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The ultimate rumble filter - far more effective than just a high pass filter!
The ultimate rumble filter - far more effective than just a high pass filter!
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Old 5th April 2020, 03:29 PM   #171
MarcelvdG is offline MarcelvdG  Netherlands
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Location: Haarlem, the Netherlands
Quote:
Originally Posted by tubewaller View Post
When I was reading about the RIAA Pre-Emphasis, I did wonder how the response could just keep going up and up. Obviously, it can't.
Slightly off topic, but you can approximate a 1st order rising slope up to a frequency fmax pretty well while limiting the boosting of ultrasonics above fmax a bit by this method:

1. Make a simple RC network of which the response starts rising wherever it needs to start rising and levels off at a frequency fL. fL must be somewhat above fmax, say 1.5 to 2 fmax.

2. Use the pole at -2 pi fL that you have created as the real pole of an odd-order low-pass filter and add stages that create the complex pole pairs.

For example, when fmax = 20 kHz, the response needs to rise from f = 1/(2 pi 75us), fL = 38 kHz, and the low-pass function is third-order Butterworth:

1. Make a network consisting of a resistive voltage divider and a capacitor, for example:

R1 in out 15.95744681kohm
R2 out ground 943.8323221ohm
C1 in out 4.7nF

This network will have a response that increases from 1/(2 pi 75 us) ~= 2122 Hz onwards and stops increasing around 38 kHz, but it will already be 1.0619 dB lower than the theoretical infinitely rising response at 20 kHz.

2. Add a second-order low-pass stage with a natural frequency of 38 kHz and a Q of 1, this realizes the complex pole pair of a third-order Butterworth filter.

1. and 2. combined will have a response that is only 0.09135 dB below the theoretical infinitely rising response at 20 kHz. Above 38 kHz, the response goes down with a second-order slope, so extreme ultrasonics get attenuated rather than boosted.
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Old 6th April 2020, 05:44 AM   #172
kissabout2002 is offline kissabout2002  Italy
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Location: Philippines
Quote:
Originally Posted by tubewaller View Post
Hi Bill,

The engineers at B&K are wizards!

You've convinced me that taming the infrasonics is very important.

What is your preferred turntable? Have you measured it and improved it? My everyday TT is a Denon DP-45 that just keeps rolling along.
I was 15 save money from my parents for one years then in xmas I bought my first TT was a Pioneer PL-112d, I do not remember exactly the cartridge was a Shure 44 or 45, I diy a pre-amp with TBA231 and the amp with 2N3055, lol...nice memories, and of course diy speaker with Philips drivers, then later I got a SUV6 Technics amp and Jensen speaker, well the TT Pioneer last for 25 years and maybe more, when I left Italy 20 years ago was still working perfectly, I just change the belt 3/4 times in 25 years, what now amazing me is that I never had rumble problem with the PL-112 but with my new TEAC TN-300 yes, so I think the quality and care of old TT was superior in the past when listening music was just possible with vinyl, radio and tapes....all the best
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Old 6th April 2020, 02:47 PM   #173
wiseoldtech is offline wiseoldtech  United States
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Location: Philadelphia Pa USA
Quote:
Originally Posted by kissabout2002 View Post
I was 15 save money from my parents for one years then in xmas I bought my first TT was a Pioneer PL-112d, I do not remember exactly the cartridge was a Shure 44 or 45, I diy a pre-amp with TBA231 and the amp with 2N3055, lol...nice memories, and of course diy speaker with Philips drivers, then later I got a SUV6 Technics amp and Jensen speaker, well the TT Pioneer last for 25 years and maybe more, when I left Italy 20 years ago was still working perfectly, I just change the belt 3/4 times in 25 years, what now amazing me is that I never had rumble problem with the PL-112 but with my new TEAC TN-300 yes, so I think the quality and care of old TT was superior in the past when listening music was just possible with vinyl, radio and tapes....all the best

I'm not surprised that your PL-112D when cared for and maintained, out-performs the new "junk".


In the past, bearings were designed and micro-polished with care, quality control inspections were rigid and strict, and company reputations were very important.
THAT WAS THEIR MAIN FOCUS - with many competing companies, they HAD to try their hardest to stay in business. And having their factories in-house, they could monitor things the "old school way".


There was none of that "farm it out to china and save money" stuff going on.
Advertising claims were truthful and accurate. - not designed to dazzle or impress a customer with meaningless junk-talk.


My older Kenwood turntable, not even a "top line" model, has a platter bearing assembly that simply amazes me. Absolutely no rumble, no bearing noise - when spun with a finger to a few hundred RPMs, it's totally silent - no "whirring sound" at all with my ear almost touching the spindle.
So at 33 1/3 RPM, I'm sure it's superior to most of the stuff out today.
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Old 7th April 2020, 10:11 AM   #174
sawyers is offline sawyers  United Kingdom
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I bought a medical stethoscope for that purpose. You can use it to track down bearing noise on a turntable, or panel resonances in a speaker,

Best vibration audio diagnostic kit I bought!
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Old 7th April 2020, 10:19 AM   #175
billshurv is offline billshurv  United Kingdom
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The ultimate rumble filter - far more effective than just a high pass filter!
Woth reading what the Korf audio guys are doing with accelerometers. Blog Table of Contents


I don't agree with all their conclusions but some very interesting findings.
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Old 7th April 2020, 11:12 AM   #176
kissabout2002 is offline kissabout2002  Italy
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For don't talking about linear tracking tonearm, here also very popular DIY linear tonearm
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