The AI-1 Dreadnought Project Pt.1

nspindel · January 2012

Larry, can you do all the same drillouts as you? I've got some spikes that I'd use, and will use binding posts just like you.

nspindel · January 2012

How much are they?

nspindel · January 2012

I'm in, sir Larry. PM me payment details.

huy · January 2012

Schurkey wrote: »

With a normal SDA, a bit of the "Left" channel electricity gets routed to the "Right" speaker, and returns to the amplifier through the right side wiring. Same on the other side--some of the Right side electricity gets routed to the left speaker, and returns to the amp through the left side wiring. If the amp is common ground, the stray bits of left and right electricity can find their way home using the chassis ground.

If the amp is not common-ground, the stray bits of electricity stay lost and angry, and cause problems with the amp, the speakers, or both.

Adding an isolation transformer (doesn't have to be toroidal) in the SDA cable assures that the left electricity never truly gets routed to the right speaker, and the right electricity never truly gets routed to the left speaker, all the electricity gets routed the correct channel of the amp, and therefore it doesn't need a common ground in the amp to find it's way home. No angry electricity, no problems for amp and speakers.

The transformer can only be used on SDA speakers new enough to use a single conductor between left and right; older speakers used two conductors. The difference is usually (not always) apparent by the style of SDA cable connector, twin blades would NOT be compatible with the AI-1 transformer, a pin and a blade is.

Schurkey,

Thank you. Could you list the minimum required specification of transformer?
I have a SDA cable made by Ben, have only one conductor (pin). How this can be worked without negative terminal (blade)?

FTGV · January 2012

huy wrote: »

Could you help me to explain why AI-1 can help non common ground amp works with SDA speakers?

....Nvm.Brain ****.

Btw. those custom chassis would be excellent for a small DIY amp.

Schurkey · January 2012

huy wrote: »

Could you list the minimum required specification of transformer?

The AI-1 as manufactured and sold by Polk had a tiny-**** transformer good for .13 amperes. The D-I-Y "Dreadnaught" project as spec'd by DarqueKnight has a transformer rated for nearly 7 amperes.

Matthew Himself suggested a transformer having a minimum of 5 amps capacity. He lists several desirable electrical characteristics and they're in the first post of DarqueKnight's Dreadnaught thread. (THIS thread! Worth studying from the beginning...)

A couple of years ago, Matthew Polk provided the following specifications for a toroidal transformer based AI-1:

"1. DC Resistance of primary and secondary should be less than 0.8 ohms and preferably less than 0.5 ohms. The lower the better.

2. Inductance of both primary and secondary should be at least 10mH. Ideal is around 14mH.

3. Current capacity to saturation should be 5 Amps minimum.

4. Of course the turns ratio is 1:1."

So transformers from .13 amps and up can be suitable; but bigger is better. The usual transformer-of-choice has more than ten times the suggested inductance. Nobody seems to care about that, and everyone seems to think the big transformer sounds just fine.

Many isolation transformers have a turns ratio of ALMOST 1:1; again this doesn't seem to get in the way of good sound. Theoretically, it would result in a slight bias to one channel. In practice--I guess it's just not that noticeable.

huy wrote: »

I have a SDA cable made by Ben, have only one conductor (pin). How this can be worked without negative terminal (blade)?

Cut the cable somewhere in the middle, attach each end to the transformer windings. You'll need to connect the other end of the transformer winding to the speaker - terminal (or to the blade terminal of the interconnect connector) with an additional length of wire on each side.

There's instructions for making an AI-1 hosted on this site. The transformer part numbers are long discontinued, but direct replacements are available--but if you're going to make the effort to do this, you'd want to use a larger transformer anyway.
(Post #6 of the following thread:)

http://www.polkaudio.com/forums/showthread.php?55888-POLK-AUDIO-Speaker-Wiring-Schematics-amp-More-Stereo-Dimensional-Array%28SDA%29

huy · January 2012

Schurkey,

Thank you very much. I am going to order isolate transformer from Toroid Corporation, the part number: 782.1202

Power (VA): 820
RATED PRIMARY CURRENT: 7.40/3.70A
Prim. 2x117V 50/60Hz
Sec. 2x117V / 3.5A

Schurkey · January 2012

I am going to order isolate transformer from Toroid Corporation, the part number: 782.1202

Power (VA): 820
RATED PRIMARY CURRENT: 7.40/3.70A
Prim. 2x117V 50/60Hz
Sec. 2x117V / 3.5A

http://www.toroid.com/standard_transformers/isolation_transformers/isolation_commercial.htm

Can that be real??? A bigass toroid that might be suitable for a "Dreadnaught" style AI-1, and it's MADE IN USA instead of the Avel being sourced from Communist China?

The price isn't even that much more than the Avel.

DarqueKnight · January 2012

I'll take it. I need to build a Dreadnought for a pair of CRS+'s.

headrott · January 2012

Ray, what do you think of the toroid that huy is using for his AI-1? Would you consider it better the same or worse than the Avel Lindberg one?

Thanks for the update on the cases Larry.

