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Old 21st March 2013, 08:14 AM   #2091
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With 8k2 for R10 Vb drops below Vc and Ve is something like 7.8V, still high enough.

The voltage across R21-R24 differs a bit in one of my quads (using 20R now): 110,5mV lowest, 113,2mV highest. The quads were matched closer (within 1% Idss). Is this a problem?
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Old 23rd March 2013, 12:06 AM   #2092
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Anyone believe there is a break in period with Pearl 2? My experience yes. One week in, listening to Santana "Welcome", huge smile on my face. This sounds awesome!
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Old 23rd March 2013, 08:43 AM   #2093
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I usually attribute perceived changes to habituation, except for speakers/phones which involve mechanical breaking in. The Pearl does need a bit of time warming up though, you can measure differences in for instance voltage across R21-24right after startup, after 10 minutes, after an hour.

Maybe experts can explain which changes occur in parts after breaking in.
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Old 23rd March 2013, 12:38 PM   #2094
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I do not profess to be an expert, but I have to agree with Wellerman, I can not understand how nor if there is any breakin period for the components used in this design. You can do some measurements THD, IMD, F response etc, but I doubt that they would change very little from the beginning to after the breakin period. I think it is more psychological than electrical. Bias point change, from initial, would be a result of heat alone, so that is why it should be performed after thermal stabilization
As far as the cascode transistor goes, the measurements show, as well as Pspice, that this device is operating in the saturation region, which I do not see any issues with this.
The I/P stage gate/source voltage measurements look fine as well, There is always going to be some slight difference. Matching IDSS is only one method, and probably the simplest method to match a jfet, but remember that this is not the mode of op in the ckt. Also important is the pinch-off V in matching jfets.
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Old 24th March 2013, 02:37 AM   #2095
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I did some searching on burn in of solid state devices - hotly debated subject! The human brain definitely comes into play. I always felt mood and mindfullness impact taste perception when eating, no doubt music.

I was also reminded that the Pearl 2 inverts the phase. I did some before and after listening switching polarity on speaker terminals. Better definition of bass with correct phase. Easy to hear the difference listening to the first 2 tracks of Massive Attack - Protection. I will likely change polarity at cartridge and switch speakers back.
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Old 24th March 2013, 06:15 AM   #2096
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Default helpful suggestions pls

my pearl II is finished and has had moments of greatness, thank you Wayne.
But one thing keeps happening, I lose gain in one ch, -3~6 db. I change the zvp 3310 and it fixes it. then it goes again. I measure voltages and they are very close, .x nothing sugesting trouble. feed back resistor are .1% and measure the same. any thoughts or questions?
Thanks in advance if you answer.
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Old 24th March 2013, 01:19 PM   #2097
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Quote:
Originally Posted by jjacks4x View Post
my pearl II is finished and has had moments of greatness, thank you Wayne.
But one thing keeps happening, I lose gain in one ch, -3~6 db. I change the zvp 3310 and it fixes it. then it goes again. I measure voltages and they are very close, .x nothing sugesting trouble. feed back resistor are .1% and measure the same. any thoughts or questions?
Thanks in advance if you answer.
Mine is doing something similar, and just pulling and re-seating the output RCAs resets it back to normal.
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Old 24th March 2013, 03:20 PM   #2098
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Default not so lucky

mine stays the same thru many ponits of measuement. the channels are the same in the first stage, the problem occures in stage 2(post eq-output)
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Old 24th March 2013, 05:08 PM   #2099
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Curious. Do you have C7 installed? Wayne suggested leaving off after his article was published. Is voltage at R16/R17 stable?
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Old 25th March 2013, 03:39 AM   #2100
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going to take it off now and check, the off set hold around .0xx , it does take time to settle and it is not in a case so air is a factor.
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