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Old 29th January 2013, 06:18 AM   #1731
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PSU is shown in post 1711. Just the one from the Pearl II article with 2 CL60 NTC's added. And a 2x24V toroid in stead of 2x22V.

I wanted to isolate the cooling fins to make the thing less vulnerable. Dropping something on the print now makes it easier to short something to ground. But maybe I will leave it like it is...
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Old 29th January 2013, 08:38 PM   #1732
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I hooked up both channels (one at a time) to a Denon PMA880R connected to a small Eltax speaker (so I'd only blow up old stuff if something went wrong).

Both channels work, but there is something wrong with the left channel: it's very noisy. Way more noisy than the phono stage of the Denon (at it's MC setting). The right channel on the other hand is much better; a bit quieter than the Denon. Any suggestions what could be wrong in the left channel? Voltages measure OK, about the same as the right channel. Only thing is I'm not so sure about the 0V DC I'm supposed to measure at R17. It tends to drift a bit. Will have to analyse that some more.

I think I could do with a bit more gain, maybe 60dB. What is the preferred method here? Lowering the value of R14 (to something like 600 Ohm) or introducing R15? And which value for R15?
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Old 30th January 2013, 08:55 PM   #1733
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On a hunch I changed out Q2 and that did the trick. Now the left channel has low noise like the right channel. P1 needed to be adjusted quite a bit with the new Q2.

Now I am going to experiment a bit with more gain. I've got some resistors on order and will try out 750 Ohm for R14 first (gain 57,5 dB). If that is not enough I will go to about 60dB gain. Trade-off between gain and noise I guess.
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Old 31st January 2013, 04:18 AM   #1734
kop89 is offline kop89  United States
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Which capacitor on the Pearl 2 board sets the capacitance loading for the cartridge?
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Old 31st January 2013, 05:17 AM   #1735
omishra is offline omishra  India
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Quote:
Originally Posted by kop89 View Post
Which capacitor on the Pearl 2 board sets the capacitance loading for the cartridge?
Its C22, (100pF). You have to consider capacitance of the cable between cartridge and phono stage, minus that from required cartridge loading capacitance and arrive at proper value of C22.
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Old 31st January 2013, 06:13 AM   #1736
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You would probably hardly need C2 as many cables from the turntable will already have 100pF capacitance themselves. But MC cartridges are not so sensitive to capacitance as MM. For my Goldring Elite, capacitive loading is specified as 100-500pF, so I have just used 100pF for C2.
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Old 1st February 2013, 04:41 AM   #1737
kop89 is offline kop89  United States
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Originally Posted by Wellerman View Post
You would probably hardly need C2 as many cables from the turntable will already have 100pF capacitance themselves. But MC cartridges are not so sensitive to capacitance as MM. For my Goldring Elite, capacitive loading is specified as 100-500pF, so I have just used 100pF for C2.
I will be using the Ortofon M2 Blue cartridge. Recommended load capacitance is 150-300pF, so looks like the default 100pF will work fine.

Any suggestion as what kind of capacitor? Silver mica OK?

Thanks
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Old 1st February 2013, 06:23 AM   #1738
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100pF probably fine, you could order some 50pF as well to experiment with. I used silver mica. Some are enthousiastic about them, some less. But with only 2 silver mica's in the cicuit (C9 as well) I'm not really afraid they will give me a grainy sound. From what I've experienced so far my Pearl has a warm sound signature.
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Old 1st February 2013, 07:08 PM   #1739
kop89 is offline kop89  United States
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Originally Posted by Wellerman View Post
100pF probably fine, you could order some 50pF as well to experiment with. I used silver mica. Some are enthousiastic about them, some less. But with only 2 silver mica's in the cicuit (C9 as well) I'm not really afraid they will give me a grainy sound. From what I've experienced so far my Pearl has a warm sound signature.
Hmmm.... maybe I will setup a 2-gang rotary switch with a couple different values to experiment with the loading caps.

Have you ever compare the Pearl 2 with other phono stage? I am wondering where it stands sonically compared with $1000-ish commercial phono stage. I was originally going to build the ONO but it is a more complicated project.
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Old 1st February 2013, 10:35 PM   #1740
6L6 is offline 6L6  United States
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Originally Posted by kop89 View Post
Have you ever compare the Pearl 2 with other phono stage? I am wondering where it stands sonically compared with $1000-ish commercial phono stage.
Comparing the Pearl or Pearl2 with a $1000 phonostage it easy - it will beat them into submission, into a bloody pulp, to within an inch of their life. The Pearl really is that good. (assuming you build it well)

A 1000 buck phonostage, using the 4 to 1 cost to retail formula costs $250 to make. Half of that is labor, giving it about $125 worth of parts.
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