Project X, Part VI, Adding the sound from compact disc

In August of 2015 I started a mini series of posts around a rather novel small inexpensive amplifier that tied into my love of experimenting and building things that had been sadly curtailed due to industrial injuries and severe disabilities.
It was called Project X, the standing for mystery as I put together a mini system based around it looking at what a person on say a limited income might be able to do and just how good these units actually are. 
We covered topics like how to add input selection, the issue of dealing with its high sensitivity input and how we might ration it, the sort of speakers best suited to a small low power amplifier and in the last entry on March First, 2016 I looked at reproduction from cassette tapes.

There recently has been some rationalization of equipment  such as outmoded VHS video tape players and also upgrades on my main stereo system and I felt like adding cd replay so I repurposed the Rotel RCD 965 LE Discrete from the main system to this because in the intervening two years, I have found the amplifier to be capable of high quality reproduction and certainly shows the benefit of good quality sources.
While its replacement is better, non the less for regular cd this remains a lovely sounding player and so an ideal candidate for  adding cd replay using a high quality lead and using another Rothwell attenuator to bring its 2 volt maximum output down to that it can handle without distortion. 

On Tuesday I listened to a program of American Classics from composers such as Copland, Bernstein and Barber that I grew up on through it and it sounded really impressive, clear capturing both the tonality and also the vibrancy of the music well.


Previous Project X Posts:
Part one - The SA 36a pro ampifier
Part two - Adding multiple inputs
Part three - Adding the loudspeaker
Part four - Attenuating inputs
Part five - Adding tape replay

Project X, Part V, playing tapes

Project X is alive and well playing music in Lossy and Lossless forms from my Fiio music players line output from one of Eight micro sd cards as well as from a elderly Toshiba cd player.
I like quite a few people have a good number of cassettes not least pre-recorded ones I bought from the mid 1970's to mid 1990's I moved from cassette based portable listening to MiniDisc and had been thinking of how to play them back on this mini system.

Enter a unused Sony TX 313 mini sized fully functional cassette deck from a MiniDisc system I got from someone who never ever used it so it was still boxed and shrinkwrapped from the late 1990's.
Oddly enough it uses a car type side slot way of loading the tapes into it but unlike car units this does record and has auto tape type sensing to read the extra tabs for type II ('Chrome') and IV (Metal) tapes although the latter are no longer available new plus I seriously doubt it's tape heads really are up to making full advantage of such tapes electrically

The rear has RCA line in and outs, with the out going via a expensive Cambridge Pacific interconnect to the input selector with a maximum of 0.5 volts out depending on the program loudness and the AV bus for Sony mini systems it was sold with for synchronized cd to tape copying.
The unit is blessed with switchable Dolby B noise reduction for proper replay and recording of such tapes plus auto reverse so it can play one  side of the tape and switch by itself to the other. 
According to the specifications it reproduces up to 14khz for type I tapes and 15khz for types II and IV which is decent if not as wide as most full sized hifi cassette decks so the high frequencies will be clear but not quite as extended as the best units can achieve.
It is making an excellent job of replaying my 1980's EMI UK dolbyized Beatles pre-recorded cassettes which were amongst the best sounded tapes manufactured and part of reason I held out so long against the cd as portable listening was and remains a big part of my life and why my Fiio is my 'to go' digital playing device on headphones or connected to this system.
I like high quality portable formats more

Project X Part IV, Rationing the sound

Just been enjoying some Nielsen here on what has been a dry sunny but cool  day.
The amplifier is working rather well but one issue is the output from things like a cd player or my digital audio players line out is a lot higher than its input stage can handle so I have to turn the volume way way back and it sounds a bit strained on very loud passages.

It's a common problem cause by the strange decision in the early 1980's to standardize the output from digital to analogue converters typical found in cd players to around 2 volts where in the past it was rare for any device to have an output over 0.75 volts r.m.s. and often around  .250 to 0.5 volt which devices were and still are designed to 'see' into.
In simple terms, it means it's likely the very first stages of an amplifier are likely receive so much signal from such a source that they distort before the volume control can ration it, sounding harsh.
I've ordered up a pair of high quality 10db inline attenuators by Rothwell to put between the signal lead and the switching box which should cure that and allow it to use more of the volume controls rotation. 
They use 'audiophile' grade metal oxide resistors in a padded network in a plug enclosure to achieve that without compromising the transparency of the sound while being neat. 
Postscript: They arrived the next day from Bacup, Lancashire, England and it cured it leaving to sound very impressive playing a 96/24bit HD version of Rush's a Farewell To Kings on Closer To The Heart and the Christian Ferras recording of Sibelius's Violin Concerto (with BPO/H v Karajan on DG) via a Fiio X1 digital audio player's line  output.

Project X part III-making a noise!

That took time! I was just combining the contents of two older micro sd cards to a newer Samsung 64gb one as the originals were smaller in capacity than those you can get today and as it was works by the same artists were split between them which made no real sense anymore.
Cards of  that capacity now can be had for around GBP £18  easily so I think in so far as anything in lossless full cd quality that'll be my minimum size.
Meanwhile on Project X, we've wired it up to the speakers it'll be used on in my rest room for when I'm feeling rough which is fairly smallish.

I've had these for a while being the bigger and more general purpose base model to my regular Wharfedale Diamond IV, which are a ported mini monitor come bookshelf speaker designed more for absolute accuracy than efficiency .
The Delta 30's go a bit lower at the bass end and are 2db more efficient which is as well as although the SMSL SA 36 Pro is quoted as delivering 20 watts per channel, when you look at the integrated circuit manufacturers website, that figure is quoted at 10% thd+n distortion where most regular amplifiers quote the output relative to 0.1% or less and so in reality it's more like 8 watts.
In practical terms, in a smallish room with these speakers you can fill the room with relatively loud music sounding clean with the volume control no further forward than '11 o' clock'  leaving some capacity for sudden peaks.
With the other speakers you'd need an output rated more like 20 or more watts at 0.1 thd+n distortion or less to achieve a similar volume in the same sized room.

Project X Pt II, the selected page

It it had arrived last Saturday and has spent the week being soak tested to make sure it had no faults on arrival and did not develop any in use as naturally it would be returned to the suppliers for replacement.

As mentioned, the matter of having just one input would be addressed as while that would be fine if say you were using to improve on the sound of your tv with a small pair of speakers, it's not convenient for changing sources, having to plug and unplug every time.

So I got this.

It's really a A/v switch unit by HQ of Denmark for home theatre systems but having looked into the cost of buying the parts and a aluminum project case there would be no real gain plus I'd have buy a few beers for whoever was gonna drill and wire it up for me.

To connect it I bought a 0.5 metre Fisual cable as you really don't want long wires to take the output from this box to the input on the amplifier. I have 3.5mm mini jack for my Fiio X1 digital music players line output to plug into the switch and several Radio Shack (RIP) "Tandy Gold" thick oxygen free copper 1 metre cables.