Hi Richard:
One question with this approach ... Wouldn't you need to make sure that the hi-z input impedence
isn't set by a resistor across the phone jack input? Otherwise, wouldn't you be putting the 49k318
resistor in parallel with a 100k or other value resistor and thus net-net something lower than 47k?
I know that on a lot of old guitar amps the input Z was a resistor across the phone jack, then into
the grid of the first stage tube. Not sure if you'd do this with an opamp input on a modern "direct
box" section of a mic preamp/channel strip.
-- Tom Fine
----- Original Message -----
From: "Richard L. Hess" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, September 09, 2009 12:46 PM
Subject: Re: [ARSCLIST] Non-RIAA curves for stereo LPs????
> At 10:42 AM 2009-09-09, [log in to unmask] wrote:
>
>>There are also high Z inputs on the MP2-MH, but they are probably 1 M Ohm, which would require
>>trimming 953k Ohm, if I were to try the custom cable/parallel Z drain. Perhaps there are
>>resistors inside the preamp that can be taken out and replaced to turn the high Z inputs into
>>supra-low Z (i.e., 47k) inputs? I almost never use those inputs for guitar, anyway... I wouldn't
>>mind just using the mic inputs for guitar, if they could be dedicated tt inputs.
>
> So, if the 1 M Ohm inputs are truly that and are quiet enough, then you need to put a 49,318 ohm
> resistor across the input and see what happens.
>
> I would consider a 100k pot and adjusting the loading to more accurately trim the cartridge. There
> is an adjustable R and an adjustable C across the cartridge in my RTS405 phono preamp.
>
> Cheers,
>
> Richard
>
> Richard L. Hess email: [log in to unmask]
> Aurora, Ontario, Canada (905) 713 6733 1-877-TAPE-FIX
> Detailed contact information: http://www.richardhess.com/tape/contact.htm
> Quality tape transfers -- even from hard-to-play tapes.
|