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Re: Pass Zen V8 (Jfet) [message #10382 is a reply to message #10381]

Tue, 24 January 2006 07:35

Skip
Messages: 27
Registered: May 2009

Chancellor

Yep, 1 inverted 1875 using Scott Nixon's boards, and two, more or
less identical non-inverting 3875's using BrianGT v.1 boards. One
of the 3875's is shown in FredT's post in Wayne's GC group build
thread below.

I never did get a good comparison of the two types. Both sounded good.
I was using the 1875 to independently drive the two drivers on a
single Tower 2 Pi with bi-wiring jacks. It worked like crazy in a
situation where good stereo was out of the questions. I believe you
have done a 3875 if I remember correctly.

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Re: Pass Zen V8 (Jfet) [message #10383 is a reply to message #10382]

Tue, 24 January 2006 13:14

Manualblock
Messages: 4973
Registered: May 2009

Illuminati (13th Degree)

Thats right; actually I built the standard model Brian GT and when that sounded pretty good I ordered the "Boutique", version. The Black gate caps and Riken and I forget the other brand of resistor but they do make the amp sound better. I used a Hammond toriodal looks like the same one you have in the picture.
I just followed Brians instructions and the schematic and it worked right out of the box.
I would like to try the JFET; I think I will order some of the JFET's from the DIY site. Maybe some of the guys here will want to do this also. Any ideas for a PS on your end?

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Pass Zen V8 (Jfet) PS Thoughts [message #10384 is a reply to message #10383]

Tue, 24 January 2006 14:46

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Messages: 27
Registered: May 2009

Chancellor

I found some very cheap 48V CT (2A) transformers, and will play with
them. I would think that PS ripple will be poisonous to this circuit,
so I have hatched a hare-brained scheme. I wonder what would happen
if, after the diode bridge and, at least, a very small cap, you ran each
leg through the secondary of a transformer like (in this case the same)
as the main transformer. If you then connect the nominal primaries of
these two transformers so they oppose one another, would this act like
a conventional PS choke in a tube amp? My goal is something similar to
a choke input supply without having to find and pay for a monster, high
current choke with enough inductance. This seems too simple to me, so
I'm expecting to learn why it's not a good idea.

The transformer in the picture is an EI 40V CT that was on closeout
at Parts Express.

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Re: Pass Zen V8 (Jfet) PS Thoughts [message #10385 is a reply to message #10384]

Tue, 24 January 2006 16:15

Manualblock
Messages: 4973
Registered: May 2009

Illuminati (13th Degree)

Can you run this in PSUD?

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Re: Pass Zen V8 (Jfet) PS Thoughts [message #10386 is a reply to message #10385]

Tue, 24 January 2006 19:15

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Messages: 27
Registered: May 2009

Chancellor

Don't know if it could be put into PSUD. I haven't tried it on
anything. I wonder if you need to know more than the nominal
ratios of the tranformers to get a good result. I have no means
of getting inductance or much anything more than the ratios and
the DCR.

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Re: Pass Zen V8 (Jfet) PS Thoughts [message #10387 is a reply to message #10386]

Thu, 26 January 2006 15:10

Manualblock
Messages: 4973
Registered: May 2009

Illuminati (13th Degree)

I noticed a good PS regulating scheme for the Zen amps in an older copy of AE written by Nelson. Maybe it is on his site but it looks usefull in this context.

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Re: Pass Zen V8 (Jfet) PS Thoughts [message #10388 is a reply to message #10387]

Thu, 26 January 2006 17:25

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Messages: 27
Registered: May 2009

Chancellor

I think you mean this article on his website:

http://www.passdiy.com/projects/zenv3-1.htm

I think you are probably right, this is probably easier, and I
may end up there anyway, but I expect to fool around with
unregulated supplies first.

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Re: Pass Zen V8 (Jfet) PS Thoughts [message #10389 is a reply to message #10388]

Thu, 26 January 2006 19:11

Manualblock
Messages: 4973
Registered: May 2009

Illuminati (13th Degree)

Yep; you're probably better off. Say, that transformer you mentioned is on sale in the Parts Express flyer that came today. It's 4$ or so, is that the one?

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