SDA2 B crossover question

2

Comments

  • Gardenstater
    Gardenstater Posts: 2,014
    edited February 1
    That little brown capacitor is a 750pF silver mica bypass capacitor and the general feeling around here is that you won't be needing it anymore when you upgrade to a decent audiophile capacitor such as Sonicap etc., in fact it is recommended to remove it.

    As far as replacing the polyswitch with a jumper goes, it is a matter of opinion regarding how much to up the value of the resistor to compenate for its removal. There is a thread by Darqueknight on that.

    The schematic doesn't show any switch on the tweeter supply or return wire.

    Even if your old caps test in tolerance for uF, they should be replaced. There will be big improvements in going to an audiophile polypropylene film capacitor. Also, there are other parameters of capacitors besides uF, like ESR and one other that I can't recall. Different capacitors of the same uF value sound much different.
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Crown D150 amp
    Logitech Squeezebox Touch Streamer w/EDO applet
    iFi nano iDSD DAC
    iPurifier3
    iDefender w/ iPower PS
    Custom Steve Wilson 1m UPOCC Interconnect
    iFi Mercury 0.5m OFHC continuous cast copper USB cable
    Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
    Custom Vibration Isolation Speaker Stands and Sub Platform
  • pitdogg2
    pitdogg2 Posts: 19,451
    Take out polyswitch and replace with 12watt 1/2 ohm resistor. Remove little brown 750pf cap leave open DO NOT JUMP.

    12watt .5ohm resistor.
  • F1nut
    F1nut Posts: 46,266
    Replace S1 with a .5 ohm 10 or 12 watt resistor. Remove C4 and do not add a jumper.
    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

  • F1nut
    F1nut Posts: 46,266
    Ha, I didn't check for a second page before I posted.
    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

  • TennMan
    TennMan Posts: 1,145
    edited February 2
    Hello all. I am new to these speaker, although I have done a bit or reading in this forum. Where to start. I got my pair a month or so ago. No Interconnect cable so I made one. I checked it for continuity and all was well. I also checked my amp for common ground It was. These are pin blade. When I used the blade, it was clearly not good. Something was grounded that shouldn't be.
    I came into this thread late so if the following has already been covered please disregard.

    I might be wrong but I think you making your own Interconnect cable is your problem. I have a like new Pin/Blade Interconnect cable made by Polk that I'm certain is in good working condition. When I connect my meter to the blades on each end of the cable there is NO continuity between the blades. I'm not an electrical engineer but when I look at the 2B wiring schematic I don't think there should be continuity between the blades on each end of the cable. If there was you would be connecting the stereo driver circuits in both the left and right speakers together. That makes no sense to me and I'm not surprised that it is causing problems with your amp trying to drive your speakers connected that way. I'm no expert on this stuff so I could be wrong.

    The Blade part of the connector on the rear of each speaker was intended to be connected to cables going to the AI-1 which is an isolation transformer that prevents the left and right speakers from being electrically connected together - like you are doing with your homemade interconnect cable. You might want to stop using your cable with the blades connecting the left and right speakers together until someone can tell you it's OK to do so.
    Post edited by TennMan on
    • SDA 2BTL · Sonicaps · Mills resistors · RDO-198s · New gaskets · H-nuts · Erse inductors · BH5 · Dynamat
    • Crossover upgrades by westmassguy
    • Marantz 1504 AVR (front speaker pre-outs to Adcom 555)
    • Adcom GFA-555 amp · Upgrades & speaker protection added by OldmanSRS
    • Pioneer DV-610AV DVD/CD player
    • SDA CRS+ · Hidden away in the closet
  • TennMan
    TennMan Posts: 1,145
    edited February 2
    I made a long post about this. Wonder why it got deleted?

    Anyway, basically what I said was that my original Polk interconnect cable does not have continuity between the blades on each end when testing it with a meter.
    • SDA 2BTL · Sonicaps · Mills resistors · RDO-198s · New gaskets · H-nuts · Erse inductors · BH5 · Dynamat
    • Crossover upgrades by westmassguy
    • Marantz 1504 AVR (front speaker pre-outs to Adcom 555)
    • Adcom GFA-555 amp · Upgrades & speaker protection added by OldmanSRS
    • Pioneer DV-610AV DVD/CD player
    • SDA CRS+ · Hidden away in the closet
  • BlueFox
    BlueFox Posts: 14,783
    TennMan wrote: »
    I made a long post about this. Wonder why it got deleted?