Greg

DarqueKnight · January 2012

headrott wrote: »

Ray, what do you think of the toroid that huy is using for his AI-1? Would you consider it better the same or worse than the Avel Lindberg one?

The TCM transformer's specs look good. I don't have any other information to make a valid comparison. TCM and AnTek were two other companies I considered when shopping for isolation transformers. Neither company responded to my (repeated) email inquiries. A-L typically responded to emails within 24 hours. I was also able to talk to knowledgeable people at A-L by phone.

The transformers at TCM and AnTek may be ten times better than the ones from A-L, but I'll never know because I don't like spending money with people who won't answer my questions.

headrott · January 2012

DarqueKnight wrote: »

The TCM transformer's specs look good. I don't have any other information to make a valid comparison. TCM and AnTek were two other companies I considered when shopping for isolation transformers. Neither company responded to my (repeated) email inquiries. A-L typically responded to emails within 24 hours. I was also able to talk to knowledgeable people at A-L by phone.

The transformers at TCM and AnTek may be ten times better than the ones from A-L, but I'll never know because I don't like spending money with people who won't answer my questions.

It seemed to me (from the somewhat limited specs on their page) that the TCM transformer would be better than the Antek one. How unfortunate that TCM did not respond to you though Ray. I would much prefer a USA (or Japan, Germany or England) made transformer to a Chinese made one, despite Avel Lindberg's good rep. Thank you for the reply Ray. I wonder if huy was able to get a hold of TCM?

What say you huy? Were you able to get a hold of TCM before deciding to order their transformer? Did you get a more detailed spec. sheet from them on the part #782.1202 transformer?

Anyway, I cannot complain about the Avel Lindberg transformer that is in my AI-1 now as it has worked flawlessly for almost 2 years now (which is not extremely long, but when I have seen multiple Chinese electronic equipment pieces go out after a few months that's saying something). With getting Larry's new case though I wouldlike to try another transformer and was thinking of the TCM one. I will try to contact them and hopefully they will actually respond this time. I'll let you know.

Greg

headrott · January 2012

Schurkey wrote: »

Many isolation transformers have a turns ratio of ALMOST 1:1; again this doesn't seem to get in the way of good sound. Theoretically, it would result in a slight bias to one channel. In practice--I guess it's just not that noticeable

I am not sure if it is me, the mixing of most CD's or possibly but not likely, my room but I do notice a slightly exaggerated SDA effect from the left channel and slightly underexaggerated in the right. I say slightly as it's not exaggerated very much at all, but I noticed it since installing the AI-1. As I said, it could just be me. But, if as you say most isolation transformers are not truely 1:1 turns ratio this could be why.

Greg

F1nut · January 2012

I see they are located in Salisbury, MD. I drive thru there from time to time, maybe I should stop in and tell them to get their act together.

About the channel bias. I read a comment from a recording engineer not long ago in which he stated something to the effect that recordings are always biased ever so slightly to the left channel. If someone wants dig into that further, please be my guest.

headrott · February 2012

F1nut wrote: »

I see they are located in Salisbury, MD. I drive thru there from time to time, maybe I should stop in and tell them to get their act together.

Please do Jesse. I'd appreciate it greatly. Also, while you are at it get a copy of the data sheet for the 782.1202 transformer too.

F1nut wrote: »

About the channel bias. I read a comment from a recording engineer not long ago in which he stated something to the effect that recordings are always biased ever so slightly to the left channel. If someone wants dig into that further, please be my guest.

Interesting, so it may be do to the mixing process. I think I remember my brother mentioning this too now that you say it. My brother went to the Recording Arts Institute in Arizona and interned at Teatro Studios under Mark Howard in Southern California. I will do a search about it. Thanks Jesse for supporting what I heard from the SDA effect and the AI-1 I built. Has anyone else heard this bias who has built an AI-1 or has used the Polk AI-1? It's starting to make sense as I heard the bias from my AI-1 using the 2B's, 3.1TL's and the 2.3TL's?

Greg

huy · February 2012

I didn't have TCM transfomer before. I will contact them shortly.

@F1nut,
I'd appreciate your help to check with TCM.

drumminman · February 2012

F1nut wrote: »

I see they are located in Salisbury, MD. I drive thru there from time to time, maybe I should stop in and tell them to get their act together.

About the channel bias. I read a comment from a recording engineer not long ago in which he stated something to the effect that recordings are always biased ever so slightly to the left channel. If someone wants dig into that further, please be my guest.

Interesting re: channel bias. I've noticed this too. I thought it was something with my front end, like a weak tube or something.

thsmith · February 2012

Larry, if you ever build anymore or someone backs out I will take one. However, I think I missed the boat on these.

Big Dawg · February 2012

thsmith wrote: »

Larry, if you ever build anymore or someone backs out I will take one. However, I think I missed the boat on these.

And for me in line after Tracey (if at all), please.

