5mV phono cart to 2.5mV pre-amp -- am I asking for trouble?

Archived from groups: rec.audio.tech (More info?)

Grado Prestige Gold cartridge, the pre-amp is in a Harman Kardon SR900
receiver & is rated at 2.5mV input. I haven't been able to find out if
this apparent mismatch is liable to fry something, I'd appreciate any
help.

Archived from groups: rec.audio.tech (More info?)

On Sun, 12 Sep 2004 23:44:28 +0200, François Yves Le Gal
<flegal@aingeal.com> wrote:

>On Sun, 12 Sep 2004 15:38:47 -0600, mescalero <mescalero@space.kit> wrote:
>
>> I haven't been able to find out if
>>this apparent mismatch is liable to fry something
>
>No problemo.
>

That was quick, thanks!

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In <a7g9k0tmoisvm6a3ojdk9ujaoo8peua1a7@4ax.com>, on 09/12/04
at 03:38 PM, mescalero <mescalero@space.kit> said:

>Grado Prestige Gold cartridge, the pre-amp is in a Harman Kardon SR900
>receiver & is rated at 2.5mV input. I haven't been able to find out if
>this apparent mismatch is liable to fry something, I'd appreciate any
>help.

It's not a problem. The 2.5mV rating means that the receiver will reach
full output when a 2.5mV 1000Hz signal is presented to the phono input.
The 5.0mV cartridge spec is the cartridge output when playing a
specific test record -- which is recorded an "average" level. The 5.0mV
is a typical magnetic cartridge spec. Had the cartridge been rated at
2.0mV, you would be turning the volume up a bit (compared to a 5.0mV
cartridge playing the same record) for the same speaker output.

"Problems" start when the cartridge plays something very loud or
crosses a record defect (which can appear as a VERY large signal). Some
receivers' phono sections overload at 80mV, others at several hundred
mV. Once overloaded, some receivers flounder around a bit while they
recover from the insult. Receiver spec sheets don't always give the
phono overload point and I don't ever recall seeing one give the
overload recovery time. (which would depend somewhat on the nature of
the overload)

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Archived from groups: rec.audio.tech (More info?)

"mescalero" <mescalero@space.kit> wrote in message
news:ap1ak0pdjbmflldphhhh110upkc4dl6vih@4ax.com...
> On Sun, 12 Sep 2004 22:30:45 -0000, dplatt@radagast.org (Dave Platt)
> wrote:
>
> >>Grado Prestige Gold cartridge, the pre-amp is in a Harman Kardon SR900
> >>receiver & is rated at 2.5mV input. I haven't been able to find out if
> >>this apparent mismatch is liable to fry something, I'd appreciate any
> >>help.
> >
> >I don't think it's likely to fry anything in the preamp. The worst
> >that's likely to happen is that the cartridge's output might overload
> >the preamp and force it (or a later stage) into clipping. This might
> >sound harsh, on the loudest peaks in the signal, but it's unlikely to
> >damage anything.
> >
> >My guess is that the H-K probably has enough overload margin that
> >it'll handle the higher-output cartridge just fine.
>
> Thanks Dave, I'll give it a try and keep an ear open for clipping. If
> worse comes to worse I have an Audio-Technica cart that's closer to
> the H-K's input specs (3.5mV), but it's not as good a cartridge as the
> Grado and I'm trying to avoid using it.
>
Please!!! Back in the old days, the signal level differences that you are
talking about were of almost no concern. The differences between the
characteristics between moving magnet and moving coil were of much
more concern. The differences between 5mv and 2.5mv are very small,
but the difference between a 100pf and 400pf load on a cartridge could
often make a very significant sonic difference.

Perhaps the biggest concern WRT the cartridge electrical characteristics
(assuming
moving magnet) would be the capacitive loading. The freq response is
often very dependent upon the capacitive loading (or the loading in
general.)

Some cartridges are more or less dependent upon the specific amount of
loading. Other characteristics of concern would be the mechanical
characteristics
of the cartridge (which affect how the arm should be set-up, or even the
choice
of arm), and the choice of needle (certain kinds of needles have different
advantages with respect to other kinds.)

Out of all of the characteristics, given a GOOD preamp design, I'd suggest
that the difference of 6dB in voltage level is of almost no concern.

John