[sdiy] LXP-1 mod?

[Michael Zacherl]

Hi Magnus,

Magnus Danielson wrote:

> I quick look in the schematics gives that you can apply this patch without
> any cuts. You take a 100k trimpot with one end wired to pin 1 through a 470k
> resistor, the other end is connected to pin 28 through another 470k resistor
> and finaly the center tap is wired to pin 27 through a 1M resistor. This would
> complete Note 1 in BBs datasheet (Note 2 and Note 3 is already applied BTW). 

Are you comparing the schemos to something like 
this http://www.audiochips.net/data/pcm54.pdf ?
How much less distortion would this correction 
effectively bring?

> The S/H is done according to the book, so if you look in the far back of the
> BB PCM54 datasheet you will learn how it should be done. The LXP-1 implements
> the S/H exactly as given. There is even a special comment about how the switch
> operates which points out that the Rds(on) is compensated for so that
> distorsion of the signal is reduced. Also, it's only a LF353 on the input S/H
> but 4570's on the output S/H.


> Why don't experiment with 20-bit DACs?

Well seems tempting, but first I've to cure my 
LXP-5 (when I finally got time) after I fixed my 
Chroma's powersupply and  before I built this 
Simplesizer Kit ... phew ... and did the mods on 
the Mono/Poly ... I need non-iron shirts to get 
more time ;-)

Maybe Peter's more attracted to that idea first.

> I could get messy. Somebody who has a
> spare LXP-1? ;O)

Well, I got two ... but ... well ... uhm ... I 
trust you but ... well ... no. ;-)))

> Let's put it this way, the PCM54 is on page 1 of 5 sheets ;O)
> 
> I am lacking the EPROM image... so if somebody has it to share... ;O)

*YAC*  (yet another clone).

Thanks mate,  ;-)
   Michael.