25 Oct
2005
25 Oct
'05
5:16 p.m.
Maybe use a crystal cartridge that puts out approximately one volt instead of a magnetic
cartridge that puts out tens of millivolts. That attacks the signal to noise problem from
the signal side. The RIAA record curve reduces bass and increases treble, and the reverse
RIAA curve for playback does the opposite. If most of the objectionable noise is high
frequency and you only filter it once wouldn't you just have to do it when the noise
was accentuated, before the reverse RIAA filter?
-----Original Message-----
From: linux-audio-dev-bounces(a)music.columbia.edu
[mailto:linux-audio-dev-bounces@music.columbia.edu] On Behalf Of Richard Smith
Sent: Tuesday, October 25, 2005 1:36 PM
To: The Linux Audio Developers' Mailing List
Subject: Re: [linux-audio-dev] Re: applying RIAA curves in software
Quite a lot of words. I´m impressed. And convinced
...
... of the fact, that these guys just want to sell their stuff.
You really think its just all hype? Sort of made sense to me. If you do click and pop
removal prior to the un-RIAA. Then that will go that much further to reduce the noise
since its all high-frequency.
If you have a decent phono preamp, use it and forget
all about that
tracertek advertising hype.
I don't have a preamp at all. Thats part of what led me to that page.
Recommendations?
--
Richard A. Smith
25 Oct
25 Oct
5:40 p.m.
New subject: [linux-audio-dev] Re: applying RIAA curves in software
signal side. The RIAA record curve reduces bass and
increases
treble, and the reverse RIAA
curve for playback does the opposite. If most of the
objectionable
noise is high frequency
and you only filter it once wouldn't you just have
to do it when the
noise was accentuated,
before the reverse RIAA filter?
Exactly. Denoise and it before the the reverse RIAA and your efforts
will be that much better. At least thats I what get out of it.
--
Richard A. Smith
6:49 p.m.
New subject: [linux-audio-dev] Re: applying RIAA curves in software
On Tue, Oct 25, 2005 at 01:51:43PM -0500, Cornell III, Howard M wrote:
Maybe use a crystal cartridge that puts out
approximately one volt instead
of a magnetic cartridge that puts out tens of millivolts. That attacks the
signal to noise problem from the signal side.
A crystal pickup requires a very high-impedance, low-capacitance input.
Wiring this, or a magnetic one directly to an input that is not designed
for the purpose will just generate trouble.
The RIAA record curve reduces bass and increases
treble, and the reverse
RIAA curve for playback does the opposite.
Sorry, but this is plain wrong. The RIAA filter used when cutting a disk
master will boost bass (below 50 Hz), and reduce high frequencies. This
actually leads to a worse S/N ratio on playback. It looks like this:
\
\______ (1)
\
\________
The high frequency shelving is (was) required to adapt to the limitations
of disk cutting technology, and the bass boost allows to reduce rumble
(mecahnical VLF noise) on playback. The inverse (playback) filter is of
course:
________
/
_______/ (2)
/
/
Combine this with the -6dB / octave required for a magnetic transducer,
(and which has nothing to do with RIAA equalisation) and you get the
familiar curve:
___
\
\_____ (3)
\
\
\
For a crystal transducer (assuming it has a flat frequency response),
you would actually need (2).
--
FA
7:10 p.m.
New subject: [linux-audio-dev] Re: applying RIAA curves in software
The RIAA record curve reduces bass and increases
treble, and the reverse
RIAA curve for playback does the opposite.
Sorry, but this is plain wrong. The RIAA filter used when cutting a disk
master will boost bass (below 50 Hz), and reduce high frequencies. This
actually leads to a worse S/N ratio on playback. It looks like this:
7:55 p.m.
New subject: [linux-audio-dev] Re: applying RIAA curves in software
On Tue, Oct 25, 2005 at 04:10:12PM -0500, Richard Smith wrote:
I'm confused then.
This page:
http://www.bonavolta.ch/hobby/en/audio/riaa.htm
Has a spread sheet that runs the math on the equation presented.
Unless I'm just backwards for RIAA reproduction it yeilds roughly 20dB
of gain for 20Hz and -21dB for 21kHz. Which seems backward from what
you are saying.
That curve, the same as (3) in my previous post, is often called
'the RIAA curve' but it isn't. It is the combination two things:
* a 1/F (or -6dB/oct) filter that is required to compensate for the
+6dB/oct response of a magnetic cartridge,
* and the real RIAA playback curve, (2) in my previous post, which
boosts high frequencies.
In other words, the general downward slope of the filter you refer to
has nothing to do with RIAA equalisation, it's there only because
that filter is designed for use in a preamp for a magnetic cartridge.
If you would have a flat frequency response from the cartridge, then
the filtering required needs to boost high frequencies, as in (2).
If you take (2), and turn it 45 degrees clockwise (that adds the
-6dB/oct slope for the transducer), you get the curve you refer to.
So the idea that the RIAA curve was introduced to improve the S/N
ratio at high frequencies is just wrong, it does the opposite.
--
FA
The RIAA record curve reduces bass and increases
treble, and the reverse
RIAA curve for playback does the opposite.
Sorry, but this is plain wrong. The RIAA filter used when cutting a disk
master will boost bass (below 50 Hz), and reduce high frequencies. This
actually leads to a worse S/N ratio on playback. It looks like this:
6913
days inactive
6913
days old
linux-audio-dev@lists.linuxaudio.org
4 comments
3 participants
participants (3)
-
Cornell III, Howard M -
fons adriaensen -
Richard Smith