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Old 25th July 2007, 03:12 PM   #1
Cobra2 is offline Cobra2  Norway
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Default RIAA / Pre mod/upgrade

Hi! I have this RIAA, (from far-east), that is fairly unusable...sounds like it is far off the curve....and no good overall sound...
Please give me some suggestions on how to upgrade, and calculate the riaa-filter...
Maybe go for other tube-types too?

Arne K

RIAA;
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Old 25th July 2007, 03:13 PM   #2
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Default Pre-amp

Arne K

PRE;
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Old 31st October 2007, 06:55 PM   #3
Cobra2 is offline Cobra2  Norway
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Default riaa-filter calc (active)

I found this: http://www.beigebag.com/case_riaa_3.htm

Arne K
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Old 31st October 2007, 11:02 PM   #4
KaDe is offline KaDe  Germany
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Series feedback is the most insufficient way to achieve RIAA and will always sound strange.
You may try parallel feedback like in this design:
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Old 3rd November 2007, 07:57 PM   #5
Conta is offline Conta  Europe
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I think with two stages and negative feedback you have too small sensitivity of RIAA corrector to reach standard output level 1Vrms. Try circuit with 3 stages and without negative feedback, like this: http://audio.ring.lt/pre/pre_en.html
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Old 3rd November 2007, 08:15 PM   #6
Cobra2 is offline Cobra2  Norway
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6N16... do not have that tube... closest replacement?

Arne K
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Old 3rd November 2007, 08:46 PM   #7
Conta is offline Conta  Europe
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You can try not pencil tubes ECC84 (6N14P)
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Old 3rd November 2007, 08:58 PM   #8
KaDe is offline KaDe  Germany
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Hi !

Passiv RIAA is a good idea, here is a simple two stage design:
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Old 3rd November 2007, 08:58 PM   #9
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Default nice schematic

KaDe,

What could be B+ value in your phono schematic, please? Thanks.
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Old 3rd November 2007, 09:15 PM   #10
KaDe is offline KaDe  Germany
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The parallel feedback circuit needs something around 320V B+
The passiv RIAA just posted works at 250V B+
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