Running Cary Pre with inverted ouptut with SDA-CRS

kcoc321

I am looking at possibly getting a Cary SLP-88 tube preamp and the manual says it has an inverted output signal. It goes on to say that the pos & neg can be reversed to deal with this before the amp (not sure how to do that? Custom RCA's?) or at the amp by switching the pos & neg speaker connections...

Just switching the pos & neg connectors doesn't sound like a good idea to me, when running SDA's..

Anyone have experience using this Preamp and a solution to being able to use it with SDA's?
Also, what is a decent price with an extra set of tubes, the remote original double box and manual?

As an aside, are there other components that invert the signal?


I am using a GF tube buffer and an B&K ST2140 amp, if that makes any difference..
I am currently using a B&K PT3ii preamp
CRS's are currently unmodified.

thanks

billbillw

Some people and some systems are more sensitive to absolute polarity. I am not one of them and neither is my system. You'll just have to test it out.

BTW, there is no problem swapping the + and - speaker wires as long as you do the same to both channels.

It is not uncommon for a preamp to invert polarity. Most balanced designs tend to preserve polarity while some single ended circuits will invert it. All depends on how many gain stages, etc.

tonyb

True ^^^, fairly common among tubed pre's to have to switch polarity. BTW-take that GF tube buffer out of the mix with the Cary pre....no need for it.

kcoc321

thanks for the feedback guys....

And yes, I would not be using the GF buffer, unless it inverted the signal itself... then I thought I could use it to "re-invert" the signal.

How do I test for inverted signal?

[Deleted User]

Hello,
It is not a good idea to reverse the polarity of speaker wires when using SDA speakers this would connect a common ground short to the positive terminals of your amplifier. In the case of a twin blade SDA this would short the amplifier, in the case of a pin blade speaker there wouldn't be any "SDA" information.
Regards, Ken

tonyb

Good point Ken, as usual my reading comprehension didn't grasp what speakers he was using.

kcoc321

That was what I was worried about Ken...
Any solution that would allow use of an inverting preamp?

[Deleted User]

Hello,
As billbillw pointed out, absolute polarity seems to be something that some listeners find noticeable and others not so. The Sheffield Labs records were recorded in opposite to standard polarity and few people heard much difference. Usually one of the components "downstream" of the preamp would flip polarity so everything would come out back the correct way. I suppose you could reverse the polarity on all the drivers and tweeters and compensate for the difference, but that hardly seems worth it.
Ken

F1nut

I had a tube pre that inverted polarity, tried it both ways on non-SDA speakers a number of times and could not hear a difference. Brgman uses an inverting tube pre with his SDA's and reports stellar sound. I'm sure he is not reversing the positive and negative, so I don't think you should concern yourself with it.

kcoc321

F1nut wrote: »

I had a tube pre that inverted polarity, tried it both ways on non-SDA speakers a number of times and could not hear a difference. Brgman uses an inverting tube pre with his SDA's and reports stellar sound. I'm sure he is not reversing the positive and negative, so I don't think you should concern yourself with it.

Thanks F1nut.. that is good news

kcoc321

kcoc321 wrote: »

From: Dan Wemmer <Dan@caryaudio.com>
Date: Wed, Dec 11, 2013 at 5:52 AM
Subject: RE: Using a Cary SLP-88 with Polk SDA speakers
To: KC O


Hello KC.

Yes it does invert phase but you may or may not need to reverse the polarity of your speaker wires. This just depends on the whole system, including the source component and CD's being played at the time. Many CD's are recorded with reverse phase unfortunately. This will have to be tested in the actual system to know if the polarity needs to be reversed or not.

Only your amplifier manufacturer can tell you if it will be OK to do or not. Usually that just means not to ground the negative terminal not that you can't reverse the phase at the speakers.

Technical Support available from 1-5 pm Mondays through Thursday. Closed Fridays
Dan Wemmer | Lead Technician & Technical Support
CARY AUDIO
1020 Goodworth Drive | Apex, NC 27539
919-355-0010 PHONE
919-355-0013 FAX
www.caryaudio.com www.aebycary.com

Not sure if that tells me anything different, but figured it might be helpful to someone else

kcoc321

BTW, I discovered my DAC has an "invert switch" so I can just invert the signal before it goes to the preamp