SDA SRS...got them to work with mono amps

autoconsortium

If you remember me, I am the guy who got Bryston 7B monoblock's to use with original (1985) Polk SDA SRS speakers. I have not had the interconnect hooked up...until today. I searched around quite a bit, called Bryston...everyone told me I couldn't strap the grounds. Well, I said f%$$ it and I did....works excellent. I took normal house electrical wire (extremely rigid and thick) and straped the grounds to each other, I also connected each chassis with another wire. This is the first I've heard my SDA's hooked up correctly. I am completely amazed. Supposedly, from what you guys had said, using the SDA's without the interconnect...you are only using half the available drivers on each side. Well, with my upgraded tweeters, and the interconnect hooked up, I am speechless. The sound is beyond words. Thanks for the info...I wouldn't have known what to do without your help.

ohskigod

glad it sounds great, but if the manufacturer said no on the connecting of the negative terminals, you might want to keep a CLOSE eye on the temp of those amps.

Ricardo

Congrats!!!! I've heard them so I know what you are feeling. Enjoy them...

madmax

I can't say that particular amp has issues or not with shorting the grounds together. Lets suppose they were the common type amp (non-bridged) design. The two grounds would be floating around slightly but when you connect them together they would be fine because there is no current trying to pull the two grounds apart from each other. In that case you are fine.

Now, if they are of a bridged type design they can appear to work. With a bridged design the two would be at the same potential but they are not floating and cannot be pulled to some other voltage without high current available. So, as long as everything is matched well between the two amps you will have no problems. In this case with the "bridged" type amps when something happens and one amp tries to keep its ground at a different potential than the other you all of a sudden have a high current condition which could damage both amps and the crossovers. This would happen if something goes wrong with one of them or if component values drift over time. You could actually have some amount of current right now and not know it because both amps are able to handle it. The thing is, you will not know for sure unless something happens.

If you are determined to use them this way (not knowing for sure) there is one test you can do to give yourself a little piece of mind. Unhook the SDA cable and remove the ground wire between the two speakers. Now take a DVM set to Current Measurement and connect the probes to both grounds. Look for both AC and DC current. If it is less than a few milliamps you are probably fine. This proves only if you are heading towards a problem more than if the amps should be used this way. If you have any questions about how to do this feel free to ask.

madmax

Dennis Gardner

Warranty claim on the horizon..................... I guess there isn't really a better choice for the early SRSs since the AI-1 cable won't work with this model.

Good luck with them.

Tour2ma

autoconsortium wrote:

I took normal house electrical wire (extremely rigid and thick) and straped the grounds to each other...

OMG... not normal wire...

Glad you're enjoying them again for the first time.

BobMcG

Enjoy and good luck.