Common ground amps

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drumiv
drumiv Posts: 171
edited December 2013 in Vintage Speakers
How can I tell if the amp I'm using is a "common ground" type. I finally hooked up the amp I got with the SDA's I bought (it was being re-capped) I assumed it was common grounded because it was part of his system. It's a Soundcraftsmen MA 5002. What happens when you hook up to a non-common grounded amp?
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  • BlueMDPicker
    BlueMDPicker Posts: 7,569
    edited September 2013
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    Check out this recent thread and don't be afraid to use the search function of the forum. Good luck!

    http://www.polkaudio.com/forums/showthread.php?152246-The-old-common-ground-issue....&highlight=common+ground%3F
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  • [Deleted User]
    [Deleted User] Posts: 7,658
    edited September 2013
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    Hello,
    What happens will depend upon which series SDA speakers you have. Do yours have the pin/blade or the twin/blade interconnect cable?
    Regards, Ken
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  • drumiv
    drumiv Posts: 171
    edited September 2013
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    Mine are blade - blade. I see by another CPer, he uses the MA 5002 for power with his SDA's, so I think I'm all right. I'm still curious what happens(not enough to try it, though).
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  • [Deleted User]
    [Deleted User] Posts: 7,658
    edited September 2013
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    Hello,
    The twin/blade speakers would short out the non-common ground amplifier. The pin/blade speakers don't short the amplifier, there just isn't anything coming from the SDA components.
    Regards, Ken
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  • Moose68Bash
    Moose68Bash Posts: 3,842
    edited September 2013
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    Kenneth Swauger wrote: »
    Hello,
    The twin/blade speakers would short out the non-common ground amplifier. The pin/blade speakers don't short the amplifier, there just isn't anything coming from the SDA components.
    Regards, Ken

    Ken,

    When I connected my SDA SRS1.2s to my Perreaux Prisma 750 monoblocks -- ignorant of the fact that the amps are necessarily not common ground -- there was an extraordinarily loud and very frightening sound. NO sound was coming from the right channel speaker -- neither SDA nor stereo. The speakers are pin-blade.

    Of course, a Dreadnought solved the problem.
    Family Room, Innuos Statement streamer (Roon Core) with Morrow Audio USB cable to McIntosh MC 2700 pre with DC2 Digital Audio Module; AQ Sky XLRs to CAT 600.2 dualmono amp, Morrow Elite Speaker Cables to NOLA Baby Grand Reference Gold 3 speakers. Power source for all components: Silver Circle Audio Pure Power One with dedicated 20 amp circuit to main panel.

    Exercise Room, Innuos Streamer via Cat 6 cable connection to PS Audio PerfectWave MkII DAC w/Bridge II, AQ King Cobra RCAs to Perreaux PMF3150 amp (fully restored and upgraded by Jeffrey Jackson, Precision Audio Labs), Supra Rondo 4x2.5 Speaker Cables to SDA 1Cs (Vr3 Mods Xovers and other mods.), Dreadnaught with Supra Rondo 4x2.5 interconnect cables by Vr3 Mods. Power for each component from dedicated 20 amp circuit to main panel, except Innuos Statement powered from Silver Circle Audio Pure Power One.

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  • drumiv
    drumiv Posts: 171
    edited September 2013
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    Thanks Ken. So the amp would take the hit, not the speakers. I'm getting rid of the Soundcraftsmen, and picking up a Parasound 2200 MKII Sunday. Does anyone know if it is common ground?
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  • zingo
    zingo Posts: 11,258
    edited September 2013
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    Sexy amp, but I don't know. Try emailing Parasound as they can probably help.
    Jake
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  • drumminman
    drumminman Posts: 3,396
    edited September 2013
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    What Zingo said.

    Also, you can touch the a probe from a VOM to each negative speaker terminal with the meter set to the lowest range, usually 200 ohms. If it's common ground the reading will be 0 or close to, like 0.5 ohms.
    "Science is suppose to explain observations not dismiss them as impossible" - Norm on AA; 2.3TL's w/sonicaps/mills/jantzen inductors, Gimpod's boards, Lg Solen SDA inductors, RD-0198's, MW's dynamatted, Armaflex speaker gaskets, H-nuts, brass spikes, Cardas CCGR BP's, upgraded IC Cable, Black Hole Damping Sheet strips, interior of cabinets sealed with Loctite Power Grab, AI-1 interface with 1000VA A-L transformer
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  • drumiv
    drumiv Posts: 171
    edited September 2013
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    OK , I'll try that. Also, contacted Parasound. Thanks
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  • zingo
    zingo Posts: 11,258
    edited October 2013
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    I'm going to piggy back on this thread since it's the same topic:

    "Each channel has an independent power supply for the power amplifier. The power amp ground of each channel is tied to a common audio ground via a 5.6ohm resistor. So there is aprox 11.2ohms resistance between the speaker grounds of the two channels.

    However, no current flows through these resistors so the grounds should both be at 0V potential."

    Does this sound SDA safe?
    Jake
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  • FTGV
    FTGV Posts: 3,649
    edited October 2013
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    zingo wrote: »
    Does this sound SDA safe?
    Yes,but strap the negative terminals.
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  • Schurkey
    Schurkey Posts: 2,100
    edited October 2013
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    zingo wrote: »
    "Each channel has an independent power supply for the power amplifier. The power amp ground of each channel is tied to a common audio ground via a 5.6ohm resistor. So there is aprox 11.2ohms resistance between the speaker grounds of the two channels.

    However, no current flows through these resistors so the grounds should both be at 0V potential."

    Does this sound SDA safe?
    No current flows through the resistors UNTIL you connect SDA speakers (including the SDA interconnect cable)

    With SDA speakers, current DOES flow through those resistors. 20 ohms of resistance between the terminals of my Aragon amps makes the speakers sound HORRIBLE. I suspect that 11 ohms will have a similar if not so extensive effect.
    FTGV wrote: »
    Yes,but strap the negative terminals.
    As long as the amp doesn't use a bridged/balanced design, yes. Made a magnificent and instant improvement on my Aragon.

    Of course, an AI-1/Dreadnought will also work, if it's compatible with the speakers.
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  • FTGV
    FTGV Posts: 3,649
    edited October 2013
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    Schurkey wrote: »
    No current flows through the resistors UNTIL you connect SDA speakers (including the SDA interconnect cable)

    With SDA speakers, current DOES flow through those resistors. 20 ohms of resistance between the terminals of my Aragon amps makes the speakers sound HORRIBLE. I suspect that 11 ohms will have a similar if not so extensive effect.
    Yes thus the need for the heavy gauge strap to jumper or short across those resistors.
    As long as the amp doesn't use a bridged/balanced design..
    Certainly as I have stated umpteen times the last few years as this question has arisen.My reply was in response to zingo's question which was obviously a non bridged/balanced amp.
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  • zingo
    zingo Posts: 11,258
    edited October 2013
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    The manufacturer did say the amp is not a bridged or balanced output, and that the additional resistance to ground should be okay with speakers requiring a common ground.
    Jake
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  • FTGV
    FTGV Posts: 3,649
    edited October 2013
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    zingo wrote: »
    ... the additional resistance to ground should be okay with speakers requiring a common ground.
    Strapping the negative terminals effectively removes the resistors providing a direct (or making common)connection between the grounds of each channel.(The resistors will still provide a connection to chassis or safety ground).Not strapping the negative output terminals could result in excessive current through those resistors causing them to fail.Also many have reported issues running this type of ground configuration sans strapping.
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  • F1nut
    F1nut Posts: 49,805
    edited October 2013
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    Given the choice between strapping and using the AI-1 or Dreadnaught, the latter two are far superior.
    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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  • headrott
    headrott Posts: 5,484
    edited October 2013
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    F1nut wrote: »
    Given the choice between strapping and using the AI-1 or Dreadnaught, the latter two are far superior.

    1000% agree with Jesse. I have heard both ways with my Aragon 8008bb amp and the Dreadnaught was definitively better in every way.

    I just remembered though that Jake's SDA 2's are blade/blade so he can;t use the Dreadnaught or AI-1 unfortunately. :sad:
    Relayer-Big-O-Poster.jpg
    Taken from a recent Audioholics reply regarding "Club Polk" and Polk speakers:
    "I'm yet to hear a Polk speaker that merits more than a sentence and 60 seconds discussion." :\
    My response is: If you need 60 seconds to respond in one sentence, you probably should't be evaluating Polk speakers.....

    "Green leaves reveal the heart spoken Khatru"- Jon Anderson

    "Have A Little Faith! And Everything You'll Face, Will Jump From Out Right On Into Place! Yeah! Take A Little Time! And Everything You'll Find, Will Move From Gloom Right On Into Shine!"- Arthur Lee
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  • Schurkey
    Schurkey Posts: 2,100
    edited October 2013
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    F1nut wrote: »
    Given the choice between strapping and using the AI-1 or Dreadnaught, the latter two are far superior.
    But not on SDAs using blade/blade connection for the SDA cable; with the exception of those very few SDA 1C and 2B that got put together with leftover blade/blade sockets; and which require minor modification to use the isolation transformer.
    drumiv wrote: »
    Mine are blade - blade.
    Far as I know, ALL OTHER blade/blade SDAs are incompatible with the AI-1/Dreadnought/isolation transformer.
    zingo wrote: »
    The manufacturer did say... that the additional resistance to ground should be okay with speakers requiring a common ground.
    Good luck with that. Have a suitable jumper wire handy. If my experience with the Aragon/SDA 1B is any indication, you're gonna hate those speakers until you bypass the resistance. In my case, it did no harm to the amp. However, I'm not making any promises.

