I came across a Pass Clone that was sold to me as an original Aleph. Looking at the amp board I'd say it must be some other version. The amp sounds very good (though one of the monos exhibits a slight hum).
My question: can aybody guess which amp was actually built here? I should add that the seller did not build those amps himself but bought them some years ago and I certainly do not think that he was trying to fool me.
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Any help will be appreciated.
My question: can aybody guess which amp was actually built here? I should add that the seller did not build those amps himself but bought them some years ago and I certainly do not think that he was trying to fool me.
Any help will be appreciated.
If you take the time to trace out the PCB and place on that the devices, you should be able to reverse engineer the sch.
Job Done.
The wiring is a mess. That needs sorting.
Job Done.
The wiring is a mess. That needs sorting.
at least read what transistors are in and write here
looks as Aleph J , but having one TO92 extra ......
looks as Aleph J , but having one TO92 extra ......
I just checked - the transistors seem to be ST 0118 TIP147 - does that help? The wiring....well - most of it is actually solid core - so a bit ricky to redo.
mystery partially solved
no Aleph - TIP147 are bipolars , while Aleph is having mosfets in output
unfortunately , no other way than to trace schm from pcb
no Aleph - TIP147 are bipolars , while Aleph is having mosfets in output
unfortunately , no other way than to trace schm from pcb
That is "unfortunate" - to put it mildly. Well, did Mr. Pass design any amp with such transistors?
I mean the amp(s) do sound good, but obviously they are not what they are supposed to be.
I mean the amp(s) do sound good, but obviously they are not what they are supposed to be.
I believe he did (lazy to check older ones) but certainly not with just one pair in output
check on FW site - articles, and on passdiy.com
though , to avoid muddy crystal ball game , best way is to trace schematic and post it here
also , measure rail voltages
I might have found something on the net. Somebody had posted about a Pass Labs a40 amp and the driver boards do seem to look similar....
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Don't be disappointed you have a nice chassis and power supply.
You could potentially get some F6 pcbs or Bablefish J pcbs and throw them in the chassis and "Bob's your uncle".
Well, actually I have two chassis as the amp had been built as mono amps. Plus I really like the way it sounds. Unfortunate only in the sense as the amp was advertised as something else - but again: I have a feeling that the gentleman seller didn't know any better.
And I just noticed that there is still some info on that amp on the Firstwatt website - amazing.
And I just noticed that there is still some info on that amp on the Firstwatt website - amazing.
I would second the A40 identification. I have one that I built myself and that matches my driver board. The original has double the output transistors. I still use mine to this day. It is a wonderful sounding realization of Class A power and if built with a good power supply is like a tank. It has run any speaker I throw at it.
Guys, you are great - now I will have to somehow try to find out, why one amp is totally silent, whereas the other one hums a bit from the speaker.
Mine used to hum a little. I believe if you look at the info on Pass DIY they talk about isolating the RCA inputs with a small 10 ohm to ground resistor. I'll have to double check that. It made mine quiet as can be. No sound out of second. Start by verifying the power supply voltages in the amp.
i believe the A40 has 2 pnp and 2 npn in parallel for the output. the amplifier posted in post#1 of this topic has the same configuration; 2 of each in parallel per heatsink. certainly not a proper setup but it does match with the A40.
I admit I cannot stop listening to the amp - what pleases me most is the way it lets you look into a recording venue - if you know what I mean. It's my first Class A amp and it's definitely a keeper.
That might come later - first I understand that the PS can be upgraded from its current, simple state. As there is still some space inside the chassis I was thinking of adding a choke and another cap to the existing PS caps.
Would the following Hammond choke 159ZE do the job (it says on the website 28mH inductance, 3A DC current etc.)?
If not could somebody please suggest an alternative?
Would the following Hammond choke 159ZE do the job (it says on the website 28mH inductance, 3A DC current etc.)?
If not could somebody please suggest an alternative?
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