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Seeking Zen V7R/T and XBOSOZ advice.
Seeking Zen V7R/T and XBOSOZ advice.
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Old 19th January 2005, 02:48 PM   #1
chemania is offline chemania  United States
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Join Date: Jan 2005
Location: TN
Default Seeking Zen V7R/T and XBOSOZ advice.

Hello all,

I am a basically a noob when talking about PASSDIY stuff and know just enough about electronics to be very dangerous. I have completed one PASSDIY project and several kit projects in the past. I built a shoestring BOZ. Final cost was less than $50.00 and it immediately replaced my YBA 3 preamp.

I have started a couple amp projects in the past but have never completed one. I am now hankering to start and complete one. I have been lurking and searching here for the past month but have not seen any answers to my questions already posted (I am sure they are around somewhere though).

I currently have 2 A40 boards stuffed but no other parts (about 8 other blank boards). I also have two original zen boards stuffed and ready but no other parts (donated by an old college buddy). This brings me to my first question.

Q1: I do not have the time or funds available to build multiple amps to “play” with different topologies. I was thinking about just trashing the Zen V1 and A40 and going directly to the V7R/T. I will be using Fostex FE206E’s as drivers. Should I do this or just go ahead and finish one of the boards I have ready? I AM going to build a XBOSOZ. I just gotta try that SuSy technology!

Q2: If I come to the consensus to build the Zen V7R/T, can I build the T circuit and run it with the power resistors in place of the inductors until I get a distortion analyzer. (I know the ccs is different but I don’t have the ability to analyze the difference (I only had Circuit Analysis I and II about 20 years ago)). I have a friend at WUSTL that will set the V7T up for me (he says he has a distortion analyzer in his lab) but I cannot make that trip until spring break. I would like to verify that the board works as expected before making the trip. My idea was to build a 50V regulated PS and then short some Zeners when switching to the inductor based version. Whadda ya think?

Finally, Q3: In Henrik’s ZBOSOX V1 the 4 bias resistors would have an Req of 750R while in the original each MOSFET would be biased by the 1500R series Req. Would this difference not change the bias of the MOSFETs?

Thanks for putting up with my questions,

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Old 19th January 2005, 03:52 PM   #2
stefanobilliani is offline stefanobilliani  Italy
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Join Date: Jun 2002
Location: Italy
Hello ,
I will answer at you final question n°3:

It will not change the bias of the mosfets .
The parallel is 750 but this will not alter the bias : in fact also if the 2 halves of the circuit would be completely separated the bias would be the same .
By the way , the mosfets mismathc will produce slightly differences in bias through each side.
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Old 20th January 2005, 01:55 AM   #3
Nelson Pass is offline Nelson Pass  United States
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Seeking Zen V7R/T and XBOSOZ advice.
Anything for a newcomer.

The big trick to playing with lots of amps is to build a reasonably
big over-kill power supply and run it with a variac. That way you
can use it for anything. Then, get a big heat sink and throw
some good power Mosfets on it. Now you can build different
amplifiers all day long. This is how I do it.

If you are running a Fostex 206E, very nice driver, you don't
need more than about 10 watts. Of the Zen series, the original
SOZ is the best yet on those, although there is a Zen coming up
aimed at these types which is more efficient, if not simpler.

check out the article on www.firstwatt.com on loading for the

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Old 20th January 2005, 06:43 AM   #4
jh6you is offline jh6you
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Join Date: Aug 2002
Location: Near to the Pacific Ocean
Additional reply to Q3:

The Henrik’s bias seems to have about 40mmA through each FET. Using 2 x 750 instead of 1 x 1500 could be simply to consider the heat dissipation shared by two smaller wattage resisters.
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