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Old 19th July 2011, 05:43 AM   #1491
AKSA is offline AKSA  Australia
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Yes, ZL series was very good but I think is discontinued.

Hugh
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Old 19th July 2011, 05:44 AM   #1492
GregH2 is offline GregH2  Australia
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I've always liked Panasonic FC capacitors. Good quality, no nonsense parts that get the job done with low esr and inductance.
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Old 19th July 2011, 06:11 AM   #1493
mikelm is offline mikelm  England
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Quote:
Originally Posted by MiiB View Post
.Wonder if Rybucon that used to manufacture the BG's have any caps similar to what they used to produce for BG..
I began with 1uF film cap

Switched to 10uF black gate - sounded awful, didn't want to wait for ages to see if it got better after burn in.

Settled with 4.7uF film cap - this will do for now

Have to say didn't really notice much of a difference with this mod - treble sounded good already

I often use Rubycon ZA/ZL - used to be called ultra low impedance, now called general purpose . . .

However, changing from irf9610 to zvp4424a had a mind blowing positive impact on sound. Had to add a few pico farads of miller cap to suppress 50MegHz 2V oscillation ( on one channel ) - used about 2" of a tightly wound CAT 6 pair for this tiny capacitance ( both channels )

The sound is much much much cleaner after this mod - can't work out if this is just due to more OLG, better PSRR etc, or because irf9610 is inherently noisy - perhaps a bit of both ? ? ?

I have some 2sj79s' so I can try sometime but as far as I could work out from the data sheets 4424a gave the best transconductance at 10mA.

Downside for me is that the DC drift just got worse with this mod.
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Old 19th July 2011, 06:19 AM   #1494
GregH2 is offline GregH2  Australia
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Mikelm,

Sad to hear the cap didn't work for you. Maybe give another type a go some time though just to be sure, and try 22uf?

Very glad that your results at least agree with mine re removing the 9610. The zetex fets really work wonders don't they?

What are the size of the resistors in your feedback network and what size feedback shunt cap are you using? My DC offset is fine even with the zvp3310 which is only a 650mW device. Perhaps it's time you made a fet based CCS?
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Old 19th July 2011, 06:20 AM   #1495
mikelm is offline mikelm  England
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Quote:
Originally Posted by AKSA View Post
Yes, ZL series was very good but I think is discontinued.Hugh
Farnell UK have them
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Old 19th July 2011, 06:30 AM   #1496
mikelm is offline mikelm  England
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Quote:
Originally Posted by swordfishy View Post
What are the size of the resistors in your feedback network and what size feedback shunt cap are you using? My DC offset is fine even with the zvp3310 which is only a 650mW device. Perhaps it's time you made a fet based CCS?
FB = 500 / 47R

I know that you have no real DC offset problems with AC coupling but once you have done all your other mods for filtering etc if you try complete DC coupling you might decide you would be happy to have the offset problems . . . . . . . you might even decide you prefer a film cap across the bias resister

My boards a due today - they are designed to accommodate DC offset measures so I will begin that soon.

Last edited by mikelm; 19th July 2011 at 06:37 AM.
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Old 19th July 2011, 06:38 AM   #1497
GregH2 is offline GregH2  Australia
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Oh, I didn't realise you were already using DC coupling for the feedback network. That explains your offset issues then.
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Old 19th July 2011, 06:46 AM   #1498
mikelm is offline mikelm  England
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oh, and I have about 50pF + 99R lead compensation
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Old 19th July 2011, 12:24 PM   #1499
MiiB is offline MiiB  Denmark
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Mike

the SJ79 may have lower trans-conductance, but that same low capacitance.. I dont think that the sound suffers by a lower OLG... and in my Sims its dead stable without miller cap .. and with limited lead compensation 220R+22pf
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Old 19th July 2011, 12:26 PM   #1500
MiiB is offline MiiB  Denmark
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Mike

the SJ79 may have lower trans-conductance, but at the soma time also low capacitance (90pF vs app 150pF).. I dont think that the sound suffers by a lower OLG... and in my Sims its dead stable without miller cap .. and with limited lead compensation 220R+22pf

(sorry for the double post, on vacation and mobile devices seem to live a life on their own)

Last edited by MiiB; 19th July 2011 at 12:30 PM.
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