HighResAudio / MQA Wars Continue on HiFiPlus

HighResAudio are to stop offering MQA encoded files. Here is a link to an article on HiFi Plus:

http://hifiplus.us11.list-manage.com/track/click?u=7c2c6adc5d8e2ef6eb0c411f0&id=5a140ac6f2&e=792bccbd1a

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Dry Solder Joints

Dry solder joint.

Dry solder joint.

Some parts in a power amp stage get very hot.  The output transistors of course but also some of the resistors in the output stage.  After years and decades of getting very hot and then cooling and running through this hot, cold cycle repeatedly, some solder joints can develop a hairline crack.  Especially if there was a weakness in the joint to begin with.  The crack, known as a ‘dry joint’ can give an increased resistance or may be open circuit completely.

Above you can see the track side of a wirewound resistor in the output stage of the power amp of the SX-5580.  To fix this, it simply needs resoldering.  The second picture shows the joint fixed.

Re-soldered joint.

Re-soldered joint.

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Pioneer SX-5580 Power Amp Module

Here are some photos of the power amplifier module.  As you can see, it’s big.  But then it would be at 120 watts per channel RMS.

This is before cleaning and changing of the electrolytic capacitors.  Given heat, electricity (generating electrostatic charge) and 30 or 40 years, there’ll be accumulation of grime and dust and that needs removing.

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Pioneer SX-5580 Receiver Refurb

Here is what I’m working on at the moment, a Pioneer SX-5580 monster receiver (amplifier with built in tuner).  As far as I’m aware, it is identical to the SX-1050 but is in black instead of all aluminium.

Pioneer SX-5580 Monster Receiver in black.

Pioneer SX-5580 Monster Receiver in black.

This photo shows what the front panel should look like if it wasn’t all dirty and a little scratched:

Pioneer SX-5580 Front Panel.

Pioneer SX-5580 Front Panel.

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High Resolution Audio, MQA and Others

Not sure where to start with this post. I suppose I should just ramble on…

CD audio was a little short of musical quality and has been bemoaned ever since its introduction pretty much. By anyone who likes quality above convenience at least. Vinyl has hung around and is now even making a comeback. That is due to the resolution of vinyl which is largely dictated by the size of the plastic molecules as much as the recording medium but may also be due to the artistic nature of the artwork with a pressing and the emotional quality of owning vinyl.

Now that computers are coming into their own, we have the opportunity to increase the resolution of digital audio. But then mp3 has become popular because of its small file size of around 1/10 of an AIFF or WAV (depending on the compression level) and apparently that small file size is bought at the expense of losing the higher frequencies. Everyone loses their ability to hear higher frequencies as we age and the older we are the less up the frequency range our ears can go. But then, there is another argument that although we cannot literally hear the higher frequencies, we can still hear the effects of higher harmonics so they are necessary.

I have a personal theory that the older we are, the better our brains are at filling in the blanks so we may not literally hear a high pitch sound, because the hairs in our ears are not there but our ears do hear the lower frequencies and our brains fill in the gaps (higher frequencies) because from experience, it knows what should be there. But that is a different discussion.

So mp3s have brought greater convenience at the expense of some musicality and that was fine since digits were still expensive when that format was designed, especially for download/streaming. But things have moved on again in computer land and efforts are now being made to increase the resolution to exceed CD quality both in terms of sampling frequency increases (44.1KHz for CD and 96KHz+ for HR) and bit depth (how many bits are used in each sample – e.g. 16 for CD, 24 for HR).

I am not convinced that increasing the bit depth to 24 makes that much difference since many recordings do not reach 16 bits in dynamic range anyway, so increasing to 24 would make no difference. On the other hand, regarding sampling rate, 44.1KHz seems utterly inadequate to me – how can you sample a frequency of 22KHz (within the frequency range of young people) with just 2 samples and expect to recreate the exact wave shape?

None of this affects my boombox or amplifier designs since I decided to leave that side to others – it has taken me nearly seven years to get this far with my design, how could I keep up with developments in digits! My boombox (ghettoblaster) and amp will both be Bluetooth connected but that unit is bought in and so replaceable as digits develop further and there are six inputs in all (including four phono/RCA) with only one for Bluetooth. The other input is two jacks in parallel (one 3.5mm and one 6.5mm) so musicians can play music from their e.g. iPod and play along with it with say a guitar or piano etc.

But here’s the main purpose of this article, to draw your attention to how some companies are taking advantage of us by doing bad things with digits and saying they are doing good things. One example would be how some companies are taking old recordings and converting them to High Res by resampling them at 24bit/96KHz. For me, these files are not high resolution if the original was not high resolution. For example, recordings made in the 60’s may have all sorts of distortions and noise caused by the lack of quality recording equipment. The HR version may simply be a high res recording of a crap original – it will still sound crap, only that crap will be accurately reproduced. In other words; beware the claims of High Res companies.

One person who really does seem to know what he is talking about (he’s an experienced recording engineer with his own studios and also a musician) and is fighting this cause (the reason I follow his blog postings) is Dr. Aix (Mark Waldrep). You can follow his posts here:

http://www.realhd-audio.com/

He is also publishing his own book about Hi Res which can be found here:

http://aixrecords.com/

Mark’s latest post gives a link to an article by Jim Collinson of Linn and I urge anyone interested in HR to give it a read.  The article claims a company called MQA is developing technology that will very much stifle new music and lock us all into their monopoly.  Here is a link to that article:

https://www.linn.co.uk/blog/mqa-is-bad-for-music

Happy listening (and reading),

Matt

Posted in DACs & File Formats, Ghetto Blaster / Portable Music Player, High Definition Sound, Media, Music, Signal Source, Vinyl | Tagged , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , | Leave a comment

DXF v SVG files – What he said!

I had problems with exporting files so the laser cutter company can understand them and they are accurate.  The reason behind it is me using the free, open source software Inkpad (and my lack of knowledge in this area).  It’s a good vector drawing app but there are limitations when exporting especially to .dxf files (Drawing Interchange/Exchange Format).  Here is the post a question of mine prompted from exeter-laser.co.uk, definitely worth a read if you need to export SVG (scaleable vector format) to DXF:

http://exeter-laser.co.uk/blog/2017/02/09/file-formats-again-dxf-vs-svg-today/

If you need to export .dxf files from an Apple Mac, here is a link to free to download (with restrictions) DXF software from a nice German company:  http://www.schaeffer-ag.de/

Posted in Amp Cabinet, Design, Ghetto Blaster / Portable Music Player | Tagged , , , , , , , , , , , , , , , , , , , , , , , , | Leave a comment

Connections Conundrum

I spoke in my last post about needing to find connectors to link the wires between the amp PCB and the outputs.  I just spent the whole day looking at the web sites of RS Components, Farnell, Maplin and eBay.  Although there are literally tens of thousands of different types, I am unable to find anything that fits all my needs: silver plated contacts, not expensive, not large, 5A+ rating.  Most connectors are either gold plate or zinc/tin plated.  They are also expensive, the cheapest costing around £16 for a full set.  I have even considered cutting up a multipole connector but it is still not right.

I hadn’t expected this being a problem, I’ll have to go and have a good ‘thinking sideways’ session to see where to go from here.

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