AlephJ Mimi! (Mini)

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lykkedk

lykkedk

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Joined 2002
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!
 
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lykkedk

lykkedk

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Joined 2002
Thanks.. all!

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

Jesper.
 

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Zen Mod

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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 .....
 
Zen Mod

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didiet78 said:
Anything to change if i use j176 or j103 to replace j271?
Click to expand...

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 :rofl:

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
 

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lykkedk

lykkedk

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Joined 2002
Zen Mod said:
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 .....
Click to expand...

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

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

Jesper.
 
Zen Mod

Zen Mod

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

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

Jesper.
Click to expand...

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

dissipation , P=U x I


lykkedk said:
I found this.

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

Jesper.
Click to expand...

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

lykkedk

Member
Joined 2002
Zen Mod said:
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
Click to expand...

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.
 

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Zen Mod

Zen Mod

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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 :clown:
 
lykkedk

lykkedk

Member
Joined 2002
Zen Mod said:
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 :clown:
Click to expand...

I wrote in first post 100w dissipations for stereo.

Thanks...

Jesper
 
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