Another common ground question

2

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  • Systems
    Systems Posts: 14,873
    edited August 2007
    jakelm wrote: »
    GV. I know you must be getting tired of explainig this.
    No I don't get tired till 1 o'clock:D
    But can you explain my Hafler , if you have time? The 2 -ve speaker posts are soldered together and soldered on the wire bridge that connects the 2 PS caps ( the wire going from -ve cap screwfrom cap 1 to +ve cap screwon cap 2). The connection is not connected to the chassis, but is still considered common ground?
    Yes your Hafler is common ground.It is a prime example of what Polk is refering to as the type needed for the SDA's.
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  • fredv
    fredv Posts: 923
    edited August 2007
    Your Hafler needs 2 rails, one +ve and one -ve. The first cap's + pin is the +ve rail, the - pin of 1st cap and + pin of the 2nd cap is ground (0 potential), and the - pin of the 2nd cap is the -ve rail. Yes, you amp is common ground and common -ve terminal and can drive SDA's :-)

    -fredv-
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  • jakelm
    jakelm Posts: 4,081
    edited August 2007
    GV#27 wrote: »
    No I don't get tired till 1 o'clock:D
    Yes your Hafler is common ground.It is a prime example of what Polk is refering to as the type needed for the SDA's.


    Tank you veddy much.

    So it doesnt have to be grounded to the chassis with the PS. Just grounded to each other with the PS. Zero ohms between the 2 -ve post.

    Then, without opening an amp, could you just use a multimeter and check the ohms reading between the 2 -ve post?
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  • Systems
    Systems Posts: 14,873
    edited August 2007
    jakelm wrote: »
    Is that cap bridge ground?
    you snuck this in while I was typing:D Correct if you refering to a metal bar or wire joining the two caps.This is the central ground point.
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  • Systems
    Systems Posts: 14,873
    edited August 2007
    jakelm wrote: »
    Tank you veddy much.

    So it doesnt have to be grounded to the chassis with the PS. Just grounded to each other with the PS. Zero ohms between the 2 -ve post.

    Then, without opening an amp, could you just use a multimeter and check the ohms reading between the 2 -ve post?
    Bingo
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  • jakelm
    jakelm Posts: 4,081
    edited August 2007
    GV#27 wrote: »
    you snuck this in while I was typing:D Correct if you refering to a metal bar or wire joining the two caps.This is the central ground point.

    Yeeahh...sorry..I'm an edit addict.
    Monitor 7b's front
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    M10's back surround
    Hafler-200 driving patio Daytons
    Tempest-X 15" DIY sub w/ Rythmik 350A plate amp
    Dayton 12" DVC w/ Rythmik 350a plate amp
    Harman/Kardon AVR-635
    Oppo 981hd
    Denon upconvert DVD player
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    Mit RPTV WS-55513
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  • jakelm
    jakelm Posts: 4,081
    edited August 2007
    But not all common ground amps are going to be wired like this Hafler right? Or is this the standard for a common ground amp? If I opened another amp that was common ground, would it be wired identical?
    Monitor 7b's front
    Monitor 4's surround
    Frankinpolk Center (2 mw6503's with peerless tweeter)
    M10's back surround
    Hafler-200 driving patio Daytons
    Tempest-X 15" DIY sub w/ Rythmik 350A plate amp
    Dayton 12" DVC w/ Rythmik 350a plate amp
    Harman/Kardon AVR-635
    Oppo 981hd
    Denon upconvert DVD player
    Jennings Research (vintage and rare)
    Mit RPTV WS-55513
    Tosh HD-XA1
    B&K AV5000


    Dont BAN me Bro!!!!:eek:
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  • Systems
    Systems Posts: 14,873
    edited August 2007
    jakelm wrote: »
    But not all common ground amps are going to be wired like this Hafler right? Or is this the standard for a common ground amp? If I opened another amp that was common ground, would it be wired identical?
    In the scricted sense of the term common ground yes.
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  • jakelm
    jakelm Posts: 4,081
    edited August 2007
    Thanks guys, you all are like an electronic wikipedia.

