from aspirations to make one in smaller form factor , same as to find use of some leftover parts (smaller heatsinks , smaller xformer)

later , term Mini is stretched to absurd - I remember seeing amps in same dissipation range as Aleph 3 (30) , called Mini

so , make up your mind , decide what you need ...... and ask exact question

this is post #16 , and we just tackled meaning of amp's name

 

[lykkedk]

pretty simple and effective logic was used in making entire Aleph series - starting from lower rails and dissipation , going to higher rails and dissipation , resulting in broad span of power figures

taking in account that there is sane limit for dissipation per mosfet , it's logical to multiply pairs as needed for particular amp

anyway , as i remember , idea for Mini Aleph came from aspirations to make one in smaller form factor , same as to find use of some leftover parts (smaller heatsinks , smaller xformer)

later , term Mini is stretched to absurd - I remember seeing amps in same dissipation range as Aleph 3 (30) , called Mini

so , make up your mind , decide what you need ...... and ask exact question

this is post #16 , and we just tackled meaning of amp's name

I wrote in first post 100w dissipations for stereo.

Thanks...

Jesper

 

[Zen Mod]

use 2x15Vac xformer , resulting in 18Vdc rails
set iq to 1A2 or something like that

use one pair of IRFP240

choose pcbs of your liking (any Aleph type) , post here what's your choice and exact schematic for that pcb and I'll wrote what to change for your needs

 

[Dennis Hui]

ZM, it's very kind of you to offer your expertise.

I'm curious that with lower rails (say 18V), is there any advantage in using lower voltage/higher
transconductance parts like IRFP140 or IRFP044?

Thanks,
Dennis

 

[Zen Mod]

why not

ppl already done that

most important thing Papa gave us is zillion of puzzles/legos and recipe use your brain and play