Aleph L Pre DIY!

[panos29]

Dear fellow DIYers, I was wondering if anyone ever built an aleph L preamplifier to drive an aleph 3 clone, and if so i would love some feedback concerning the sound quality. Moreover which of the 2 available versions is more desirable? I am going to build the newest version (the non inverting one). I allready designed the pcb.
Thanks in advance,

"Sound" Christmas to everybody!

[Nelson Pass]

I much prefer the later L, partly because of the
(I think) clever passive/aggressive volume control,
where below unity gain the volume control simply
passes on the input signal, tapping into active gain
at the top of the pot.

I don't know why this invention didn't bring me fame
and fortune, but who can explain it.....

[panos29]

Dear Nelson,
I really thought the same! This is one absolutely fabulous invention, clever and extremely usefull! However there are times that people do not understand a good idea! But, in the lomg run recognition always occur for bright people as in your case (remember the invention of colour TV? nobody thout it as usefull back then!).
Anyway, I would like to thank u once more for sharing your inventions with some poor devils as all of us DIYers who really appreciate your spirit!

[SDF]

I see to build an Aleph L last version , which with the passive preamp under unity gain, it seems really good (like all the Pass product...) . Looking the schematic, I ask me how many is the input impedance ? I calculate about 1,5KOhm, IS IT RIGHT ????

If anybody knows, I will be happy to know more...

Thank. Best regards.

[Dennis Hui]

Originally posted by Nelson Pass
I much prefer the later L, partly because of the
(I think) clever passive/aggressive volume control,
where below unity gain the volume control simply
passes on the input signal, tapping into active gain
at the top of the pot.

I don't know why this invention didn't bring me fame
and fortune, but who can explain it.....

I too think this is one nifty and useful invention. This
is especially useful for those whose main source is CD's.
I find that most of the time, I'm using my preamp as
an attenuator anyway.

I think the problem is that your attenuator scheme is clever,
and yet so simple (once it is pointed out) that people
may either think that's how attenuators have been all along
or that there's nothing there because they could have
thought of it.

Dennis

[PaulyG]

I am also getting close to building my Aleph L version 2 clone. I agree the passive/active nature of the preamp is a quite elegant solution to the age old debate of passive versus active preamps.

[hugonot]

Take a look at input imedance, it depends only on series resistors, I don't like series resistance. R107 and R108 form a feedback loop, an input impedance ( except series ) R107||R108 divided by circuit gain. I don't like output capacitor, especialy when I know what is the next stage, but in this project output voltage chenge about 7 times with VDS temperature change. Series resistance on output. I don't like this things in my DIY.
You can change a little this project like symmetrical voltage rails, some portion of feedback with source resistor to take a better gain control. Maybe one to get VDS + Vr to compensate temperature voltage factor, 27 - 33 Ohms. You could, also get a regulated current source ( wilson circuit ), to form a DC servo which controls output voltage and correct current, then you can use pot parallel with output. If you like experiments, be free. I have built one some time ago. It sounds great with bipolar AB power follower ( Nakamichi's output circuit ). If you want schematic I can scan and send you.