Digital Drive: REVIEW: Apogee Digital DA-1000-20 DAC Processors by Busybusy

I have been using the Apogee Digital DA-2000 for more than 3 years. The DA-2000 was the basis for Mark Levinson's Cello reference DAC that sold for $10,000. Anyway, I came across the DA-1000 and I decided to buy it for couple reasons (1) it is very small, and lately, I come to conclusion that a very compact design has short signal path, and can result in great sound; (2) it runs with 12V DC, so I can easily develop a battery-powered solution.

Initial Impression

The DA-1000 is like an old Hayes external modem, housed in an aluminium case, with a power supply of same size. All the connection are XLR, and the digital also excepts S/PDIF in BNC and optical. Power connection between the power supply (12V, 1000mA) is via a DB-HD15, like a VGA cable. It has a solid, no nosence feel, and very complicated with cryptic controls that require reading the manual (extremely poorly written). When I plugged it in, I let it burn-in for 3-day before seriously listening to it. I thought it will sound similar to the DA-2000, but I am quite surprised by its presentation. The DA-1000 has a very immediate and forward sound (not in the bad way), and the bass is especially the strongest, with very good rhythm, impact, and no over hang. With a heavy drum, you hear bang, and the vibration of the drum skin. The sound is fast, vivid, very high-impact. However, when the passage gets complicated and loud, a certain compression of sound takes place in the upper midrange, and almost becomes bright. I checked the Absolute Sound 101 review, and it seems the reviewer heard the same problem.

Compared with DA-2000 (which by itself, one of the best red book sound I have heard), the DA-1000 is more immediate, much faster, on the edge sound. The DA-2000 has more 'high-end' feel, and more gentle sounding.

Battery Power Supply

I spent the better part of the weekend working out a battery power supply. The final form, I have a 10AH Lead Acid 12V battery, filtered with couple film-caps, and wire to the Apogee. Improvement! There are more air, a lot of detail floats out, the sound is more relaxed. However, when it gets loud, the brightness and compression happened again. I had a feeling that that brightness is probably caused by a inadequate power supply. I proceed to open up the unit to try to find ways to solve the brightness.

Modification

Limited by what's available, I analysed the circuit. This is a most sophisticated DAC I have seen, with lots of customized module in custom pacakge. The power supply is a DC-DC converter that takes on the 12V DC and converts to +/- 15V, and the DC-DC converter is bright purple and says Apogee Customed. Then, I spotted a pair of Burr Brown PCM63, but the Digital Filters are 2 pieces of nice looking 'Apogee Custom" modules. The output stage has 3 NE5534's on each channel. I assumed that 2 op-amps were used for balanced output, and one for DC offset compensation. The circuit is DC-coupled. The digital part is beyond sophisticated. I think Apogee spent lots of design effort there, with two layer of circuit boards stacked, with custom made digital parts, even the input transformers look like customed products. My DA-2000 has a memory buffer design, much like a Genesis time lens, to eliminate jitter, but I cannot see any buffer, but I did not want to remove the stacked PCB just for the sake of peeping for the buffer.

However, I am quite surprised that the op-amps did not have adequate by-pass caps, and all of the bigger electrolytic caps did not have a high quality by-pass. So I replaced the ceramic by-pass caps with high-quality film caps.

Modified impression

Now, the DA-1000 sounds even better. Compared to the DA-2000, the DA-1000 still sound very fast and direct, but with lots of detail (using the battery power supply). The brightness is tamed, but I can still hear it; since I had worked out all the related issue, the only thing left to try is to replace the DC power cord (the factory power cord is a microphone cable, looks like a Mogami).

REVIEW: Apogee Digital DA-1000-20 DAC Processors Review by Busybusy at Audio Asylum