    I hope you all dont mind all the questions, I just absolutly love this stuff.
    Monitor 7b's front
    Monitor 4's surround
    Frankinpolk Center (2 mw6503's with peerless tweeter)
    M10's back surround
    Hafler-200 driving patio Daytons
    Tempest-X 15" DIY sub w/ Rythmik 350A plate amp
    Dayton 12" DVC w/ Rythmik 350a plate amp
    Harman/Kardon AVR-635
    Oppo 981hd
    Denon upconvert DVD player
    Jennings Research (vintage and rare)
    Mit RPTV WS-55513
    Tosh HD-XA1
    B&K AV5000


    Dont BAN me Bro!!!!:eek:
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  • fredv
    fredv Posts: 923
    edited August 2007
    jakelm wrote: »
    But fred, my understanding is, when most amps are bridged , the common ground goes out the window and becomes an inverted phase ground (my new lingo)..IPG..lol.
    Out of window? Maybe true in Polk's common ground sense. From the electrical point of point, the ground potential is not changed and is still at the same location. Take your Hafler as example, switching to brdige mode doesn't change the fact that the -ve output terminal and the ground potential (0 volt) remain the same. The only diff is on how to connect the speaker - you connect the speaker to the 2 +ve output terminals which none is the ground. Guess what, the 2 -ve output terminals are still at ground, you just don't use them in bridge mode.

    -fredv-
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  • Systems
    Systems Posts: 14,873
    edited August 2007
    jakelm wrote: »
    Thanks guys,
    Your velcome.
    I hope you all dont mind all the questions
    not at all.
    I just absolutly love this stuff.
    Im kinda fond of it as well.

    btw in my previous post I meant to type strictest not scricted.:D
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  • Systems
    Systems Posts: 14,873
    edited August 2007
    fredv wrote: »
    Guess what, the 2 -ve output terminals are still at ground, you just don't use them in bridge mode.
    Exactly.
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  • jakelm
    jakelm Posts: 4,081
    edited August 2007
    fredv wrote: »
    Out of window? Maybe true in Polk's common ground sense. From the electrical point of point, the ground potential is not changed and is still at the same location. Take your Hafler as example, switching to brdige mode doesn't change the fact that the -ve output terminal and the ground potential (0 volt) remain the same. The only diff is on how to connect the speaker - you connect the speaker to the 2 +ve output terminals which none is the ground. Guess what, the 2 -ve output terminals are still at ground, you just don't use them in bridge mode.


    No Fred, your absolutly right. I was just stating that the ground the speaker uses in a bridged amp is not the same ground as if it were in stereo. The ground in a bridge amp (the ground the speaker uses) is 180 degrees out of phase from the +ve. Only acting as a ground but not the zero ground otherwised used in stereo mode. Unless I'm mistaken.

    If the +ve is +10 volts then the ground or -ve (in bridge mode) is -10 volts
    Monitor 7b's front
    Monitor 4's surround
    Frankinpolk Center (2 mw6503's with peerless tweeter)
    M10's back surround
    Hafler-200 driving patio Daytons
    Tempest-X 15" DIY sub w/ Rythmik 350A plate amp
    Dayton 12" DVC w/ Rythmik 350a plate amp
    Harman/Kardon AVR-635
    Oppo 981hd
    Denon upconvert DVD player
    Jennings Research (vintage and rare)
    Mit RPTV WS-55513
    Tosh HD-XA1
    B&K AV5000


    Dont BAN me Bro!!!!:eek:
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  • DarqueKnight
    DarqueKnight Posts: 6,765
    edited August 2007
    heiney9 wrote: »
    Another common ground amplifier question. What exactly is the concern with running a non-common ground amp with a pair of SDA’s? Is to protect the amplifer or the speakers?

    The concern is the same as with a short circuit condition in any electronic device. Even if there is little to no risk of destroying the equipment (as in shorting the battery terminals of a flashlight), the device is not going to function as designed.
    heiney9 wrote: »
    I certainly don’t want to damage the speakers in any way, but would a particularly stout amplifier which could absorb having its outputs shorted for short periods of time be alright running a pair of SDA’s?

