Aleph Pass One Monoblocks

[Marc PLAISANT]

Hello

I'm Marc from France
I'm new on this forum...
I have a pair of Aleph Pass One monoblocks
Not a lot of informations about those amps...
I think they need to be recaped
Can you please tell me what kind of caps I could find for those amps ?
Do I have to do something else ?

Thanks a lot
Marc

 

[Zen Mod]

post pictures, plenty of them

then we can help

do you have schematic ?

 

[Marc PLAISANT]

No sorry.... no shematic
I willpost pictures

 

[Zen Mod]

we need pictures to determine which exact gen/version of amp you have

so , then I'll know on which exact schematic to look , for reference

 

[Marc PLAISANT]

Those amps were builded in 1994
Serial numbers are 4199 and 4200
It seem they have 3 stage gains

 

[moe29]

Aleph 1
120 lbs. per channel
150 watts at 8 ohms.
300 watts at 4 ohms.

The Aleph 1 doubled the power of the Aleph 0. and had the same 3 gain stages.

All following Alephs from the 1.2 on - went to two output stages - sounding better, but losing
the ability to double down their power into tougher loads. The new improvement was the
"Aleph current source".

-->i never saw a service manual for the 1, but i'm sure if you looked at the Aleph 0 manuals
you'd get some help

 

[Marc PLAISANT]

Thanks for your reply
Do you thinks my Aleph One can be modded into 2 gain stages ???

 

[needtubes]

Do you thinks my Aleph One can be modded into 2 gain stages ???

Doubtful. The Aleph 1 uses a complementary N+P output stage instead of the somewhat quasi-complentary N+N output stage of the two-stage Alephs (e.g. 3/30, 5/60, 2, etc.)

 

[Marc PLAISANT]

The pictures !!!

http://img15.hostingpics.net/pics/713380IMG0441.jpg

http://img15.hostingpics.net/pics/498246IMG0442.jpg

http://img15.hostingpics.net/pics/659046IMG0443.jpg

http://img15.hostingpics.net/pics/850396IMG0445.jpg

http://img15.hostingpics.net/pics/738524IMG0446.jpg

http://img15.hostingpics.net/pics/671152IMG0447.jpg

http://img15.hostingpics.net/pics/932326IMG0449.jpg

 

[Zen Mod]

I'll be back later tonight

 

[Dennis Hui]

Found this:

PassLabs Aleph1 Service Manual free download,schematics,datasheets,eeprom bins,pcb,repair info for test equipment and electronics

Hope it is of use.

Cheers,
Dennis

 

[Marc PLAISANT]

Thanks for your help
Can you tell me the benefit of changing the caps ?
How do you feel this amp ?
Balanced, dynamic, smooth, tight low... ?
I listen only Pop, Blues, Rock and I like a good low and a fat sound

 

[Dennis Hui]

If the original caps have aged and deteriorated to the point where the ripple
(and noise) is higher than you would like, then new caps should address that.

Just curious why do you think the caps need replacing?

Cheers,
Dennis

 

[Marc PLAISANT]

I actually have an important hum in the loudspeakers

I think caps in every amp need to be replaced every 20 years
(I'm a professional guitarist and I do that for my tube amps)
The sound comes clearer and more dynamic

 

[Zen Mod]

from pictures - obviously late amp iteration , without much electrolyt caps ..... except main reservoir ones

if you have hum , even without preamp connected (or with XLR shorted on all pins) , there is definitelly need to replace those caps
however , due to physical execution of contacts to pcb , it seems you're pretty much stuck with cap dimensions , primarily regarding pinout spacing .

height and dia , that can be varied , with some ingenuity

so , 22 to 33mF per each , 75Vdc ....... good luck in finding them ......

it'll help if you measure their dimensions (dia , height , pin spacing) and post here ....... and - maybe it will help you in search - that type of cans is usually called computer grade

 

[Dane]

CGS253U075X4C - MALLORY - Mallory CGS253U075X4C Type CGS High-Cap Screw Terminal Aluminum Electrolytic Capacitor, 75 WVdc (95 Vdc Surge) 25,000 µF Capacitance, 0.014 (O) Typical ESR 120 Hz 15.0 A RMS Max. Ripple 120 Hz +85 ºC, 3.000 in / 4.

3.0 X 4.125 inches

 

[Marc PLAISANT]

Pinout spacing : 31/32 millimeters
Diameter : 78/80 millimeters
Height : 105 millimeters

 

[Dennis Hui]

It seems like the original part is still available:

http://www.mouser.fr/ProductDetail/...Ux/Er7vwMzb2x%2bIg50xtCcw1AX6u9W4lwrtZa4hrA==

Here's a slightly lower capacitance, higher voltage and cheaper alternative:

http://www.mouser.fr/ProductDetail/...RpZPHVy%2bjtQuXjWPKFKB4rpZCm6%2bHpYmBZUXJsZFR

This one should be a good fit, but not stocked:

http://www.mouser.fr/ProductDetail/...=sGAEpiMZZMtZ1n0r9vR22caJrJGgYX4Idp3QbjM3BjU=

Good luck with your search and restoration effort.

Dennis

P.S. Beautiful amp you have!

 

[Zen Mod]

nothing wrong with second and third alternative

 

[Marc PLAISANT]

Thanks a lot for your help !
In the first link, the caps are very expensive ?
Is it justified ?