AI-1 Built. I have an issue.

riglehart · March 2006

OK. Using the directions supplied (thanks everyone) and using the BETTER Stancor P-6012 tranformer, I have built the AI-1. I am pretty sure it is correct.

I still have the 2.3TLs hooked to the same original Yamaha receiver (not the NAD 2200). I didn't destroy my old SDA cable, I built from scratch. When I use the AI-1 cable and turn my balance all the way to the right, the SDA effect on the left is probably twice as loud with the original SDA cable compared with the AI-1.

I have an Electrical Engineering degree, so I'm not just winging it.

Using a multi meter I proved that the old SDA cable simply is a straight through connection from pin-pin (diag 1). Also, the blades are hooked to nothing electrically. However, taking the plate off the back of the speaker, I found that the blade plug goes to the negative mid/bass connector (see picture). The diagram for the Left and Right spaker binding posts and plug are also posted.

This makes perfect sense, based on the direction that say to hook up to the pin and the negative post. I've never seen a factory AI-1, but I assume it doesn't use a wire to the negative binding post. It doesn't need to, since it probably does the same thing, only through the blade (which connects to the negative post anyway).

The last picture shows how the transformer is used to isolate the two speakers from each other. This is how I have it built.

So, I guess what I am saying is that it appears that you sacrifice some SDA effect when you use an AI-1. The side by side sda vs AI-1 comparison definately shows a degradation.

Have I done something wrong??? If not, I need to find a common ground amp.

riglehart · March 2006

Also, I used 16ga wire (not phone wire). So that shouldn't be an issue.

SCompRacer · March 2006

Here is a pic of my factory non-common ground IC. It uses the same connector found on the standard pin/blade cable, and of course the pin and blade are connected in that application.

http://www.polkaudio.com/forums/attachment.php?attachmentid=14065&d=1139703116

Here is a pic of the innards.

http://www.polkaudio.com/forums/attachment.php?attachmentid=10975&d=1126759595

Your last picture shows how the isolation transformer should be connected.

I recall reading in the instructions provided by Ken that after connecting one speaker, you experiment by swapping the pin/blade wires on the remaining speakers winding until you get the best SDA sound. In other words, connect 3 and 4 temporarily, listen, then swap the wires on 3 and 4 and have another listen. Did you try that?

Ken had suggested to me that I would get a better SDA signal without the transformer. doro mentioned he couldn't tell the difference between using the two, and when I swapped my standard for the non-common ground cable I don't recall any difference.

F1nut · March 2006

I've never heard a difference either.

dbnh · March 2006

SCompRacer wrote:

I recall reading in the instructions provided by Ken that after connecting one speaker, you experiment by swapping the pin/blade wires on the remaining speakers winding until you get the best SDA sound. In other words, connect 3 and 4 temporarily, listen, then swap the wires on 3 and 4 and have another listen. Did you try that?

I was wondering this as well. When I had an AI-1 built for me, we did this test before the final connections were soldered. There was a distinct difference, and we went with the wiring that producted the best SDA effect.

Good luck.

BobMcG · March 2006

F1nut wrote:

I've never heard a difference either.

Plus one.

Tour2ma · March 2006

Seems like 'reeltrouble' fought through the same issue a while back. As I remember he bought a different transformer and all was well.

There's a thread around here somewhere. Will post it if I can dig it up...

riglehart · March 2006

Tour2ma wrote:

There's a thread around here somewhere. Will post it if I can dig it up...

I'ver read that thread carefully. He fixed his problem by using the better 6012 transformer, instead of the 6011. I have the 6012.

When I started this project I was worried about the transformer. These transformers are designed for power conversion application (60 Hz). They may be choking off the other frequencies. I'd say my SDA volume is about 1/2 compared to the straight cable, plus the highs seem to be missing more, but it is hard to tell due to the change in volume.

Also, in the other threads, where they comparing the SDA cable to the AI-1 using a non-common ground amp? I have a common ground, so am getting the best result possible with the straight cable. If they were comparing using their non-common ground amps, the SDA cable might have already been at a disadvantage, so it sounded the same when compared to the AI-1. Just a theory.

I am going to look for a different transformer. If anyone can get a part number off their polk AI-1 transformer, I'd have no more excuses.

riglehart · March 2006

Also, changing the 3&4 connections doesn't effect the volume, but it does change the phase 180 degrees. This is important to get an SDA effect.

This is a stretch, but, does anyone out there have an oscilloscope to check the input vs output voltages on a transformer at different generated frequencies?

Tour2ma · March 2006

riglehart wrote:

I'ver read that thread carefully.

Would you mind posting a link to Ted's thread? I can't find the bugger.

riglehart wrote:

If they were comparing using their non-common ground amps, the SDA cable might have already been at a disadvantage, so it sounded the same when compared to the AI-1. Just a theory.

Others have reported "dull sound" when they used a non-common ground amps with SDA's and the standard IC.

rskarvan · March 2006

Correct me if I'm wrong... but, I thought you didn't need an A1-transformer-interface with the TL series speakers.

Tour2ma · March 2006

OK... you're wrong...

The tl's (and a few pre-tl's) are the only ones that can accept/ utilize the AI-1.

Zen Dragon · March 2006

riglehart wrote:

This is a stretch, but, does anyone out there have an oscilloscope to check the input vs output voltages on a transformer at different generated frequencies?

So you need someone with an oscilloscope and a frequency generator to supply fixed stable test frequencies.

Polk65 · March 2006

Newark? http://www.polkaudio.com/forums/showthread.php?t=23442

reeltrouble1 · March 2006

Waaaaaaaaa,,,,,,,,

At the risk of (w)rankling our fine new INTELLIGENT member.

Ringle--If this gets too long please excuse me.

My Pop was a ME, I spent YEARS toiling in schools with various calculus and physics, etc. but it just was not me, it almost killed him when I came home one semester and declared "being an EE major sucks for me". When forced to think analytically I can quite well and systems analysis comes easily. I very much enjoy the science of audio. However, its just not me. I am much much better at concepts, so I found my ultimate employer, the US Government, great on concepts, End World Hunger, Fight Drugs, Stamp out Terrorism, details? ah throw more money at it!!!!

OK, so I and some others simply use our ears, we use our receptors to determine whether or not something sounds good. Others, including most Engineers need to have the scope data you seek to prove this or that to themself. Not a bad thing by any means. But different, many hybrids along the way, actually I had to use meters and my ears to build my cable.

It makes sense to me that any interruption of the signal via a connection will result in some change in the signal, however minute.

As the listener of your system I would encourage you to do all the scope tests you need to base your final decision on. By chance I was gifted with a golden musical ear, I look forward to seeing how it stands to your future findings. Scopes though cannot hear, they can only sense in a different manner. Therein lies the paradox that befuddles many a post here.

When I built my AI-1 and used it in my rig with some bridged mono-blocks, the system sounded better than when I used the original cable with a stereo amplifier I had and that was just peaches and cream for me. It proves nothing, but this does not bother me in the least.

Let us know what you decide and why.

RT1

Zen Dragon · March 2006

From the original reeltrouble thread.

madmax wrote:

Think about it this way. The peak voltages on most amps is about 70 volts. Power is voltage times current. At the most the xformer you are using would be 0.13x70=9.1 watts. Not very gutsy but then again the SDA drivers are fairly quiet anyway. A problem with the smaller xformer is you might be saturating it. Don't know much about where that happens and what it would cause exactly.

The current rating does seem a bit meager at .13A or even the .3A of the larger transformer. RT was also working with the SDA-1C's and there could be some impedance differences, or differences in the size of the signal being sent to the SDA drivers. Also the SDA signal likely increases in proportion to the amplification being supplied to the speaker. In Reeltrouble's case he was driving 400WPC. I'm going to make the assumption your Yammy receiver is not driving over 400WPC so you are not driving a higher level than his system was..
Testing the input/output signal level of the transformer would give you an idea of if there is loss occuring through the transformer. AS RT states it will not ascertain audio quality, but it is a good place to begin.
One other thought. Perhaps the fact that you are using a common ground amp into the isolation transformer is part of the problem. You have a trnasformer designed to operate isolated with a common connection from the input to the output.

riglehart · March 2006

reeltrouble1 wrote:

Others, including most Engineers need to have the scope data you seek to prove this or that to themself. Not a bad thing by any means.
RT1

The only reason I mention the scope is that it would be able to test the transformer characteristics, not the sound of the speaker. However, you are right in saying that if the set up sounds better, who cares. I think it doesn't hurt to question whether or not you have shortchanged yourself in your solution, though. That's all I'm doing.

