Pass DIY Addict
Joined 2000
Paid Member
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
There's a comment over this on Analog Devices' AN-242.
Carlos
another project "HYBRIDIZES TUBES - MONOTRANSISTOR."
http://perso.club-internet.fr/fdzours/amplys.htm
http://perso.club-internet.fr/fdzours/amplys.htm
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.
Just wonder why he hasn't been tempted to share his experiences.
And Carlmart, thanks for the tip.
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.
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.
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.
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.
Pass DIY Addict
Joined 2000
Paid Member
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".
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".
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
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
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