Can Someone Explain How the AI-1 Transformer (Dreadnought) Works?

drumminman

I finished and installed mine and had a several hour listening session. The review can be found here: http://www.polkaudio.com/forums/showthread.php?129134-AI-1-Dreadnought-with-common-ground-amp post #14.

I am truly surprised (and delighted) by the improvement. I just don't understand exactly what's going on. The transformer used is an isolation transformer, so how does the SDA signal communicate between the speakers? Doesn't the transformer prevent that? My knowledge of EE is severely limited, like almost non-existant, so I'm having trouble understanding this

Thanks!

heiney9

Could you please go into more detail about how you are using it and what specifically has you surprised and delighted, specifically as in the difference between the regular and Dreadnaught? IIRC, you have a common ground amp?

H9

heiney9

Maybe you could layout all the parts you used (model numbers, etc) as well as the cost, etc. I have been thinking about doing this for awhile.

H9

drumminman

heiney9 wrote: »

Maybe you could layout all the parts you used (model numbers, etc) as well as the cost, etc. I have been thinking about doing this for awhile.

H9

See my op - click on the link, post #14 has all that.

As I said, the difference in my system is not subtle.

heiney9

drumminman wrote: »

See my op - click on the link, post #14 has all that.

Lmao......was the link there the entire time? Ha...ha... right in front of me!

drumminman

heiney9 wrote: »

Lmao......was the link there the entire time? Ha...ha... right in front of me!

:cheesygrin:

What amp are you running?

heiney9

Pass Labs Aleph 30

mhardy6647

drumminman wrote: »

... I just don't understand exactly what's going on. The transformer used is an isolation transformer, so how does the SDA signal communicate between the speakers? Doesn't the transformer prevent that? My knowledge of EE is severely limited, like almost non-existant, so I'm having trouble understanding this

Thanks!

A transformer will "block" DC, but it will, and does, pass AC by electromagnetic induction from the primary to the secondary windings. Music is an AC waveform and passes happily through a transformer (good thing, too, or most vacuum tube amps would be very quiet indeed). The bandwidth of AC it will pass depends upon the construction of the transformer and the amount of power being transferred.

Other than that I know nothing about this particular transformer or its application.

drumminman

I have to echo TF66, who hooked one up to his Pioneer receiver: once you hear it you'll wonder why you hadn't done it before.

drumminman

mhardy6647 wrote: »

A transformer will "block" DC, but it will, and does, pass AC by electromagnetic induction from the primary to the secondary windings. Music is an AC waveform and passes happily through a transformer (good thing, too, or most vacuum tube amps would be very quiet indeed). The bandwidth of AC it will pass depends upon the construction of the transformer and the amount of power being transferred.

Other than that I know nothing about this particular transformer or its application.

Thanks for that! That helped lift my fog of ignorance.

This interface is necessary for non-common ground amps for stability of both speakers and amps. IOW either or both can be destroyed if using SDA speakers with the IC cable connected. Do you have any idea how the AI-1 interface effects this problem? Is it the same DC blocking feature that prevents melt down?

mhardy6647

Probably :-)

A transformer (referred to above as an "isolation transformer", which indeed it is) consists of two separate coils of wire. The two coils are electrically isolated from each other; there is no physical connection between the "primary" coil (or "winding") and the "secondary" winding. An AC signal has an electromagnetic field associated with it. When the primary is energized with an AC signal, it can induce that signal into the secondary coil. By varying the number of turns of wire in one coil compared to the other, a transformer can "transform" low voltage to high or vice-versa, while still maintaining the fidelity (qualitative characteristics) of that AC waveform (signal). It's pretty amazing, actually.

Now, DC. If you feed DC through the primary coil, 1) you've made an electromagnet :-) and 2) there is no alternating electromagnetic field (in the steady state) and thus nothing is induced into the secondary.

What does this have to do with breaking a ground while transmitting a music signal? There's another kind of transformer called an "autoformer". In an autoformer, the primary and secondary windings are electrically connected; there's continuity across the autoformer - but not from the primary to the secondary of an isolating transformer. That's the trick, I imagine, in the SDA application. The music flows through the transformer, but the ground is broken. No short circuit to the amp. That's my guess.

As an aside, the power transformer in modern AC-powered equipment serves the important role of ISOLATION of the equipment from the AC "mains" powering it! In the old days, to save money, many TVs and radios used power transformer-less "AC/DC" circuits for their power (the classic example is the "All American 5" 5-tube AM radio found in zillions of American kitchens in the 1950s and 1960s). Since there is no isolating power transformer... when these are plugged in, there is a 50-50 chance that the whole chassis of the radio is "hot" (connected to your town's AC power grid). Stand on a damp basement floor in bare feet and touch a metal part on such a "killer" radio or TV... and death by electrocution is a very real possibility.

(ahh, the good old days...)

FTGV

drumminman wrote: »

Do you have any idea how the AI-1 interface effects this problem? Is it the same DC blocking feature that prevents melt down?