    No. Even an amp that can remain stable into a dead short is not going to sound its best under such a stressful condition. Plus, the SDA drivers are not going to work.
    heiney9 wrote: »
    I’m looking seriously at getting a Pass Labs X150 and am trying to determine if 1) It’s common ground (sent an email to Nelson which I’m sure he’ll answer shortly) 2) If it’s not common ground and the neg terminals cannot be tied together can I run this amplifier w/o damaging my SDA’s.

    I can understand your frustration at the prospect of the amp you want not being compatible with SDA's. When I was doing research for my last amp upgrade, I considered the Krell FPB 700CX and the Pass Labs X600.5, both of which are high power, balanced output (non common ground) amps. If you are going to use SDA's you have only four options with regard to amplification:

    1. Use a common ground amp where the ground terminals are tied to the same ground potential.

    2. Use a non-common ground amp or mono block amps that are capable of having the ground terminals tied together (strapped).

    3. Use the AI-1 interface (if your particular SDA model can work with the AI-1).

    4. Run the SDA's without the interconnect cable.

    By now you must have come to the realization that "common ground" can mean different things to different manufacturers. That is why Polk was so explicit in explaining what they meant about common ground.

    I briefly considered getting the Pass x600.5 and making a custom AI-1 with a heavy duty, high current transformer. I decided against that because I know that the AI-1 is a "workaround", and is thus a sub-optimal solution. A loss of information can occur with the AI-1, although some have said they heard no diminished sound quality with the AI-1 in place. I did not want to make a significant investment in a quality amp, then make a custom AI-1, and then end up with diminished sound quality. I am thrilled with my JC-1 monoblocks and I think that, in some performace areas (speed, heat generation, price/performance ratio, suitability for the type of music I listen to), they were a better choice than the X600.5's.
    heiney9 wrote: »
    I know Madmax...runs his SDA’s with the Carver Silver 9T mono’s in a non-common ground configuration.

    Carver mono amps can be used with SDA's if their output grounds are strapped together. So, Madmax was in luck...and so was I with my JC-1's.:)
    heiney9 wrote: »
    I saw Ken perusing this thread yesterday and I was hoping he'd chime in.

    I can imagine Ken reading this thread and shaking his head from side to side. It is probably going to be difficult to get anyone from Polk to address this since it has been extensively written about in Polk's literature and on the forum.
    heiney9 wrote: »
    I just really need to know the risk to the SDA's if run in a non-common ground config.

    1. Loss of SDA effect.
    2. Damaged drivers.
    3. Damaged crossover components.
    heiney9 wrote: »
    The amplifier in question is certainly robust enough to handle just about any type of load.

    But for how long and at what output levels and signal frequencies? Furthermore, what is the point of having a nice set of SDA's and a nice amp and having to "walk on eggshells" when using them?
    Proud and loyal citizen of the Digital Domain and Solid State Country!
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  • hearingimpared
    hearingimpared Posts: 21,137
    edited August 2007
    Awesome information that cuts to the simple chase! AS usual.
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  • fredv
    fredv Posts: 923
    edited August 2007
    jakelm wrote: »
    No Fred, your absolutly right. I was just stating that the ground the speaker uses in a bridged amp is not the same ground as if it were in stereo. The ground in a bridge amp (the ground the speaker uses) is 180 degrees out of phase from the +ve. Only acting as a ground but not the zero ground otherwised used in stereo mode. Unless I'm mistaken.

    If the +ve is +10 volts then the ground or -ve (in bridge mode) is -10 volts
    If you want to call the -ve of a speaker as ground, then yes. Technically speaking, speaker sees the voltage difference between the 2 posts, one +ve and one -ve. + and - means one (+) always has higher ground potential than the other (-). The difference makes up of the amptitude => loudness => output. In 99.99% of the cases, the -ve post are at zero potential or ground, but in bridge mode, the -ve post is indeed at -ve voltage.

