A1 Blade / Blade for SDA SRS 2 ???

inspiredsports

I just purchased a vintage pair of BLADE / BLADE SDA SRS 2's that used SL2000's (I've upgraded to RDO194-1) and all MW6509 6-1/2 inchers.

All of the original drivers were ink stamped with test dates of December 05, 1986 and assembly dates of January 30, 1987.

The Serial Numbers are:

R SDA-SRS-2 1514
L SDA-SRS-2 1570

I've pulled both sets of crossovers and am having the poly switches snipped, bypass caps snipped and bypassed, and all capacitors and resistors replaced with Sonicaps and Mills with the exception of 2 X (100uf + 82uf) Aeons on the low-pass where Sonic Craft has nothing with a large enough value.

I have a 1987 NAD 7600 Receiver I purchased new when I also purchased my first set of Polk SDA-2B's. The 7600 does a great job of driving those 4+ ohm loads and I am sure it will do well with the 4 ohm SDA SRS 2's.

I now have the opportunity to buy (at a great price) an NAD 2600A amplifier which is the identical mate to the 7600 Receiver for use in mono bridged mode.

HOWEVER, the NAD Literature clearly states "IN BRIDGED MODE THE SPEAKER WIRES MUST BE "FLOATING" WITH RESPECT TO THE CIRCUIT GROUND. DO NOT CONNECT THE SPEAKER WIRES TO ANYTHING THAT SHARES A COMMON GROUND BETWEEN STEREO CHANNELS."

I'm guessing the Blade / Blade Interconnect causes a problem and that an A1 for Blade / Blade is needed.

I've been told some SDA SRS 2 Serial Numbers work with the A1, and that you might have a Blade / Blade A1 available.

I also clearly understand the SDA SRS 2's will then present a 2 ohm load to the NAD Amps and I have heard mixed reviews as to their ability to drive at 2 ohms for sustained periods at high volume.

Please Advise if these serial number can work with the Blade / Blade A1 or if their is a "cross-grounding" protocol possible.

hoosier21

I bet the 7600 will do just fine with the SRS 2's.

inspiredsports

hoosier21 wrote: »

I bet the 7600 will do just fine with the SRS 2's.

Thanks Hoosier,

Yes, I know it will be great by itself. Many use it to drive the big boys without strain. It's just ego. I wanted larger speakers and a 2600 with my 7600 in 1988 when I bought it brand new and compromised because my wife was pregnant with our first. It's like a midlife crisis now to get all the stuff I wanted way back when :-)

By the way, am I in the right spot where the actual Polk employee type tech folks check the thread and provide guidance?

hoosier21

inspiredsports wrote: »

By the way, am I in the right spot where the actual Polk employee type tech folks check the thread and provide guidance?

I would not count on it, I did a search and can't find it on this forum, but there is a post or several actually listing the serial numbers of blade blade type SDAs that can use the A1, you might be lucky and fall within those, if you don't your out of luck on the mono amps. Send an email directly to customer service, you should get a reply, they don't always answer qustions on this forum.

I have had most every one of those Monitor Series units from NAD, love them, I still have a 1300 preamp. That 7600 is a great receiver, power, great tuner, good phone, very nice preamp section with tons of flexibility.

F1nut

The speakers must have a S/N greater than 1945, so the AI-1 will not work with yours.

inspiredsports

hoosier21 wrote: »

I have had most every one of those Monitor Series units from NAD, love them, I still have a 1300 preamp. That 7600 is a great receiver, power, great tuner, good phone, very nice preamp section with tons of flexibility.

If I still buy the 2600A and can't bridge it with the 7600, I will need a preamp for it for another application. Do you know which preamp is recommended?

inspiredsports

inspiredsports wrote: »

If I still buy the 2600A and can't bridge it with the 7600, I will need a preamp for it for another application. Do you know which preamp is recommended?

I answered my own question by finding your post at . . .

http://www.polkaudio.com/forums/showthread.php?t=73617&highlight=nad+1300

Thanks

inspiredsports

With so many tweaks / mods / hacks in place in these forums, I'm surprised that no on has found a way to use non-common ground amps with vintage SRS 2's.

Does anyone know what the circuitry issue is and why it can't be tricked out?

Maybe asking for the A1 is the wrong question. I'm looking for a circuitry work-around that will keep the SDA effect in play, and accomodate a non-common ground amp.

F1nut

The forum is full of info on this matter. Bottom line, it can't be "worked around" other than the methods discussed already.

DarqueKnight

inspiredsports wrote: »

With so many tweaks / mods / hacks in place in these forums, I'm surprised that no on has found a way to use non-common ground amps with vintage SRS 2's.

Like who, for instance? Polk's engineering department?

inspiredsports wrote: »

Does anyone know what the circuitry issue is and why it can't be tricked out?

The blade/blade and some of the earlier pin/blade SDA's use a more complex grounding scheme, so only two options are available:

1. Disconnect the SDA cable for use with non-CG amps.
2. Use CG amps per the manual instructions to avoid smoke, sparks and flames.

inspiredsports wrote: »

Maybe asking for the A1 is the wrong question. I'm looking for a circuitry work-around that will keep the SDA effect in play, and accomodate a non-common ground amp.

Let us know when you find that pot o'gold. Best bet is to get a proper set of pin/blade SDA's. The 1987 version of the SRS 2 would fit the bill, provided the serial numbers are 1945 or higher.

inspiredsports

DarqueKnight wrote: »

Like who, for instance? Polk's engineering department?

Yes, actually I was hoping they would weigh in :-)

DarqueKnight wrote: »

Let us know when you find that pot o'gold.

That pot o'gold seems mighty elusive! I've spent hours and hours reading the exceptionally informative postings that you and others have placed in the forums hoping for a simple "hook the blue wire to the blue wire" fix with no luck. That's why I posted here.

I am green enough that I don't know what I should about the possibility of strapping my particular models of amps and I am going to educate myself in that area next.

I did learn that my other set of Polk's, SDA-2B's, are of the proper serial number sequence to work with the AI-1, but are Blade/Blade so I need to do more research there also.

Thanks,
Greg