Semi-Customized DAC, Part V: Rollin', rollin', rollin'...
Cap rollin', that is.
In this corner, ladies and gentlemen: The AudioCap Theta, a film and tinfoil capacitor very well thought of for its price (rated among the "Tier AA : Top Shelf Performers" in an extensive cap comparison at The Great Capacitor Shoot-Out ).
And in the other corner, the UpTone Audio MusiCap, another film and foil cap (not sure of the metal used). The MusiCap name was widely known as a product of Hovland Audio. Now that Hovland Audio is no more, Robert Hovland puts out SuperCaps, and the other former Hovland principal, Alex Crespi, offers audiophile capacitors under the MusiCap brand. If that Crespi name sounds familiar, it's because Alex posts at CA frequently as Superdad.
If you look at the photos from the last edition of this blog ( Semi-Customized DAC, Part IV: Photos and Filters - Blogs - Computer Audiophile ), you'll see that the DAC output board originally had four red caps, two per channel. They were each about 5/8 inch in diameter and about 1 and 1/4 inches long, with a value of 4.7uF. In comparison, the AudioCap Thetas are substantially bigger, an inch in diameter and about 1 and 3/4 inches long in the 4uF value I used. The MusiCaps, also 4uF, are quite a bit bigger: an inch in diameter by 3 inches long.
Looking at web sites about audio and caps, one of the things you see frequent reference to is that even though these particular caps don't have positive and negative polarity (caps for some applications do), many people feel there is still a particular orientation that provides the best sound. It has to do with "outer foil," which lead is to the "shield," better noise rejection.... For caps where the leads aren't marked, like the AudioCap Theta, testing involves hooking the cap up to a scope and seeing which orientation gives better noise behavior. Happily the MusiCaps are clearly marked: one lead is red, the other white. In my application, the preferred orientation is with the red leads toward the output.
To avoid having to rely on medium or long term auditory memory and repeatedly installing and uninstalling caps, I hooked up two MusiCaps for the left DAC channel, and two Thetas for the right. I have some good mono recordings, including a rip of the DCC Gold version of the Beach Boys' Pet Sounds, so getting identical signals to both channels was not a problem. And even with normal stereo, instruments or vocals in the center of the soundstage provided plenty of opportunities for direct comparison.
A substantial difference in sound was evident from the very first instant, but I wanted to allow for break-in, so my listening took place over several days.
For the sound of the Thetas, I think the author of The Great Capacitor Shoot-Out linked above nailed it: "[T]he Theta is a bit smoother. The down-side with the Theta is a slight loss of detail, but many listeners may prefer its more liquid (and forgiving) sound." Upper bass and midrange in particular sounded very musical to me.
But the MusiCaps provided an entire level of musical information and detail lacking with the Thetas. Music in general, and anything involving transients in particular - the thwack of a kick drum, the pluck of a guitar or bass string, the expressive details of vocal enunciation and phrasing - was far more realistic with the MusiCaps. For example, Ottmar Liebert's guitar playing on Dune (HDTracks 88.2/24 download, excellent sound) was beautiful and resonant with the Thetas, but with the MusiCaps it was beautiful, resonant playing of a nylon-stringed flamenco guitar. It just was not a close comparison, and this remained true throughout the several days of my listening. The difference was so marked that I got to the local electronics repair shop the minute it opened Monday morning so I could have MusiCaps installed on the right channel. I couldn't wait to listen to the DAC at its best. Also, frankly, listening to a DAC with two different-sounding channels got old very fast. I could never just settle back and enjoy music, because none of the auditory images were fully integrated. Every center stage vocalist was the audio equivalent of Two-Face from the Batman comic strip:
(By the way, this means I now have four spare AudioCap Theta capacitors - free to a good home for the cost of shipping. PM me if interested.)
A couple of interesting things regarding break-in, at least for capacitors: Yes, I did feel the sound of both sets of capacitors changed during my testing. And when I did have the remaining two MusiCaps installed, the new pair did sound different the first 24 hours or so from the old ones - slightly different, not nearly to the extent the MusiCaps differed from the Thetas. (I have my music collection playing on "shuffle" through the DAC 24/7 for break-in purposes.) But the most interesting aspect of all to me was that while over the first several days of listening to the MusiCaps, I thought there was a slight thinness to the sound in the bass and low midrange, last night when I sat down to listen, wham - a whole different system. All the bass you could want. I'm not talking sloppy and reverberant; it's just as controlled and rich in transient information as anything in the upper register. I'm now into the mode we all know and love, where everything that plays sounds new and remarkable. I didn't even bother to queue up anything in particular - just left it on shuffle, it was all good. And my wife danced and sang along (this latter not necessarily a good thing), except for the classical pieces.
I used my phone to take a couple of photos of the DAC board with MusiCaps last night, but in the cold light of day they're not up to snuff to show here. Hope to post a photo or two within the next day or so.
And here's the photo: