Aaron No.1 specifications

Brand : Aaron

General

Connections

Technical data

Special equipment

Caution! Low-power China transistors with fake brand imprint available! Rega rdless of whether MJ15015, MJW3281 or MJ15003 - Please use only assured quality, preferably brand goods matched to current amplification.

If you calculate the current limit and take into account the key data of the end transistors, not everything can be right with the manufacturer's specification "450W at 1 ohm", in my opinion there is at least a time specification missing - 450W for how long? Firstly, the current limitation would have been used here for a long time (as it is present in the module), secondly, at 450W an (effective alternating) current would flow from the root of 450 at an ohm (P = I2*R)... so above 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 alternating current, this is already the permissible maximum current of the "output devices". An effective average current of 10A, 30A peak current - extremely limiting for 15-A types (whose chip is only about 3.5mm square)! In my opinion, the 450W stage at 1Ohm does not compete for a long time anyway, and only models without current limitation can deliver that much at all (for a short time).

Other models of the same series:

Manufacturer: Aaron
Model: No.1
Years of construction: 1989 - 2002
Manufactured in: Germany
Color: Silver, for an additional charge: Black, Chrome, Gold
Type: analog
Remote control: no
Power consumption:
Weight:
New price approx.: 1.990 Euro (silver version)

Number of inputs:
- Phono (DIN)
- Aux (RCA)
- Tuner (RCA)
- CD (RCA)
- Tape In (RCA)
- Number of Outputs:
  - Tape Out (RCA)
  - Pre Out (RCA)
  - 1 Speaker pair
Phono (DIN)
Aux (RCA)
Tuner (RCA)
CD (RCA)
Tape In (RCA)

Pre Out (RCA)
1 Speaker pair

Continuous power (with total harmonic distortion)
- 8 ohms: 2x 80 W
- 4 Ohm s: 2x 140 W
- 2 Ohm s: 2x 250 W
- 1 ohms: 2x 450 W
Dynamic power
- 8 Ohm s:
- 4 Ohm s:
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: none Sound control available

8 Ohm : 2x 80 W
4 Ohm : 2x 140 W
2 Ohm : 2x 250 W
1 Ohm : 2x 450 W

8 Ohm :
4 Ohm :

Bass: no
Treble: no

here, if available

at 230V mains voltage approx. +/- 41V operating voltage at idle.
Quiescent current setting: set 2.5mV at the 5W emitter resistors of the output stage - between the charging electrolytic capacitor and the heat sink (corresponds to about 16mA/1.5W quiescent power per channel), warm up for half an hour at 10W/8Ohm - and let cool down again. If necessary, after several minutes, recalibrate a few times until the value (without load/ signal!) remains constant at +/- 0.1mV.
The first two stages of the power module have a complementary-symmetrical design, while differential and voltage amplifiers have a stabilized 24V operating voltage.
This variant of a kind of compound Darlington output stage has ground-down TO3 end transistors and TO220 drivers. Motorola MJ15015 / MJ15016 (the larger brothers of the types 2N3055 / MJ2955 mentioned in the same data sheet: 15A 120V 180W - this can be calculated and relatively well understood by the chip shape and size with the case cut open) were probably used here (selected according to the manufacturer's statements, but cannot be traced by measurement). By the way, I probably only write because I am not authorized - on some copies of the power amplifiers such as the driver, you could still clearly recognize the writing. By the way, the quiescent current transistor is a BD139 (both from experience and according to the recognizable imprint), but at this point (switching as an adjustable zener diode) the exact type is rather uncritical. MJW1302 / MJW3281 (15A 200W), for example, would also be suitable as a faster amplifier replacement type. This type has a much higher cut-off frequency, is more linear and more resilient than the original transistors, only unfortunately in the TOP3 housing, which can be mounted on TO3 heat sinks without much difficulty. To do this, the board drill holes (base /emitter) must be widened to 1.5mm, a suitable insulating washer is required, the mounting hole is provided with a screw M3x16. The other screw hole is provided with insulating nipple, soldering lug and locking washer, as well as the original screw. The 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 soldering lug. The use of the 20A types MJ15003/15004 is also possible to a limited extent, but these are slower than the original and may thus provoke a tendency to oscillate.

The current limitation of the power amplifier is designed for a peak current of approx. +/-16A and a continuous current of approx. +/-4A, but was no longer equipped with later power modules - since it is almost ineffective for its actual purpose anyway, but it reduces sound.

Drivers are BD243/BD244. The output stage is connected to the collectors of the Darlington pairs at the speaker output and has a voltage gain of about 3. Please do not change the type of the driver transistors, otherwise the compensation of the output stage is incorrectly adjusted.
Should an idle oscillation tendency nevertheless occur after repair, a sable element with 10 Ohm / 150nF counteracts this directly on the soldering lugs of the loudspeaker sockets (this is my empirically determined value / location, I have also seen factory-repaired modules with an attached 10Ohm / 100nF sable element on the underside).
The unpleasant overdriving behavior (negative feedback caused by dead time of the output stage) can be achieved with fast, low-capacitance Schottky diodes (min 90V! e.g. SB190) in each case in the blocking direction between the collector and the base of the BD243/244. There are also later modules in which 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-shifting (= unstable) output stage. Other capacities of the module also vary over the years, both in the values and in the types used. At some points, additional capacitors were temporarily soldered on the underside, for example 2x100nF foils on the stabilized supply of the input stage, or the above-mentioned 1NF capacitor in the 1 to 3 pre-driver stage.
In some specimens, the Roederstein Ladelkos are defective (bubbles on the cup, stink!), a complete refitting of all electrolytic capacitors is an advantage here (e.g. Panasonic HA / FM / FC).
Attention: please use 50V charging capacitors with No.1 (diameter max. 30mm), these electrolytic capacitors are operated in the original 40V configuration at 230V mains voltage at the edge of their dielectric strength.
Should the resistors in the vicinity of the BD243/244 be burned due to a defect: the two closer to the heat sink have 100 ohms, the two behind them have 470 ohms (please use non-flammable types and clean the board sufficiently!)
Please also make sure that the collectors of the driver and end transistors (in this case the speaker output!) do not have any contact with the heat sink block on both channels, this would lead to unpredictable effects.