By the way, I haven't touched a scope in 20 years (college lab). I do software now.

Zen Dragon wrote:

Perhaps the fact that you are using a common ground amp into the isolation transformer is part of the problem. You have a trnasformer designed to operate isolated with a common connection from the input to the output.
RT1

Now, you might be on to something here. Since my amp is common ground, connection 2 & 4 of the transfer are actually connected through the amp's common ground.

Tomorrow I'll hook up the NAD and see what happens.

riglehart · March 2006

OK. I took a piece of advice from reeltrouble1 and used my ears to check the transformer. I did a simple test. I put it directly in series with the amp and drove a 6x9 coax speaker through the transformer. The transformer has a HUGE effect on the signal, both volume and fidelity. Same as the SDA drivers.

I won't be able to sleep until I try an AUDIO transfomer and see if there is a difference. I'm going to get something like this...

http://www.jensen-transformers.com/datashts/11bmcf.pdf

These are designed for audio and distinctly provide specs to indicate a flat response 20-20,000. Compare that to the Stancor which mentions nothing, since it is designed as a 60hz power transformer....

http://www.newark.com/NewarkWebCommerce/newark/en_US/endecaSearch/partDetail.jsp;jsessionid=RXYNUI5BOYBFMCXDUY0CFGAK2OTCIIV1?SKU=05F1432&N=0

As reeltrouble1 says, my ears will have the final word.

reeltrouble1 · March 2006

Good deal then. We have been using the Stancor as it was the recommended transformer per Polk. If something better is out there I am all for it.

RT1

F1nut · March 2006

If they were comparing using their non-common ground amps, the SDA cable might have already been at a disadvantage, so it sounded the same when compared to the AI-1.

That can't be done or at least shouldn't be done as using the regular SDA cable with non-common ground amps will result in bad things happening to the amp and/or speakers.

Perhaps the fact that you are using a common ground amp into the isolation transformer is part of the problem. You have a trnasformer designed to operate isolated with a common connection from the input to the output.

I've run a common ground amp in the past with the AI-1 and didn't notice any issues.

FWIW, the SDA drivers are never as loud as the stereo drivers with either cable in use.

whitetruk · March 2006

Tour2ma wrote:

OK... you're wrong...

The tl's (and a few pre-tl's) are the only ones that can accept/ utilize the AI-1.

my srs`2 accept it,and my 1.2 tl`s, (why only a few pre tl`s) just wondering

whitetruk · March 2006

sorry for double posting,but i guess my ? is do i not need my AI-1 cable on the tl`s with mono amps.
scott

reeltrouble1 · March 2006

whitetruk wrote:

sorry for double posting,but i guess my ? is do i not need my AI-1 cable on the tl`s with mono amps.
scott

You need it.

RT1

riglehart · March 2006

anonymouse wrote:

That is a line transformer - its unlikely to have the juice to drive speaker level loads.

I think you may be correct, but I have been looking all weekend and can't find a "high power" audio isolation transformer anywhere. I called Hammond (who specialize in transformers for tube amps) and the tech guy said he has never been asked for a 1:1 audio isolation transformer the operates at those levels. He also said I'd probably only find the line level ones unless there is a specialty place somewhere that does them.

I'm going to take a long shot and see if polk tech support can give me a model number from what they used to use. Someone sent me a picture and it looks "beefier" than anything I can find that is made for audio.

I'd order the Jensen Jt-11SS and try it, but the darn thing is $71. Already have $30 into the stancor. I have a feeling it will work well until I turn up the volume and saturate it, which is exactly what you want to do when you require an AI-1.

reeltrouble1 · March 2006

Ringle--Newark is a very good company, when I bought the first one the 6411 and told them it was not working out they credited my CC account and did even want me to return the item. I suspect the Polk original is not around otherwise Ken S. would be putting us on to it.

