Pass Son of Zen w/current sources (etc.) - Page 2 - diyAudio
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Old 27th September 2001, 04:07 PM   #11
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Jason,
Thanks kindly...but don't ask me, ask them. I already know what the silly thing looks like, I'm sitting here next to it.
(So what's it look like, Grey? Pretty ugly! Lotsa wires stickin' out everywhere. Looks like it's having a bad hair day, but it works, which is all I care about at the moment.)
grataku,
How's it look to you?
As long as the schematics are legible, I reckon we'll get by. The circuit will get more complex as we go, hence larger, but we'll cross that bridge when we come to it. Perhaps by breaking it down into functional blocks.

Grey
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Old 28th September 2001, 12:45 AM   #12
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Smile Peltier Effect

Hi all,

OK, I just had to speak up on this one, being an out of work physics researcher, and Pass Labs aficionado. I have heard mention of using Peltier Effect devices to cool Zen amps, Son of Zen, and the like. Sounds like a fun, albeit silly exercise.

This falls under the “laws of thermodynamics” edict of there being “no free lunch”. A Peltier cartridge is not a passive device…… it requires input power, that power dissipates as heat within the device.

Yes the cold junction can be used to cool something like an amplifier, but by virtue of doing work the hot junction needs to dissipate more Kcal of heat than that radiated by conduction through the cold junction.

The net result is that you will need to throw away more heat with, than without.

I just count on all those smoldering FET’s as my winter heat, enjoy the music and smile, smile, smile.

Kent

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Old 28th September 2001, 06:48 AM   #13
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As Kent said Peltier devices are not the best solution for amps. They do need of course power to work, but their main function is to get rid of ammounts of heat from one small place and move it qickly to somewhere else. So there is still the need to use cooling of some sort. Also they are not cheap, they cost a lot. When you make an amp like these you have to love with the heat.
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Old 16th November 2001, 03:32 AM   #14
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I am trying to adapt this style of circuit to a ZEN line stage with current sources but I can't get circuit maker to simulate it right. Nelson said to replace the 2 sets of 750 Ohm resistors with 40mA current sources. If I just put in 2 "symbol" I sources it works but when I try to fill in the whole tail end of the circuit with discrete components it goes pear shaped. Can anybody suggest values for the resistors or tell me where I could be going wrong?

Cheers

Dan
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Old 16th November 2001, 04:50 AM   #15
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Dan,
Try using values on the order of 15 or 16 ohms for R18 & 19 above. If it still doesn't simulate properly...build a quick and dirty version and try it out. I've never trusted simulation software anyway. Note all the trouble Petter ran into in his X amp thread.

Grey
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Old 16th November 2001, 05:05 AM   #16
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Alright, how the hell did you do that? It works a treat and now simulates exactly the same as the block CCS circuit.

Is this black magic or simple math?

If it's the latter can you enlighten me.

Dan
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Old 17th November 2001, 12:58 PM   #17
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Dan,
Nuthin' to it...
This particular design of current source uses the value of the resistor to set the current. The voltage between the base and the emitter (Vbe) of the MPSA18 will be about .6-.65V. This will change a bit with the value of the resistor above the collector, but can be taken as being fairly constant.
So--
Your desired current is 40mA
Just for giggles, let's say that Vbe is .65V
Then it becomes a simple matter of plugging the values into Ohm's Law and cranking the handle:
.65V/.04A= 16.25 ohms
Since 16.25 ohms isn't a standard value, by the authority vested in me by myself, I just kinda rounded things off and said 16 ohms or so.

Grey
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Old 17th November 2001, 05:03 PM   #18
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What is the difference in operation between a single current source (sink?) and the dual option you have put forward. I'm not sure of the subtlties of the operation of a differential pair, but won't having two current sources reduce some of the benefits of a differential pair, eg CMRR, distortion reduction (if any).

If the only reason to have dual current sources is the power dissplation in each transistor, then why not parallel them. The total current has to be the same in either the dual or single versions.
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Old 19th November 2001, 03:59 PM   #19
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Hi All,

I have been reading this thread with a lot of interest as I have always been interested in building a SOZ but have never done so because I can´t live with the very low efficiency of the amp. I did build a copy of the ZEN though and love the result.

Since this thread is about impoving the efficiency of the SOZ I was wondering if anyone has considered putting some large inductors in parallel with R1 and R2 as this will significantly improve efficiency (OK, some redesign of other parts of the amp will be nessecary as well.)

As a matter of fact I have and some time ago I had two large inductors made (150 mH; 3 Amp; 0.4 Ohm). I have been using these to modify my ZEN amp and the preliminarry results are very encouraging. In the end I want to use them to make a SOZ-like amp, but since I don´t have a balanced source to drive such an amp I will keep it unbalanced for the time being.

I am very courious as to your thoughts about this idea.

Tom
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Old 19th November 2001, 07:15 PM   #20
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We have a project scheduled which does something
similar to that, and it works great, particularly
with 1 Henry air core coils.
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