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From: Ben Bradley on 18 Jun 2008 00:49
On Sat, 14 Jun 2008 05:03:19 -0500, "jtp_1960" <jtp_1960(a)hotmail.com>
wrote:

>>If you are really set on doing this in DSP, then by all means do so.
>>I hope that you will report back with your results later.
>>
>>Greg
>>
>
>Of course I will report back w/ some measures but, as I'm not very good in
>such type of math needed in this and my DSP/electrical engineering skills
>are in level of n00b, I'll need some time to 1st solve those needed
>formula(s) before to try anything (even there were formula given earlier
>.. I try to solve what those
>
>R(w) - the RIAA response (I think this is already in my RIAA filter
>calculation procedure),
>L(w) - the response of the 47k/200pf network and

The thing about that network is the cartridge's frequency response
is not specified with anyhing BUT that network connected, so I don't
know for sure that you could "get the response" for it.

But as a first approximation, I'd look for the spec of (or even
measure!) the DC resistance and inductance of the cartridge, and
assume the signal is a voltage source with those two things in series.
Then knowing the response is "flat" [neglecting the RIAA curve for the
moment] into the standard 47k/200pF load, you could calculate what it
would be into the soundcard impedance (which might be as low as 10k or
as high as 1 meg - look at the specs. If there's no spec for line
input impedance, go buy a better soundcard).

>S(w)
>
>keeps inside when demolitioned and how to calculate those if needed.
>
>
>Juha

From: Jerry Avins on 18 Jun 2008 12:57
Ben Bradley wrote:
> On Sat, 14 Jun 2008 05:03:19 -0500, "jtp_1960" <jtp_1960(a)hotmail.com>
> wrote:
>
>>> If you are really set on doing this in DSP, then by all means do so.
>>> I hope that you will report back with your results later.
>>>
>>> Greg
>>>
>> Of course I will report back w/ some measures but, as I'm not very good in
>> such type of math needed in this and my DSP/electrical engineering skills
>> are in level of n00b, I'll need some time to 1st solve those needed
>> formula(s) before to try anything (even there were formula given earlier
>> .. I try to solve what those
>>
>> R(w) - the RIAA response (I think this is already in my RIAA filter
>> calculation procedure),
>> L(w) - the response of the 47k/200pf network and
>> S(w)
>>
>
> The thing about that network is the cartridge's frequency response
> is not specified with anyhing BUT that network connected, so I don't
> know for sure that you could "get the response" for it.
>
> But as a first approximation, I'd look for the spec of (or even
> measure!) the DC resistance and inductance of the cartridge, and
> assume the signal is a voltage source with those two things in series.

For a magnetic cartridge, the magnitude of the voltage source with
constant groove displacement is proportional to frequency. The load
capacitance resonates with the inductance to provide peaking at the high
end.

> Then knowing the response is "flat" [neglecting the RIAA curve for the
> moment] into the standard 47k/200pF load, you could calculate what it
> would be into the soundcard impedance (which might be as low as 10k or
> as high as 1 meg - look at the specs. If there's no spec for line
> input impedance, go buy a better soundcard).

Jerry
--
Engineering is the art of making what you want from things you can get.
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