Reducing Record Surface Noise - I want to know all Approaches

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#581
tiefbassuebertr said:
Any news ?
Are there measurements concerning S/N ratio of RIAA phono preamps and record surface noise at the same time ?
Click to expand...
I built a tube phono preamplifier, here are my measurements:

Phono preamplifier acceptable S/N ratio

I did not measure the S/N of an unmodulated groove, I can do it for you if that gives any valuable information. But I am sure it won't exceed 60 dBA.

For others reference (since you also contributed), there are a lot of useful pieces of information in this thread, especially around the end:

an mm/mc phono stage
 
#582
^^^ Quick measurement from the test record SLPD19134 of MHV (Hungarian Phonograph Record Co.), L-channel:

https://www.diyaudio.com/forums/attachments/analogue-source/641019d1508401539-test-lp-buy-slpd19134-pdf

Reference level: 8 cm/s @ 1kHz
S/N (A-weighted) on unmodulated track: 62 dB
S/N (A-weighted + 400 Hz HP filter) on unmodulated track: 67 dB
Phono preamplifier residual S/N (A-weighted) with pickup lifted: 76.2 dB

R-channel is nearly identical. This test was done with a Denon DL-103 pickup, Lundahl LL1678 MC SUT (1:16) and my DIY phono preamplifier based on E88CC tubes in SRPP topology, gain about 50 dB @ 1kHz, passive RIAA equalization between the stages.
 
#583
tiefbassuebertr said:
under
Shunt feedback in phono preamplifiers : new topics on this forum
I read this in the last posting:

Interesting in this system is the presence of a nearly ideal noise reducer which cleans up LP surface noise along with the preamplifier's input 47kOhm thermal noise. This circuit is very effective in reducing both vinyl and cassette tape noise.

From this approach I have never heard before.
Any experiences (go to the schematics in one of previous postings) ?
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URL is dead. go to
Shunt feedback in phono preamplifiers : new topics on this forum
Vinyl Reproduction Equipment
RIAA amp using shunt feedback
JLH Shunt feedback phono amp construction
https://www.angelfire.com/sd/paulkemble/sound3.html

there are similar topic here
Phono preamplifier acceptable S/N ratio
 
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#585
Apart from the fact that it concerns shellac instead of vinyl, mono and 78rp, the writer fails to explain why added recording noise should lead to intermodulation.
Also the images shown do not help a lot to understand his point.

And turning the cutting head to stay perpendicular to the groove may result in a better S/N, but this does not reflect the playback process where the Cart’s stylus doesn’t rotate. For stereo recordings played with a LC stylus this would mean a completely wrong groove tracking.

Hans
 
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