Solid State DIY

[Eric]

So Noted

I knew I heard that from someone else, thanks for the reminder!

 

[Hoffmeyer]

Sorry, just read the previous posts, and saw it.

 

[carlmart]

One question that should be relevant when using protection zener diodes is that they can have excessive non-linear capacitance. Only lower voltage types (less than 7.5v) shoulod be used.

There's a comment over this on Analog Devices' AN-242.


Carlos

 

[tvi]

another project "HYBRIDIZES TUBES - MONOTRANSISTOR."
http://perso.club-internet.fr/fdzours/amplys.htm

 

[Hoffmeyer]

What do you know, Mark Finnis, to whom I've been refering to in a previous post, is a very active member of this community.
Just wonder why he hasn't been tempted to share his experiences.

And Carlmart, thanks for the tip.

 

[Thoth]

Snubber caps

Your original parts list shows you're using 100pf 50V ceramics as snubber caps. I think this is a mistake. Snubber caps are typically rated to be >3X mains voltage. Also, the capacitance is normally 0.01uF - 0.1uF. I'm sure there are several sources for these, but All Electronics (www.allectronics.com) has some 0.01uF 1KV ceramics at 5 for $1.00. These should do a much better job. Also, you could place one on the input line, after the switch, to clean up even more noise.

Good luck.

 

[paulb]

I'm looking at the A-40 design as well. I had previously not considered it because Pass's original article said no substitutes; now he's posted generic substitutes http://www.passlabs.com/tech.htm . I also thought there must be something more advanced around somewhere. The Zen looks a little primitive for my liking, although Hoffman's version in Audio Electronics 4/98 (very similar to the Aleph 3) looks interesting.
I would build a reduced-power version to match a power supply I've already built. I figure to get somewhere around 24 watts with my supply, which has a 36 V, 8A transformer.

Here are the Class A designs I've looked at so far:
The Pass A-40;
The Aleph-3 or Hoffman "Zen Cousin";
The Pass Zen;
Rod Elliot's designs: projects 10 & 36 (http://www.sound.au.com/index.html);
Dick Crawford's 10 watt op-amp / MOSFET design in Audio Electronics 3/96.

If anyone has any other suggestions I would love to hear them. I've got the big transformer, caps and heatsinks and am just looking for a topology.

 

[Eric]

Snubbers

Thoth: You are correct, I had inadvertantly linked to the wrong item for the snubber caps. I have updated my list. Since I have been keeping a copy of this on my personal web page, I've moved the one in the discussion above and placed a link to my web page in its place. This will make sure I don't get the two lists "out of synch".

 

[dutch diy]

DIY Amp's

Check the JLH-Class A amp thread in this forum for another amp.
Currently I'm in the progress of building a dual-mono setup of that design.
(and blew a couple of voltage regulators today..)

Succes