[sdiy] Re: Source of 2N5459 FETs

[fmg]

Hi Oren,

Oren Leavitt wrote:
> 
> Hi Fabio,
> 
> The way Z5 is  set up, as a differential amp with the 10.7K and 787K
> resistor dividers on both inputs, the input impedance will be 797.7K at
> either input regardless of the op amp used. Load on the filter ladder
> output needs to be kept minimal so that it will perform its best. That
> is what the JFETs or JFET input op amp buffers accomplish.
> The capacitors, C6 and C7, block DC offsets from reaching the diff amp.
> 
> Oren
> 

I understand that this mod lead to a degradation (don't know if this is
the correct term) of the filter characteristics. My point is if these
changes are noticeable for a ear accustomed to the original filter
sound. That's why I asked to the list, I don't have an original ARP filter
and a modified one to compare.

I made this (url below) based on the Oakley Sound System schematics, but
again, this is a modified version and I've never made the original to
compare.

http://www.geocites.com/eqys/var_tmp/01_lpf_2.pdf

Regards,

Fabio



-- 
Fabio Gonzalez
Posadas, Argentina