Working Out Pad resistor values for -10dB on V672/2

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Kid Squid

Well-known member
Joined
Jun 4, 2004
Messages
1,011
Location
Port Toilet, South Wales
Hiya Chaps,

Sorry to be a pain in the arse,
but,
how, do i work out pad resistor values for a -10dB drop, on the V672/2

I'm a little unsure of how to do it (in general),

for a mic input, am i looking at 150ohm, i/p impedance ??
i think there's something about setting the i/p impedance with the V672 ??

I think there's a lot of truth in the saying ' walk before you can run'!!!!!
I got to get my head back into Maths, can't remeber a thing tidy, from my college years. :oops:

Best Regards,
Steve
 
You also have to pay attention to what the mic preamp sees. Presenting 1-2K to the mic is all well and good, but the preamp may behave in a way you don't like if it's not seeing its design source impedance.

For a 10:1 input/output impedance ratio (say, 2K:200), it's easy to design when the needed pad loss is 20dB (10:1) or greater. But less attenuation than that requires a compromise of the input impedance, the output impedance, or both.
 
Kubi,

been looking tru the v672 service manual, but I must say, that my German is about as good as my electronic principles :oops:

thats BAD.....

anyway, what does it mean, when you talk about the V672's Zero ohm i/p ?
Also, how did you come to the conclusion that 1.5 - 2K would be better for a mic input.
I apologise again, for my muppetic behavior :wink:

Dave,
what would be typical figures for what a mic preamp sees, I've only been dealing with 600 ohm impedances so far, and i'm slowly getting my head around instrument impedances say , 1meg, but i haven't got into Mic pre's as such.
I've built a couple of other peoples designs, but at the moment , it's like an airfix kit ! - just following the patterns, I can faultfind o.k. tho........
however, I would absolutely love to start designing my own circuits ( one day),
but i think college is on the horizon...
was a long time ago, and i suppose, if you don't use the principles regularly, it's the same as anything, you start to forget..

and with looking after my nine month old baby girl, diy time is getting more and more scarce by the day , but it's all good :grin:

BTW, thanks for the replies guys :thumb:

Regards
Steve :guinness:
 

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