Hong Kong Lawrence CS4397 Cheapo DAC modified to work as it should
Many months ago I bought a DAC to use with my computer in the bedroom. Just to connect to my Musical Fidelity X-Can V2 for some serious headphone listening. I have used it, but not been impressed by it at all. But when surfing around, I got in to this amazing/crazy page about installing a tube amp output on CD players and DACs. And he listed the cheap one I have as one of the best DACs he ever heard. The guy bypasses the output stage and replaces it with a simple tube buffer/amp. This got me interested.
Due to the fact that I was in the middle of modding my Tianyun Zero DAC, and wished that I had done some measurement on it before starting the mod, to be able to compare and see if it’s really is an improvement. But I forgot.
So I took out the CS4397 DAC and measured it.
Here’s the frequency response. As you can see it’s horrible! -3db down at around 12.000 hz. No good.
I knew that oversampling Digital to Analog converters usually have a lot of noice in the higher frequencies but the applied low pass filter is obviously wrong. So I started to search the net, and found this forum. So I tried all the classical mods first, like beefing up the power supply. Changed the surface mounted capactors to low ESR (Panasonic FM). Removed the output caps etc.
All this changes made for a better sound quality, but did not fix the big dip in the upper frequency. So out with the soldering iron again and changed the C32, C33, C34, C35 to 150pF surface mounted caps. And as always when dealing with surface mount parts you realize that your getting old. Shaky and with bad vision. But I managed to get them mounted. The DC output offset on it used to be 0.300V but is now 0.006V on both the RCA connectors.
Did it make an inprovement? Well, let the measurement do the talking…
I say! That obviously worked!
And here’s the really annoying part. My wife thinks that this cheap DAC sounds better and more open than my extensivly modified Zero DAC. That I’ve been working on for weeks. And she’s right.
So now, I have to rebuild and improve the power supply to try to lower the noise level to the same I have on my ZERO DAC.
After that, I’m going to rebuild the SPDIF input with a transformer. And then modify it so that it will work with 24/192khz input.
Hello,
thank you very much for this post, it’s being very interesting to read.
Do you happen to have a detailed list of your mods ? (I am not a pro but would love to do it. My DAC is coming next week and I am ready for some soldering work).
Best, Pepe
Hi, reads fine! Congratulations! I recently also got the Lawrence, but in NON-SMD Version. It is my first DAC, and I enjoy it . Now I would like to add an USB input and have two questions:
How could I connect my computer through USB cable to the Lawrence DAC (bypassing the SP/DIF Format)? Can you name suppliers for an appropriate USB input stage?
How could this be realized without creating ground loop hum (PC and Amplifier on different power sockets)?
With kind regards,
Pete
Pepe, I have put up a page with some more detail on my mods. Check http://www.jackenhack.com/blog/audio-hifi-diy/modded-lawrence-hong-kong-dac/
An easy and good sounding alternative is to get hold of an Trends Audio USB DAC UD-10. They are cheap and have a nicely designed board. Only 16-bit 48 khz out. Works on Mac and Windows without a driver.
Hi Jacken, Thanks for your interesting modification. I bought the same DAC several weeks ago and did some modifications and measured the result as well. Did you do distortion tests as well? If you are interested, please have a look at my web site, I am very interested to share suggestions for further improvements to the DAC.