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Alpha Office Update – Our measurement setup

Alpha measurement system

Those of you who follow Alpha Audio on Youtube and Facebook will have noticed that we recently became the proud owners of a Prism dScope III and a Rigol digital scope. Your author has been busy for a couple of years saving up the financial means and the necessary knowledge to make the right choices. But it is finished…!

Already after the first post about the measurement equipment, we were told that HiFi is about the sound and not the measurement results. We expected that, of course. And yes… partly that is true. However, we are not a retail store or a consumer. Alpha Audio is a journalistic medium. The important thing is to cover both sides and to try to be as objective as possible in reporting what we hear and what we can measure. Add to that our sound samples, photos and sometimes videos and you should get a very complete picture of a device.

The measurement setup

The Prism dScope III is a true Swiss army knife. With the Prism it is all about what you want… But hey… then you need to know exactly what you want to measure and how you are going to do it. Fortunately, we have some contacts who are very handy with this device ánd know all about measuring audio. For example, we were given two big, heavy books as homework. The Audio Precision Measurement Handbook and Dunn’s book on digital audio measurements. Although this is mainly focused on Audio Precision, the methodology is the same.

Last Wednesday we also got a crash course in Prism dScope. Which is very nice, because not everything is easy or logical if you don’t work with this apparatuses every day. A mistake is easily made and to publish wrong measurements is worse than not publishing measurements at all. Besides the Prism we have a Rigol digital scope as an addition. Not everything is always visible on the FFT analyzer of the Prism. To have a ‘normal’ scope next to it is nice. The range of the Prism is 0 – 90,000 Hz. Fine for audio – we can measure up to 24 bit / 192 kHz – but if you want to measure HF noise from a Class D amplifier, for example, that is not enough. That’s where we put the Rigol scope in. It measures up to 50 MHz. And with an update to 100 MHz. You can look just a little deeper.

What are we going to measure?

Basically, we want to measure everything. Including power conditioners for which we have also built a set-up. We can make the noise and distortion visible very well that way. The Amplimo transformer has no influence up to 200 kHz which is sufficient for these measurements. The test measurements were very promising!

For (power) amplifiers we have non inductive 4 and 8 Ohm dummy loads that work stable up to about 200 watts. They are now quite heavily cooled, so perhaps they can handle (a little) more. Basically, we measure fairly short – no endurance tests – which also allows for less heat generation. The question is also how useful it is to measure much heavier and longer.

For DACs and streamers, we don’t need any special gear except good cables and decent adapter plugs. The Prism software has a number of scripts that perform basic measurements. Think Jtest, various types of distortion and noise. You are going to see the pictures soon.

Reviews are coming again!

You may have noticed that a little less reviews have come online. That’s what happens when you’re a bit short on time. But rest assured… they will come again. And more complete than ever! Thank you for your patience.

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