    -fredv-
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  • fredv
    fredv Posts: 923
    edited August 2007
    hearingimpared wrote: »
    Awesome information that cuts to the simple chase! AS usual.
    Authority has spoken, end of the thread, no more chance to BS :D

    -fredv-
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  • heiney9
    heiney9 Posts: 25,171
    edited August 2007
    Thanks a lot DarqueKnight. Your explanation was very helpful, as usual :)

    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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  • jakelm
    jakelm Posts: 4,081
    edited August 2007
    All of this info is fantastic. I learned more about common ground amps in 1 day, with you guys, than I did reading about them for 3 days.

    Now all I need are some SDA's. And hope my Hafler has enough cahoonas, to drive them.

    ...heaven forbid I should try to shop for a common ground amp...lol:p :p
    Monitor 7b's front
    Monitor 4's surround
    Frankinpolk Center (2 mw6503's with peerless tweeter)
    M10's back surround
    Hafler-200 driving patio Daytons
    Tempest-X 15" DIY sub w/ Rythmik 350A plate amp
    Dayton 12" DVC w/ Rythmik 350a plate amp
    Harman/Kardon AVR-635
    Oppo 981hd
    Denon upconvert DVD player
    Jennings Research (vintage and rare)
    Mit RPTV WS-55513
    Tosh HD-XA1
    B&K AV5000


    Dont BAN me Bro!!!!:eek:
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  • jimbo1421
    jimbo1421 Posts: 772
    edited August 2012
    DarqueKnight wrote: »
    If you are going to use SDA's you have only four options with regard to amplification:

    1. Use a common ground amp where the ground terminals are tied to the same ground potential.
    2. Use a non-common ground amp or mono block amps that are capable of having the ground terminals tied together (strapped).
    3. Use the AI-1 interface (if your particular SDA model can work with the AI-1).
    4. Run the SDA's without the interconnect cable.

    By now you must have come to the realization that "common ground" can mean different things to different manufacturers. That is why Polk was so explicit in explaining what they meant about common ground.

    Resurrecting an old thread, here, regarding #1.

    I have been trying to verify that my new NAD T955 is, in fact, a common ground amp. I have measured 197 ohms between each and all of the 5 channels on this amp. Does this mean that they "are tied to the same ground potential" (I don't know what that means)? Does it matter that the resistance is so high?

    Spearit's contact at NAD says that the T955 is common ground and provided this illustration to prove it:
    image003.png


    So, does this mean that the T955 meets the requirements as an amp for my SDA-CRS+ or SDA-1B?

    Sorry to keep flogging this question, but I think I am in a grey area here. The T955, 5 mono blocks on one chassis, is a type that may not have even existed in the 1980s when Polk wrote the specs.

    I am awaiting an answer from Spearit and NAD about #2 — strapping.

    Jim
    5.1 System:
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    Front: SRS-3.1TL
    Center: CS400i
    Surround: Monitor 10B
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    Onkyo PR-SC886P Pre/Pro
    NAD T955 5 channel power amplifier
    Technics SL-1710 MK2 turntable
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    Oppo BDP-103 Blu-Ray
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  • nspindel
    nspindel Posts: 5,343
    edited August 2012
    Brock, a shameless plug here - you did see that I'm trying to assemble a group buy for the 1000VA isolation transformers, right? I see a Dreadnought in your future my friend....
    Good music, a good source, and good power can make SDA's sing. Tubes make them dance.
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  • nooshinjohn
    nooshinjohn Posts: 25,421
    edited August 2012
    You do know this thread is 5 years old, right? By the looks of it, this was started BEFORE H9 knew everything!:cheesygrin: :wink:

    j/k Brock.:lol:
    The Gear... Carver "Statement" Mono-blocks, Mcintosh C2300 Arcam AVR20, Oppo UDP-203 4K Blu-ray player, Sony XBR70x850B 4k, Polk Audio Legend L800 with height modules, L400 Center Channel Polk audio AB800 "in-wall" surrounds. Marantz MM7025 stereo amp. Simaudio Moon 680d DSD

    “When once a Republic is corrupted, there is no possibility of remedying any of the growing evils but by removing the corruption and restoring its lost principles; every other correction is either useless or a new evil.”— Thomas Jefferson
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  • nspindel
    nspindel Posts: 5,343
    edited August 2012
    Hahahahahah. Missed the part about this thread being old. You're all still welcome to participate in my group buy though!!!!
    Good music, a good source, and good power can make SDA's sing. Tubes make them dance.
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  • F1nut
    F1nut Posts: 50,572
    edited August 2012
    The T955, 5 mono blocks on one chassis

    Not really, it's a 5 channel amp with each channel sharing the same power supply making it common ground.
    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."

