Common ground question

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Phil Dawson
Phil Dawson Posts: 288
edited June 2007 in Vintage Speakers
I have a pair of SDA-SRSs that I have bi-amped with PSE mono blocks on the bottom and a single PSE stereo on the top. Do I have a problem since the mono blocks are separate and thus can't be common ground. I don't seem to have any performance issues.
Thanks, Phil
Post edited by Phil Dawson on
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  • F1nut
    F1nut Posts: 49,834
    edited June 2007
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    That shouldn't work as in, the lower feed has to be common ground. I'd check with the amp maker to see if you can ground strap the mono blocks and I wouldn't use your set up until you do.
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."

    President of Club Polk

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  • Phil Dawson
    Phil Dawson Posts: 288
    edited June 2007
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    I have been using this set up for quite a while without problems. The mono blocks have 3 prong plugs plugged into a power strip. Could this be this be acting as a common ground? Are mono blocks a bad idea with these speakers?
    Thanks, Phil
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  • heiney9
    heiney9 Posts: 25,092
    edited June 2007
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    Phil Dawson wrote: »
    I have been using this set up for quite a while without problems. The mono blocks have 3 prong plugs plugged into a power strip. Could this be this be acting as a common ground? Are mono blocks a bad idea with these speakers?
    Thanks, Phil

    Doesn't matter; no; yes!

    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 Pass Labs XA25 | EE Avant Pre | EE Mini Max Supreme DAC | MIT Shotgun S1 | Pangea AC14SE MKII | Legend L600 | BlueSound Node 3 - Tubes add soul!
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  • Phil Dawson
    Phil Dawson Posts: 288
    edited June 2007
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    I just got off of the phone with Polk tech support (I tried to find PSE - the amp builder but they are gone). Polk tech support basically told me that if I was not having any problems that I shouldn't worry about it as the system has been working fine for several years. In other words if it ain't broke don't fix it. I still don't understand all I know about this issue but I guess I'm in good shape.
    Thanks, Phil
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  • F1nut
    F1nut Posts: 49,834
    edited June 2007
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    That shouldn't work, but you say it does........Hmmmmmmm?
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."

    President of Club Polk

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  • DarqueKnight
    DarqueKnight Posts: 6,765
    edited June 2007
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    Phil Dawson wrote: »
    I have a pair of SDA-SRSs that I have bi-amped with PSE mono blocks on the bottom and a single PSE stereo on the top. Do I have a problem since the mono blocks are separate and thus can't be common ground. I don't seem to have any performance issues.
    Thanks, Phil

    Are you using the SDA interconnect cable?

    Have your SDA's ever been modified?

    The SDA cable creates a short between the terminals of non-common ground (isolated ground) and mono block amps.

    Some people have reported being able to use mono block or non-common ground amps with SDA's provided they played at low to moderate levels. When the volume was turned up, the shorting condition appeared. It is like putting your fingers across the terminals of a low voltage battery, a short condition exists, but because the voltage/current is so low compared to your body's resistance, nothing bad happens. Now, put your fingers across two uninsulated wires plugged into a 120V outlet and....:eek:

    I have never heard of PSE amps and therefore am not familiar with their design. If your SDA's are unmodified and you are using the SDA cable and your mono blocks are isolated from each other and you are able to play above moderate volume levels, there must be (1) some protection circuitry in the amps that is preventing the shorting condition from appearing, or (2) some odd electrical interaction between the SDA's and your amps that is preventing the shorting condition from appearing.
    Proud and loyal citizen of the Digital Domain and Solid State Country!
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  • Phil Dawson
    Phil Dawson Posts: 288
    edited June 2007
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    I believe that the SDAs are not modified. I am using the SDA factory original cable. The mono blocks are two separate units. I can crank the system to very very loud (your ears ring for a bit). Professional Systems Engineering made amps, pre-amps and a tuner for several years. They were based in Saint Paul Minn. It was basically a one man operation and the products were always rated very highly and are still sought after by some individuals. They sound very good - some folks feel that they are the best sounding SS amps out there. I don't know what to say.
    Thanks, Phil
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  • Phil Dawson
    Phil Dawson Posts: 288
    edited June 2007
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    I downloaded the tune and I will try it tonight and let you know the results.
    Thanks, Phil
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  • WilliamM2
    WilliamM2 Posts: 4,716
    edited June 2007
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    The mono blocks have 3 prong plugs plugged into a power strip. Could this be this be acting as a common ground?

    If the third prong is grounded directly to the chassis (it probably is), then yes, this would be like strapping the two amp chassis together.
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