Arcam Delta Black Box D/A processor Robert Harley and the Black Box 2

Robert Harley reviewed the Black Box 2 in October 1989 (Vol.12 No.10):

The Arcam Black Box 2 essentially is an upgrade of the highly successful Black Box reviewed by JA last February (Vol.12 No.2). The newer 2 version includes an optical input and has the ability to decode both 44.1kHz sampling rate (CD) and 48kHz (DAT). Dealers can upgrade a customer's original Black Box to 2 status for $150 by installing the optical input board. Arcam claims that the Black Box 2 can accept the professional AES/EBU digital audio transmission format. Technically this is not correct. The AES/EBU format specifies a balanced line with XLR connectors, which the Black Box 2 does not have (footnote 1). However, the consumer S/PDIF and professional AES/EBU formats are nearly identical: connecting an AES/EBU output to an S/PDIF input works about 80% of the time.

Cosmetically, the unit is very simple: the front panel has only power and phase-invert pushbutton switches. A green LED illuminates to show correct polarity, a red LED indicates phase inversion. The rear panel has an RCA digital input, EIAJ optical digital input, and a data-inversion switch. This data-inversion switch sometimes helps if the processor has problems decoding. The pushbutton switch is usually left in the out position for normal polarity. Two pair of output jacks are provided, labeled "CD Level" (nominal 2V) and "Line Level" (nominal 0.8V). The CD-level jacks output a signal level more typical of a CD player, while the line-level jacks produce a signal that more closely matches the output level of phono sections, tuners, and tape decks. The line-level jacks are especially convenient when switching between sources: there is no jump in sound level when switching to CD.

Inside, the Black Box 2 reveals separate power supplies (even transformers) for digital and analog circuitry, a Philips chip set (TDA1541A dual-DAC and SAA7220P/B filter), high-quality capacitors and metal-film resistors, and discrete transistors in class-A configuration in the audio signal path, instead of op-amps. Interestingly, the printed circuit board is cut out around the DAC, leaving it connected in just two small areas. To support this isolated section of the board, four Sorbothane pads are mounted beneath the cutaway section.

I was surprised to find a proprietary Arcam chip inside the unit: custom IC fabrication is an expensive proposition. This chip, called an Application Specific Integrated Circuit (ASIC), performs the job of about 25 separate CMOS chips. In addition to reducing the parts count and improving reliability, a single chip reduces the amount of radiated electromagnetic noise. In general, the Black Box 2's construction is very simple and basic, yet well thought out and executed.

The sound
Before listening to any of the converters, I left them turned on for several days. Digital/analog converters are very temperature sensitive, working their best only when warm. Arcam recommends two hours of warmup. Another digital-processor manufacturer advises that their converter needs three days' warmup for optimum performance!

The first thing I noticed about the Black Box 2 was its slightly forward sound on the acoustic guitar I had just recorded. I attributed this more to a slight midrange coloration than to a forward soundstage. Other source material confirmed this impression of a change in tonal character. The midrange had a dry, slightly etched character. Adding to this impression was the reduced sense of depth through the Black Box 2. Flora Purim's vocal on the Chick Corea album Light as a Feather moved more to the front of the soundstage, as did solo instruments, especially Joe Farrell's flute and sax. Although the soundstage was open and quite pleasing, it lacked the three-dimensionality of some other decoders and CD players. However, this did not detract substantially from the listening experience. Laterally, the soundstage was big and open, with a nice sense of air. In general, I found the soundstage one of the Black Box 2's best characteristics.

Treble presentation also leaned toward the forward, while bass had the distinctly opposite character. Playing Harmonia Mundi's Handel Water Music CD (HMU 907010) revealed a slight edge to violins not present in the recording. Cymbals, on a variety of discs, were brighter through the Black Box 2 than, for example, through the Digilog. Bass detail (again using my own acoustic guitar and bass recording) tended to be obscured, the transient of the attack being somewhat muted. Low frequencies somewhat lacked definition, making it harder to clearly hear bass lines.

These criticisms reflect my impressions of the Black Box 2 compared to some stiff competition: live music, mic feeds, and other, excellent decoders. I don't want to appear overly critical: I enjoyed listening to music through the Black Box 2, despite its minor faults. It's not in the same league as some of the better (and more expensive) decoders, but it certainly merits classification as a true audiophile component.

The Arcam Black Box 2 is a well-designed, good-sounding decoder. It offers significantly better performance than many CD players' D/A sections at a reasonable price, making it an affordable upgrade. If you don't mind giving up the optical digital input, the original Black Box is an excellent value at $649. Its primary strengths are a wide soundstage and a nice sense of air. However, the midrange coloration and soft bass performance limit its musicality when compared with other (albeit more expensive) digital processors.—Robert Harley

Footnote 1: "AES Recommended Practice for Digital Audio Engineering—Serial Transmission Format for Linearly Represented Digital Audio Data," AES3-1985 (ANSI S4.40-1985).
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