AI-1 Shootout

F1nut

First, let me thank Rob (Riglehart) and Ted (RT1) for letting me borrow their custom made AI-1 interconnect cables.

This simple test involved three AI-1 isolation transformer cables. One Polk factory issue, one Stancor P-6012 and one Avel-Lindberg Y236605. I used the first track, Babylon Sisters, from Steely Dan-Gaucho on SACD because of the excellent sonics and I know the song very well. I was able to swap cables in about 15-20 seconds and did this repeatedly over a few weeks.

Ok, the meat....

I found little difference between the stock transformer and the Avel. Both had a nice, wide and proper soundstage, detail, air, tone and decay. However, the Avel was a little more forward and slighty less euphoric because of it. I have to wonder if an Avel transformer of the exact same spec as the factory transformer would fix that? I think it would. The Stancor, while not sounding poorly, just didn't have the soundstage, air, detail or decay of the others. This was evident every time and I can't recommend it.

Thanks again guys, I had fun.

strider

I was interested to hear what your results were going to be, thanks for doing the work. It sounds like the Avel might be the way to go, trying to find an original AI-1 for sale has been fruitless so far. There were 2 mentioned by DarqueKnight in the thread I found regarding the building of the interconnect with the Avel:

"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."

I'm guessing either one of these would be a good choice?

BTW- what is meant by "decay"?

reeltrouble1

Excellent Jesse, I recall the Stancor Transformer as being 30.00, it is not torridial like the Avel, it weighs a couple pounds or so, good example of weight/cost ratio.

If I build another one the Avel is a no brainer based on your finding. Please note the Stancor I used is not the same as the one in the Polk issued directions, the one I used was actually larger having more current flow. I seem to recall the one I built was rated 1.3 amp, any idea on the Anvel?

RT1

Strong Bad

This is an ok review, but i'm waiting for an indepth review comparing Chaps Pitbeef VS that other joint you speak of so highly.

Back to your regularly scheduled review program...

F1nut

Strider, I can't say if those are a better choice. If it were me, I'd spend the extra money and have them build a spec'd one. If you were to find a factory AI-1, they go for at least $100.00, so keep that in mind.

Decay is the nature fading of a sound. If you pluck a stringed instrument the sound doesn't stop a second later, it continues on as it fades away.

F1nut

I'll do that one later, John.

schwarcw

Thanks for the test Jesse! My A1-1 is still unused as it rolled off the factory floor. It's interesting to note that your test didn't reveal any difference between the stock and the hand built with a good transformer. My impression just looking at the A1-1 is that it is a cheaply built component.

Good choice of songs!!!

"So fine, so young . . .

Tell me I'm the only one . . "

madmax

I looked into those avels awhile ago and was interested but figured I'd try the stancor that I have waiting on the bench first. I may not even try the stancor now. If I do it I may have them make the one matt suggested but like most things at this time, its on the bottom of a long list. Thanks for the review!
madmax

hoosier21

Thanks Jesse good information

schwarcw

Jesse, I assume there was no difference (in your judgement) between the A1-1 and a standard Polk interconnect cable?

Carl

BobMcG

Nice job Jesse, thanks.

Curious though, Avel has to utilize 10lbs + of electronics to do the same job of Polk's what... 2.5 +/- pounder? They can't just build one based on the same design (copy cat) as the Polk?

hearingimpared

Jesse, must you use the AI-1??? I opted to trade mine for the straight interconnect and strap my amps. I was afraid the AI-1 would diminish the soundstage and mess with the pinpoint imaging.

PS: I am planning to do Raife's upgrade on that interconnect very soon.

danger boy

so does a signal pass thru the SDA cable or what? would building my own cable using better quality wire improve the sound in my case? Know though that i have the older blade/blade sda cable.

hearingimpared

danger boy wrote:

so does a signal pass thru the SDA cable or what? would building my own cable using better quality wire improve the sound in my case? Know though that i have the older blade/blade sda cable.

Raife has write ups on this. I'll try to find them.

hearingimpared

Here you go Al.

RuSsMaN

What are the specs, requirements etc for a tranny to be used in AI-1? I'm wondering if some sought after, vintage iron could be used - esp since you reported obvious changes in sound.

Cheers,
Russ

danger boy

Joe, thanks for the link.. i never paid attention to the thread at the time it was posted.. it was several months before I got my SDA's. tons of good info. and yeah.. it appears that upgrading and replacing the aging SDA cable would benefit some for sure.

hearingimpared

danger boy wrote:

Joe, thanks for the link.. i never paid attention to the thread at the time it was posted.. it was several months before I got my SDA's. tons of good info. and yeah.. it appears that upgrading and replacing the aging SDA cable would benefit some for sure.

I'm upgrading mine with good old fashioned Monster Powerline 2 Time Coherent cables. That is what I have connected between my Adcoms and 1.2 TLs.

hearingimpared

RuSsMaN wrote:

What are the specs, requirements etc for a tranny to be used in AI-1? I'm wondering if some sought after, vintage iron could be used - esp since you reported obvious changes in sound.

Cheers,
Russ

Russ have you seen Sid's Kharma posts recently???

F1nut

reeltrouble1 wrote:

I seem to recall the one I built was rated 1.3 amp, any idea on the Avel?

RT1

Ted, it's rated at 1 amp.

Carl and Joe, I can't use the standard cable with my present rig, but I have in the past with a different rig and could not hear a difference.

