Zen I/V Converter

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#324
Zero Cool said:
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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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
 
#325
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?
 
#327
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?
 
#328
At weekend I have experimented both with D1 (non symmetric, i. e. one half) and ZEN-I/V topologies as showed about
http://www.diyaudio.com/forums/diyaudio-com-articles/172983-zen-i-v-converter.html

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 ?
 
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#329
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
 
#332
I found some K147's and some J72's at work which are the same family as the J74/K170 just a higher current rating. I am going to attempt to use those however they are house marked so I don't know what the gain code is? is there a quick and easy way to set up a test jig to figure it out?

and what if the N and the P devices are different gain codes? would there just be asymmetrical distortion?
 
#338

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