Improving current source for Aleph

I just started modifying one of my A75 into Aleph 2 today.;)
Since it's A75 I have available 50V regulated power supply for the input stage. I was thinking about using it for differencial pair current source and somehow improving it as well. Any suggestions?
Any improvements when current increased? What would be recommended value then?
The drain resistors (392 ohm) would be connected to output stage supply.


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He's talking about output current sources and I'm talking about input.

It's a shame that something so nice has to be dismantled, but some people do anything for better sound.;) This might well be the first DIY Aleph with TO3 output devices. I'm also playing with idea of turning it into Aleph X instead of Aleph2, don't know yet.

I like the way the transformer is isolated from the rest of the circuitry. I also used special damping materal for vibration reducing. Also I used Panasonic HFQ capasitors for PS (quite a lot of them).


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It's been my best work so far and it looks like it still remains with an upgraded interior.

Checking other threads I noticed that Harry placed 5 green LEDs instead of zener with a small bypass cap. Is that the best that can be done?;)

The heat sink are removed. This allows for easy access in case of repair, modification. As you see mounting TO3 devices is not as easy as those plastic ones and special bars had to be used.


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2002-01-31 5:48 pm
As always, wonderful craftmanship...

Switching with triac I would say is just fine provided you mean that it is used only for switching on and off (like A75). The concern about it causing noise I would expect to be from when used as a mains regulator which will cause huge amounts of noice as the cutting of the sinusoidal mains creates massive overtone spectra. On the other hand I could have misunderstood what you use it for. If it is for on and off then of course it will create noise at switch on or off , if you have not provided for zero-crossing switching, but only for a period or so (20 ms). That is not for long and goes away til the next time you switch something...

Re: What am I gonna do with them if not using here, Harry?

HarryHaller said:

P.S. I bet you loved show and tell in school when you were a kid.......

Quite the opposite, maybe that's why I'm doing it now.;)

What's the reason for Pass Gallery? Didn't you noticed that since I started posting my pictures the overall quality of DIY work from other members improved as well. Some people even mentioned something about competition going on. I also received requests to post more pix.

I personally would like to see as many good quality, innovative and inspiring projects as possible. The latest Cello pictures were good example. It's a great source of useful ideas. It's not about how it looks, but what it's about.

I learned quite a lot from your pix of Tex-X BTW.;)
And thanx for your last suggestion:)
The LM329 needs a capactitor across it. Select anything good looking ... I usually go with about 1uF bypassed by about .01uF, all film of course.

However, the proposed design is not optimal. You could use an additional bipolar transistor to act as a feedback device to increase impedance of the current source. I think NP posted something on that a few months back in response to my suggestion of using an op-amp (for maximal output impedance and minimum power loss).

If your sense resistor is large (you drop several volts), your current source will be fine. If it it small, you might want to replace the MOSFET with a BJT, use a small BJT in a feedback configuration, switch to an op-amp (something tells me you don't want that) ...

BTW, beautiful work. Your mechanical skills are out of this world!