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Old 29th January 2010, 08:53 PM   #3041
Salas is offline Salas  Greece
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Trim trim trim.
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Old 29th January 2010, 09:35 PM   #3042
RCruz is offline RCruz  Switzerland
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Very rewarding work this is
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Old 29th January 2010, 11:35 PM   #3043
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Quote:
Originally Posted by RCruz View Post
Confused with the different sonic results from bypassing riaa caps in my three riaa, I decided to buy a decent LCR.

I got a TENMA 72-8150 that states an average precision of 0.5% in capacitance reading.

After that I desoldered the 47n caps in the 48dB unit and measured 47.6 R 47.1L.

No wonder the sound lost magic when I added 680p //

In this design we should not overshoot 47n
Congratulations for the new LCR, could you post a picture? How much cost it?Now I will ask you to measure mine caps

Thks for advice not overshoot RIAA caps.
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Old 30th January 2010, 11:18 AM   #3044
RCruz is offline RCruz  Switzerland
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Here you have.... quite inexpensive but correct reading

TENMA|72-8150|MULTIMETER, CR | Farnell Portugal
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Old 30th January 2010, 11:19 AM   #3045
RCruz is offline RCruz  Switzerland
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Now the 48dB is sounding right !

Must do the same procedure in the 57dB machine..... It is a pity I must disassemble everything again.
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Old 30th January 2010, 10:27 PM   #3046
RCruz is offline RCruz  Switzerland
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Today I dismantled the 57dB machine, desoldered one leg of the 47n cap, measured 46.5 and replaced the // 680p by a //560p.

This happened in both chanels..... The difference is amazing.... Now it really sings (and it uses only one shunt) ... maybe a second shunt is redundant but I will try it anyway
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Old 31st January 2010, 03:50 PM   #3047
RCruz is offline RCruz  Switzerland
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Now I completely removed hum !!!

It is incredible.... using an inboard r core and beeing carefull about GND I got even lower noise with the 57dB than on the 48dB I built before with external double psus.

After studying the schematic for a while, I decided to lift the psu GND and now there is no hum.

Maybe I will need to rethink this when I add the second shunt but for now I have a "floating GND" psu.

Attached Files
File Type: pdf 57dB GND setup 1 shunt floating GND.pdf (8.0 KB, 115 views)
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Old 1st February 2010, 12:55 AM   #3048
Salas is offline Salas  Greece
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Well done Ricardo. Maybe its suitable to the 4 pole cap as it seems.
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Old 1st February 2010, 09:32 AM   #3049
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I am really happy because with an r core we can have even better results than with toroids in an external box.
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Old 1st February 2010, 01:12 PM   #3050
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Ricardo, in mine tests the external EI-cores give better results than external R-cores or Toroids, if you can not do it external the best are R-Cores. Could you try external EI-cores?
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