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Old 4th February 2013, 02:25 PM   #1771
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Pearl1.5

1st stage from the Pearl2
Positive Power supply from the Pearl2

2nd stage from the Pearl1



The 2nd stage from the Pearl1 uses the Positive Power supply on the Pearl2 PCB.
Instead of using the dual 389FET in the Pearl1, I used two 170s in parallel (like 1in the first stage of the Pearl2)

I'll try to draw up a schematic ...

Cheers,
Jeff

Last edited by AudioLapDance; 4th February 2013 at 02:28 PM.
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Old 4th February 2013, 02:43 PM   #1772
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Quote:
Originally Posted by 6L6 View Post
I recall Wayne mentioning that it was really difficult to overload the input of the Pearl2. Try it in a stock configuration or maybe with a reduced gain and see if it's an issue. I bet it won't be.
I will give the Bias 2 with stock config first. It will probably be a huge upgrade from the Pyle PP-999! I had not touched vinyl in 20-25 years until a few months ago. What a slippery slope!
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Old 4th February 2013, 05:11 PM   #1773
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Pearl 1.5 2nd stage

Pearl1.5 2nd stage.png

Pearl 1 and Pearl 2 ... Frankenstein! frankenstein.gif
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Old 4th February 2013, 06:14 PM   #1774
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Not sure I follow the why. No time to stuff the Pearl2 boards and swap out?
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Old 7th February 2013, 05:12 AM   #1775
kop89 is offline kop89  United States
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Quote:
Originally Posted by dcbingaman View Post
6L6 - here are some more photos of the back panel. 2PDT and 4PDT switches which have three positions (on-off-on) give you lots of possibilities for this application. In addition, unlike those 8-section dip switches, these big dudes have large contacts, and are easy to switch "blind" from the front side without pulling the thing out of your rack.
Hi dcbingaman,
when you use 50R and 100R for the loading, they will be in parallel with the base 47K on the PCB, so the total loading for each switch position will be:

load 1: (50 x 47K)/(50 + 47K)

load 2: (100 x 47K)/(100 + 47K)

Is this correct?
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Old 7th February 2013, 08:09 AM   #1776
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Kop89, yes that is correct. In reality, the values you calculate will be so close to the desired load values that you just use them instead....the cartridge sees the 50 ohm resistor across the switch, and the voltage produced drives the much higher impedance of the input stage. In this way you can get three values from one 2PDT switch with a center off position - in your case: 50 ohms / 47K ohms / 100 ohms.

I picked values based on the two MC's and the MM I use most often - 50 ohms for an Ortofon Synergy SPU, 150 ohms for a Shelter 90X, and 47K ohms for a Clearaudio Maestro.

You can do the same with capacitance as well - shunt the input at the switch with those little polystyrene caps or silver mica caps to get XXX pf on either side, and use the center off position for MC's where you want to minimize input capacitance.
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Old 7th February 2013, 09:27 PM   #1777
kop89 is offline kop89  United States
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Originally Posted by dcbingaman View Post
I picked values based on the two MC's and the MM I use most often - 50 ohms for an Ortofon Synergy SPU, 150 ohms for a Shelter 90X, and 47K ohms for a Clearaudio Maestro.
Thank you dcbingaman, your connection diagram has been very helpful.
I plan to use Ortofon 2M Blue, so maybe 45dB gain will work best. Recommended resistive loading is 47K, and capacitance loading is 150-300pF. Considering capacitance already in tonearm cable, what kind of capacitor value do you think I can try for the loading?
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Old 7th February 2013, 10:10 PM   #1778
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dcbinaman, I guess you're not in the "MC sounds best via MM+SUT" camp? I ask because I have a Denon DL-103D that I'd like to try with this phono pre. Right now I'm using a 6DJ8 stage with Cinemags.
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Old 7th February 2013, 11:06 PM   #1779
6L6 is offline 6L6  United States
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There is no proper answer to the ?Transformer or no Transformer? question... It's a matter of taste. Some combinations will sound better with it, some without, and in every case it will be your preference that matters.

Try the 103 with the transformer into the Pearl, you are not going to overload it. It will most likely be awesome!
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Old 7th February 2013, 11:17 PM   #1780
6L6 is offline 6L6  United States
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Quote:
Originally Posted by kop89 View Post
I plan to use Ortofon 2M Blue, so maybe 45dB gain will work best. Recommended resistive loading is 47K, and capacitance loading is 150-300pF. Considering capacitance already in tonearm cable, what kind of capacitor value do you think I can try for the loading?
Most tonearm cables are enough for 'normal' cartridges. If you want to try adding some capacity to the input, start small. Maybe 50-100pf. Add to taste.

Also, please report your findings back here, we will be curious as to how your tuning goes!
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