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.