    Anyway, basically what I said was that my original Polk interconnect cable does not have continuity between the blades on each end when testing it with a meter.

    Are you sure you didn't post it in another thread?

    Lumin X1 file player; Sony XA-5400ES SACD; Pass XP-22 pre; X600.5 amps
    Magico S5 MKII Mcast Rose speakers; SPOD spikes

    Shunyata Triton v3/Typhon QR on source, Denali 2000 (2) on amps
    Shunyata Sigma XLR analog ICs, Sigma speaker cables
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    Mapleshade Samson V.3 four shelf solid maple rack, Micropoint brass footers
    Three 20 amp circuits.
  • F1nut
    F1nut Posts: 46,266
    TennMan wrote: »
    I made a long post about this. Wonder why it got deleted?

    Anyway, basically what I said was that my original Polk interconnect cable does not have continuity between the blades on each end when testing it with a meter.

    I saw that post.
    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

  • Interesting. I guess I should ask the simple and maybe dumb question. I made my interconnect pin to pin and blade to blade. I assumed and believe I read that was correct. Was this original wire bad or does it swap, pin-blade, blade-pin?. Im not sure how that one cable carries left to right and right to left? This may open a new can of worms but I have often wondered about that. If the interconnect is carrying some left to the right and some right to the left, but we only have a one cable?
  • I just want to say. I am of an age that makes me appreciate all that this forum has to offer. Having almost instant access to so many people with so much knowledge about all of this is not something I take for granted. I love to learn, and through technology and the generosity of these members I can cut my learning curve way down. A big thanks to all who have taken time to contribute to my education here.
  • pitdogg2
    pitdogg2 Posts: 19,451
    There is no switch at the cable pin is pin blade is blade. All the SDA signal is at XO level.
  • TennMan
    TennMan Posts: 1,145
    Interesting. I guess I should ask the simple and maybe dumb question. I made my interconnect pin to pin and blade to blade. I assumed and believe I read that was correct. Was this original wire bad or does it swap, pin-blade, blade-pin?. Im not sure how that one cable carries left to right and right to left? This may open a new can of worms but I have often wondered about that. If the interconnect is carrying some left to the right and some right to the left, but we only have a one cable?

    I'm not an expert on this stuff so someone correct me if I'm wrong...

    I believe my original Polk cable is working as Polk intended by not reading continuity between the blades on each end of the cable. Maybe someone here with an original Polk Interconnect cable will check the blades on their cable for continuity and confirm this.

    Only the pin in my cable has continuity and that's all that's needed to to connect the left and right speakers together to carry the SDA signal.

    The blade connector on the back of the Polk speakers is only needed when using the AI-1 or Dreadnought isolation transformer. The SDA signal is transferred between the left and right speakers through the isolation transformer but there is never a direct electrical connection between the speakers like you have with your cable.

    Your homemade cable is making a direct electrical connection between the left and right speakers with the blades. I don't believe Polk intended for that to happen with their pin/blade Interconnect cables.

    The direct electrical connection you are making with your homemade cable between the left and right speakers is probably what is causing your amp and speakers to sound bad with the cable connected. If you continue using that cable it might damage your amp or speakers.

    • SDA 2BTL · Sonicaps · Mills resistors · RDO-198s · New gaskets · H-nuts · Erse inductors · BH5 · Dynamat
    • Crossover upgrades by westmassguy
    • Marantz 1504 AVR (front speaker pre-outs to Adcom 555)
    • Adcom GFA-555 amp · Upgrades & speaker protection added by OldmanSRS
    • Pioneer DV-610AV DVD/CD player
    • SDA CRS+ · Hidden away in the closet
  • F1nut
    F1nut Posts: 46,266
    ^ This ^
    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

