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Old 3rd March 2009, 12:05 PM   #101
iko is online now iko  Canada
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Quote:
Originally posted by keantoken

http://www.diyaudio.com/forums/showt...05#post1759105

The 2N6387 is a power darlington! Is this an error?

- keantoken
It is indeed a power darlington. And in that circuit it gave me the best performance, in reality, as you see the attached scope pic, of the regulator output when attached to the phono preamp, sadly just a prototype without a good layout, etc. There is room for improvement. Lower trace is the scope channel on its GND setting (thinnest trace possible), upper trace is the regulator, scope on 5mV/div. I expect even better results from a Jung regulator.

I will get back with more comments about the rest a bit later.
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Old 3rd March 2009, 12:08 PM   #102
Salas is offline Salas  Greece
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I would see about TIP110 too, which gives higher hfe when the current is lower. 6387 is at its best when the currents are very strong.
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Old 3rd March 2009, 01:44 PM   #103
Salas is offline Salas  Greece
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Out of curiosity, I run your test too, setting my scope on dual channel 5mV/div. Channel one is the output of my standard LED MOSFET CCS shunt @ 200mA when feeding my NJFET phono (upper trace). Lower trace is channel two, just on scope's own GND. I don't see any difference in thickness or any fuzziness. Maybe you pick up some spurious noise?

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Old 3rd March 2009, 02:16 PM   #104
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salas, that looks very nice; I have yet to get such a clean trace from any of the regulators I built, including the schematic you have shown.
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Old 3rd March 2009, 02:27 PM   #105
Salas is offline Salas  Greece
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Getting a visually much thicker and fuzzier line even with your ''turbo'' version is suspect IMHO. Points to some grounding issue or noise pick up possibly. In page one there are some analogous scope pics from a CRC pre filtered Jung in a Marantz. It thickens there too when applied to the machine. Environmental noise or total loop gnd issues again maybe.
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Old 3rd March 2009, 03:01 PM   #106
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Quote:
Originally posted by salas
Getting a visually much thicker and fuzzier line even with your ''turbo'' version is suspect IMHO. Points to some grounding issue or noise pick up possibly. In page one there are some analogous scope pics from a CRC pre filtered Jung in a Marantz. It thickens there too when applied to the machine. Environmental noise or total loop gnd issues again maybe.
I noticed that too, and I agree with you. This probably points to the fact that if the implementation is done well (grounding and all else) this discussion about the different regulators becomes very much just academic.

As far as academic discussions go, simulating with the TIP110 does indeed improve performance a bit. I'll look for a tip110 to try in the real circuit and see what happens.

Thanks for the tip (no pun intended) I don't know about others, but I've learned to appreciate the quality of your advice.
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Old 3rd March 2009, 03:20 PM   #107
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The scope is helpful when you measure noise -- better yet, it is helpful to have an "envelope" function -- so you can see what's going on over time. You have to baseline everything. Texas Instruments has a nice circuit for measuring regulator noise -- it's on the product folder for the TL431 regulator.

Almost all "True RMS" meters I measured for an AX article fall down when measuring noise -- except the Hewlett Packard 3403C or the Fluke 8620A -- the latter is usually on EBay for the price of a decent Cote du Rhone. Folks reported back to me that the older HP's, GenRad's and Boonton's worked well too. The true RMS converters from Linear Tech are almost as good as the HP and Fluke meters cited above.

I will stick with the Jung/Didden -- Jan's testing of the noise and impedance was well documented -- while WJ certainly had a expressed fondness for the AD797, I have used the AD825 and various Linear Tech devices and the performance is only slightly inferior to the AD797.
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Old 3rd March 2009, 04:09 PM   #108
juma is offline juma  Germany
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Giasou Salas,
I like your shuntreg from post #103 but one thing is not entirely clear to me: you bias JFETs (Q2 and Q5) at Idss and you use R5 (100 R) and R3 (10 R) just to lift JFETs a bit from the ground. What is it good for (using R3 and R5 like this)?
Thanks
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Old 3rd March 2009, 04:12 PM   #109
Salas is offline Salas  Greece
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Gave me quicker transient response in this particular implementation.
How is your current mirror one doing? Still on LM317 CCS?
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Old 3rd March 2009, 04:18 PM   #110
juma is offline juma  Germany
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Quote:
Originally posted by salas
Gave me quicker transient response in this particular implementation.
How is your current mirror one doing? Still on LM317 CCS?
On the scope I can't see the difference - it looks the same with LM317 as CCS but with MOSFET/LED CCS there is a certain positive quality of sound in highs, so I'll stick with it
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