Tentlabs and op amp modifications

Discussion in 'DIY Discussion' started by michaelc, Jul 2, 2010.

  1. michaelc

    michaelc colombeverte

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    This CDP upgrade review comes in two parts: the TentLabs workshop I attended two months ago and then the opamp changes.

    Background
    I listen to music for fun, not for a living. It's mainly in short sessions on my own as here in Spain one's spare time really occurs out of doors. I get little opportunity to listen to my CDs now in all truth. I listen to relax after work.

    I have some 400 CDs. I listen mainly to brazilian chorinho, modern XX century classical music, lots of Rodrigo's vocal repertoire (in a time of his own), CCmixter funk and modern electronica (William Orbit, Towa Tei and Bah Samba). I also listen to Mancini, Schifrin and Al Green. The CCMixter and Orbit stuff is kept on the computer. Computer feeding the hifi is probably a year away for me right now. I go the front rows in concerts: more treble, less “depth†and more separation between instruments.

    My system consists of Roksan Kandy (MkI) amp and CDP, Magnum Dynalab tuner, Dynaudio Audience 42 speakers on Atacama stands, TNT Ubyte II , LAT International AC2 and Nordost Blue heaven cables and no particular shelving at the moment. Speaker and listening positions affect the perceived sound significantly. With the help of a friend, I found that listening across the short wall of the room, around 60-70% of the way out from the front wall, and listening at about 1.8m in an equilateral triangle with the speakers, works best overall for me. I have the speakers firing nearly straight down (what's left of) the room. It measures 28m2. A low bookcase divides the listening from the dining areas of the room, and protects the stand mounters from getting knocked over. I live in a flat with quite thin walls. Books, CDs and a carpet reduce primary reflections; room treatment is the next big task for me however.

    The headache
    After 8-10 years of my current audio system, I started to tire of the hard upper mids and treble of the CDP. I know this was so because the radio was a lot better in this area. The "imagescape" as well incidentally, even though the instruments can sound a bit larger than life on all transmissions. The analogue sound of radio is relaxing for extended listening; my Indian CDs and some other ones could grate and screech a lot, and after 20 minutes at medium volume would give me a slight headache. The transparency was good, and the system gave me something of the feeling of "being there": I could hear the mid and treble reverberation of the halls on live recordings, chair squeaks, coughs and splutters. Fascinating as it was, the headaches simply became unacceptable.

    The price of a “worthwhile†upgrade for me (on the basis of internet reports and not auditions) of thousands of pounds, euros or dollars was not on the cards for me.

    Tentlabs modifications
    After finding Guido's website and with the chance to start my own DIYing, I signed up for one of his Saturday workshops. Guido was helpful in taking me to the workshop from town, and offered us four work shoppers a morning theory session on improving the sound from CDPs prior to the practical afternoon session. He conducted the theory part in English only because my Dutch wasn't up to it. I am a beginner to modifying PCBs, and am thus very grateful to Guido for organising the workshop. His friend Wim was on hand, and in fact did most of the modifications for me. Wim went with the unit's Burr-Brown 1716 D / A converter but installed an XO 2.2 digital clock, a shunt regulator for it, changed some active stage capacitors for better ones, gave the output stage its own power supply, eliminated the mute kill function that works between songs to improve the sound further and put in two sockets so I could try out different op amps. The ones installed were OPA2134. After coffee and sandwiches, a short listening session followed, and then the good byes.

    The sound
    Back home, three things became immediately apparent. The bass was much deeper and clearer, possibly the bloom of my ported Dynaudios too. There was an organic or natural tone: treble sounded much sweeter and there was a good "roundness" to the sound I had never heard before. Mission accomplished, I thought. Imaging: easily more spacious but above all, much clearer; not the etched, post-card size image when I first bought the player and used QED Silver anniversary wires with it. It sounded like Van den Hul cable more than Nordost in tone. But friends, I prefer the latter. I had indeed traded away some transparency for musicality, of sorts. Trumpets, brass and violins did not have the bite or sheen I really liked, and hear constantly in concerts. (This system used to play trumpets best, if that makes any sense.) Female vocals had a more “veiled†sound. Clearly I was not going to accept this either.

    The op amps
    The original NE5532 had been more transparent than the 2134, but had had hard sounding upper mids and lower treble. The 2134 gave instruments a “rounderâ€Âmore analogue sound and in every way other than transparency trounced the 5532. They had the best depth of all the op amps. The search was on for other op amps. Over the following two months I listened to the OPA2604AD, LM4562, LF353, LM318, 5532 again and AD827JN.

    This last one (two 8-pin duals) finally bring the tonal balance of my system to just where I wanted it. It gives me a brighter tonal balance but a little less bass compared to the OPA2134. As I have the Dynaudios firing almost straight down the room this just fine with me. Upper mids and treble sound cleaner to me than on the OPA2134. They retain most of the imaging magic of the 2134s, and present fairly "rounded" acoustic instrument sounds. There is a little more "greyness" to the notes than on the 2134, but for me the tonal balance has to match that of real instruments and voice or all bets are off. The tone does not seem fatiguing, and I can hear more of the hall's acoustics. I can finally crank up my Indian bollywood collection! I think this is a product of the XO 2.2 clock, and not entirely of the op amps as I had thought. Bad recordings from 1992 or 2002 do not have grating treble any more. Hard treble and mids still sound hard, but they no longer burn my ears in acid. Poorer studio recordings can at least be played at medium volumes now comfortably. I suspect the slight grey sound and narrowness of stage rear images are products of the Type 2 -DIL/8-Pin Dual op-amps I am constrained to using. Remedying this may be more than I am willing to pay for just now. Holst's The Planets (London 417553-2) sounds wide front AND rear in my collection, but very few others do. I found it tricky getting the balance right between sound image size versus tonal balance. I did not want to accept having such a wide stage image (front row) with such a dark, deep sound (back hall) on the OPA2134.

    I derive more enjoyment from the modified system, and that's the main thing. Studio-recorded music sounds clear erand allows me to hear pretty deeply into the recordings. Each recording does sound distinctly different, as before, yet I can listen to any number of CDs without fatigue. I finally decide when to turn the music off when playing loud and I do not have a headache! And this is thanks to Guido's engineering and experience.

    Brief Op Amp evaluations
    OPA2134 €2.30- (organic, sweet, darker than radio, coloured)
    OPA2604AD €4.80- each (clearer, worse)
    LM4562 (clearer, thinner, grey)
    LF353 (mid-balanced, hard, separated sounds)
    LM318 (no sound, overheats)
    NE5532 cents (transparent, narrow stage, front row, hard mid/treble)
    AD827JN €10- (realistic timbral balance, clear treble, sweet)

    Michael :)
     
    michaelc, Jul 2, 2010
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  2. michaelc

    RobHolt Moderator

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    Interesting comments.

    Worth pointing out though that different op amps are better suited to some situations than others. So if you are perceiving a difference in one circuit position it might evaporate or change completely in another.
     
    RobHolt, Jul 4, 2010
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