Aaron No.1

Data

General

• Manufacturer: Aaron
• Model: No.1
• Year of manufacture: 1989 - 2002
• Made in: Germany
• Color: silver, against surcharge: black, chrome, gold
• Type: analog
• Remote control: no
• Power consumption:
• Dimensions:
• Weight:
• New price approx.: 1,990 euros (silver version)

Connections

• Number of inputs:
  • Phono (DIN)
  • Aux (Cinch)
  • Tuner (Cinch)
  • CD (Cinch)
  • Tape In (Cinch)
• Number of outputs:
  • Tape Out (Cinch)
  • Pre Out (Cinch)
  • 1 pair of speakers

Technical Data

• Continuous power (at distortion factor)
  • 8 Ohm: 2x 80 W
  • 4 Ohm: 2x 140 W

2 Ohm: 2x 250 W 1 Ohm: 2x 450 W

• Dynamic power
  • 8 Ohm:
  • 4 Ohm:
• Total harmonic distortion:
• Attenuation factor:
• Frequency Response:
• Signal-to-noise ratio:
• Stereo channel separation:
• Tone control:
  • Bass: no

treble: no

• Loudness: no
• High Filter: no
• Low Filter (Subsonic): no
• Mute: no
• Direct/Line-Straight: no tone control available

Special Features

• here, if available

Service power modules:

• at 230V mains voltage approx. +/- 41V operating voltage in no-load operation.

Adjust the quiescent current at the 5W-emitter resistors of the output stage - between the charging capacitors and the heat sink - to 2.5mV (corresponds to about 16mA/1.5W quiescent power per channel), warm up for half an hour at 10W/8Ohm - and let it cool down again. If necessary, adjust a few times after several minutes until the value (without load/signal!) remains constant at +/- 0.1mV.

• The first two stages of the power module are of complementary symmetrical construction, differential and voltage amplifier have a stabilized 24V operating voltage.
• This variant of a kind of compound Darlington output stage has ground TO3 output transistors and TO220 drivers. Presumably (according to manufacturer's statements selected, is however not comprehensible by measurement) Motorola MJ15015/MJ15016 were used here (the larger brothers of the types 2N3055/MJ2955 mentioned in the same data sheet: 15A 120V 180W - that can be relatively well comprehended by recalculation and on the basis the chip form and size with cut open housing). By the way, I'm probably only writing because I'm not authorized - On some copies of the power amplifiers like the drivers, you could still clearly see the writing. By the way, the quiescent current transistor is (both from experience and according to the recognizable imprint) a BD139, but at this point (circuit as adjustable Zener diode) the exact type is rather uncritical. As faster output stage replacement type would be suitable e.g. also MJW1302/MJW3281 (15A 200W). This type has a much higher cutoff frequency, is more linear and more loadable than the original transistors, but unfortunately in a TOP3 package, which can be mounted to TO3 heat sinks without great difficulties. For this, the PCB drill holes (base/emitter) have to be widened to 1.5mm, a suitable insulating washer is necessary, the mounting hole gets a screw M3x16. The other screw hole gets an insulating nipple, solder tag and lock washer as well as the original screw. Base and emitter must be bent vertically downwards, exactly so that no short circuit can occur - the collector leg is shortened and soldered to the solder tag. Limited use of the 20A types MJ15003/15004 is also possible, but these are slower than the original and may provoke oscillation.

Caution! Low power China transistors with fake brand imprint available! No matter if MJ15015, MJW3281 or MJ15003 - Please use only guaranteed quality, preferably branded goods matched for current amplification. The current limiter of the power amplifier is designed for a peak current of approx. +/-16A and a continuous current of approx. +/-4A, but was no longer fitted to later power modules - as it is almost ineffective for its actual purpose anyway, but reduces the sound. If you recalculate the current limitation and consider the key data of the final transistors, the manufacturer's specification "450W at 1 Ohm" can't be correct, in my opinion at least a time specification is missing - 450W for how long? First, the current limitation would start here long ago (if present in the module), second, 450W at one ohm would cause an (effective alternating) current of the square root of 450 (P=I2*R)... so over 21A, the roof current is even 30A. Even if you include the time halved distribution of the power to the two output stage transistors with AC current, this is already the maximum allowed current of the "output devices". An effective average current of 10A, 30A peak current - extremely borderline for 15A types (their chip is only about 3.5mm square)! In my opinion, the 450W stage at 1Ohm is not long-lasting, and only models without current boost can deliver that much (for a short time). Drivers are BD243/BD244. The output stage is connected to the speaker output with the collectors of the Darlington pairs and has a voltage gain of approx. 3. Please do not change the type of the driver transistors, otherwise the compensation of the output stage is incorrectly adjusted.

• If there is still an idle oscillation after repair, a sable element with 10 Ohm/150nF directly at the solder lugs of the speaker sockets will counteract this (this is my empirically determined value/location, I have also seen factory repaired modules with attached 10Ohm/100nF sable element on the bottom side).

The unsightly overdrive behaviour (intermittent negative feedback due to dead time of the output stage) can be tamed with fast, low-capacitance Schottky diodes (min 90V! e.g. SB190) in the reverse direction between collector and base of the BD243/244. There are also later modules, where the last emitter follower stage (MPSA06/56) was compensated with two capacitors C-B (47pF, Miller capacitance) - all probably because of the basically very slow, and therefore phase-rotating (=unstable) output stage. Other capacitances of the module also vary over the years, both in values and in the types used. At some places additional capacitors were soldered on the bottom side, e.g. 2x100nF foils at the stabilized supply of the input stage, or the above mentioned 1nF capacitor in the 1 to 3 pre-driver stage.

• On some units the Roederstein charging electrolytic capacitors are defective (bubbles on the cup, stink!), in this case a complete re-equipping of all electrolytic capacitors is advantageous (e.g. Panasonic HA/FM/FC).

Attention: please use 50V charging capacitors for the No.1 (diameter max. 30mm), these electrolytic capacitors are operated in the 40V original configuration at 230V mains voltage at the edge of their dielectric strength.

• If due to a defect the resistors near the BD243/244 are burnt: the two closer to the heatsink have 100 Ohm, the two behind have 470 Ohm (please use non-flammable types and clean the board sufficiently).
• Before putting the unit back into operation, please also make sure that the collectors of the driver and end transistors (in this case the loudspeaker output!) on both channels have no contact whatsoever with the heat sink block, this would lead to unpredictable effects.

Other models of the same series: