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Old 20th January 2013, 08:43 PM   #1721
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I fired it up tonight and the good news is that it didnīt blow up (or at least, so it seems). The bad news is that I am not completely satisfied with some voltages, so I need some help:

1. How stable should the 0V DC at R17 be? Mine fluctuates, somewhere in the range of -20mV to +30mV. It goes up, then down, then up again etc (mostly staying positive). Is this normal?
2. The voltages around Q3 are lower than they should be. I get 7V at the base and 6.4 at the emitter and collector. That's 3V less than other measurements I've seen. I remember vaguely someone else having this problem in this thread. Could it have something to do with the Idss of the quad Q6-Q9? (9,3 mA in my case). Voltages at the source of Q6-9 are 68mV. This is also somewhat higher than Wayne's figures (10-40mV) and measurements of someone else who got 53mV.

Other voltages are quite close. Maximum deviation 0,6V at the emitters of Q10 and Q11 (I've got -22.4 in stead of -23). But I've got + and - 23.5 V at the regulators in stead of + and - 24.
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Old 20th January 2013, 08:53 PM   #1722
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Already found post 1578 where someone else has exactly the same problem, so I will try to replace R9 with 333 Ohm.
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Old 22nd January 2013, 01:58 PM   #1723
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Ehm, I won't as I just read that R9 is part of the RIAA network.

Still confused about what Voltages around Q3 should be. Wayne gets 9.5-10, but user Siberia after modification of R10 got 4.7-7 which according to Pierrequiroule was also good.
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Old 22nd January 2013, 02:22 PM   #1724
Siberia is offline Siberia  Lithuania
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Hello,

As you have read further, I did away with lowering R10 and everything sounding fine. Although, I have addressed the same question about voltages to Wayne in PM, there were no replies.

Here's the Waynes values sheet: http://www.diyaudio.com/forums/attac...rl2votages.pdf

BTW I've got the same +-30mV drift as you've got and I consider it a safe one.

I very much admire you P2P build.
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Old 22nd January 2013, 04:50 PM   #1725
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Thank you for your reply. I indeed read some more and I think PierreQuiRoule stated that the voltages around Q3 can differ with Idss of the quad. Higher Idss, lower voltages. That could explain the lower voltages with my quad (Idss around 9.3 mA). I'll start with replacing R10 with 6.81k, I've got some spare ones of those.
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Old 22nd January 2013, 08:04 PM   #1726
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measured Q3 voltages:

with R10 = 10k:
Vc = 6.45 Vb = 7.07 Ve = 6.40

with R10 = 6k81:
Vc = 6.28 Vb = 6.87 Ve = 6.21
still not Vc > Vb > Ve

but with R10 = 4K75:
Vc = 6.32 Vb = 5.95 Ve = 5.31
Here Vc > Vb > Ve

Is this looking good in the eyes of the experts? Move on to building the left channel?
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Old 27th January 2013, 03:05 PM   #1727
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Wellerman. - Catching up to you. Looks good.

Finished my PSU done today. Had to sort hack the wiring between the rectifier boards, caps and and all the signal ground connections - I guess you cannot always have a nice PCB! Not pretty but safe and solid. I followed the PSU from the Pearl 2 article except added the missing signal ground between the 2 caps that 6L6 pointed out. Measured -31.6 and + 31.2 v on the output. All seems good. Drilled a small hole and glue gunned a blue led on the front panel with a 4.7k, 3 watt resistor for a power indicator. Ready to move on to the amp boards. My in-laws bought me a Hakko fx-880 soldering station - my wife emailed them my Amazon wish list. Thanks again to 6l6 for providing an great online build guide and plenty of offline help and advice.
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Old 27th January 2013, 08:32 PM   #1728
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OK, nice to see another Pearl II in the making. I will finish the left channel this week I hope. If that measures OK as well, I will then test both on an old amplifier and old speakers. If they pass that test, I will put them in their case and hope I will not have problems with hum.
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Old 28th January 2013, 08:38 PM   #1729
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I finished the left channel today (shown on the right in this picture):

Click the image to open in full size.

Voltages measure well, mostly within 0.1V from right channel voltages.
Voltages around Q3: Vc = 6.09, Vb = 5.95, Ve = 5.31. Vc is 0.2 lower than in the right channel, but I guess this is still OK.

I still need to isolate the voltage regulators from their cooling fins, and then later this week I can start testing them with some real music.... Oh yes, and trim the leads of those 4k75 R10's
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Old 28th January 2013, 09:19 PM   #1730
6L6 is offline 6L6  United States
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Looking really good! What are you doing for the PSU?

Quote:
Originally Posted by Wellerman View Post
I still need to isolate the voltage regulators from their cooling fins,
Why bother? They don't touch anything, and this way they will have better thermal transfer to the heatsink.
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