[sdiy] OT: scratch filter for vinyl

[KA4HJH]

>I have a record player with a build in "scratch" filter.
>There are no user parameters for the filter.
>With this filter you still hear most scratches and ticks,
>only the big ones are muted so they don't damage ears or speakers.
>Indeed one hardly notice the muted ticks compared to not using the filter.
>But when your records are well cared after there simply are
>no scratches bad enough to trigger the filter.
>
>Other scratch filters may be more sensitive though.
>
>Theo

I have an SAE 5000A "impulse noise reduction system". What it does is mute
the sound briefly whenever a loud _out-of-phase_ transient comes along.
This works surprisingly well on things like scratches and some pressing
defects. Adjusted properly you can kill some of the pops and clicks without
stepping on the percussion (electronic percussion and weird mixes give it
the most trouble). It is NOT a panacea, but if you have old vinyl you want
to play or dub it would be worth grabbing a used one cheap. BTW, the
process works better the closer it is to the cartridge so an analog device
is desirable here--doing it in software after digital conversion will be
more difficult. There was one commercial unit that did this that acted as
the phono preamp.

Of possibly even greater use is a rumble filter. This consists of mixing
everything below a certain frequency to mono, which is what was done during
mastering anyway so it doesn't damage the sound to do it again later. Since
most of the low frequency noise from the turntable is out-of-phase the
rumble just magically disappears. I haven't seen a commercial unit that
does this--I built mine from a kit ages ago. Curiously, none of the "record
dubbing software" I've seen has this feature--perhaps what Jay was talking
about does, I don't know.

>
>
>
>From: Stephen Begin <trypannon at hotmail.com>
>
>
>
>> I've seen some DIY projects in old magazines (if anybody wants I could
>scan
>> them probably) featuring a processor that eliminates pops from records...
>> As I understand they work by simply blocking the signal completely when
>they
>> encounter a pop, and since it's a very small silence it goes unnoticed
>> (supposedly).
>> I was just wondering if anybody has ever used one of these devices and if
>> it's worth building one.
>>

-- 

Terry Bowman, KA4HJH
"The Mac Doctor"