I assume using the IC creates a dead short between the negative outputs of each channel.Since the negative output of non common ground amps is not at ground potential but an inverse of the postive signal, shorting them together would be as undesirable as shorting the two positive terminals together.Using the transformer allows signal transfer while isolating the negative ouputs from each other.

drumminman

As an aside, the power transformer in modern AC-powered equipment serves the important role of ISOLATION of the equipment from the AC "mains" powering it! In the old days, to save money, many TVs and radios used power transformer-less "AC/DC" circuits for their power (the classic example is the "All American 5" 5-tube AM radio found in zillions of American kitchens in the 1950s and 1960s). Since there is no isolating power transformer... when these are plugged in, there is a 50-50 chance that the whole chassis of the radio is "hot" (connected to your town's AC power grid). Stand on a damp basement floor in bare feet and touch a metal part on such a "killer" radio or TV... and death by electrocution is a very real possibility.

(ahh, the good old days...)

I think we had one of those radios when I was a kid in the 50's! No kidding! The top of the case broke and I remember looking inside and seeing all these glowing tubes - :eek: Glad I never reached inside!

Thanks for the education mhardy and FTGV.

mhardy6647

FTGV's answer was more correct than mine and its signal to noise ratio was higher! :-P

heiney9

FTGV wrote: »

I assume using the IC creates a dead short between the negative outputs of each channel.Since the negative output of non common ground amps is not at ground potential but an inverse of the postive signal, shorting them together would be as undesirable as shorting the two positive terminals together.Using the transformer allows signal transfer while isolating the negative ouputs from each other.

So in a sense part of the signal is transformer coupled? I still need to understand why this results in an improvement in sound for a common ground amp. Is it likely because of a better grounding scheme with the isolation transformer? It seems more cables and a transformer in the signal path isn't what would be desired. I wonder if the improvement is amp dependant? Again talking using the isolation transformer with a common ground amp.

H9

drumminman

heiney9 wrote: »

So in a sense part of the signal is transformer coupled? I still need to understand why this results in an improvement in sound for a common ground amp. Is it likely because of a better grounding scheme with the isolation transformer? It seems more cables and a transformer in the signal path isn't what would be desired. I wonder if the improvement is amp dependant? Again talking using the isolation transformer with a common ground amp.

H9

I'm guessing it is a better grounding scheme as the sound is stronger, cleaner and clearer with better imaging. It sounds like a layer of noise (that I didn't realize was there) has been removed. Don't know if this helps, but see post #6 for why I thought it might be worthwhile:

http://www.polkaudio.com/forums/showthread.php?129134-AI-1-Dreadnought-with-common-ground-amp

Is your Pass Aleph common ground?

heiney9

drumminman wrote: »

I'm guessing it is a better grounding scheme as the sound is stronger, cleaner and clearer with better imaging. It sounds like a layer of noise (that I didn't realize was there) has been removed. Don't know if this helps, but see post #6 for why I thought it might be worthwhile:

http://www.polkaudio.com/forums/showthread.php?129134-AI-1-Dreadnought-with-common-ground-amp

Is your Pass Aleph common ground?

Yes it is and I am a believer that less in the signal path is better so I need a better understanding about why this seems to improve a common ground amp. I could see if you had a lesser designed amp or receiver that didn't do the ultimate to isolate the grounds for best performance. But on higher end amps I would assume the ground is as good as it could be, I maybe wrong however.

H9

P.s. I'm sure if I built one and it didn't improve anything I'd have no problem selling it for what I have in it.

drumminman

heiney9 wrote: »

Yes it is and I am a believer that less in the signal path is better so I need a better understanding about why this seems to improve a common ground amp. I could see if you had a lesser designed amp or receiver that didn't do the ultimate to isolate the grounds for best performance. But on higher end amps I would assume the ground is as good as it could be, I maybe wrong however.

H9

P.s. I'm sure if I built one and it didn't improve anything I'd have no problem selling it for what I have in it.

No, I don't think you would. It's not difficult to build, and some folks would rather buy than DIY. One thing I should mention is I have power conditioning on most everything in my system: balanced isolation transformer for digital, separate isolation transformer for tube linestage, separate iso transformer for subwoofer, separate 1.5 kva balanced iso tranformer for power amp. Everything is fed clean power and with the Dreadnought connected it was still an easy to hear improvement.

You know you're curious, and you'll never know unless. . .

heiney9

If I build one, then the next time a pair of Pass Aleph 60 mono's come up FS I can pull the trigger easier. Or if I decide to get the Pass XA-30.5 amp, which is not common ground. I'll already have the Dreadnaught......lol

H9

heiney9

drumminman wrote: »

No, I don't think you would. It's not difficult to build, and some folks would rather buy than DIY. One thing I should mention is I have power conditioning on most everything in my system: balanced isolation transformer for digital, separate isolation transformer for tube linestage, separate iso transformer for subwoofer, separate 1.5 kva balanced iso tranformer for power amp. Everything is fed clean power and with the Dreadnought connected it was still an easy to hear improvement.

You know you're curious, and you'll never know unless. . .