  • Wow. Ok. Thanks for that explanation. I only had that blade connected for a few seconds because it was clearly wrong. I do like the explanation and it makes sense. They worked fine with just the pin, I just wanted to make sure I was using things correctly.
  • I also wanted to comment on the use of the .5 ohm 10 or 12 watt resistor. On Gimpods site, when I look at my board and what to put where, it looks like he favors not putting anything in that space. Am I reading that wrong. I don't know what function that resistor is performing.
  • pitdogg2
    pitdogg2 Posts: 19,451

    The half ohm resistor makes up for the resistance of the poly switch. You can jump it, your Tweeter will be much brighter. It's personal preference and the half ohm is what most people have replaced the poly switch with.
  • Ok. Does brand matter on those boys?
  • Gardenstater
    Gardenstater Posts: 2,014
    edited February 2
    When I look at the schematic for the SDA 2B with the blade/pin IC, it just shows that the blade is connected to the negative (black) binding post. I certainly get that the IC cable needs to only have pin to pin conductivity. I don't really understand why it would cause weird things to happen if it had blade to blade as well. In a common ground amp this would be basically like having infinitely short speaker cables because the negative binding posts on the amp are connected anyway.

    Edit to add - Is it possible that a ground loop is created due to the impedances of the negative legs of the R and L speaker cables not being precisely matched?
    Post edited by Gardenstater on
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Crown D150 amp
    Logitech Squeezebox Touch Streamer w/EDO applet
    iFi nano iDSD DAC
    iPurifier3
    iDefender w/ iPower PS
    Custom Steve Wilson 1m UPOCC Interconnect
    iFi Mercury 0.5m OFHC continuous cast copper USB cable
    Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
    Custom Vibration Isolation Speaker Stands and Sub Platform
  • OK fellas, here is that tweeter "do-dad" that is a mystery to me. It came this way to me. Blue and white were connected to tweeter Sl2000. ybgk5qxu0gca.jpg
  • Gardenstater
    Gardenstater Posts: 2,014
    Is that cover removable? If so, open that sucka up! Definitely didn't come from Polk I'd say, but who knows?? Perhaps it has a fuse in it or some sort of additional polyswitch circuit breaker device, which is rated at 0.6A.
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Crown D150 amp
    Logitech Squeezebox Touch Streamer w/EDO applet
    iFi nano iDSD DAC
    iPurifier3
    iDefender w/ iPower PS
    Custom Steve Wilson 1m UPOCC Interconnect
    iFi Mercury 0.5m OFHC continuous cast copper USB cable
    Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
    Custom Vibration Isolation Speaker Stands and Sub Platform
  • pitdogg2
    pitdogg2 Posts: 19,451
    edited February 2
    That's not stock. It appears to just be another thermistor device.
  • I will open it. I was thinking of deleting it anyway. Strange eh? Have not seen it. Maybe F-1 knows. If he doesn't then Im gonna say it didn't come that way. Ill open it after dinner.
  • pitdogg2
    pitdogg2 Posts: 19,451
    They never came that way afaik
  • Or now. Its a relay of some sort looks like. mbmf6s557gz0.jpg
  • pitdogg2
    pitdogg2 Posts: 19,451
    it does the same thing as a poly switch it opens to break the circuit a poly switch is just a fancy name for a thermistor they're used in thousands of devices they're either on or they're off in our case they're on until they're off and then no signal goes through
  • Hmm Maybe why my left tweeter quit. I should remove yes? I am re capping.
  • F1nut
    F1nut Posts: 46,266
    Not stock. Get rid of it.
    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

  • Gardenstater
    Gardenstater Posts: 2,014
    This looks pretty close if you want to replace it. Just kidding

    szdhur83gpx4.jpg
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Crown D150 amp
    Logitech Squeezebox Touch Streamer w/EDO applet
    iFi nano iDSD DAC
    iPurifier3
    iDefender w/ iPower PS
    Custom Steve Wilson 1m UPOCC Interconnect
    iFi Mercury 0.5m OFHC continuous cast copper USB cable
    Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
    Custom Vibration Isolation Speaker Stands and Sub Platform
  • Its a addition becoming a subtraction
  • So.... soldering question. Of course I left the worst for first. I put the 30 cap on top. When I put the 10 under the board, can I solder the 10 cap to the 30 caps legs? Not sure how to get them Both through the hole?