Trouble with SDA 1B's

[bert26]

I picked up some SDA SRS 2's this weekend :D , and had to move my 1B's to the basement. I hooked them back up to a Nakamichi PA-5/CA-5 rig (borrowed from a friend). Now two things are happening:

1). I am getting a hum once the power amp is turned on.
2). I no longer get the SDA signal from the right channel when doing the balance test.

I have pulled the drivers and all of the connections are still made. From what I can tell, the crossover is ok too (although I really don't know what I am looking for).

Any one else ever have issues like this?

Chris

[BlueMDPicker]

Issue #1 sounds like a ground loop in the Nak gear. Lift the ground from one piece with a cheater cord (ground plug removed).

Issue #2 sounds like the reciever/amp is not common ground. Check across the negative output binding posts with a VOM. 0 ohms makes it common ground, any other value means the channels don't share a ground. You may be able to create a common ground by bridging the negative outputs. Research it first, though.

[TroyD]

Agree with Mike.....

Issue 1 is a ground loop....

Issue 2 sounds gear related and not speaker related.

BDT

[bert26]

Thanks Blue,

Could you give me some more instruction on lifting the ground with a cheater cord? Just asssume I know nothing about it (which is pretty much the case). If non-common ground, would I still get the SDA signal on the left channel?

I am also going to try an old Carver and see if I get the same results.

Thanks!

[BlueMDPicker]

Break the ground lug of a junk IEC cord (if the gear uses them) or get a 3-prong to 2-prong adapter at the hardware store.

Yes, you could hear the effect in one channel. That's part of the setup/test procedure for SDAs. Verify it by swapping the speaker connections. I'd guess what you're hearing would go to the other channel.

Edit: fingers not cooperating with keyboard.

[bert26]

Thanks for the clarification. Just so I get it straight, you mean don't use a three prong plug into "the wall" for one of the Nak pieces.

Glad you and Troy are in agreement on the issues, especially the part about the speakers being ok.

[TroyD]

Yup, go down to the hardware store and pick up a three prong to two prong adaptor. The are less than a dollar. A ground loop CAN be a PITA to find.

Yup, try another amp, the carver will be fine.

BDT

[whitetruk]

Yup, go down to the hardware store and pick up a three prong to two prong adaptor. The are less than a dollar. A ground loop CAN be a PITA to find.

Yup, try another amp, the carver will be fine.

BDT



great advice, but i wonder why, i`ve had that same problem before.
now i keep some of those plugs in drawer.
hope it works for you too

[bert26]

The "remove the ground" suggestion worked for the hum on the Nak stuff.

However ... I still am not getting the SDA signal from the right channel, even using the Carver amp, which I am certain is common ground.

I am going to pull the drivers again and look for anything loose. Other than that I am lost. :(

Anything anyone has to add will be appreciated.

[BlueMDPicker]

Did you swap channels on the outputs (put the right channel cables in the left output and left in right)? Make sure you do that to eliminate the equipment as a problem.

[bert26]

Hey Blue. I just switched things as you suggested, and still no signal from the right channel. I can't see anything unattached internally for what that's worth.

[BlueMDPicker]

Do you have a copy of the SDA setup procedures? If I recall, your source should be mono for the check, or switch the preamp to mono (if that's an option.) You could Call Ken at Polk CS and have him send you a copy if you don't have one.

I guess the next thing to try absent that is swapping the SDA drivers from cabinet to cabinet. If the problem switches sides, you have a bad driver. Did the speakers accidently take any rough handling on the trip to the basement?

[bert26]

I do have a copy of the setup procedures and they mention first using just the balance control to listen for lower output on the opposite side from where the balance is turned. Then it mentions using the mono switch (or a monaural recording) listening for signal seeming to come directly from in between the speakers with full base response.

I hand carried them down myself with no drops or wall bounces, but they were shipped to me, so maybe I completed some damage begun then.

Looks like it's time to start swapping out drivers.

If I do call CS, should I just ask for Ken?

[BlueMDPicker]

Yeah, Ken (Swauger) is the man: 800-377-7655 toll free phone.

[bert26]

Can you say "connected out of phase"?! :eek: I switch ONE wire and BINGO! SDA signal everywhere.

Blue - sorry I wasted your time troubleshooting. I should have noticed that earlier. That what I get for being too damn lazy to get a flash light. I did however learn a lot today.

Now I can go to bed and not stress about having trashed something I really care about.

Thanks again everyone.

(and from everything I have read in here, Ken Swuager IS the man.)

[BlueMDPicker]

No problem, Chris. I should have asked that question (but, some folks get a bit indignant about the basics.)

I'm glad the "mystery" was solved. TAG, you're it -- you have to help the next member with a similar problem. BTW, be sure to ask them if their ICs are in phase. :D

[bert26]

It'll be my pleasure to pass along your sage wisdom and start contributing. ;)

That's what makes this such a great forum. A wealth of knowledge coupled with some humility and tempered with patience. (where did that come from?!)