Conditioning and isolation outside the gear doesn't fix a poorly designed piece of gear with regards to it's ground scheme internally.

H9

drumminman

heiney9 wrote: »

If I build one, then the next time a pair of Pass Aleph 60 mono's come up FS I can pull the trigger easier. Or if I decide to get the Pass XA-30.5 amp, which is not common ground. I'll already have the Dreadnaught......lol

H9

That was part of my original thinking, it would make the upgrade path easier. But now I want to live with this for a while, let it fully burn in and hear how good it gets.

thsmith

Is it possible people are hearing improvments in SQ with DN because they are using better cables vs what they were using between the speakers previously?

I know the AQ T4 I am using vs OEM P/B cable has made a very positive improvement in SQ.

Just a thought.

mhardy6647

Not to change the subject (who? me?)... but, just for shoots and googles, here are a completely random couple of "AA5" radios... from the collection :-P

Joe08867

Mhardy, we had the Motorola on the right. I remember getting zapped by that sucker a few times. Now I know why my dad had me change the station all the time. Nice huh?

My only guess on why the dreadnought might make things better is silence. The transformer is so isolated from any other gear that it would in effect make no noise at all. In that case it would only let a purer sound through to the drivers. Plus don't the grounds on the Aleph get coupled to the transformers?

mhardy6647

They're both Motorolas, interestingly enough. Try as I might, I cannot figure out how to send a text message or take a photo with either one of them...

My work is done here :-P Back to the original topic (about which I, rather obviously and unfortunately, know nothing).

FTGV

heiney9 wrote: »

So in a sense part of the signal is transformer coupled?

Correct.

I still need to understand why this results in an improvement in sound for a common ground amp.

Nor do I if it's connected like I think.With a common ground amp the grounds would still be interconnected through the transformers windings.

heiney9

Fred, do you think perhaps this results in an improvement for an amp whose grounding scheme isn't optimized vs. an amp that has an optimized grounding scheme. Just grasping in the dark here as to why there would be an improvement for a common ground amp.

H9

drumminman

Is it possible people are hearing improvments in SQ with DN because they are using better cables vs what they were using between the speakers previously?

I know the AQ T4 I am using vs OEM P/B cable has made a very positive improvement in SQ.

Just a thought.

In my experience, better SDA IC cables improve the SDA effect and clarity. With my DN I used an inferior cable geometry for initial listening just to get everything hooked up, and I still experienced the improvements I described in the other post. Then I cut into two pieces my better cable and connected it and the sound was a little better still. More of what I found appealing.

Fred, do you think perhaps this results in an improvement for an amp whose grounding scheme isn't optimized vs. an amp that has an optimized grounding scheme. Just grasping in the dark here as to why there would be an improvement for a common ground amp.


I'm afraid my knowledge of amp design is not enough to give you an answer. I had a serious listening session last night with one of my go to CD's, Susan Tedeschi, and Yes "Close to The Edge". No question the improvement is there and very consistent. The amp sounds like it simply has more power and better control. I also noticed last night that since I installed my better SDA IC cable, the soundstage is a little wider, especially on the left, with the front to back depth maybe slightly more enhanced.

My guess is if the DC (or other electrical grunge) riding with the signal is not being passed by the AI-1 transformer, but the audio signal is, the improvement would be from the amps grounding scheme not having to deal with this. Even though it may be designed for it, removing it before it gets to the amp seems like it would be a better strategy than dealing with it once it reaches the amp.

Maybe we can get someone with more knowledge to post about this - hey Darqueknight, what do you say?

drumminman

mhardy6647 wrote: »

Not to change the subject (who? me?)... but, just for shoots and googles, here are a completely random couple of "AA5" radios... from the collection :-P

We had a GE, and it looked similar to the Motorola on the right. Even the same '50's turquoise!

FTGV

drumminman wrote: »

My guess is if the DC (or other electrical grunge) riding with the signal is not being passed by the AI-1 transformer, but the audio signal is, the improvement would be from the amps grounding scheme not having to deal with this. Even though it may be designed for it, removing it before it gets to the amp seems like it would be a better strategy than dealing with it once it reaches the amp.

Are you hearing a greater contribution from the dimensional drivers when the DN is used in combination with the common ground amp?I ask because while I may be missing something it appears to me that with that config you are effectively tieing the dimensional negative connection to the stereo sections negative(ground) via the transformer winding.If this were the case the dimensional drivers would no longer be producing the SDA(R-L L-R) signal but the stereo signal as the dimensional array would be operating in parallel with the stereo array.

drumminman

FTGV wrote: »

Are you hearing a greater contribution from the dimensional drivers when the DN is used in combination with the common ground amp?I ask because while I may be missing something it appears to me that with that config you are effectively tieing the dimensional negative connection to the stereo sections negative(ground) via the transformer winding.If this were the case the dimensional drivers would no longer be producing the SDA(R-L L-R) signal but the stereo signal as the dimensional array would be operating in parallel with the stereo array.

The SDA effect sounds enhanced and slightly more balanced (even) and wider horizontally. It's deeper front to back than before, with a strong center image (that's unchanged).