    Do I remember right? Headrott's Aragon (same as mine, but used with different SDAs) was actually shutting down, or emitting hateful noises when not used with jumper or Dreadnought??? I don't remember which speakers he has, though.
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  • headrott
    headrott Posts: 5,484
    edited October 2013
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    That's correct. My Aragon 8008bb would go into protection mode over and over when hooked to my 3.1TL's. I never tried it with the 2.3TL's, however.

    Edit: What serial number(s) do the 2B's need to be to have a blade/blade connection and still be used with the AI-1/Dreadnught? I know I've seen it before, but I don't remember. Mine have the single crossover board, I'd have to check the serial number(s).
    Relayer-Big-O-Poster.jpg
    Taken from a recent Audioholics reply regarding "Club Polk" and Polk speakers:
    "I'm yet to hear a Polk speaker that merits more than a sentence and 60 seconds discussion." :\
    My response is: If you need 60 seconds to respond in one sentence, you probably should't be evaluating Polk speakers.....

    "Green leaves reveal the heart spoken Khatru"- Jon Anderson

    "Have A Little Faith! And Everything You'll Face, Will Jump From Out Right On Into Place! Yeah! Take A Little Time! And Everything You'll Find, Will Move From Gloom Right On Into Shine!"- Arthur Lee
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  • Schurkey
    Schurkey Posts: 2,100
    edited October 2013
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    headrott wrote: »
    That's correct. My Aragon 8008bb would go into protection mode over and over when hooked to my 3.1TL's. I never tried it with the 2.3TL's, however.
    Never had that problem with the 1Bs, but maybe I didn't turn the Eviction Control Knob far enough.
    headrott wrote: »
    Edit: What serial number(s) do the 2B's need to be to have a blade/blade connection and still be used with the AI-1/Dreadnught? I know I've seen it before, but I don't remember. Mine have the single crossover board, I'd have to check the serial number(s).
    http://www.polkaudio.com/forums/showthread.php?131691-2B-and-EARLY-1C-AI-1-modifications

    The quick answer is "ANY 1C or 2B that has blade/blade sockets." Add a foot of wire inside each of the cabinets, and provide a suitable socket to connect the AI-1/Dreadnought to. If you aren't hooked on original pin/blade sockets, you could connect one leg of the isolation transformer directly to the negative speaker wire binding post, and not need to add the foot of wire inside the cabinet. It's SOOOoooo easy!
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  • F1nut
    F1nut Posts: 49,805
    edited October 2013
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    But not on SDAs using blade/blade connection for the SDA cable; with the exception of those very few SDA 1C and 2B that got put together with leftover blade/blade sockets; and which require minor modification to use the isolation transformer.

    Good point :)
    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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  • headrott
    headrott Posts: 5,484
    edited October 2013
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    Schurkey wrote: »
    Never had that problem with the 1Bs, but maybe I didn't turn the Eviction Control Knob far enough.

    Could be.
    Schurkey wrote: »
    http://www.polkaudio.com/forums/showthread.php?131691-2B-and-EARLY-1C-AI-1-modifications

    The quick answer is "ANY 1C or 2B that has blade/blade sockets."

    Thanks very much! My 2B's are both 15300 and higher so I am good to go! I just need to do the wire modification internally and install a binding post for the "pin". Never knew I could use the Dreadnaught with my 2B's until now. Learn something new everyday! Thanks again! :smile:

    Edit: Actually I will need to install 2 binding posts. One for the pin and one for the blade to use my Dreadnaught.......
    Relayer-Big-O-Poster.jpg
    Taken from a recent Audioholics reply regarding "Club Polk" and Polk speakers:
    "I'm yet to hear a Polk speaker that merits more than a sentence and 60 seconds discussion." :\
    My response is: If you need 60 seconds to respond in one sentence, you probably should't be evaluating Polk speakers.....

    "Green leaves reveal the heart spoken Khatru"- Jon Anderson

    "Have A Little Faith! And Everything You'll Face, Will Jump From Out Right On Into Place! Yeah! Take A Little Time! And Everything You'll Find, Will Move From Gloom Right On Into Shine!"- Arthur Lee
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  • F1nut
    F1nut Posts: 49,805
    edited October 2013
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    Edit: What serial number(s) do the 2B's need to be to have a blade/blade connection and still be used with the AI-1/Dreadnught? I know I've seen it before, but I don't remember. Mine have the single crossover board, I'd have to check the serial number(s).

