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Old 9th April 2001, 01:28 PM   #11
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Grey,

First off, thanks! It's been a long time since I considered this design, but I couldn't pull it off by myself. Thank you for your time!

Some of the circuit considerations you mentioned go over my head, but not very far...

One thing you said in your post made things especially more clear: Current Sources per V leg, e.i., 2 CCS instead of just one per side.

Second, I thought about just building a CCS for the neg. rail, as it is the side that will give me most of the effeciency, and keeping the power resistors for the pos. rail, since they would only give a small fraction of
power->heat savings. Your saying that they may also have the added benefit of better sonic quality?? GREAT!! Leaving the 8ohm power resistors in the circuit would negate the need for feedback or reference resistance for the pos. side, as per N.P.? I think?

But, they should be kept at the same wattage rating? e.g., 8 ohm - 250w for 50w amp? Or is there a reduction in wattage rating because of the more effecient neg supply? I bet you have to keep them as the original design says, despite the changes to the neg. side.


Using the ZEN CCS as an example, could I modify it for the negative rails? Like say- Change the P-CH to an N-CH MOSFET? And doing the same for the small transistor; minding also the direction of the caps & zener?? Would this work?

I'd like to keep the wattage around 25 to 30 watts.

If you could answer these questions at your leisure, and I don't have to re-design a neg. CCS, I'll start this right away.

Vince

ps. I just started to learn more about basic electronics and the whole idea of which way current flows. - to + or
+ to -....I just want to memorize OHM's law first.

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Old 9th April 2001, 03:55 PM   #12
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Vince,
Plug in the soldering iron and roll up your sleeves...
I'm not clear on what you're referring to in Nelson's E-mail. Could you post the relevant portions?
Regarding the wattage of the 8 ohm resistors up top--yes, they'll still need to be pretty hefty. I'm in a rush at the moment, but I'll snag my copy of the SOZ dingus and take a look at it later today with an eye towards determining *how* hefty. (Keep in mind that a 1W SOZ wouldn't need 250W resistors.)
The Zen current source (with N-channel instead of P and other polarities attended to-->I seem to recall Nelson uses an MPSA92 in the Zen current source, use an MPSA42 instead) will be perfect.
Cross fingers that I have time to do a little Zen meditation during the day...I'll get back with you ASAP. Hopefully, the above will give you enough to futz with for a few hours.

Grey

A digression on current direction: Once upon a time, it was thought (kinda by default) that current flowed from positive to negative. Then Science came storming in and asserted the existence of such things as electrons--something that hadn't been realized before. Only, there was one tiny little inconvenient problem...all the electrons live in the *negative* part of the circuit. It was then realized that current actually flowed from negative to positive. How rude! Thus for historical reasons current is regarded as flowing from positive to negative, as it was considered too difficult to change horses in mid-stream. *Sigh* I suspect they did it on purpose. If they made electronics *too* easy, the hoi polloi would come crowding in and there's no telling what would happen. Some six year-old kid would probably discover the ultimate gain device, put on his grandfather's old Glen Miller record, spin it backwards, and discover the true meaning of life. Can't have that; life's not meant to be that easy.
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Old 9th April 2001, 04:35 PM   #13
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Talking Starting SOZ Project!

Ok, well, that does it. I'm building this circuit.

I have the issue of AA w/ the SOZ artice, I can find the correct wattage for a 8ohm value from it. But, I'm going to use several lower wattage (50watt) resistors in parallel to share the current dissipated. They are easy to find and are cheap. I saw this done by someone who's project is dispalyed on the Pass Gallery.

I'm going to scan the email W/ Q & A; I'll put it on my web site under DIY Audio. You can get to my site from the icon on the bottom of this post...just so you know.

Thanks again Grey,

What I read last week said that the idea that current runs from + to - was a Ben Franklin era idea. Being that he captured electricity, and seeing that electricity went from the sky to ground, I can see the logic. Then again, what do I know....



