What is the ideal conventional rumble filter?- Douglas Self

[DouglasSelf]

Those of you with an interest in vinyl may be aware of the long thread on rumble filtering by removing subsonic anti-phase information (from vertical stylus movements) that has been running at:

http://www.diyaudio.com/forums/analo...s-self-81.html

This has so far resulted in an article to be published in Jan Didden's Linear Audio in April, and a planned talk at the AES convention in Paris this June. Hopefully a PCB is going to be produced.

In the course of doing this, it struck me that very little seems to have been written about conventional subsonic/rumble filters, unless I've missed it. I would be glad to hear of any articles or papers you know about, and very interested to hear what people think is the ideal conventional rumble filter response.

I have a few ideas on this myself, but what do you think?

[Jenyok]

Super deRumble filter.
See circuits.
.

[Jenyok]

The Derumbleizer cancels rumble 3 octaves higher than any filter
.
Good article.
.

[bulgin]

Pardon my ignorance. I have been reading through diyaudio member montypig78's thread but most of it is way above my comprehension.

If I read correctly, the rumble and its proposed 'alleviator' schematics refer both to vinyl lps/vinyl 78's and 78rpm shellac records.

My naive question - is the rumble turntable or cartridge and tonearm related?

I play both vinyl and 78rpm shellac records and use Garrard 301's and Micro/Micro Seiki turntables.

bulgin

[DouglasSelf]

Originally Posted by Jenyok

The Derumbleizer cancels rumble 3 octaves higher than any filter
.
Good article.
.

Not an article, but an advertisement.

There seems to be something amiss with the graph labelled
"Frequency response for signals applied to this channel only."
with frequency response deviations up to 400 Hz.

But this is all Off Topic. This thread is intended to canvass opinion on conventional rumble-filters- ie just filters, one per channel, with no crossfeeding or antiphase cancellation.

[mjf]

the only schematic i have with a rumble filter at the input.........but i have never built it.

[DouglasSelf]

Originally Posted by mjf

the only schematic i have with a rumble filter at the input.........but i have never built it.

This looks like an idea put forward by Tomlinson Holman in the 80's. I've never tried it either- I would be nervous that the noise performance would be impaired, and those relatively small caps at the input would make the circuitry after them very susceptible to capacitive pickup of hum etc.

'flankensteilheit' means 'edge steepness' which I assume is the rolloff slope, but I don't see how it could ever be 25 dB/octave. Could be a typo for 24dB/octave, of course, but the circuit looks like a second-order filter to me, which would give only 12dB/octave. There could be some subtle interactions with C4,C5 and C9 that yield 24dB/octave; a quick sim would answer that but for the reasons above this doesn't look like a promising path to explore.

[Bigun]

do transformer inputs provide a natural rumble filter due to roll-off of transformer response?

[DouglasSelf]

Originally Posted by bulgin

If I read correctly, the rumble and its proposed 'alleviator' schematics refer both to vinyl lps/vinyl 78's and 78rpm shellac records.

My naive question - is the rumble turntable or cartridge and tonearm related?

I play both vinyl and 78rpm shellac records and use Garrard 301's and Micro/Micro Seiki turntables.

bulgin

My understanding is that with a half-decent turntable almost all the subsonic rubbish comes from disc warps, usually amplified by the cartridge/arm resonance . (say 8 -12 Hz) I very much doubt if 100kg platters do any good at all.

[rif]

Originally Posted by DouglasSelf

This looks like an idea put forward by Tomlinson Holman in the 80's. I've never tried it either- I would be nervous that the noise performance would be impaired, and those relatively small caps at the input would make the circuitry after them very susceptible to capacitive pickup of hum etc.

I'm quite ignorant of these things - are they also called infrasonic filters? That's what I found in a brief search of the Apt Holman service manual. If it's on topic, I can try to post the relevant sections.