Tuesday, September 9, 2008

DIY Class T amplifier - listening to it

I have finally assembled my own T-amp today (06.09.2008) although it is still yet to be fitted into its wooden casing (which needs more time to complete as its sidewalls are very thick and require some chipping away of wood beneath the 10 manually drilled holes). I made a power wire with some AWG-26 multi strands wire (doubled and twisted per side) soldered to a DC male connector for use with a computer-notebook-styled 12V DC 2.5A SMPS (switched mode power supplies). I then proceed to de-solder out the 3-pins input connector from the PCB board, thoroughly sucked away all the stale solder and cleaned the 3-holes area with thinner before soldering in a pair of Neutrik RCA-plugs plus a 50K (Dale resistors) 24-steps attenuator.
I connect the T-amp to my Q-Acoustics 1010 bookshelf loudspeakers (sitting directly on the wooden flooring) with some el-cheapo hotwires. Source is a sub RM200 mass-market LG DVD player. After ensuring all connections are proper, I powered up the T-amp, hit the play button on the DVD machine and waited eagerly. No sound, the whole setup is dead quiet, no hum, no buzz – either a very good sign or I may have wired-up the amplifier wrongly somewhere. Momentary suspense. I cranked up the volume and now the sound comes about, softly at first but gradually gets louder as I turn the knob of the attenuator. Great!

What did I hear?

- Initial impression is a well-defined and clean sound with highs a little lacking and some boom to the lower mid / upper bass region. Clarity is good but nothing spectacular as yet.

- Midway through playing the third CD, I began to notice both macro and micro dynamics have improved substantially with great swing from the quietest to loudest passage. The forceful rendition of voice by a female vocalist, sound of her breathing and her lips parting come out so well pronounced.

- Playing the fourth CD (a female vocalist rendering some 90s pop songs in jazz style), timing and rhythmic swings are thought to be great. Sibilance associated with this CD is almost all still there. But hey, wait a minute, bass digs deeper now with less boom than earlier.

- Tonality / tonal balance and timbre of acoustical instruments are thought to be good. Liquidity of vocals, a sign of great midrange, however, could not be attained, probably a limitation of CD playback through a DVD player rather than by the T-amp.

- Size of image is big, I have yet to position my loudspeakers properly to try out the 3-dimensional sound staging capability of the T-amp. Currently, they are positioned 3 feet apart from one another and each of them sits on a stack of magazines. Within this setup, I hear the T-amp images well, vocals well fleshed out (as opposed to cardboardy sound) with decent sound stage and depth. I would think the sound staging capability would not be any lesser than most other amplifiers and shall comment once I have fitted my T-amp into its casing proper and after listening to it in my main hifi system.

- Details through the T-amp playing at moderate level is good; sound of people talking, glasses clicking and cash register at the background of beginning of Limehouse Blues of Jazz at the Pawnshop 1 come out crystal clear. (When this track was played through a mid price Marantz integrated amp few years’ back, an acquaintance had sarcastically enquired whether we were actually listening to silent music!) Listen also to the ending passage of Randy Crawford’s Diamante to a dog barking and sound of waves hitting on shores in the background of Priscilla Chan (陈慧娴)'s 痴情意外.

- Bass – a lot of energy in this region but its definition is rather vague at this juncture; the T-amp certainly needs more hours to be run-in. However, I must admit with good recordings, definition of bass is all there and well defined.

- Treble – Clean and extended yet not harsh nor ragged sounding.

- Overall, the T-amp is sounding much more musical and relaxed now after 8 hours of playing music non-stop compared to when it was just powered up for the first time. Its well-timed rhythmic swing and slightly forward sounding midrange certainly makes listening to music through it addictive enough for me in not wanting to stop listening to more. I am listening to Jazz in the Pawnshop now - great music sounding even better through the T-amp. And I thought it sounded pretty close to analogue (a fellow forumer at LYN reminded me I was actually insulting the digital medium!).
My T-amp has clocked approximately 20 hours by now (07.09.2008); still a long way to go before it is fully run-in. It now sings much better and sounds more beautifully than yesterday and by right I should have just left it alone to continue singing. However, the curiosity to tweak got the better of me and armed with my soldering iron, I removed the 4 capacitors on board. I replaced the input capacitors with a pair of Vishay Roederstein MKT1813 2.2uF 63V Metalised Polyester Film Axial Type capacitors and as for the buffer capacitors, with a pair of Panasonic FM 1000uF 16V electrolytics.
How did the change in capacitors affect the sound of my T-amp? I shall come back to this shortly after describing the bookshelf loudspeakers that I paired with my T-amp. Q-Acoustics 1010, to me, have almost perfect highs and midrange which are seamlessly integrated and at their selling price, are second to none. Their weaknesses though, are they do not have any ‘real’ bass to speak of and they do not throw a big soundstage like many other loudspeakers. Being a midrange guy, I could easily live with such shortcomings.

