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RA03

GRAMOPHONE PREAMPLIFIER WITH FEEDBACK CANCELING FILTER


[RA03 front panel photo]
Features:
  • Feedback canceling filter.
  • Selectable pick-up load capacitance.
  • Fully gold plated phono connectors.
  • Optional XLR output connectors.
  • Optional output transformer balancing.
  • Pick-up balance adjustment.
  • Superior sound quality.
  • Low noise.
  • Half-rack enclosure saves valuable rack space.
  • Rugged anodized aluminum enclosure.
  • Graphics on front- and rear-panels are negatively anodized for best possible wear resistance.
  • Serial number engraved in front panel for easy identification.
  • Bracket mountable external mains transformer.
Introduction
RA03 is a high performance half-width 19" 1-unit RIAA preamplifier for discotheque and PA use.
The feedback canceling filter reduce the acoustical feedback from the loudspeakers to the gramophone and enables up to 10 dB higher SPL before feedback becomes audible. The filter adds the two channels to a mono signal at low frequencies with a special differential filter.
The idea of summing low frequencies into a mono signal to avoid feedback is not new, but all earlier implementations uses some sort of cross-over network to extract low frequency information, adds the two channels and then add this signal back into the stereo high-frequency signals. This topology gives an undesirable phase response and will in some cases make the feedback problem worse. The Feedback Canceling Filter in the RA03 uses a special differential filter that acts like a wire if it's input is a mono signal, but will add the low frequency content of the channels if they differ.
Minimum use of rack space
RA03 is housed in a 86 mm deep, 1 unit, half width 19" (Half-Rack or HR) aluminum enclosure, and may be built into in a standard 19" system.
A single unit can be mounted be means of a rack ear extender, two units can be mounted side by side or 10 HR enclosures can be mounted vertically in a 6 unit high 19" frame.
Due to its modest depth, the RA03 can also be mounted in a flight case vertically behind a gramophone.
Rugged construction for "on the road" use
The anodized aluminum enclosure is constructed from two 6 mm side profiles, a 5 mm front panel, a 3 mm rear panel and 1.5 mm top and bottom covers. Graphics on front- and rear-panels are negatively anodized, rather than just printed, for best possible wear resistance.
Front panel
The front panel contains a balance adjustment for the pick-up and a power LED.
Rear panel
The rear panel contains two gold plated phono sockets and a laboratory binding post for the gramophone cable, an 8-way DIP switch for pick-up load capacitance selection, two gold plated phono sockets and optionally two XLR connectors for the outputs and a FCC68 connector for the low voltage cable from the external mains transformer.
Configurations
RA03 is available with 3 different output configurations:
RA03A: asymmetrical outputs on phono connectors and symmetrical ground referred outputs on 3 pin male XLRs.
RA03B: asymmetrical outputs on phono connectors and transformer balanced outputs on 3 pin male XLRs.
RA03C: asymmetrical outputs on phono connectors.
Accessories available for RA03.
L01: Link-bar set for mounting two HR-cabinets side-by-side in a 19" rack.
M01: Rack-ear set - 1 set supplied with RA03.
R01: Rack-ear extender for mounting a single HR-cabinet in a 19" rack.
TD7405: 230 VAC mains transformer with mounting accessories - supplied with RA03.
RA03MAN: RA03 user manual - supplied with RA03.
RA03 Technical specification
Unless otherwise noted, specifications are for 20 Hz - 20 KHz with 600 ohms load on outputs.
 
Input connectorsGold plated phono sockets and laboratory binding post for chassis.
Input resistance47 Kohms.
Input capacitance22 pF / +22 pF / +47 pF / +100 pF / +220 pF in any combination.
Maximum input level, 20 Hz / 1 KHz / 20 KHz-40 dBu / -20 dBu / 0 dBu
Maximum input level, non destructive10 V RMS
Voltage gain, 1 KHz40 dB
Balance adjustment range± 3 dB
Linearity ref. RIAA/IEC curve± 0.6 dB
Output connectors, unbalanced outputsGold plated phono sockets
Output connectors, balanced outputsXLR3M, pin 1 : chassis, pin 2 : signal+, pin 3 : signal-
Output resistance, unbalanced outputs22 ohms
Output resistance, symmetrical outputs (RA03A)44 ohms
Output resistance, transformer outputs (RA03B)< 50 ohms
Maximum output level, unbalanced outputs20 dBu
Maximum output level, symmetrical outputs (RA03A)20 dBu
Maximum output level, transformer outputs (RA03B)10 dBu
Minimum recommended output load impedance600 ohms
THD+N, output level : 20 dBu, BW : 80 KHz
 - unbalanced outputs< 0.01 %, typically 0.005 %
 - symmetrical outputs (RA03A)< 0.01 %, typically 0.005 %
 - transformer outputs (RA03B), 1 KHz< 0.01 %, typically 0.005 %
 - transformer outputs (RA03B), output level : 10 dBu< 0.5 %
Output noise, CCIR 468-2 Q-peak / RMS
 - unbalanced outputs< -74 dBu / < -80 dBu
Channel separation, 20 Hz< 1 dB
Channel separation, 1 KHz> 20 dB
Channel separation, 20 KHz> 50 dB
Ground liftInternal jumper
Power supplyExternal 18 VAC
Supply voltage range, 230 V version190 VAC - 255 VAC
Power consumption< 20 VA
Operating temperature range0 - 50 °C
Cabinet, height / width / depth43.6 mm / 214.6 mm / 86.0 mm
Overall, height / width / depth43.6 mm / 214.6 mm / 100.0 mm
Mains transformer, height / width / depth56 mm / 92 mm / 91 mm
Weight1100 g
Mains transformer weight650 g

All specifications subject to change without prior notice.PP 900630

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