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Dual mono Zen (Read 1194 times)
crazy bill the eel killer
Ex Member



Dual mono Zen
01/07/06 at 03:16:33
 
Hey guys,
Hope your holidays were great!        :)

Several questions.
When I build my new amp, either monoblocks or a dual mono variation are high on the list. Since I've never heard monoblocks, ( I'm aware of the usual audiophile drivel the high end reviewers associate with those configurations ), I'd like to hear your opinions.
Those of you who have compared the monoblocks to the standard Zen, what have ye to say? Do you hear improvements and in what areas?

Next area is the implementation.
I have several choices, First, is to keep a single power transfo and split dual mono after the rectifier, I'm figuring that since the current draw is now split between the two channels, the 1k50watt now needs to be a 2K, and the 6.8k needs to be a 13.6k, and the 10ks stay the same.

If I make monoblocks, obviously I'll need an extra power transfo and rectifier. From what I've read, if the current draw is less than what the transformer specs list, the voltage on the secondary goes up. The transfo I'm using for the standard or single transfo version is the Hammond 372FX, rated 300-0-300 @ 150 ma. I'm figuring if I go to monoblocks, I'm thinking I should drop down to the Hammond 372BX, which is 300-0-300 @ 100ma, so the voltage on the secondary doesn't raise as much. Also, if the current draw through the rectifier is now 1/2 of what it was, does that change the forward voltage drop through the rectifier and require totally different values for the voltage dropping resistors instead of just doubling the values.

Either way I'm thinking I'll also need to change the cathode bias resistor on the SV83 to a 200 ohm for each channel.

First, you guys convince me that dual mono or monoblocks are worth the extra cost and complexity. Second, if you do convince me, should I completely separate and build monoblocks,or build a single chassis and go dual mono after the rectifier, or should I stick with the standard configuration as designed by Steve.

As always, I thank you in advance for your help.

Bill                :D
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Eli Duttman
Ex Member



Re: Dual mono Zen
Reply #1 - 01/07/06 at 12:16:28
 
If you decide to go the pseudo dual mono power supply (PDMPS) route, put a pair of chokes (1/channel) after the shared 1st filter cap.  2 H. parts are adequate.

The rationale for a PDMPS is to avoid interaction between the 2 channels.  Inductors do a BETTER job of isolating the channels from each other than resistors.
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chrisby
Ex Member



Re: Dual mono Zen
Reply #2 - 01/08/06 at 00:23:24
 
Well,  since the parts required for dual mono power supply will consume more real estate than currently available, you'll probably need a larger chassis or sub chassis like some others have done.

If that's the case, then you could have the space to experiment with some more exotic caps (such as Solen films or Oil in paper, etc) and definitely worth trying would be chokes after the first filter cap as per Eli's recommendation.

One way to relieve some of the heat load on the mains transformer would be a separate filament transformer for the signal and power tubes.  Radio Shack has a decent and affordable  6.3v-0-6.3v 3A model that I've used several times myself for this exact purpose.


Stick with Steve's operating points though, unless you think you can find something better Lips Sealed  

The result of course would likely be something that sounds quite different from a stock Zen, and the proud poppa syndrome with almost certainly guarantee that you like it a lot. That was certainly the case for me Cheesy  :D

have fun
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« Last Edit: 01/08/06 at 00:25:44 by chrisby »  
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