I had initially placed the pair of loudspeakers sitting directly on the wooden flooring in my bedroom but after a couple of hours of listening to music through them on Saturday afternoon, my ears could no longer take to the hard and ‘overpowering’ bass I was getting from them so much so I inserted a stack of magazines under both loudspeakers. I had also mentioned with normal recordings, bass definition of T-amp was a little vague.

Immediately after the capacitors change, I only detected subtle differences. First, the hardness and ‘overpowering’ bass I was hearing through the stocked capacitors are now gone. Bass is now softer with bass lines slightly better defined (less of the mini-compo effect in bass I thought I was hearing at times earlier). I thought this is how my Q-Acoustics 1010 should actually sound.

I also thought the highs now sounded more refined and slightly airier and midrange especially in vocals sounded less forceful than before. Is it a good thing? Hmmm ……

Previously, I had asked whether the midrange and highs of my T-amp are really better after the capacitors change by me. I have listened to several more CDs since then and my answer now (08.09.2008) is a resounding YES. Vocals sound airier, livelier and less forceful (hardness in midrange greatly reduced). I would think a CD player proper is required in my setup to totally remove any hardness remaining. The overall sound now is a touch more gentle compared to before.

A CD I used of late to test vocals and resolving ability of amplifiers is Il Divo’s first album (Sony BMG 828766765427) where 'Unbreak My Heart' is the first track therein. This is a non-audiophile CD and I only owned a local-pressed copy. With most amplifiers, this CD would sound rather noisy as Il Divo is a group comprising of 4 male soprano singers brought together by Simon Cowell (yes, the outspoken judge of American Idol). After the capacitors change in my T-amp, Il Divo sounded extremely close to what I am hearing through my Simaudio Moon i-3 integrated amp and this is really stunning as the resolving ability of my T-amp has now surpassed that of Exposure 2010S integrated amp, a Stereophile Class A component currently retailed at RM4,300 in our country.

In concluding my review, I would say even in its stocked form, the T-amp kit (TA2024 chip) at RM55 (throw in another RM100 or so for some decent RCA plugs, speaker binding posts, wires, a volume potentiometer and casing) is a well-designed amplifier which sounds great and in fact a giant killer. It would easily surpass the sound quality of many entry level integrated amplifiers, my former Sony TA-F5000 (with some very good Japanese internal parts) included. If any of us are on the lookout for an amplifier, it would be almost a sin not to explore and consider picking up the T-amp. And after some modifications which include the change in input and PSU capacitors plus others (change in critical SMDs to decent-grade capacitors, resistors and inductors), its sonic qualities should be raised to even greater heights, the sound after that surpassing many mid-priced integrated amplifiers. Many of us would be pleasantly surprised, charmed and could live happily-ever-after with this little gem.

added on 16.09.2008:
I replaced the LG DVD machine with a RM300 NOS Sansui CD-X310 CD player in my T-amp system on 11.09.2008 and after some 30 over hours of running-in the CD player by playing music, the system is sounding really marvelous. My tiny Q Acoustics 1010 (86dB/1W/1m) loudspeakers do not sound like small loudspeakers at all as I am getting lots of bass both in quantity and quality (goes very deep) and overall, a relaxed yet extremely dynamic, expressive and high on PRaT sound and the system certainly is giving my main system a run for money and in fact better in certain areas.

Which areas, you may ask? It is the directness, expressiveness and micro dynamics …that magical thing that it's hard to put a finger on. Magic is about as close as I can come to describing it. The sort of thing that triode lovers rave about although they don't really sound like triodes.

Listening to Nigel Kennedy performing Vivaldi's Four Seasons (EMI 724355635328) would easily endear the tone of his violin, mood and totally different interpretation of these pieces. And certainly not all affordable amps or systems could attain this!


arjen said...

Here Arjen Helder from China, The distributer of This PCB.
Well thank you for taking the time to write this review! youve done some very nice writing.
I must say i agree with your opinion, i use the T amp every day at work in the office and i have made portable speakers for my laptop with intergrated battery with this amp and wow ive never been so happy with somthing so small and cheap :-D

Y.C. said...

Arjen, thank you for comments and for making the T-amp so affordable. It has no reason to sound this good but it actually does. I love it tremendously and will be getting one unit for my office too. Yes, I saw pictures of your portable speakers at diyAudio Forum. Cheers