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  • jimbo1421
    jimbo1421 Posts: 772
    edited August 2012
    F1nut wrote: »
    Not really, it's a 5 channel amp with each channel sharing the same power supply making it common ground.

    Thanks, F1nut. With respect to SDA performance, does it matter that the resistance I measured between negative speaker terminals, 197 ohms, is so much higher than anyone else here has reported on any other amp? Less than 20 ohms, less than 2 ohms, these measurements seem to be the norm in all the threads about common ground amps that I have read here.

    Jim
    5.1 System:
    TCL R613 55" 4K
    Front: SRS-3.1TL
    Center: CS400i
    Surround: Monitor 10B
    PSW10 subwoofer
    Onkyo PR-SC886P Pre/Pro
    NAD T955 5 channel power amplifier
    Technics SL-1710 MK2 turntable
    Audio-Technica AT14Sa cartridge
    Parasound P3 pre-amp
    Oppo BDP-103 Blu-Ray
    2014 MacBook Pro 2.8 GHz

    2.0 Office System:
    Monitor 10A (Peerless)
    Outlaw 1050 receiver
    Parasound HCA-1000A power amp
    MacPro
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  • F1nut
    F1nut Posts: 50,572
    edited August 2012
    Yeah, that's weird. Since I don't want anything bad to happen, best to confirm with NAD before hooking the SDA's up.
    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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  • bookshelf^love
    bookshelf^love Posts: 10
    edited August 2012
    Or just find a cheap ol receiver?
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  • F1nut
    F1nut Posts: 50,572
    edited August 2012
    bookshelf^love wrote: »
    Or just find a cheap ol receiver?

    That is not a good suggestion.
    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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  • jimbo1421
    jimbo1421 Posts: 772
    edited August 2012
    Thanks for your comments, F1nut. I just got off the phone with Polk tech support. He said that measuring 197 ohms between the negative speaker terminals on the T955 meant that it was not a common ground amp with respect to their expectation for use with SDAs. He further qualified this by saying that SDAs with the pin/blade type IC (my CRS+) did not require a common ground amp, but that the blade/blade type (my SDA-1B) did. Plugging the 1Bs into this T955 would produce a high pitched squeal and destroy the polyswitch an possibly do other damage. I could turn this amp into common ground by strapping the negative terminals together if NAD says this is OK.

    My expectations for this amp were for it to handle any type of SDA.

    Jim
    5.1 System:
    TCL R613 55" 4K
    Front: SRS-3.1TL
    Center: CS400i
    Surround: Monitor 10B
    PSW10 subwoofer
    Onkyo PR-SC886P Pre/Pro
    NAD T955 5 channel power amplifier
    Technics SL-1710 MK2 turntable
    Audio-Technica AT14Sa cartridge
    Parasound P3 pre-amp
    Oppo BDP-103 Blu-Ray
    2014 MacBook Pro 2.8 GHz

    2.0 Office System:
    Monitor 10A (Peerless)
    Outlaw 1050 receiver
    Parasound HCA-1000A power amp
    MacPro
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  • F1nut
    F1nut Posts: 50,572
    edited August 2012
    He said that measuring 197 ohms between the negative speaker terminals on the T955 meant that it was not a common ground amp

    Yeah, I would tend to agree, but I have a hard time believing it's actually a non-common ground amp. You need to contact NAD.
    He further qualified this by saying that SDAs with the pin/blade type IC (my CRS+) did not require a common ground amp

    That is correct, but you have to use the AI-1 with non-common ground amps.
    but that the blade/blade type (my SDA-1B) did.

    Correct because you can't use the AI-1 with blade/blade SDA's.
    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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