    1C right channel #6001 through 6310 and #6501 though 6678
    1C left channel #5975 though 6370 and #6532 though 6656
    2B right channel #14124 though 19036
    2B left channel #14115 though 19075
    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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  • headrott
    headrott Posts: 5,484
    edited October 2013
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    Thank you Jesse. Mine are both 15300 and higher (as I posted above :wink:). Thanks for taking the time to post though Jesse.
    Relayer-Big-O-Poster.jpg
    Taken from a recent Audioholics reply regarding "Club Polk" and Polk speakers:
    "I'm yet to hear a Polk speaker that merits more than a sentence and 60 seconds discussion." :\
    My response is: If you need 60 seconds to respond in one sentence, you probably should't be evaluating Polk speakers.....

    "Green leaves reveal the heart spoken Khatru"- Jon Anderson

    "Have A Little Faith! And Everything You'll Face, Will Jump From Out Right On Into Place! Yeah! Take A Little Time! And Everything You'll Find, Will Move From Gloom Right On Into Shine!"- Arthur Lee
    · Share on FacebookShare on Twitter
  • Schurkey
    Schurkey Posts: 2,100
    edited October 2013
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    headrott wrote: »
    Never knew I could use the Dreadnaught with my 2B's until now. Learn something new everyday! Thanks again!
    Glad to help, but folks other than me did all the heavy lifting. I looked at schematics and serial-number lists, put 2 + 2 together until I got "4".
    headrott wrote: »
    Edit: Actually I will need to install 2 binding posts. One for the pin and one for the blade to use my Dreadnaught.......
    I edited my post above, and perhaps you didn't see the revised version. You can just use the negative speaker-wire binding post that's already there. You only "need" one more binding post per speaker, to take the place of the "pin" connection.

    Or use speakon connections. Or whatever electrical terminal style that suits your fancy.
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  • zingo
    zingo Posts: 11,258
    edited October 2013
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    After asking the manufacturer whether the negative binding posts could be strapped:

    "Cross-talk performance may slightly degrade and it may be slightly more vulnerable to grounding induced noise, but it shouldn’t cause any damage to the unit."
    Jake
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  • mikemokr
    mikemokr Posts: 150
    edited December 2013
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    Another piggy-back in case this info is of use to anyone else:

    I recently bought an Outlaw 7075 7.1 ch amp, have been considering buying some sort of vintage SDAs, and thought I'd check with Outlaw. They have advised that none of their amps are common-grounded and that using speakers requiring such a configuration would damage the amp and not be covered under warranty. Glad I asked ...

    I also have an old Outlaw 1050 receiver and Outlaw says that unit is common-grounded at the speaker binding posts.

    I now have confirmed the above using a VOM as noted by drumminman:
    drumminman wrote: »
    Also, you can touch the a probe from a VOM to each negative speaker terminal with the meter set to the lowest range, usually 200 ohms. If it's common ground the reading will be 0 or close to, like 0.5 ohms.

    I read 21.4 ohms on the 7075, 0.4 ohms on 1050.
    Main HT (family room): Polk Monitor 7 (1987-original owner) (L/R) / CSi40 (C) / RTi38 (SL/SR) / SVS 20-39PC (sub), Outlaw 975 pre/pro / Outlaw 7075 amp, Oppo BDP-93 Blu-ray, LG 42LM5800 teevee
    2ch (family room): CRS+ (1987), Outlaw 1050 AVR, Denon DCM-420 CD
    Kitchen satellite 2ch: Polk M3II, Topping TP-20 Tripath amp fed from 975 rec line out
    Home office: Model 5 (1978-Danish Peerless), Lepai 2020A+ Tripath amp fed by laptop dock
    Awaiting assignment: PSW202 (NIB) to be wired inline in home office rig; Monitor 5JR (1988), Model 4 (1983-US Peerless)
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  • began1
    began1 Posts: 2
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    Hi, I have the SDA 1a's and love them. Was using them for years without the interconnect cable and powered with a Denon AVR 4802. Now, a little bit of knowledge can be a dangerous thing and in reading, the consensus was that I was missing out on the full affect of the speakers without the cable. Sooo...I hooked up the cable (forgetting about the need for a common ground amp/receiver) and over a couple of days various inputs on the receiver failed. Bought Denon's x8500h (non-common) but now am gunshy. So, the question is: is it safe to use this receiver with the SDA 1a's as long as I don't use the interconnect cable? Just need some reassurance and it seems you are the people to ask. Thanks..
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  • [Deleted User]
    [Deleted User] Posts: 7,658
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    When the SDA cable isn't used there isn't a common ground given to the amp.
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  • pitdogg2
    pitdogg2 Posts: 24,582
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    I don't know most all receivers are common ground. I think the problem involves the fact that the speakers start at 4ohm and drop much lower. The new receiver stated minimum 4ohm. I think the other receiver died due to over heating from the low 3ohm load they seen. The power supplies are not built to give the current needed for the apeakers needs therefore lots of heat inside the receiver can't get away fast enough so you cook parts of the boards.
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