This is a review and detailed measurements of the Alpine UTE-73BT Digital Media Receiver. It was kindly purchased new by a member and drop shipped to me. It costs US $99.99 on Amazon including free shipping.
Can't say that the UTE-73BT looks any different than a thousand other head units:
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What was remarkable was how light this unit is. I don't think I have ever held a head unit that weight this little. Taking out the CD mechanism helps of course but still, it feels like it is made out of plastic even though it is not.
An Aux analog input is provided in the front as well as the USB input (I left the door open). I used both for my testing. Alas, the unit could only read one of my test files on the flash drive. It would refuse to read any other. The files were all uncompressed FLAC which it seemed to recognize but wouldn't read. Strange.
Back panel shows pre-outs which I used for testing:
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Standard multi connector is used for power and speaker outs.
To test the unit, I had to power it with my bench power supply. This causes a problem in testing because we now have AC ripple that does not exist with a battery as a source. I tried to work around it as you see below but I am not happy about it. The standard solution is to power it using a battery but I can't bring one indoor. Have to see if we will be testing a lot more auto audio and if so, I will invest in proper way to power them.
Alpine UTE-73BT DAC Measurements
Per above, I put my standard 1 kHz test tone on the flash drive and had the unit play it while I measured the performance out of pre-out. I adjusted the volume one notch to get the output to be 2 volts:
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This is obviously not good performance. Noise floor is quite high by desktop standards as are distortion components. You are getting about 10.5 bits of performance which is dismal for a home system. I have not tested a lot of head units to give this a precise rating. I did test a
Sony RSX-G9 which scored far better with a SINAD of 89 so much better job can be done in this form factor.
Analog Input Measurement
I fed the unit analog signal through Aux input. I started with 2 volt input but that severely clipped it so I backed that down to get a dashboard view:
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So no hope of improving performance by using an external DAC. Sweeping the input shows the clipping behavior:
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Running a frequency response sweep shows that the input is digitized at 44.1 kHz:
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There are parametric EQs in this unit so likely it digitizes the input to allow for that even for analog input. They could have done a better job though by keeping frequency response more flat.
Signal to noise ratio shows that we are missing dynamic range of 16 bit CD:
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Crosstalk is fine:
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Power Amplifier Measurements
I used the Aux in to test the power amplifier left and right channels:
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Now you see the problem I talked about at the outset. We have a 60 Hz mains peak that dominates the measurements. This is actually the better of two bench power supplies I have. To reduce the impact of this noise, I activated a-weighting filtering in the analyzer and got this:
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So we are back to 74 dB SINAD.
Frequency response is dominated by the Aux In's own bandwidth:
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Signal to noise ratio is much worse now due to power supply noise but even using a-weighting, we are still coming up short:
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I was surprised to see the heavy rise in distortion as frequencies got lower:
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This is usually due to lack of capacitance storage in the power supply.
At 4 ohm, this thing puts out the old standard 5 watts of power:
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Very sad. Switching to 8 ohm surprisingly gets you more power:
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Back to 4 ohm, if you allow distortion go up higher, you do get about 10 watts:
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Conclusions
Hard to have high expectations when paying just $100 for a head unit. Putting that aside, there is nothing here to get excited about. Performance is limited in multiple ways to around 74 dB which is quite disappointing by desktop standards. But maybe most of them are this bad, I don't know yet.
I don't have a recommendation for you either way. Need to get more data to have a good reference. Personally though I have no use for a head unit with just 5 watt of power. That is a recipe for poor performance by itself. Either get an external amp or one of the few 25 watt/channel units.
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