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Pass Pearl Questions
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Old 17th November 2018, 05:05 PM   #1
hirscwi is offline hirscwi  United States
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Pass Pearl Questions
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Greetings. I have a Pass Pearl 2 phono premp that I built several years ago. I love it! I would like a version that would work for Moving Magnet cartridges. My questions are:

Was the Pearl 1 a MM version? Any chance of those boards being available?

Is it possible to convert the Pearl 2 for MM carts? Even better would be a switch to enable both options.

I've heard a bunch of phono sections and the Pearl is my all-time favorite.

Thanks for the information.
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Old 19th November 2018, 01:42 PM   #2
McQuaide is offline McQuaide  United States
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The Pearl 2 is a MM phono stage. If you read the original paper by Wayne you'll see it has 47K loading resistors in R19 and 55DB of gain. Decreasing R14 provides more gain for MC cartridges and R20 lets you change the loading for MC. Some people including myself report too much gain with MM that overwhelms the preamp, but this is an easy adjustment.
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Old 19th November 2018, 02:08 PM   #3
hirscwi is offline hirscwi  United States
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Greetings and thanks for your helpful information. May I ask a couple clarifying questions?

I built my Pearl 2 with R14=1K as per the original and have plenty of gain for MC cartridge (van den Hul with .65mV output). I was worried that an MM cart would overload the phono section so did not try that.


In my notes, I have the following information. It seems reasonable but I have not verified it.

• Increase gain changing R14 from 1K (original value) to 300 increases gain by 10dB.

• Reducing Gain:
o Changing R16 from 100K (original value) to 50K drops gain from 55dB to 45dB which might be OK for MM cartridges (second stage)
o If still had too much gain, can reduce the first stage gain by increasing R21-R24 from 10R to 20R.


Does this appear correct to you?

Thank you.
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Old 19th November 2018, 02:18 PM   #4
McQuaide is offline McQuaide  United States
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Quote:
Originally Posted by hirscwi View Post
Greetings and thanks for your helpful information. May I ask a couple clarifying questions?

I built my Pearl 2 with R14=1K as per the original and have plenty of gain for MC cartridge (van den Hul with .65mV output). I was worried that an MM cart would overload the phono section so did not try that.


In my notes, I have the following information. It seems reasonable but I have not verified it.

Increase gain changing R14 from 1K (original value) to 300 increases gain by 10dB.

Reducing Gain:
o Changing R16 from 100K (original value) to 50K drops gain from 55dB to 45dB which might be OK for MM cartridges (second stage)
o If still had too much gain, can reduce the first stage gain by increasing R21-R24 from 10R to 20R.


Does this appear correct to you?

Thank you.

There was a discussion about this in the main thread recently. Don't change R21-24. You can increase R14 above 1K to reduce gain, I have mine at 1.6K and will bump this up to 2K for a 5mv MM cartridge. Or change R16 to a value that works. I found that R16 at 50K isn't enough gain for a .2mv LOMC.


I have a 3 position selector switch on R14 so it's quite easy to experiment.
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Old 19th November 2018, 05:52 PM   #5
metalman is online now metalman  Canada
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Another option to reduce gain is to use the open spot of C15 and add a resistor there, which parallels R16. A 46k2 resistor there will reduce gain by 10dB. Personally, I installed breakaway SIP sockets in R20, R15 and C15 locations which allows me to adjust gain and loading without needing to desolder/resolder for every change.
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Old 20th November 2018, 04:18 AM   #6
hirscwi is offline hirscwi  United States
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Thanks for the great information. It's just what I needed. I will check out the main thread - I haven't been there for a while.
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