Common ground amps
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My power amplifiers show ~20 ohms between the negative binding posts. In this case, it's because each negative terminal is connected to chassis ground via a 10-ohm resistor. From one binding post to the other, you're testing through the two ten-ohm resistors; for a meter reading of 20 ohms. 20 ohms of resistance in the negative circuit made my 1Bs unlistenable.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.
Eight inches of copper wire and a couple of banana plugs, and the resistors are bypassed. As far as the speakers are concerned, the amp is now common-ground.
IF your 21.4 ohms is due to similar resistors...all you need is the jumper wire connecting the negative terminals.
IF your 21.4 ohms is due to something else, yes, you could damage the amplifier by connecting the SDA cable between the speaker cabinets.
"I" would be looking for a schematic of that 7075. Trace the negative binding posts to chassis ground.
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Kenneth, appreciate your response. I like good sound but am not on the audio level of knowledge that you certainly are..so you are saying if I don't use the cable I run no risk using my new non-common ground receiver. Right?
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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..
Every AVR made is 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."
President of Club Polk -
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..
Every AVR made is common ground.
To further satisfy your curiosity, buy yourself an inexpensive volt/ohm meter and test the AVR yourself.
*edit, that was directed at @began1, not you Jesse
So, are you willing to put forth a little effort or are you happy sitting in your skeptical poo pile?
http://audiomilitia.proboards.com/ -
It looks like I'm a decade late to this thread, but I just bought a mint pair of SDA 1.2TL's from the original owner. This is my first hi-fi set up and, as discussed here by others, I believe I'm having the issue of using a balanced amplifier instead of common ground. Would anyone know where I could find a AI-1? I hooked the tl's up for the first time last night and they didn't sound good. A friend of mine has a pair of these speakers and when I heard his, I was blown away. But these have almost no bass response, they are harsh and bit muddy. Could this be an issue of the amplifier being balanced instead of common ground? Any advice is appreciated. Thanks!
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As said, use an ohmmeter/multimeter to check resistance between the negative speaker terminals on the amplifier. Anything over one ohm is too much, and less than one ohm is preferred. What amplifier are you using? In general a "balanced" or "bridged" amplifier is not going to be compatible with the SDA speakers if the speakers have the interconnect cable between them plugged-in. So perhaps the first test is to disconnect the SDA cable at one or both ends, and listen.
No bass? Are the speakers wired in-phase, and placed near the wall behind them? Harsh and muddy? Have the electrolytic capacitors in the crossover network been replaced? They're way past their expected service life. Unless the speakers have had service work, there's NO SUCH THING as "mint" 1.2TLs. They may LOOK nice, but internal degradation is guaranteed.
"Real" AI-1 isolation transformers are long out of production, somewhat rare, and entirely inadequate from the perspective of current capacity. They do "work", preventing damage to speakers or (balanced/bridged/non-common-ground) amplifiers. However, enormously more current capacity is required for proper and complete signal transfer.
Search this site for "Dreadnaught" or "Dreadnought" for enough threads and instructions to keep you up late at night. -
Couple of things...
Post a picture of your setup so we can see the speakers and the walls around them.
Next, which amp are you using? Many claim to be balanced, few really are.
Is the SDA cable connected? Try unplugging it and see if things improve.
Also, does your friend have the exact same SDA 1.2TLs? Drivers (esp tweeters) and same crossover?
I'm sure others will chime in soon enough.Sonus Faber Liuto / Coda Continuum / Anthem STR Preamplifier / Oppo BDP-105D / Technics SP-15 w/SAEC WE-308SX & Ortofon AS-309 arms / Ikeda 9C2 & Dynavector XX2 Mk II carts -
Here you go. It's not the cable, it is a very good option for an off the shelf build. The link and stock number to buy direct should you choose that path.
https://forum.polkaudio.com/discussion/131848/avel-lindberg-y236906-transformer-800va-for-sda-dreadnoughts
Realistically you may get lucky on an original cable. They rarely come up on ebay.
I Started with a cable, went to the 800va and then to the 1000va torrids. Each way was a step up.
What gear are you running ?2-channel: Modwright KWI-200 Integrated, Dynaudio C1-II Signatures
Desktop rig: LSi7, Polk 110sub, Dayens Ampino amp, W4S DAC/pre, Sonos, JRiver
Gear on standby: Melody 101 tube pre, Unison Research Simply Italy Integrated
Gone to new homes: (Matt Polk's)Threshold Stasis SA12e monoblocks, Pass XA30.5 amp, Usher MD2 speakers, Dynaudio C4 platinum speakers, Modwright LS100 (voltz), Simaudio 780D DAC
erat interfectorem cesar et **** dictatorem dicere a