Good luck.

RT1

riglehart · March 2006

I almost wet myself when I got this today from Ken...

Kens Email wrote:

Hello Rob,
We are searching for the original transformer specification and will forward them if we find them. However here are Matthew's comments:
"Ken -

I don't know if we have a spec in the files. However, a high current
1:1 toroidal transformer will work very well. The key specs are:

1. DC Resistance of primary and secondary should be less than .8 ohms and preferably less than .5 ohms. The lower the better.
2. Inductance of both primary and secondary should be at least 10mh.
Ideal is around 14mHy.
3. Current capacity to saturation should be 5 Amps minimum.
4. Of course the turns ratio is 1:1

Multiple transformers can be used in parallel to lower the DC resistance and increase the current capacity. Just remember that the inductance is half for two transformers in parallel and one-fourth for 4 transformers in parallel.

-msp"
Regards, Ken, Polk Audio

I feel like I'm standing in front of a burning bush.

Dennis Gardner · March 2006

riglehart wrote:

I feel like I'm standing in front of a burning bush.

Classic.....:D

I read the quote with a deep resounding voice and got the gist of the message.;)

reeltrouble1 · March 2006

Ya just have to love this company.

Maybe Ken will find that old last box of transformers, the one Stu hid with the specs.!!!!!!!!!

RT1

riglehart · April 2006

I got a toroidal transformer and tested it out last night. The sound quality driving a seperate speaker directly through the transformer is WAY better than the Stancor. I couldn't find any with the specs that Ken/Matthew recommended, so I took a shot at this one. I'm pretty happy.

It is pretty big (4.6 lbs), but the sound through the toroidal transformer is almost as good as a direct connection. *MUCH* better than through the Stancor. If you've built an AI-1 using the Stancor, I think you will want to upgrade the transformer to this one.

I got an Avel-Lindberg 230 VA Y236605. ($48 shipped)

http://www.avellindberg.com/transformers/y23_range_specs.htm

I'll post pics in a couple days.

F1nut · April 2006

Very interesting and thanks for posting the info. I eagerly await the results.

DarqueKnight · May 2006

riglehart wrote:

I got a toroidal transformer and tested it out last night. The sound quality driving a seperate speaker directly through the transformer is WAY better than the Stancor. I couldn't find any with the specs that Ken/Matthew recommended, so I took a shot at this one. I'm pretty happy.

It is pretty big (4.6 lbs), but the sound through the toroidal transformer is almost as good as a direct connection. *MUCH* better than through the Stancor. If you've built an AI-1 using the Stancor, I think you will want to upgrade the transformer to this one.

I got an Avel-Lindberg 230 VA Y236605. ($48 shipped)

http://www.avellindberg.com/transformers/y23_range_specs.htm

I'll post pics in a couple days.

I sent Matt Polk's transformer specs to Avel-Lindberg. They recommended the following two toroidal transformers:

Avel Part No: Y236856, $66.26, 5.4" diameter, 2.6" high, 10.8 pounds weight.

Avel Part No. Y236906, $69.93, 6.3" diameter, 2.2" high, 13.2 pounds weight.

A nice metal enclosure of approximate size 4" high x 12" wide x 10" deep can be purchased from Newark Electronics ( www.newark.com ) in the range of $30 to $55. They can probably be found cheaper elsewhere. I have not done a lot of shopping around.

Avel-Lindberg can also custom manufacture a toroidal transformer that is an exact match for Matt Polk's specs, but this would be 2x to 2.5x the cost of an off-the-shelf transformer.

I have been looking into building an AI-1 interface cable because I want to upgrade to a higher power amplifier in the range of 500 to 700 watts. All of the amps I like are non-common ground designs, plus, I am not comfortable with using the Stancor transformer and its equivalents because of saturation issues.

Looks like my outlay for the transformer, enclosure, cable, and terminations will be in the $200 to $250 range.

AI-1 Built. I have an issue.

Comments