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  1. #21
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    Input and output impedance?

    I thought there was also a question of input impedance of the power amp and output impedance of the SB product. IIRC there is a ruleof thumb that the downstream device should have ten times the value of the upstream device. I am not an EE so I'd appreciate some help on this.

    In practice, my SB3 seems so drive a Linn 2250 power amp with quite good results, but I am still wondering whether a passive or active line stage would offer any improvement, such as better buffering and impedance matching.

  2. #22
    Guys... am i reading this thread correctly the analog attenuation only works on the RCA outs ? I really would prefer balanced outs if at all possible, as I believe these sound best on my amps.

    My system at the moment is the Transporter into a pair of Bel Canto Ref1000 power amps into a pair of Zu Druids. Problem is the Druids have a sensitivity of 101db and whilst the volume control on the Transporter brings the volume down sufficiently I am worried that taking it down to like -30db is taking a little of the quality away.

    Help please

    BTW if i am playing FLAC files from a DVDa would this be much more likely to lose quality due to 24bits vs 16 bits and no room for the digital vc to do it's thing unhindered.
    Last edited by dlite; 2006-12-08 at 04:12.

  3. #23
    Senior Member
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    May 2005
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    London
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    LOUD buzzzzzzz/Hummmmmmm

    Yes re-erecting a nice old thread :-)

    Not long purchased what looks like a nice example of a Transporter :-)

    However - Plugged it in for a quick test, Transporter unbalanced outputs -> Behringer X-air (basically a pre amp with eq) -> Mackie powered speakers
    All sounds good, Transporter needs to be turned up max to get a normal input signal to the X-air and works nicely.

    BUT - I would like the transporter to replace my Squeezebox touch and TAG pre amp / dac, so the Transporter will go straight in to my Adcom power amp (unbalanced).

    Even when the TP is not playing and muted I get a loud electrical buzzzzz/hummmm and have to switch power amp off Fast! Yeah it seems if the TP volume is say half way the buzz is deafening!!
    Only tried it twice with a re-plug in to the x-air in between... x-air / mackie output musical and fine.
    TP straight in to the Adcom NOISE... ???

    I have tried my touch and SB2 straight in to the Adcom and works as it should, same leads but with the TP in place, bad buzzzhmmm ??

    I am confused any thoughts / pointers much appreciated

    Cheers
    :-)

  4. #24
    Senior Member
    Join Date
    Nov 2007
    Posts
    144
    Quote Originally Posted by Deaf Cat View Post
    Yes re-erecting a nice old thread :-)

    Not long purchased what looks like a nice example of a Transporter :-)

    However - Plugged it in for a quick test, Transporter unbalanced outputs -> Behringer X-air (basically a pre amp with eq) -> Mackie powered speakers
    All sounds good, Transporter needs to be turned up max to get a normal input signal to the X-air and works nicely.

    BUT - I would like the transporter to replace my Squeezebox touch and TAG pre amp / dac, so the Transporter will go straight in to my Adcom power amp (unbalanced).

    Even when the TP is not playing and muted I get a loud electrical buzzzzz/hummmm and have to switch power amp off Fast! Yeah it seems if the TP volume is say half way the buzz is deafening!!
    Only tried it twice with a re-plug in to the x-air in between... x-air / mackie output musical and fine.
    TP straight in to the Adcom NOISE... ???

    I have tried my touch and SB2 straight in to the Adcom and works as it should, same leads but with the TP in place, bad buzzzhmmm ??

    I am confused any thoughts / pointers much appreciated

    Cheers
    :-)
    As to the reduced volume output on the TP, check the internal attenuation jumpers. I know on our TP, I have to attenuate down quite a bit to accommodate a vintage preamp, and that would certainly cause some volume range issues with more modern gear.

    Also be aware that using digital volume attenuation in the SB will lose you some resolution compared to a 100% output with downstream analog attenuation. If maximum resolution is your objective, you may be better served with a preamp.

    For the hum, I would check your cables for a ground loop. If your cables are directional as to shield, try flipping them. Also make sure that your input/output impedances for both instruments are within design limits. Again, placing a preamp between the TP and the amp may also alleviate that situation. I would also open up the TP to make sure it is still stock, and has not suffered any poor repairs or mods.

    FWIW, I ran a TP direct to amp for about a week while awaiting some equipment to install. It sounded ok, with none of your hum issues. But the SB, even at the TP level, is really a front end device, and benefits greatly from further pre-amplification. They simply donít have the analog chomps to drive higher end amps all by themselves without some help.

