Reviewer: Paul Candy
Source: Rotel RCD-971 CD player, Sony SCD-XE670 SACD player, both modified with IEC jacks instead of captive AC cords, HIT Audio/Cayin CD-22 CD player (in for review)
Preamp/Integrated: Bryston B60 integrated, Audio Zone AMP-1, Manley Labs Stingray (in for review), Vasant_K GA-120S Final Edition (in for review)
Amp: n/a
Speakers: Meadowlark Kestrel 2, Angstrom Omega 5
Cables: DH Labs Q10 loudspeaker cables, DH Labs Revelation and Air Matrix interconnects, DH Labs D-75 Digital cable, DH Labs Power Plus power cords, GutWire Power Clef SE and C Clef power cables (in for review), JPS Labs Ultraconductor interconnects & loudspeaker cable
Stands: Premier three-tier, filled with sand
Powerline conditioning: Blue Circle BC86 MkII Power Line Pillow, GutWire MaxCon AC line conditioner (in for review)
Sundry accessories: Caig Pro-Gold contact enhancer, Walker Audio Vivid CD treatment, GutWire Notepads, AudioPrism Isobearings, Vibrapods, dedicated AC line with Hubbell outlet
Room size: 13' x 17' x 8', long-wall setup
Review Component Retail: $2,640

Since I started on my ongoing exploration of the unsung hero of audio amplification -- the affordable integrated amplifier -- I've deliberately sought out as many differing topologies as possible to give readers and myself a general sonic sense of each design approach. The 50wpc Mambo hails from Roy Hall's very attractively priced Music Hall line and, besides operating in pure Class A, is further distinguished by the inclusion of a 24-bit/96kHz upsampling DAC. My particular review unit had been subjected to the tender ministrations of component modders extraordinaire Walter Liederman and Chris Johnson and brought up to their Underwood Hifi/Parts ConneXion Level 2 status. Specs and details of the stock unit are as follows:
  • 24-bit/96kHz upsampling Crystal CS8420 sample rate converter w/Burr-Brown PCM1738 DAC that processes all standard digital audio signal rates from 8 kHz to 96 kHz.)
  • Digitally-controlled analogue volume control PGA 2311 IC by Texas Instruments
  • 50 watts/channel class A amplifier
  • 600-watt power transformer
  • 6 pairs of K1529/J200 Mosfet output transistors
  • Two digital inputs (1 optical/1 coaxial); 5 analog inputs
  • 5-way insulated gold binding posts
  • High quality gold input jacks
  • Full remote-control operation
  • Heavy duty power cord
  • Dimensions: 17" x 16.5" x 5" WxDxH.
  • Weight: 50 lbs.

Details of the mod without DAC upgrade are as follows: Level-2 mod $2,190 + shipping ($1400 retro-fit)

  • We replace the current $2.50 Burr-Brown 2604 dual op amps in the preamp section with two adapter PCBs allowing the use of the worlds finest op amp, the Burr-Brown OPA-627 single surface-mount. These boards sell for $70.00 each if purchased separately
  • Two REL-CAP Teflon TFT bypass caps for amp section's input coupling cap
  • Two .22uf Auricap metalized polypropylene power supply bypass caps
  • Twelve BlackGate FK, C and STD grade electrolytic caps for both the amps power supply and feedback loop in critical coupling cap positions
  • 46 Japanese RIKEN ½ and 1 watt signal path carbon composition resistors with gold-plated leads
  • Three feet of DH LABS Revelation series pure 99.999% silver solid core input signal wire with Teflon tape-wrap dielectric (replacing internal connectorized interconnect between preamp/DAC and power amp)
  • One pair of premium Vampire direct gold-plated-over-copper body RCA female jacks (plus, elimination of internal RCA plugs/sockets between preamp/DAC section and power amp)
  • Four WBT 0763 single output binding posts
  • Four International Rectifier Hexfred ultra-fast soft recovery diodes
  • Four EAR large Sorbothane isolation feet
  • Two sheets of SoundCoat chassis damping material cut & applied where applicable
  • TRT WonderSolder is used throughout
  • 10 hours labor
  • The 12-month Music Hall factory warranty is honored on these modified amps.

The dedicated mod for the DAC section runs $450 if done during the amp mod, $550 by itself.

  • Replaces current Burr-Brown 2604 dual op amps in I-V and output buffer stage of DAC with three adapter PCBs allowing the use of the world's finest op amp, the Burr-Brown OPA627, a single surface mount op amp (two per adapter)
  • Six Polystyrene film and tin foil caps for DAC section's analog reconstruction filter
  • Two BlackGate C grade electrolytic caps in the critical DAC section's output coupling cap positions
  • Sixteen Japanese RIKEN ½ and 1 watt signal path carbon composition resistors with gold-plated leads
  • TRT WonderSolder used throughout
  • Two hours labor

As a breed and in generalized terms, Class A amps are highly regarded for their rich, warm tube-like smoothness and attendant lack of solid-state edge or grain. This may be due to their freedom from crossover distortion as Class A output devices maintain conduction for the entire waveform cycle and never turn off unlike Class AB amps which constantly switch on/off. Many believe this 'switching' noise is the culprit for the grain and hardness that can characterize many a silicon-based output device. But as with anything in life, there's no free lunch. The downsides of Class A are high current draw, inefficiency and concomitant high levels of throwaway heat, usually requiring a chassis with substantial heat sinking. Still, to many audiophiles, Class A amplifiers are the proverbial cat's meow to justify living with higher hydro bills and a box that can double as space heater.

The Mambo is one brute of an amplifier. With its attractive silver finish, it weighs in at a substantial 50 lbs. The front is dominated by a large circular display very similar to the Music Hall Maverick SACD player I reviewed last year. It indicates volume level and active source. The display is flanked by two large aluminum knobs that operate volume and source selection. Both controls are digitally actuated and don't quite exhibit the same reassuringly solid action of analog switches. The power standby button is on the far left. The back panel offers provisions for five analog and two digital (coax and optical) sources. The Level 2 mod replaces one pair of analog inputs with Vampire RCA jacks. The binding posts have been upgraded to WBT 0763s. The central IEC power inlet sits next to the power mains switch. Lacking are pre-out out connections, a headphone jack or a processor loop for multi-channel home theater integration. The Mambo is designed to remain powered up, the front switch shutting down to standby mode to limit energy consumption while keeping the electronics warmed up. Also included is an above-average power cable with hospital-grade connectors and what appear to be ferrite beads on either end.

Overall, I was impressed with the build quality of the Mambo. As with the modified Music Hall Maverick and Unison Research Unico I reviewed last year, PcX's interior modifications are indistinguishable from original factory work. There was no sign of loose solder balls rolling about, no finger prints, shoddiness or any other visible indicators of post-factory alterations.

The Mambo warmed up quickly after switch-on and became very hot after an hour of operation. This is definitely not an amp you'd want to position on a middle shelf of your rack. Ensure plenty of space around it and life will be grand. The hefty metal system remote (almost identical to the one provided with the Maverick) and front panel controls worked flawlessly and I experienced no operational problems with this piece.

For three weeks, I burned in the Mambo on my 2-channel TV system 24-/ before getting down to some serious listening in my main system. I listened to digital playback via the Mambo's DAC as well as my Rotel flying solo.