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Old 7th April 2013, 09:26 AM   #11
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Join Date: Mar 2013
Location: British Columbia
Quote:
Originally Posted by omishra View Post
Sorry it's MV 109 diode. Also there are lot of 1SV 149 diodes are available which could used for changing capacitance ~20-500pF.
I like your idea. Very exciting! if you manage to do it i would love to see photos.
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Old 20th June 2013, 02:22 AM   #12
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Join Date: Mar 2013
Location: British Columbia
Update:
So ive finished my pearl 2 and it sounds fantastic. Truly top notch. If youre considering it, stop and just get started on your own!

In my build ive intgrated 4 rotary switches mounted to the front pannel to allow custom tuning a few key components to accomidate any cartridge one could ever dream of using. Ive made my selections made on a few assumptions about the pearl and cartridges, but im not a circuit designer and just a music enthusiast who enjoyed adding a little flair. The benefit was that i can instantly compare one set of variables to another, and swap cartridges and cartridge types at a moments notice. Ive had few oportunites to do so at this time, but thus far ive discovered that i enjoy slightly different settings for my fidelity research fr1 mk3f mc cart than the manufacturer recommends. For example, instead of 10 ohm loading resistance, i find that 30ohms sounds better, and gets more output from this extremely low output cartridige. My 10 ohm setting had this low output cart input signal so low thati was having to turn my preamp up and use the highest gain setting of 65db on my pearl... This made the pearl demonstrate its max amount fo normal hiss which was audible, but quiet at normal listening levels when the record wasnt playing but resting on a still record. There was no audible hiss while playing as it was deep enough in the background to not hear. But, by uping the input resistance to 30 ohm or 50 ohm the input level was greater and the hiss was so low it could no longer be heard at playback levels.
This also permits me to use a lower gain setting and attenuate the slight background hiss further. The bass and mids are more authoritative, though not over blown, at these settings. The 10 ohm setting displayed perhaps more neutral character but required so much more gain to achieve the same listening level that amplification noise was starting to creep in .. So.. With my set up i can please my picky ear as the music calls for it.

There are 9 resistor settings from 10ohm to 1000ohm plus "blank" on one knob wired to R-user for mc cart load setting, and 10 settings for 14.7k to 110k wired to R-19 for mm load settings. The blank setting allows me to bypass the mc resitor load settings and use the mm settings. When using the mc settings the parallel reisitors are of such a magnitute of difference that the input values are virtually the same as indicated by r-user.

There are 10 selectable polystyrene capacitors for C22 from 43pf to 470pf.

there is also 10 selectable gain settings for variable gain tuning from about 45 to 65db.

Ive done this by using rotary switches and matched components. if you consider doing the same, It is important that these are make before break type to avoid noise when switching in the r-user resistor for mc settings. You van use break before make switches in the r19 and capacitor locations withput any switching noise. The gain and r-user slots require make before break type to prevent noise.

The results are pleasing and clean.


Ive noticed that 10ohm and similar lower resistance values in R-user decrease the input and ultimately the volume from the phono stage, requiring higher gain settings. Higher values in mc playback empart more weight and energy to the recording without changing the equalization. This is undoubtably due to less signal loss at input as im guessing low input resistors permit more signal being shunted to ground than say the default 47k. I dont understand what goes on with loading resistance though so id love to be educated!

Changing capacitance settings hasnt had any big change to the music that ive noticed yet, but ive been using a mc cart so this may be why. Mm may be more affected by input capacitance loading.

---- if anyone has experimented with the cx, r15x, or any of the riaa caps to move the subsonic roll off back, id love to hear about your results. I think i may have read that increasing c12 just a pinch can move the subsonic rollback down a bit. I havent felt the need to change this or anything about the riaa equalization as it is simply superb as it is.

Last edited by FormosaWest; 20th June 2013 at 02:23 AM. Reason: Typo
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