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Old 8th February 2013, 02:44 AM   #1781
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Default Input Capacitance and SUT's

I agree with 6L6. Start small and work up. Most good phono cables have on the order of 20-30 pf per foot. Most MM cartridges need a TOTAL of 250 to 400 pf to control the resonant peak of the fixed coil inductance...100 pf comes from the preamp, 60-90 pf from the cable, so theoretically you may only need 50-200 pf for the load cap.

SUT's - it all depends on the MC cartridge. Low impedance cartridges need low impedance inputs, hard to get with an SUT. Cartridges with air core coils (Fidelity Research, Denon DL-S1) are very low output and are compromised by ANY SUT due to interactions with the transformer inductance.

In my opinion a phono preamp with high enough gain to handle any cartridge, and high input impedance provides the flexibility to load the cartridge non-inductively to best match it's characteristics. That is the definition of the Pass / Colburn approach and provides the best way to match a wide variety of MC's. Using an SUT can provide good sound, but the SUT must be matched to the particular cartridge you want to use for best results.
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Old 8th February 2013, 07:37 AM   #1782
Marra is online now Marra  United Kingdom
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I use a pair of Sowter 1299's with my Denon DL-S1 and it sounds brilliant.Its a new design specifally for such low impedance and output cartridges.
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Old 8th February 2013, 09:38 AM   #1783
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Sounds like you found a good match. The difficulty with the Denon is that it has an unusual combination of about .15 mv output level with an output impedance of 40 ohms. I have one that I use with my Pass XP-15 and it sounds wonderful. It is a much underrated cartridge.
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Old 8th February 2013, 09:44 AM   #1784
Salas is online now Salas  Greece
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There audio files from that cart amongst several other MC/MM/MI models to download and listen to. From that nice gent: Hi-Fi Cartridge Reviews - Moving Coil Cartridges
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Old 8th February 2013, 10:49 AM   #1785
Siberia is offline Siberia  Lithuania
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Wonderful link. Hard to settle on one preference. What's your pick over those samples, Nick?
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Old 8th February 2013, 01:18 PM   #1786
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Thanks to all of you for your informative posts. It seems the Pearl Two is ideal for my needs.
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Old 8th February 2013, 01:43 PM   #1787
6L6 is offline 6L6  United States
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soldersmoker - This phonostage is truly incredible. I am sure you will be pleased with it.

If you have any (general or specific) questions along the way please feel free to contact me or ask them in the forum. There are a whole bunch of people here who would love to see you have a successful build.
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Old 8th February 2013, 07:10 PM   #1788
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Mine is making its stereo debut on the main amp and speakers for the first time tonight. It is sounding very good. Not a world of difference with the phono stage of my Sony ES amp, but subtle improvements is my first impression. But I will have to compare them more to make any definitive statements. Now that it is star grounded to the chassis, all hum is gone. Noise/hiss is about the same as the Sony, which is very good. I would't call it dead silent (the cd input is what I'd call dead silent) but considering all the extra gain it is very silent.

What is now left to do? I have some 0.5mm pure silver wire and pfte insulation on the way and plan to use that for internal wiring. Don't know if it will make an audible difference, but it just seems right to use noble materials for a great amp like this Then I will try to set P1 one more time, fix the prints in the case with their self ahesive feet, close the case, enjoy music and post some pictures over here...
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Old 8th February 2013, 07:27 PM   #1789
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Quote:
Originally Posted by 6L6 View Post
...

I would love to see a schematic of your circuit! Can you draw it out?
Pearl1.5 full schematic:

Pearl1.5 full schematic.png

It's just cobbled together from the Pearl2 pdf (I hope Nelson and Wayne don't mind! )

And that's pretty much what the circuit is too! A Pearl2 with only the positive power supply, the first stage and riaa ... and then a Pearl1 2nd stage with 2x 170 instead of one 389.


Last edited by AudioLapDance; 8th February 2013 at 07:30 PM.
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Old 10th February 2013, 05:45 PM   #1790
6L6 is offline 6L6  United States
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I think your schematic is great!

I wonder what Wayne thinks... (Hey Wayne! Any observations??)

It's certainly a 1.5 if there ever was one. A great blend of both Pearls. Arguable closer to the one, but that's no slight towards it at all - the One and the 2 are both fantastic.
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