![]() ![]() Audio Precision APx555 B-Series analyzer.Tests conducted with standard 4V line level XLR input Test Setup LCR (Capacitance, Inductance, Resistance).So, other than the slight concern in regards to the shorting issue, the construction seems to be pretty nice, with an attractive price to match, but can this switch be considered ‘transparent’? Measurements Measurements Include: The only complaint I could possibly make about the build quality is just that because of the lightness of the product, the cables can sometimes pull the box back if it’s not held down with something such as blu-tac. It would really have been ideal to see a ‘break before make’ switch used in these products just in case.īesides that, the build quality seems quite nice for the money, with a grey, sandblasted metal exterior, a satisfyingly firm and clicky knob, and Neutrik connectors used for the XLR ports. This is not an issue for the ‘1 in 3 out’ version, as shorting the inputs of amplifiers is no problem, but for the ‘3-in 1-out’ option, you will short the outputs of the two DACs together, which could potentially cause damage if they are playing at the time, and have insufficient short protection. It is also worth warning that the switch is a ‘make before break’ design, meaning that as you switch between say X and Y, they will be temporarily shorted together. There is also an MC303 with a ‘3-in, 3-out’ configuration facilitated by two switches instead of one.ħ1cw7ti9WQL._AC_SL1200.jpg 940×886 138 KB The MC103 comes in a ‘1-in, 3-out’ variant and a ‘3-in, 1-out’ variant. The MC103 is a fairly simple design, with the XLR ports connected to a rotating switch, allowing the user to select between three options. The Nobsound MC103 is a popular choice as an XLR switch mostly due to its affordable price. The only question is will the switch degrade audio quality? It’s a passive device and in theory shouldn’t have an effect on audio quality in the way that an active device like a preamplifier might, but does that hold up in practice? Lets find out! Design By using a switch, we keep the DAC connected to only one amp at a time, avoiding the effect of resistance (input impedance) in parallel, keeping our impedance matching ratio nice and high, and we don’t have to fumble with cables either. This gives us a result of 1666 Ohms! Lower than either of the two individually! This means that using a splitter in this setup, our impedance matching ratio would be less than ideal, even though either amplifier connected directly to the DAC would be fine. The effective input impedance for the two when connected via a splitter is calculated using the same formula as two resistors in parallel: The output impedance to input impedance ratio for the SU9 and 23R is 50:1, plenty! And for the SU9 and A90 it’s 10:1, so a little low but still fine.īut when we use a splitter, things change. You’re using an SMSL SU-9 which has an output impedance just over 200 Ohms. A topping A90 with an input impedance of 2000 Ohms, and an Enleum AMP-23R with an input impedance of 10,000 Ohms. (See our glossary for some info on input/output impedance!) Ideally you want the output impedance to input impedance ratio to be as high as possible, though keeping it above 10:1 at a minimum is an ok rule of thumb. But it does introduce a new problem: Impedance Matching.Ī DAC has an output impedance, and an amplifier has an input impedance. Option 2 addresses these problems, no cable swapping needed as the DAC will just feed both amps all the time. Option 1 is not particularly convenient, no one wants to be fumbling with cables behind their desk each time they want to listen to something different, and also if you’re doing this a lot then there is the risk you may wear out the connectors of the cable or your amplifier over time. Use an XLR switch to let you select which amp to input to. ![]()
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