[Edited by vdi_nenna on 04-09-2001 at 11:40 AM]
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Old 10th April 2001, 01:48 AM   #14
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Vince,
Drat your hide! You've got me thinking about the SOZ (and possible modified versions thereof) again. And me working all available hours to see if I can whip this water-cooled thing into shape. Fiddlesticks! (Found a local source for copper bars. I plan to pay them a visit tomorrow if possible.)
Not that a convenient way to dissipate heat wouldn't come in handy when working on a SOZ...
Sounds like you're in good shape for the moment. Let out a holler if you get stuck. The only variable I can see is whether to build the circuit with or without the 'vertical' 1 ohm resistors. I suspect it will work both ways, but with slightly different performance. I may even break down and model the blasted thing if I can find some MOSFET models to plug into PSpice.
Of course, once I get a model set up, I might as well go full bore and try out the 'differential Aleph' idea I outlined above. I'm happier if I have actual parts in front of me, though. I may just build a miniature one out of 2N5457s or something, just to see what happens.
As of earlier this evening, I checked your site and did not see correspondence. Of course, if you're busy slaving over a hot soldering iron, I'll understand.

Grey
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Old 10th April 2001, 12:51 PM   #15
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Grey,

I scanned the email last night and it's now on my web site under DIY Audio Electronics.

I know how you feel. Too many great ideas floating around regarding these excellent amps. It's hard to pick a base design. But, I think I'm set w/ this SOZ CCS design.

I think I'll be busy for a while before anymore questions come up.

A gentleman I have been corresponding with sent me some links for water cool heat sinks. You may already have them, but I'll post them here, in case someone else is interested.

Vince
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Old 29th May 2001, 03:48 PM   #16
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I made SOZ with two 1A CCS on neg. rails, and 7.55 ohm (20W) resistors on pos. reils. Sounds WOW!!! ... pretty ideal !!!.
My SOZ is without 1 ohm vertical resistors ,and has only 3.8W power (+12,0,-12 PSU) , I increas source resistor to 2.2 ohm for better performance.
I use two heatsink 25x17x3,5cm they has 63 degrees Centigrade.
For such small amp I use four IRF540 for one chanell.
I plan to make 30W versin of this amp.
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Old 30th May 2001, 07:50 AM   #17
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Hi everybody !
1. First of all I think the 1 Ohm resistors "have" to stay. They are part of the Symmetry circuit that reduces distortion. If you take them out you have 2 single ended power amps working in bridge mode. So in this way the best performance is equal to that of the individual amps. That means no further cancelation of distortion or noise not more then the matching of the 2 amps can do.
2. That leaves us to use 2 current sources towards the negative rail. With or without a current mirror. They are both current sources. I think either use a current mirror or biasing both current sources from one reference voltage will do.
3. I think the best is to keep the 8 ohm power resistors to positive power rail because if you only get 3% better efficiency from that itīs a lot simpler to leave it that way.
4. About active current sources ?....I donīt really know how it will work with my opinion towards yeah it should work.
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Old 30th May 2001, 02:58 PM   #18
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Question Mr. Pass what do you think??

When using a constant current source on the neg. side of the SOZ, should the vertical 1 ohm resistors be left in the circuit, or should only the horizontal 1 ohm resistor be left in the circuit?
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Old 1st June 2001, 12:03 PM   #19
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I was doing some simulations on the SOZ and I had a stange result. When I feed a balanced singnal in the input I have normal results. When I feed it with a single ended signal it has low bandwidth around 10 KHz and the two outputs are 180 degrees dif. but with different amplitude. Has anyone had the same problems ?
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Old 1st June 2001, 12:40 PM   #20
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It's functioning as a poor phase splitter. To get good balance between the outputs from the two sides, you need a lot of resistance under the sources. In my tube amp, I accomplish good balance by using a current source--essentially an infinite resistance. Having 4 or 5 ohms under the tail of the differential isn't enough to do the trick.

Grey
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