Greg Mayman wrote in a message to Roy J. Tellason:

 -=> Roy J. Tellason said to Greg Mayman
 -=> about "BAG OF CHIPS" on 01-29-04  04:05.....

 GM> They were unity gain, remember.

 RJT> I don't think that's likely to be a problem.

 GM> It would be if it was a magnetic pickup. The output of those
 GM> usually needs quite a bit of gain.

 RJT> It's a ceramic pickup,  basically the same idea.  The only thing I
 RJT> need to put in there is something to give me the proper equalization...

 GM> Usually no equalization was used.

No?

 GM> I don't know whether the pickups contained some inbuilt correction 
 GM> for the "wiggle" in the RIAA curve, but I rather suspect it was 
 GM> ignored.

 GM> If you want, you can use the following network either between the
 GM> pickup and the preamp or between the preamp and the following
 GM> stage.

 GM> in ------+---- C1 ------+------- out
 GM> .        |              |
 GM> .         ---- R1 ------+----- R2 ---- gnd

 GM> Typical values:

 GM> (a) between p/u and preamp: R1 = 510k, R2 = 2.2M, C1 = 150 pF    
 GM> R2 is chosen to give a suitable load to the pickup.

 GM> (b) following preamp: R1 = 2200, R2 = 10k, C1 = .033uF
 GM>     R2 may be a 10k volume control.

Sounds reasonable to me.  What really bugs me is that I *know* I've seen
schematics for this sort of thing,  bunches of times over the years,  and
can't remember where the heck they've gotten to.  I've done a little bit of
digging,  but having a 4-drawer file cabinet of stuff all mixed together I
didn't get too terribly far into it.  One of these days I'll probably get
back to that,  when I can get to that file cabinet again.

 GM> Values have been rounded to nearest readily available values.
 GM> Values may be scaled as long as the time constants are preserved;
 GM> C1R1 = 75uS, C1R2 = 318uS

Noted.

Worse yet,  I kicked this around quite extensively a while back,  and lost
a bunch of the archived echomail when a drive failed,  so I lost all that
discussion.  Oh well.

 RJT> I have plenty of small caps and ferrite beads and such stuff around to
 RJT> deal with those issues,  and no particular strong sources of radio
 RJT> nearby,  so I'm not terribly worried about it.

 GM> The only other factor is the possible noise in the amplifiers. 

Yes.  But the output of a ceramic cartridge is pretty hefty,  so I suspect
that won't be much of a problem either,  particularly if I end up using a
unity-gain buffer and some equalization as a "preamp".  The load
is going to be the line input of my sound card...

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