Bob, as far as I know Avel only builds torridial transformers. However, they can build a torridial to the Polk spec's.


The answers to some of the other questions can be found here, http://www.polkaudio.com/forums/showthread.php?t=39278&highlight=avel

riglehart

schwarcw wrote:

Jesse, I assume there was no difference (in your judgement) between the A1-1 and a standard Polk interconnect cable?

Carl

I originally built one with the stancor and was really dissapointed compared to my straight cable. So I bought the Avel and it was much better. However, I still think anything less than a straight cable is a work around and less than optimal on a "cheap" rig. One could probably argue/prove that the benefits of biamping far outweigh what you give up with the required transformer.

I'm back to a 50 watt tube amp on my 2.3TL with the straight cable and have never been happier. I can't afford a bunch of halos (or the divorce that would follow).

schwarcw

Thanks for that input Rob!

Were you vertically or horizontally bi-amping?

Carl

riglehart

schwarcw wrote:

Thanks for that input Rob!

Were you vertically or horizontally bi-amping?

Carl

I was using a single NAD2200 amp, which I was told was not common ground. After having it on the AI-1 for a few months I found out it is in fact common ground. I immediately put the straight cable back on. That's why I have experience with the same "cheaper" rig on both cables.

When I did finally try biamping (which was a definate improvement), I was biamping top/bottom with common ground amps. So, I could still use the straight cable. I had the top on my 150wpc NAD receiver and the bottom on my 2200. (That's Horizontal, right?)

schwarcw

Hi Rob!

That's vertical. Horizontal is when you use separate amps for the left and the right. I'd like to try bi-amping some day.

Carl

hearingimpared

schwarcw wrote:

Hi Rob!

That's vertical. Horizontal is when you use separate amps for the left and the right. I'd like to try bi-amping some day.

Carl

I'm definetely going to vertically bi-amp my 1.2 TLs. I've read just too many articles and reveiws that make bi-amping vertically or horizontally a necessity. It makes all the sense in the world to have a separate amp for the bass and one for the high frequecies.

The question or problem is I can't decide whether I want to use a tube or SS amp for the tops. I'm also torn between going very high on the wattage (200 wpc or more) or just maybe a simple 100wpc amp. I'm going to need to borrow an amp from one of my buddies locally to try out the configuration before I go out an purchase a new or used amp for this purpose.

The thing I keep looking at is that I can really push the 1.2 TLs hard with the current configuration and no matter how painfully loud a level I can get to there is absolutely no distortion or degradaton of signal quality and the speakers just keep asking for more and playing faithfully what is shoved down their throats.

read-alot

My user manual reads like this.

"Recommended Amplifier Power 1000 w/channel"

That's some serious wattage.

reeltrouble1

We bi-amped BDT's SDA at the fest, used a pair of Anthem 150 watt channel amplifiers, more than enough juice. They sounded very nice. The tweets actually draw very little power. I would look for an amp with a fast slew rate to capture quick transients.

You just have to try bi-amp to see how you like it, I mono-bridged the 1C's with the Stancor transformer, I used a pair of NAD 2700, bridged they ran at 440 or something like that with headroom so high I just cant remember. The 1C cannot be biamped.

Anyway, I found the 1C's sounded better this way with the Stancor Transformer than with the straight cable and a single NAD 2700. As suggested I suspect this is do to the increased available power overcoming any signal loss with the transformer. I wary that the sound might be gritty in the bridged mode, however, this was simply not the case, I would say the NAD are on the warm side of things, not the most detailed of amps, but quite musical, one of favorites for sure.

RT1

schwarcw

reeltrouble1 wrote:

I wary that the sound might be gritty in the bridged mode . . . RT1

RT, for this reason, I was wondering why you would bridge horizontally vs. biamping vertically when you have two amps? I appreciate your insight as I have very little knowledge in the biamping area. Thanks!

Carl

RuSsMaN

RuSsMaN wrote:

What are the specs, requirements etc for a tranny to be used in AI-1? I'm wondering if some sought after, vintage iron could be used - esp since you reported obvious changes in sound.

Cheers,
Russ

anyone?

reeltrouble1

schwarcw wrote:

RT, for this reason, I was wondering why you would bridge horizontally vs. biamping vertically when you have two amps? I appreciate your insight as I have very little knowledge in the biamping area. Thanks!

Carl

Well, in my application bi-amp was not an option as the speakers only have one set of binding posts.

If pressed I favor bridging as it makes the increased power available to all of the drivers in any given moment. Running on a 6ohm load (1C's) never had a problem, when I put the NAD 2700 bridged mono on the Original Amazings (4 ohm), I could hear them start to strain at volume, the soft clip never kicked in, but at volume it was a bit much for the 4 ohm load. Bridging at 4 ohm, not really a great idea safety wise.

In a Bi-amp you can mix a certain amp for the top a different one for the bottom end, say tubes on top, ss on the bottom for slam and so on. You will have to deal with slew rates, which may not matter to you, or just use the same amp.

Remember, you have not experienced audio till you blow something up, playing with all this stuff.

Russ--I really dont know, the Stancor was recommended by Ken.

RT1

strider

RuSsMaN wrote:

anyone?

Is this what you're looking for?

Originally Posted by Kens Email
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'm not real certain if this is enough info or not. This stuff is waaay over my head....