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Amplifiers                Loudspeakers               How to order

Power amplifier monoblock 50 W / 8 Ohm. Top quality Hi-Fi sound and reliable long-term stability.

Not just the "pretty good" sound most DIY amplifers emit, but really top-of-the-line Hi-Fi quality.
Every little detail will be rendered with fantastic clarity, which makes the music enjoyable for hours without listening fatigue.

Careful design and using exactly the right discrete components result in pure amplification, there is no audible addition or subtraction to the sound. No coldness and no extra warmth. Just amplification.
So, Hi-Fi in = Hi-Fi out. Garbage in = garbage out. A live recording of a concert will sound (and feel) like being there, a close-to-the-microphone voice will sound (and feel) like if the singer is close to you.

For people who are used to mass-produced "off the shelf" amplifiers, hearing music from these amplifiers connected to our SQ-50 loudspeakers in our shop is often a WOW- experience. They did not think Hi-Fi could sound this natural. And it does not matter if you listen to classical music, jazz, pop or rap. If the recording is good, so is the sound from this amplifier.

The stability of the quiescent current (current at no signal) of a power amplifier is critical. If it gets too low, sound quality will deteriorate, the cross-over distortion will increase until it passes the level where you start hearing it, and that is a very irritating distortion. Or, even worse:
If it gets too high, the amplifier will overheat, the most common reason for the "death" of most amplifiers. The trimm potentiometer oxidizes, or the temperature stabilizing components don´t age exactly the same. If you want a "normal" class AB amplifier to keep behaving like new, you should re-adjust the quiescent current regularly.
CM-50-16 is totally immune to any of these problems. As you can see one the picture above, there is no trimm potentiometer. And there are no thermal feedback componensattion and no need for re-adjustment. The quiescent current, and therefore also the sound quality and reliability, will keep the same over time.

So, you get both superb sound quality and long-term stability without any need for re-adjustment. We have used this concept in industrial electronics since the 1980´s, so it is a well proven feature.

CM-50-16 is the same amplifier module used in our famous CM-100V power amplifier (2 pcs of course).
The input sensitivity is about 0.9 V for full output (50 W / 8 Ohm) so a CD- or DVD player, computer sound cards and DAC:s with 1V or more maximum output can be connected directly without need for any preamplifier.
Output power with our recommended power supply (se below) is 50 W at 8 Ohm load.  Notice: Unless using a power supply with lower voltage, loudspeaker impedance must be 6 ohm or higher. Otherwise the current limiter will activate.

You don´t get the usual "pretty good" sound that many DIY kits deliver, but really top-of-the-line, so called reference quality. All details in the music will be amplified. Nothing added, nothing substracted. So, Hi-Fi in = Hi-Fi out. Garbage in = garbage out. A live recording will sound and feel live, a close-to-the-microphone voice will sound and feel close.
For people who are used to mass-produced "off the shelf" amplifiers, this is usually a WOW! experience, which we are used to when people come to our shop and listen to our CM-100V amplifier (with these monoblocks) + our SQ-50 loudspeakers for the first time.

Prices incl shipping until april 1 2017, when PostNord adjust their shipping costs.
Prices in brackets are approximate equivalents as exchange rates vary day by day. These figures were calculated based on the following exhange rates here in Sweden, on march 10, 2017:

1 € = 9.57 SEK, 1 USD = 9.02 SEK, 1 GBP = 10.97 SEK, 1 NOK = 1.05 SEK, 1 AUD = 6.80 SEK, 1 NZD = 6.24 SEK

European customers in EU countries (VAT included in product cost, shipping is VAT free):
1 x CM-50-16: 1440 SEK (150.47 € / 131.27 GBP)
2 x CM-50-16: 2560 SEK (257.50 € / 244.51 GBP)

European customers in non-EU countries (no VAT):
1 x CM-50-16: 1220 SEK (127.48 € / 1162 NOK)
2 x CM-50-16: 2110 SEK (220,48 € / 2009.52 NOK)

Non- European customers (higher shipping cost, more paper work, no VAT):
1 x CM-50-16: 1255 SEK (139.13 USD / 184.55 AUD / 201.12 NZD)
2 x CM-50-16: 2150 SEK (238.36 USD / 316.18 AUD / 344.55 NZD)

We ship by PostNord which is not a low-cost shipping company, but they are very reliable. They have not damaged or lost a single package during the decades we have used them for our export shipments. They are also relatively fast: Normal shipping time to european customers is 3 - 6 workdays, to the rest of the world 1 - 2 weeks.

Connecting the terminal block of the CM-50-16 to the power supply, speakers and input:

1: Power supply minus (<35 V)
2: Power supply ground for loudspeakers
3: Loudspeaker minus
4: Loudspeaker plus
5: Power supply ground for input
6: Input ground
7: Input signal
8: Power supply plus (<35 V)

Power supply recommendation. (PDF for printing, containing this drawing and volume control, click here.)

One 2 x 24 V (150 VA or more) transformer, four 5A / 100V (min) diodes, two 6800 - 10000 uF, 40 - 50V, electrolytic capacitors, one DP switch for the input voltage (both wires), one 1.6A slow fuse (input) and four 1.6 A quick fuses (outputs).

About the electrolytic capacitors: Ripple current should be at least 4 A (max working temperature, normally 85 °C).
When making the PCB, make certain the ground starts at the center connection of the transformer, then goes to the capacitors, and then to a point where the different ground output points are connected. Like on the drawing above. To one of these ground points, connect the ground connection from the mains voltage plug. If you don´t have grounded wall sockets, try to find another ground point to connect here, both for safety reasons and to avoid any background hum. re is a risk of a low humming noise if the amplifier has no real ground connection. Or, use a metal cabinet connected to this point.

Notice: There is a thin brass strip connecting the PCB ground to the heatsink (below the block terminal). If the heatsink is also grounded through a metal cabinet there might be (but not necessarily)
a ground loop causing a 50 or 60 Hz background tone.
If so, cut off the brass strip so that there is no direct connection between the PCB and the heatsink. However, if your heatsinks are not grounded elsewhere, like in our CM-100V amplifier, the brass strip is necessary to stop any static discharge reaching the output HEXFET transistors.
(If you walk on a synthetic carpet and build up a static charge, and then touch the heatsinks, they must be grounded. Otherwise the discharge can pass through and damage the HEXFET:s.)

Volume controls:

(Input to RCA sockets, Output to 6 (gnd) and 7 (sig) on CM-50-16.

Even if you use a preamplifier with volume controls, we still recommend using volume controls also with the power amplifier.
The CM-50-16 has a very low noise level, and to keep noise to a minimum set the power amp volume controls so that you get the volume you need when the pre amp volume controls are at close to maximum.
That way the background noise of the pre amplifier is kept low. We recommend 10 kOhm log potentiometers, even if up to 100 k work, as lower impedance results in less sensitivity to interference from other electric / electronic equipment.

/Valutronic, Stefan Berge, 2017-03-10

Questions and orders by email: email@valutronic.se