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Old 10th July 2013, 01:48 PM   #2211
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Still not convinced that there really is a problem. Line inputs are dead quiet (but also a bit audible hiss if you turn the volume way up). Phono adds 57dB (my Pearl) or around 60dB (built in phono) gain, so no wonder there is more audible hiss. Built in phono also hisses more than line inputs. It is only that my Pearl hisses a bit more than the built in phono stage (which by the way has very good noise specs) and other people seem to describe their Pearl as dead quiet.
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Old 11th July 2013, 05:38 AM   #2212
kop89 is offline kop89  United States
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Quote:
Originally Posted by Wellerman View Post
I still think mine is noisier than other people's builds. With the volume turned up, I have no difficulty hearing hiss. With the volume WAY up, I can even hear it from my listerning position 2.5m away. Then again, when playing music with the volume in this position, it would produce earshattering levels. It is a bit noisier than the built in phono in my amp, but this can only be heard with my ears next t the speaker. No hum in my build.

Edit: all with inputs not shorted. Never tried that.
From your description, it sounds like my build is as "noisy" as yours. I have both hiss and a very faint hum - my tube preamp probably contributed to the hiss, too. But most important, it is not noticeable when playing music. I think in this case time is better spent listening to records than hunting for hum.

I haven't compared the noise between the lowest and highest gain settings since I installed the switch - I will probably try this tomorrow.
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Old 11th July 2013, 05:40 AM   #2213
kop89 is offline kop89  United States
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I have also tried shorting the inputs - only very slighly better, but the hiss and faint hum still there.
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Old 11th July 2013, 05:45 AM   #2214
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I agree, time to give the Pearl some "burning in". I'm also not too worried about the noise. A silent groove produces a noise level higher than that of the Pearl, so it is quiet enough.
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Old 11th July 2013, 07:11 PM   #2215
Salas is online now Salas  Greece
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You never know who's got the quietest JFETs for nVsqrtHz from build to build unless measured one by one. K170s can vary +/- 15% for self noise.
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Old 28th July 2013, 02:46 AM   #2216
kop89 is offline kop89  United States
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Aha - hum gone (well, almost)!

I found that if I plugged all my hifi gears into the same power strip, the Pearl two is a lot quieter. Still have very tiny amount of hum/hiss at full volume, but now it is super-duper quiet at listening level.

The hum/hiss goes louder at higher gain (65dB) as expected.

Previously, my power amp went into a different power outlet.
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Old 28th July 2013, 04:12 AM   #2217
Lavcat is offline Lavcat  United States
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Quote:
Originally Posted by kop89 View Post
Aha - hum gone (well, almost)!

I found that if I plugged all my hifi gears into the same power strip, the Pearl two is a lot quieter. Still have very tiny amount of hum/hiss at full volume, but now it is super-duper quiet at listening level.
I'd stick a transformer at the input of the amp, myself, but then I am a fan of transformers.
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Old 28th July 2013, 04:40 PM   #2218
c_door is offline c_door  Italy
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Hello guys,
here is my try at Pearl 2.
External unregulated PS and two Salas shunt regulators (half Mezmerize boards), one per channel.
The boxes come from HiFi2000 (Modushop). R-Core transformer from Selectronic. Most part of components are from
Mouser, but for the additional jfets that come from an Israeli ebayer. Shunt heatsinks from a surplus fair.
RCA sockets from hificollective.
Everything measures fine, close to Wayne's values. Offset is stable and close to zero mV.
Only noticeable difference are the Q3 tensions:
Vb=8.12V, Vc=7,58V, Ve=7.54V (the other channel is close).
So Vb is greater than Vc. Should I tweak anything?
I made a fast listening test with a very old TT and a Stanton 681 EEE cart. It's a MM with 2.5mV output, not an ideal source for the Pearl2.
There is no hiss, only a moderate buzz at high volume. Still have to work on this.
The sound, with this far than ideal set, is full, vivid, with wide image and great realism.
It lacks openness at high frequencies, but I plan to hook the Pearl to my friend's super TT set, and see how it compares to his megabucks phono preamp.
I will report the forum about the showdown verdicts
Thanks a lot to Wayne and Salas for sharing the projects, and to the forumers for a lot of useful hints. The 6L6's building thread, as usual, was of great help.

Ciao. Carlo.
Attached Images
File Type: jpg Pearl2-1.jpg (352.5 KB, 267 views)
File Type: jpg Pearl2-2.jpg (395.1 KB, 226 views)
File Type: jpg Pearl2-3.jpg (343.0 KB, 231 views)
File Type: jpg Pearl2-5.jpg (214.7 KB, 233 views)
File Type: jpg Pearl2-6.jpg (708.5 KB, 230 views)
File Type: jpg Pearl2-7.jpg (217.7 KB, 144 views)
File Type: jpg Pearl2-8.jpg (220.1 KB, 163 views)

Last edited by c_door; 28th July 2013 at 04:46 PM.
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Old 28th July 2013, 06:02 PM   #2219
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I had the same as you around Q3. I have lowered R10 to 8k2 and raised the value of R21-24 to 20R. See discussion at pages 204/205.
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Old 29th July 2013, 01:18 AM   #2220
Gooch is offline Gooch  United States
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Very nice Pearl 2
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