Zen Revisited mono PCB

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Hello folks,

I happen to have built a couple of Zens for friends in the past so there is a pcb layout and stuffing guide that I would like to contribute. It concerns the Zen Revisited version. Tracks are copper side, actual size. Stuffing is component side (you may use a 220 Ohm gatestopper instead of J1 depending on the mosfet type capacitance). You need 2 pcbs as they are designed for separate channel/heatsink construction in order to have air to breathe.
The Revisited version with 3amps idle current really made a big sound difference over the original Zen. I used a 600VA 2x30VAC toroid, 2x25Abridges, 10mf Samwa-3mh 2 Ohm rdc aircore coil-20mf Aerovox pi filters. The 1/2 cap relation sounds best and the output cap quality makes a very noticeable contribution concerning tone. No hum on 93db/8 Ohm speakers ('The Slim' PF Vol. 8 No. 3 www.positive-feedback.com) with head in the woofers. It also drives an 86db/8 Ohm 3-way with absolute ease not in a so small a room. Both are benign loads.
I did not bypass the input cap since an Elna Starget blends niceley and sounds worse when bypassed. Ditto for the output cap, an Aerovox. In a variation I used multiple lesser grade output caps with good results. So the PCB can acommodate a single big one on its side or multiple small ones upright. I wouldn't use less than 3x2200uf/25v. Many choices on special caps then, since you can really hear their signature in that position. Dont go over than 30mf per channel of PSU caps for 3amps idle. It gets the sound dryer. I have found that for the Zen 10mf per A is quite balanced.I always prefer a coiled pi filter over a stabilized supply. It sounds smoother and more organic. How fast it will sound is a juggling act. Stick with the values above for this particular construction.
Havent listened to the new versions with the sliding bias, but the Revisited version as built, managed a purer and more fluent sound compared to an Aleph 3 on the 93db speakers. The Aleph was more dynamic and spacious but a tad Hi-Fi. Maybe the sensing circuit and current slide is contributing some mechanical attribute. There are more stages too.
Its not a safe comparison, I dont swear by it. 30 Watt and a nice damping factor means better sound with normal speakers for sure though. Whoever built the newer versions may shed some light on this, having access to some controlled comparison.
A single triode stage with 23dB gain and a BUF 634 buffer was all the preamp that I used, to good effect.
The Zen treads a fine path between good vacuum and sand amp sound. Thanx Mr. Pass, its no accident its so popular.
Hope some you may find my (belated) info useable.


Nick Salamouras



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