An SDA question

**oldhifiguy** · 05-21-2002 05:34 AM

I have been running an old pair of SDA-2s(which i really love) with a Carver m400t amp. I have recently dragged out an old pair of McIntosh mc250 amps and put in place of the Carver. I am running these as mono amps...one on either side. This works only without the crosstalk cable and you loose that nice soundstage of the SDAs. Is there a way to do this and keep the crosstalk? I am not a technical person so the simpler the better...

**TroyD** · 05-21-2002 07:42 AM

I'm not an SDA guy but why would monoblocks make a difference?? IF the SDA interconnect cable is in place it shouldn't make a difference, should it??

Troy (of the Big Dumb Dions)

**RuSsMaN** · 05-21-2002 09:33 AM

Non-common ground, or some such. Hoosier or max, jump in here......

-R

**rskarvan** · 05-21-2002 09:35 AM

There is something called an A-1 interface transformer that you need to use with non-common ground amps. Polk can sell you one - or, if you go to the yahoo mikespolkpage website, there is a technical description/design that you could probably put together yourself.

**hoosier21** · 05-21-2002 09:57 AM

If you have the interconnect cable that has two blades, you are SOL.
If you have the interconnect with a pin and blade, you are in luck but you are in for some work.
1. You can look and look for an original Polk A1 interconnect cable (very rear to find one for sale)
2. you can make your own.
Making your own is easy, call Ken Swagger at Polk he can fax you the material list and directions (these are also at Mike's Polk SDA group at Yahoo)

**dylan** · 05-21-2002 11:28 AM

I believe this is the link to Mike's SDA Page

**oldhifiguy** · 05-23-2002 05:19 AM

Thanks for the info. I can see I have a little research to do!

**Punitiv** · 12-19-2011 06:21 PM

Hopefully you guys will forgive me for resurrecting such an old thread, but it seemed pertinent: I have a set of SDA2B's that I just love. I've got a lead on a pretty cheap Carver M400T amp. I'm getting mixed answers as to whether this amp is safe to use with my SDA's. It appears that Oldhifiguy was doing it, but I'm not sure if he used the crossover cable.

Anyone know if it's safe to use?

**inspiredsports** · 12-19-2011 06:25 PM

Originally Posted by Punitiv

Hopefully you guys will forgive me for resurrecting such an old thread, but it seemed pertinent: I have a set of SDA2B's that I just love. I've got a lead on a pretty cheap Carver M400T amp. I'm getting mixed answers as to whether this amp is safe to use with my SDA's. It appears that Oldhifiguy was doing it, but I'm not sure if he used the crossover cable.

Anyone know if it's safe to use?

First, Do not use the SDA Interconnect Cable until you are sure you have everything sorted out. There is no harm in running SDA's without the IC, you just lose the interaural crosstalk cancellation that is the hallmark of the SDA sound.

The folks from this thread should know for sure and I'll send them a PM to respond here on your behalf.

http://www.polkaudio.com/forums/show...er-**-The-CUBE

**Punitiv** · 12-19-2011 06:57 PM

Wow, thanks for the quick response!

**dudeinaroom** · 12-19-2011 08:51 PM

If you have a multimeter(dmm) check the resistance between the two black posts on the back of the amp. If you get 0 you should be good to go. You could also check with carver to see if it is a common ground amp. If you have or can find a schematic if both negative/grounds connect to the same point it should be fine. There maybe someone with that amp that chimes in. Better off to start your own thread as it will show up as something new, instead of an outdated thread. The topic might have already have been covered, you could use the search feature at the top of the page, or use google with your search citeria with "site:www.polkaudio.com/forums" after it.

**Tour2ma** · 12-20-2011 08:22 AM

The M-400 is fine to use with SDA's.

The only Carver amps that are not common ground are the M-500, M-500t and, as I recently learned, the 1st generation M-1.0t (ones without the switch to bridge them).

And I believe the OP could have strapped his Mac mono-blocks... but that I'd definitely check on...

Welcome to the Club, Punitiv...

**Punitiv** · 12-22-2011 01:09 AM

I pulled the trigger on the M400t and scored a good deal on a Carver C-1 preamplifier. They have been driving my SDA 2B's beautifully all evening. I can't get over how crisp these speakers sound compared to my Klipsch KLF-10's. I can close my eyes and the speakers just disappear, leaving a room full of music.

**Tour2ma** · 12-22-2011 07:33 AM

Post 13 by tor1 reported...

Originally Posted by Punitiv

I can close my eyes and the speakers just disappear, leaving a room full of music.

Kinda what SDA is all about... glad you're enjoying your 2B's.

If you still have your Klipsch, try them with the C-1's Sonic Holography in play just for grins.

**Gavin.Wright** · 12-22-2011 09:38 AM

The M-400A that I have at home is NOT common ground - internally carver inverts one channel and then swaps the +/- output jacks on that speaker output. (Basically the + of one channel's speaker output is actually ground) I believe this was done to maximize power supply efficiency on more demanding mono musical sections as both sides of the power supply would be taxed equally. I believe the original M-400 had an impedance switch on the rear to help the power supply better deal with bridged loads ? this however was not a ?bridge? switch in the traditional sense and did not invert one output signal.

**dudeinaroom** · 12-22-2011 11:21 AM

That's how they would make bridgeable amps with out a switch.

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