    I donít care what all the TP fanboys and scopeheads say, looking under the hood, the TPís analog output stage is unimpressive. And compared to higher strata DACs, sounds unimpressive. I wound up using the TP as a digital head end into a separate DAC in the $3-5,000 range. And that DAC makes the TP by itself sound like a 1979 Walkman by comparison, primarily due to a vastly superior analog output stage, very robust power supplies throughout, and extensive overbuild in the conversion stage. You get what you pay for, and premium build analog stages are unavoidably expensive. The TP was never more than a $1,000 instrument inside, and was somewhat overpriced when new due to its market position at that time.

    However, unless you are prepared to move up to that level, the TP is still reasonably competitive with todays sub-$1,500 DAC offerings, but with a good following preamp.

  5. #25
    Senior Member
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    London
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    Thank you for your reply :-)

    Quote Originally Posted by sgmlaw View Post
    As to the reduced volume output on the TP, check the internal attenuation jumpers. I know on our TP, I have to attenuate down quite a bit to accommodate a vintage preamp, and that would certainly cause some volume range issues with more modern gear.
    Had a quick look and L & R are both on Zero attenuation, just realised the Beringer is a piece of pro sound equipment so is used to the higher voltage of balanced signals, not the 'low' 2Vrms of domestic gear, this explains the max volume being low, I think!



    Quote Originally Posted by sgmlaw View Post
    Also be aware that using digital volume attenuation in the SB will lose you some resolution compared to a 100% output with downstream analog attenuation. If maximum resolution is your objective, you may be better served with a preamp.
    Hmmm very good point thank you for mentioning this, I don't want to plug the TP in again directly to the power amp, without having it professionally tested, as I think the blast of electrical buss/humm has aged my speaker by about 40 years or so as they now sound really quite bad :-( It is not going in my main system at all until its got the all clear from a professional, or I'll send it back.
    But yes thanks for the advice, once I have a correctly working TP I shall try it with a pre and without, to see if I can hear the difference :-)


    Quote Originally Posted by sgmlaw View Post
    For the hum, I would check your cables for a ground loop. If your cables are directional as to shield, try flipping them. Also make sure that your input/output impedances for both instruments are within design limits. Again, placing a preamp between the TP and the amp may also alleviate that situation. I would also open up the TP to make sure it is still stock, and has not suffered any poor repairs or mods.
    The cables are normal RCA single ended cables, so shielding should be connected both ends as far as I know. My SB Touch and my SB2 both work fine straight into the power amp... This is why I am confused!?
    The output impedance of the TP is 100 Ohm and the input impedance of the amp is 100,000 Ohms, as I understand it 10* 100 Ohms is the minimum for the two to work okay together, the higher the input impedance the better, so we should be fine. But obviously not :-o
    All looks like new inside, nothing out of place, no iffy soldering, so guessing all original.



    Quote Originally Posted by sgmlaw View Post
    FWIW, I ran a TP direct to amp for about a week while awaiting some equipment to install. It sounded ok, with none of your hum issues. But the SB, even at the TP level, is really a front end device, and benefits greatly from further pre-amplification. They simply donít have the analog chomps to drive higher end amps all by themselves without some help.

    I donít care what all the TP fanboys and scopeheads say, looking under the hood, the TPís analog output stage is unimpressive. And compared to higher strata DACs, sounds unimpressive. I wound up using the TP as a digital head end into a separate DAC in the $3-5,000 range. And that DAC makes the TP by itself sound like a 1979 Walkman by comparison, primarily due to a vastly superior analog output stage, very robust power supplies throughout, and extensive overbuild in the conversion stage. You get what you pay for, and premium build analog stages are unavoidably expensive. The TP was never more than a $1,000 instrument inside, and was somewhat overpriced when new due to its market position at that time.

    However, unless you are prepared to move up to that level, the TP is still reasonably competitive with todays sub-$1,500 DAC offerings, but with a good following preamp.
    Thank you for these points, much appreciated :-)
    I don't fancy testing the TP in different set ups until I know its not going to harm anything else. But yes I will at some point try it directly into a power amp, then into the TAG as an analogue input, and then as a digital input, just to see what I prefer the sound of :-) I bought the TAG about 12 years ago, boy time flys! bought from an audio repair guy, I did not have it long and was soon on the phone to him, asking if he could make it more musical, its attention to detail was amazing IMO, that is why I bought it, but I missed the involving musicality side of things, the guy said he could try a few things and it came back sounding much nicer, about 4 years after that I pitted it against 2 dacs around the 2 -2.5k range, I came back thinking the repair guy did a fab job! But yes I can imagine 4-5k dacs would improve once again, but ummm yes cash needs to go else where ;-)
    I had not thought of analogue pre amp after the TP :-) good call :-) I shall try it.

    Cheers!

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