[sdiy] LXP-1 mod?

[Michael Zacherl]

Hi Peter,

Peter Grenader wrote:
> I just picked up an Lexicon LXP-1 for a good price on ebay and I notice it's
> one of the ones made in Hong Kong, and I hear there's some mod for them
> that's supposed to be especially kewl on the Hong Kong ones.

I just became aware of that I don't know some of
the stuff  I have. I'm the original owner of two
LXP-1, one LXP-5 and this MRC.
What's the deal with the LXPs made in Hongkong?

> I know, I probably have this all backward...but if any of you have the
> slightest idea of what I'm speaking about, please share the wealth as it
> were.

For more then 11 years I obviously just didn't
care how the guts of this gadgets look like.
A couple of months ago, the LXP-5 died.
Just not doing a peep. Only the overload LED stays
  on. Until now I didn't find the time to take
care of it.  :-(

> I did find something on the web about upgrading the D to A and the amps for
> 'true' 16 bit and better sig to noise....is that THE mod?

I now have a very small bit of a slight idea, and
I googled around and found this for instance.
While I'm pretty sure that you found yourself 
those informations I post it anyway, just in case:

http://edanders.home.attbi.com/diy/lxp_mod.txt
(also
http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&th=f9e59647f3c36ce9&rnum=14 

for the original posts)

"The DAC chip used for the A/D and D/A converters
is the Burr Brown PCM-54HP which can be replaced
by the PCM-54KP.  This yields 10dB less
distortion and is probably the best single thing
to do to the device."

and further on:

"If one were looking for a way to "soup-up" an
LXP-1, one might well start by adding a pot to
adjust the MSB erro on the PCM 54, in order to
lower harmonic distortion.  This would be a very
easy mod, involving one pot and three fixed resistors.
The Burr-Brown data book shows the recommended
circuit.  The next are of investigation might be
the sample-and-hold circuitry, since I rather
doubt the CD4053/LF353 combination is really good
to sixteen bits.  Sample-and-hold design is not
for the faint-of-heart, however!"

Currently I'm lurking around in the usenet
archives and I found things like this:

http://groups.google.com/groups?q=lxp-1+mod+group:rec.audio.pro&hl=en&lr=&ie=UTF-8&group=rec.audio.pro&selm=49nemh%24o8o%40newsbf02.news.aol.com&rnum=1

"Their LXP-1 mod ("replace op-amps, sample & hold
amp, caps and demultiplexer, new converter and
comparator" and which costs $150 plus shipping &
insurance both ways) results in a superior
reverb sound--one more like that produced in $2000
reverbs"

Well - THIS would be a thing I would be interested
too (although I doubt this $2000 improvement of
quality ;-)
But I don't like to see my Lexicons on a two times
6000 mile travel.

Also this (which is obviously the original thread
of the first link)
http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&th=2c5265bc080376d5&seekm=4s69a7%24u7%40chass.utoronto.ca&frame=off

Another thing about LF hum:
http://groups.google.com/groups?q=lxp-1+mod+group:rec.audio.pro+group:rec.audio.pro&start=10&hl=en&lr=&ie=UTF-8&group=rec.audio.pro&selm=eist-1609960321410001%40rs4-annex5.sfu.ca&rnum=11

I'm looking for the service manuals for LXP-1/5
but couldn't find them until now.

> thanks in advance,
I've to thank - least I learned something new
about my gear ;-)

Hope this is a start,
     Michael.