CM-50 monoblock, connection

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The connection is rather simple. You need a power supply of +/- 30-35 VDC. A 24 V transformer delivers about + / - 33 V after the rectifier and capacitors.
Red cable goes to plus, yellow cables to zero and chassis ground, and black to minus. Notice that you should use quick 2 amp fuses (F2A) for protection on both plus and minus.

The loudspeaker is connected via the white 2-lead wire. Black strip = plus.

The input is connected via the screened cable. Screnn = ground, inner wire = signal.

The ground connector of both input and loudspeaker (minus) should NOT be in contact with the chassis.

CM-50 has no high demands on the power supply. If grounding is made the right way, the CM-50 is rather unsensitive to interference. Diodes for rectification, two electrolytic capacitors and transformer is all you need.

Theoretically two 0.1 uF capacitors should be fitted in parallell with the diodes to minimize interference, but in practice there is no audiable difference.
The electrolytic capacitors: 10.000 uF / >= 40V.
The diodes: 100V, 10A (or more) with a single 24 output from the transformer, 5A (or more) with a 2 x 24 V transformer output.

Be careful not to direct the diodes or capacitors the wrong way, electrolytic capacitors charged backwards may explode.
The primary fuse is 2A slow with a 1 x 24V transformer, 1A slow with a 2 x 24V transformer.

Secondary fuses are 2A quick, often marked ”F2A”.

The reason for having two plus and two minus on the drawings is that most customers build stereo amplifiers with our modules, and each module should have its own fuses.

1. DC supply using a single output 150VA 24V transformer.

Notice the grounding! From the transformer a wire goes to one of the electrolytic capacitors, then to the other, and then to a point to witch all the yellow zero connections from the modules and the wire to the chassis run.

2. DC supply using two 75 VA 24V transformers.
Make sure the two transformers are connected so that the output polarity of the windings work in anti-parallell. How?

Just measure the AC output voltage between the transformer outputs that are not connected to each other. The voltage should be about 44-55VAC.

The two 230V inputs of the transformers should be in parallell.

(If the output voltage is about zero, just reverse the inputs of one of the transformers.)

3. CD supply using a singler transformer (150 VA) with 2 x 24VAC output.

Our own DC supply circuit:

Notice the way the zero goes from the input (on hte left, between the diodes):

First to one of the capacitors, then to the other and then to the point to which the yellow zero-cables from the modules go as well as ground cable to the chassis.
You can see the 0.1 uF capacitors in parallell with the diodes on the left, but in real life we don´t use them anymore. They don´t make any difference.

An old amplifier...

...can also be used. If you have space for the CM-50´s inside, and the output power of the old amplifier was in the region of 30 to 60 W per channel at 8 Ohms load, the old DC supply should work also with the CM-50´s. For safety, check the DC voltage of the old power supply, if it is

20 – 35 V you can use it.
If you want the amplifier to work on its own, without a pre-amplifier (the sensitivity is enough for normal CD, DVD and other modern players), you will need to fit volume controls:

För växling mellan olika inenheter (tuner, CD, DVD, dator...) används en vanlig audioväxel (finns bl.a. hos Clas Ohlson).

Mekanisk montering: Kylvinkeln på CM-50 fästs på kylfläns med två M3-skruvar. Kylpasta (kiselfett) appliceras mellan kylvinkeln och kylflänsen för bästa värmetransport.

Om slutsteget skall kunna köras på full effekt kontinuerlig behövs en kylfläns på c:a 1,2°/W men vid musiklyssning (även om musiken toppar på fulleffekt) räcker hälften (c:a 2,2 – 2,5 °C/W) utan problem.

OBSERVERA att CM-50 är avsett för 8 Ohms högtalare.

Om högtalare med impedans under 6 Ohm skall anslutas, måste drivspänningen sänkas (till +/- 20-24V vid 4 Ohm) och tomgångsströmmen därefter justeras till c:a 30 – 40 mA i tomgång.

Högtalare:

Anslut den vita dubbelledaren till uttag för högtalare.
Svart markering = plus (omarkerad ledare = minus).

Bygg helst i metallåda, det är relativt riskfritt.
Om man måste (eller vill) bygga i trä/plastlåda, skruva fast en metallbottenplatta som ansluts till stjärnjordpunkten. Alla andra metalldelar (kylflänsar, potarnas ytterhölje, eventuell omkopplares ytterhölje mm) ansluts till bottenplattan. Metall som elektriskt sett "hänger i luften" kan fånga upp statisk laddning som sedan kan laddas ur via CM-50-blocken och skada dem.

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