Aleph 2 into Mini?

[Narcisse91]

About 2 years ago, I started building a pair of Aleph 2s. About a year and a half ago, I stopped working on it, due to a lack of free time. Well, now I'm wondering what to do with all my parts.

I bought all the transistors and a bunch of PCBs, I believe it was from Harvardian, when I started the project. The project is mainly missing a completed chassis and a power supply. I'm wondering if it would be a good idea to convert this over to a mini. I think it would better suit my needs and to be honest, my budget has diminished over the last 18 months due to other expenses that have come up, and I think it would be significantly less expensive to finish as a mini, as opposed to an Aleph 2.

So comparing the schematics, it looks like a lot of resistor swaps to compensate for the lower rail and different output transistors, and one capacitor swap. There are some other differences, like the lack of R26 and R27 and the location of C9. The mini adds two more caps, one across D1 and one from the collector to the emitter on Q5, and C7 is gone. There is also a potentiometer and 750ohm in place of R21. (reference designators are all from the Aleph 2 schematic on PassLabs.com)

So, is there any reason this won't work? Like I said, I've got PCBs and a bunch of parts. It looks like I'll need resistors and caps, and then a different power supply then the design I have for the Aleph 2, but I never actually built that, so no big deal, and I'll need some more output devices. Did I miss any of the changes?

If I can't pull this off, anyone need any Aleph 2 PCBs and devices?

[MikeW]

Just a few resistor changes, a different power supply and one or two output devices.
Less heatsinking.
Send me an E-mail. I have some extra parts.

[kilowattski]

You should be able to pull this off pretty easily but if you decide against it, I may be interested in some of your parts. Best of luck.

[Brian Donaldson]

Actually, the my Aleph 2 works fine as low a 25V (mini aleph realm) with the variac between tnanny and 120V outlet. you don't need anywhere near as many fets because of less needed bias current and lower dissapation due to les volts across fets. Throw together a psu and play with it.

[GRollins]

Not even a challenge.
The Aleph is a remarkably forgiving circuit. Adjust the value of the resistor that biases the Zener in the front end CCS and you can kinda fudge on most everything else. A little fiddle factor here and there and you're up and running. I did the original Mini-A by cutting down an Aleph 3, but you can gussy up the front end with other things, like the extra stuff found in the Volksamp versions of the circuit. Check all the schematics for the various Aleph versions. Nelson left a generous trail of breadcrumbs for us to follow. Once you get the idea of the common denominators between the different front ends, you can mix and match as you please.

Grey

[Narcisse91]

Thanks, you've all gotten me motivated to get going again on this project. I cleared off my work space and I'm going to start taking stock of what I've got floating around.

MikeW,
email sent.

Kilowattski,
I have tons of parts, looks like I bought most common parts at the price break. I've got populated PCBs for four monoblock amps, and I will probably only build two. I also have PCBs for the output stage, and I will have matched sets of output devices, if I convert to a mini. Anyway, I have extra parts, regardless of whether or not I build anything, so send me an email with what you need.