• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Soundcraftsmen DX4200 surprise

Racingh11

Racingh11

Super Member
I recently bought a Soundcraftsmen DX4200 preamp equalizer to go through and sell. It was already an unusual unit, it does not have rack handles. First time I have seen that. I also noticed it felt heavy. Upon opening the top cover, I found a big attempt at reducing noise in the power supply section. This thing has power caps added that are big enough for a power amp. It also has a line EMI filter, and what looks like a couple chokes on the DC side. The rest of the unit is factory stock. I tested it out on the distortion analyzer. The preamp section came in at .001% THD+N, and 103dB S/N relative to 2 volts. They are usually about .0015% and 97-98dB stock. Those improved numbers are about what I get with replacing caps, ICs adding local film caps, and moving wires to best locations. I will retest after I service it. It's also getting new sliders. The THD is about as low as my equipment goes, so I'm not expecting much there. But hopefully I can see further improvement in noise reduction.

IMG_4781.JPGIMG_4780.JPGIMG_4779.JPGIMG_4778.JPGIMG_4777.JPG
 
Register to hide this ad
After recapping the unit, minus the added big caps. And new ICs with film caps added to the power leads; the S/N improved to 106.7dB on both channels. I have gotten around 106 on a few before, so this might be a record for this model. That is relative to 2 volts, which is how Soundcraftsmen rated their stuff. I could not measure an improvement in distortion. It also got new sliders and paint.
 
Now it is a piece of art. Have you tried reworking with high precision resistors to further reduce noise from circuit?
 
You must log in or register to reply here.
Back
Top Bottom