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Thread: SDAs unplugged

  1. #61

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    So you don't know anything about the design of the OP's amp? You are just "punting" in this case. I doubt getting rid of the .9 ohms is going to make any difference at all. I would ALWAYS check with the amp manufacturer before doing things like strapping the negative terminals. But that's just me.

    H9
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass

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  2. #62

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    Default ignorance is bliss

    Oh man, now my head hertz :) (*sorry*). I have to admit I usually just lurk in the forums cause I feel like I would need to get an EE degree to intelligently discuss XO's / film caps / inductors, etc. (Not that I mind... there is nothing better than these forums for free education!) But I'll qualify my statements by saying that I don't fully understand the electronic details of how the SDA phase canceling is made to work, so I'm going to confine my comments to my opinions and empirical observations after playing with a pair of SDA2's (with the stereo SL2000 tweeter and two mid-woofers + a dimensional tweeter and mid-woofer in each box).

    I purchased my SDA's used, and some of the hard plastic on the interconnect receptacles had broken out making the stock cable fit loosely and make poor connection. It was so much so that the bass would rattle the cable loose and I could hear when the SDA effect cut out. I spent a bunch of time trying to get a jury rigged cable to work and listening with and without the interconnect.

    On cleanly recorded stereo music (like Dave Brubeck's Time Out), the SDA effect is awesome. If you're in the sweet spot it definitely improves the stereo imaging. If you're outside the sweet spot, the effect is different. My "listening room" is one sort of a living room + kitchen, great room thing, so unless I'm doing some critical listening I usually am hearing the speakers outside the sweet spot. Then, the speakers sound more than any other I've had like I'm in a great jazz club. There's a fullness and an "everywhereness" (just made that up) to the sound that I really love.

    On some recordings, however, the interconnect bugs the hell out of me. If the recording itself has been engineered with any echo or reverb, then the sound just bounces at you from everywhere and sweet spot or not, I find the result unpleasant. I assume intentionally or otherwise the recording engineer is trying to create something of that good jazz club sound that I like when the SDA's are creating it, but when there's too much of it, it's like the horrible "concert hall" surround sound setting on cheap receivers. Recordings that I otherwise love can become a muddy cacophony of overlapping sounds. Then, I disconnect the interconnect and those recordings are listenable again.

    The only thing that strikes me weird about this thread is the religious fervor around the SDA effect, like unplugging it will damn you to audiophile hell and turn your speaker into a clock radio until you repent by recapping all your friends' crossovers while they sleep. I don't mean to pick on anyone for their opinions, but I think unplugging the interconnect is just the cheapest and most easily reversible tweak anyone could make to radically tailor the sound of their speakers to the source material. I definitely agree that if you're never using the interconnect then you might as well go with a different set of speakers altogether.

    Seriously though, I love these forums and wish I had more to contribute than just an opinion. Back to those EE textbooks! ;)

  3. #63

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    Quote Originally Posted by On3s&Z3r0s View Post
    Oh man, now my head hertz :)
    What a marvelous first post!

  4. #64

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    Don't tell anyone on here but I run a 15 Ohm 25W wire-wound pot in the interconnect cable to adjust the SDA amplitude. On some recordings, as stated, the out of phase program information added by the audio engineer is exagerated by the SDA drivers and sounds artificial and annoying.
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  5. #65

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    Quote Originally Posted by Schurkey View Post
    The 9.6mh coil will NOT function the same if it were in the positive side of the circuit,
    I believe it does function as a low pass filter feeding the stereo bass in to the DA sections drivers.As I mentioned above testing if the DA drivers are only reproducing the low bass when the IC is removed would be telling.With the IC connected there are other things going on ofcourse and it appears the 50uf+130uf combo is used to hi pass filter the bass from the effects signal.
    I know that if you disconnect the + speaker cable at ONE speaker, with the SDA cable connected, the speaker will still produce sound (program material dependent) at the tweeters due to the SDA signal back-feeding through the crossover. Spooky.
    Thats interesting.

  6. #66

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    Quote Originally Posted by Schurkey View Post
    If there's less than one ohm between negative posts already...

    And some of that .9 ohms will be lead resistance.;)

  7. #67

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    OK guys I've gone back to running plugged, the SDA effect is back in my good graces. I finally isolated my problem. After a lot of A-B testing I came to the realization that only a small percentage of my CDs sounded better unplugged, and those that did were ones that were over processed. On the other hand, when playing vinyl more than half sounded better unplugged. That got me thinking, it might be the phono section in my amp. I dug out a Kenwood Basic C1 pre that I have (always loved the phono section in this sucker), hooked it up, qued up some Rolling Stones, and wham instant magic.
    Looks like my amp needs a visit to the tech, something is definitely wrong with the phono section. I guess it just goes to show how a cap, resistor, op amp, etc. can slowly go bad over time and you don't really notice it till it hits a certain critical stage. I've owned this amp for about 2-1/2 years, bought it from the original owner who never owned a turntable, so the phono section had never been used. When I first bought this amp, the phono section sounded fantastic, it's one of the main reasons I've hung on to it.
    Thanks for all the help and suggestions, you guys got me to think outside the box and figure this thing out.
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  8. #68

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    Quote Originally Posted by Schurkey View Post
    What a marvelous first post!
    LOL, thanks for the compliment! Although my wife will tell you it's best not to encourage me. ;)

    And to Big Al, big congrats. I know from past experience that a successful diagnosis is almost as gratifying as the eventual resolution. Nice work!

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