Question on SDA cable with isolation Transformer

**peckgary** · 07-12-2003 07:21 PM

I hope that somebody who has SDA speakers can help me out or at least point me in the right direction. I have been trying to make an SDA interconnect cable with an isolation transformer in it for the last couple months :-(.

The problem is I can get it to work, but the volume coming out of the SDA driver is about 1/3 of what it should be. This is using the test tone on the B&K Ref 20. I can run the same test with my common ground amp that I use to drive my other pair of SDA2B's with the standard interconnect and the speakers and SDA effect sound great. This comparison is where I get the 1/3 volume comparision.

When I use the cable with the isolation transformer in it, I might as well not have it connected at all, because it makes no difference in the sound. Does somebody have a part # for the isolation transformer they are using. Maybe I got a cheap one and need a more expensive one. I have tried 2 that Ken Swauger sent the part numbers for.

Sorry for the long post. It is to hot here to do anything else but sit inside with the AC. It is currently 107

Thanks for any help,

Gary

**scottdawg** · 07-13-2003 01:27 AM

I can send you a pdf file of the instructions, it includes a few part #'s for different iso xfmers.

**F1nut** · 07-13-2003 02:24 AM

If you trying to use the transfomer set up with a pair of 2B's it isn't going to work. Those speakers were not designed for it.

**peckgary** · 07-13-2003 02:53 PM

I already have the instructions from Ken at Polk, but thanks for the offer. Ken did say that the crossovers that I have in the 2b's should work with the isolation transformer. Maybe they just kind of work and that is the problem? Gee I wonder how the wife will react when I say can I have another grand for an amp. If I do not post for a while, I am just trying to reattach my head :-)

Thanks for the input guys

**hoosier21** · 07-13-2003 06:35 PM

Originally posted by F1nut
If you trying to use the transfomer set up with a pair of 2B's it isn't going to work. Those speakers were not designed for it.

huh, why not F1?

I think it will work with the 2B's, I always assumed that any of the pin blade interconnect style SDA's could use the A1 (or DIY iso transformer interconnect) Please tell more.

**F1nut** · 07-13-2003 09:53 PM

According to the info I have with my AI-1, it will only work with some 1C's and above. It wasn't even an option for my 2B's that I purchased back in '89. Of course, I will defer to Ken's wisdom in this matter, but something isn't working for peckgary and I believe the 2B's aren't designed for it.

**Zero** · 07-13-2003 10:03 PM

They BETTER work with the 2B's!

**F1nut** · 07-14-2003 01:44 AM

Alright guys, I kinda got a oops here.

The AI-1 will work with 2B's whose left channel s/n is 14115 or greater and whose right channel s/n is 14124 or greater. Also that certain units of the above require the TB 1 plug adaptors. Sorry for the confusion.

**peckgary** · 07-14-2003 09:58 AM

Thanks for the information. Now if I could only figure out why the volume is only about 1/3 of what it should be :-(

My guess is that I probably need a better isolation transformer. One that is more like in the original A1 interconnect cable. If somebody had a part number it would be greatly appreciated. I have tried 2 of the 3 on the list that Ken gave me, but both seem to have alot of signal loss. Ken had made a suggestion about trying to use an isolation transformer more designed for audio, but I am at a loss as to what one or where to get it.

Thanks for your help guys.

Gary

**F1nut** · 07-14-2003 10:35 AM

Here are 3 transfomers to try,

SPC Technology # 81N5406

Stancor # 01F043

Magnetek Triad # 03F1017

**peckgary** · 07-14-2003 10:54 AM

Thanks F1nut I will give them a try.

**har_navalta** · 07-14-2003 12:31 PM

You can order those isolation listed by f1 here:

http://canada.newark.com/

or in the U.S.
http://www.newark.com/

**peckgary** · 07-14-2003 02:52 PM

Hi Guys,

I have already tried SPC technology and the Stancor one. The only one I have not tried is the Magnetek. Maybe if I twist my brothers arm real hard, I could get him to sell me my Adcom GFA-555II back. He does have a Adcom GFA-545II that I could probably get him to sell me for $150. That might be cheaper in the long run. The last isolation transformer I ordered from Newark cost me more for shipping then the isolation transformer :-(

These are the 3 options I have:

1. Buy a third isolation transformer and hope it works.
2. Run the SDA2B's in the rear without the interconnect cable.
3. Purchase the Adcom 545II for the rears and use the B&K amp for the center and evenutally for 7.1 when I upgrade.

Another question regarding amps. This may seem stupid, but what exactly is the difference between a common ground amp and a floating ground amp like the B&K ST1430.

**soupbone** · 07-16-2003 08:35 AM

Check the output impedance of the amp. The sda effect will be diminished if it is too high. Most tube amps usually have this problem. What is too high you ask. Check with Ken. He helped me out a couple years ago when I tried to use an Audio Electronics Superamp.

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