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Old 19th October 2011, 09:23 AM   #321
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Quote:
Originally Posted by PA0SU View Post
on my web site: by-rutgers.nl
thank you very much for this advice.
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Old 19th October 2011, 12:58 PM   #322
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Quote:
Originally Posted by jazz View Post
Yes, I built it and it hasn't been out of the system since.

grtz
Joris

I want to build 4 of them for balanced operation. I just need to acquire some J74's! I have access to lots of K170's.
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Old 19th October 2011, 02:13 PM   #323
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Has anyone tried this Converter as MC section?

Regards,
Reinhard
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Old 20th October 2011, 11:52 AM   #324
jazz is offline jazz  Netherlands
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Quote:
Originally Posted by Zero Cool View Post
I want to build 4 of them for balanced operation. I just need to acquire some J74's! I have access to lots of K170's.
Hi,

In that case it might be easiest to just order some sets through the vendor forum. iirc there are a few members offering matched sets of em. I say this cause my own attempts at matching did not quite suffice for my tastes (I used v-grades and matched em to 0.3 ma idss and had about 50 j74's versus 100 k170's which resulted in an offset of about 10mV at the input but some variance in the load resistors might be at play there as well). I would expect someone with better stocks to do better.


I'd also incorporate the suggested voltage divider to the gates from the onset so you gain a bit more flexibility in matching from the start. Then you can save the k170's you've got for an output buffer like the B1 or the one used by Borbely.



regards,
Joris
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Old 24th October 2011, 05:20 PM   #325
ctong is offline ctong  United States
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Default Capacitor issue

I have a question on a related issue. When I build an IV stage I also add better ones to the DAC chip decoupling capacitors, which are often SMD type. Is it a bad idea to leave the original ones in place? In other words, is paralleling a good cap to a bad cap of a similar capacitance worse than just using the good one alone?
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Old 25th October 2011, 01:49 AM   #326
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Quote:
Originally Posted by reinhard View Post
Has anyone tried this Converter as MC section?
Some time ago. Works great if you want low input impedance. Generally you
will want to increase the Drain resistance for more gain.

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Old 30th October 2011, 03:41 PM   #327
ctong is offline ctong  United States
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Default Another capacitor issue

In preparation for building a Zen IV stage I am experimenting with the output coupling capacitors in the D1 IV stage. I am considering trying some boutique brands. I intend to use >10uf total. Due to cost and space, I can only afford 1) a 10uf polypropylene film, such as a Axon and a 0.47uf polystyrene (Rel Audiocap RT), or 2) a more expensive 10uf polypropylene Rel Audiocap PPT Theta, and a 0.01uf polystyrene. Which option is likely to perform better? I would appreciate other suggestions.

Also, I consider the bypass capacitors for the positive rail in the signal path. The influence of the negative rail might be less strong. Has anyone experimented with different capacitors?
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Old 2nd November 2011, 10:49 PM   #328
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At weekend I have experimented both with D1 (non symmetric, i. e. one half) and ZEN-I/V topologies as showed about
Zen I/V Converter

There are audible differences, but the perception differences was very low and a statement regarded a better sonic quality was not clearly possible.

With perfect quality studio productions ("Nightclub" - http://www.patriciabarber.com/discs/index.html and various cd's from OPUS Records e. g.) I prefer the D1 topology because of the more soft and smooth character at the upper end, i. e. less harsh.

By older recordings, where the high frequency aera is already weakened, I prefer the ZEN I/U push-pull converter with the complimentary J-FET's.

What is now the theoretical disadvantage of the IRF610 using in the D1 ??

Which of audible influences are to expect from each of the three present parasitic and unwanted capacitors of the IRF610 or IRF710 (Cin-Cout-Crev resp. Cgs-Cgd-Cds) ?

And a second question: How can I convert the complimentary ZEN I/V in a circlotron topology, so I don't need a P-Channel jFET from the 2SJ series ?

Last edited by tiefbassuebertr; 2nd November 2011 at 10:59 PM.
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Old 2nd November 2011, 11:15 PM   #329
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I have some 2SJ72 Jfets I can get from work, can i use those in place of the J74's? from the sparse datasheet i have seen, they are the same family. but the 72 will handle 600mw where as the 74 is good for 400mw. everything else appears to be the same. any reason why I couldn't or shouldnt use them??


Zc
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Old 2nd November 2011, 11:47 PM   #330
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Not much fun if you don't have the K147 counterpart, at $7.5 the pop (N)OS average value a bit over the top maybe.
And don't even say they're Violets.

(btw Dave, was fun to shake hands 7 years after the first encounter)
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