DarqueKnight · February 2012

headrott wrote: »

I am not sure if it is me, the mixing of most CD's or possibly but not likely, my room but I do notice a slightly exaggerated SDA effect from the left channel and slightly underexaggerated in the right. I say slightly as it's not exaggerated very much at all, but I noticed it since installing the AI-1. As I said, it could just be me. But, if as you say most isolation transformers are not truely 1:1 turns ratio this could be why.

I have not heard, or measured, any difference in output levels between the left and right channels when playing mono music or using test signals. See post #62 in this thread.

headrott wrote: »

It seemed to me (from the somewhat limited specs on their page) that the TCM transformer would be better than the Antek one. How unfortunate that TCM did not respond to you though Ray.

I assume they sell enough that they can't be pestered with audiophile concerns such as the type of copper used, dielectric properties of the insulation, lead gauge, coil inductance, etc. All those things can have an effect on sound quality.

headrott wrote: »

I would much prefer a USA (or Japan, Germany or England) made transformer to a Chinese made one, despite Avel Lindberg's good rep.

Chinese contract manufacturers build to the specifications set by their American clients. I don't understand the bad rap the Chinese contract manufacturers get when all they are doing is fulfilling their American clients' manufacturing specifications.

headrott · February 2012

DarqueKnight wrote: »

Chinese contract manufacturers build to the specifications set by their American clients. I don't understand the bad rap the Chinese contract manufacturers get when all they are doing is fulfilling their American clients' manufacturing specifications.

It's not the specifications that are the problem Ray (from my experience). It is the build quality; that is, the actual assembling done in the Chinese factories. This is true for the anything from shoes to toasters to DVD players. The American clients set the specifications (in the case of electronics) and the Chinese factories build them to those electrical specifications, but the actual solder joints as an example that are in question. Electrically it may meet the American clients specs, but physically the solder joints are poorly done (there are exceptions to this of course). In other words, the solder joint will pass the signal fine for a while, but given enough time it will faill and your electronic equipment will fail. This has been what I have expreienced seeing this first hand with cheap Chinese made $59.00 DVD players or even higher priced Pioneer recievers made in China.

My motive is not say that China is bad and America, Japan, Germany and England rule! My motive is that from my personal experience with multiple items made in China that they don't last as long as American, Japanese, Eglish or German made items.

Greg

heiney9 · February 2012

I would speculate that 85% of most consumer goods come from China. American spec'd products built and assembled in China. If there was such shoddy work I doubt all this time Americam companies would still be using China for assembly.

That's not to say there aren't more issues than if they were assembled here, just that China gets a bad rap and these days it's not as well deserved as it was say 10 years ago. I still prefer to buy American, but even American made stuff has issues unless you buying higher end products in which you pay 3-5-10X more for. With the extra cost comes the expectation of higher quality.

Not wanting to take this off topic and I'm not even all that much pro-China...........but I get tired of hearing the "poor quality" parroted over and over.

H9

headrott · February 2012

Brock, I've been "parroting" this about Chinese made goods for about 20 years now. The reason American companies still use Chinese factories to produce thier products is because:
1) They make a bigger profit from them
2) People keep buying them even though they are (in general) made pooer and fail sooner. But, with the cheaper price people are apparently willing to buy another one to replace the one that failed.

If you make a bigger first sale profit and also end up selling more of the item due to a higher failure rate, plus people keep buying them of course American companies will continue to use China factories to assemble their products.

Greg

DarqueKnight · February 2012

headrott wrote: »

It's not the specifications that are the problem Ray (from my experience). It is the build quality; that is, the actual assembling done in the Chinese factories. This is true for the anything from shoes to toasters to DVD players. The American clients set the specifications (in the case of electronics) and the Chinese factories build them to those electrical specifications, but the actual solder joints as an example that are in question. Electrically it may meet the American clients specs, but physically the solder joints are poorly done (there are exceptions to this of course). In other words, the solder joint will pass the signal fine for a while, but given enough time it will faill and your electronic equipment will fail. This has been what I have expreienced seeing this first hand with cheap Chinese made $59.00 DVD players or even higher priced Pioneer recievers made in China.

Quality control and reliability are ultimately the American client company's responsibility. The buck cannot be passed back to the Chinese contract manufacturer if they are doing what they are contracted to do. A general contractor cannot pass the buck for poor construction quality back to his subcontractors. It is the GC's responsibility to make sure that the work of plumbers, carpenters, electricians, etc. is up to standards before a building is released to the customer.

If I get a bum product, where it was made is irrelevant to me...the entity whose name is on the product is responsible for quality and reliability.

heiney9 wrote: »

Not wanting to take this off topic and I'm not even all that much pro-China...........but I get tired of hearing the "poor quality" parroted over and over.

Same here.

headrott wrote: »

Brock, I've been "parroting" this about Chinese made goods for about 20 years now. The reason American companies still use Chinese factories to produce thier products is because:
1) They make a bigger profit from them
2) People keep buying them even though they are (in general) made pooer and fail sooner. But, with the cheaper price people are apparently willing to buy another one to replace the one that failed.

If you make a bigger first sale profit and also end up selling more of the item due to a higher failure rate, plus people keep buying them of course American companies will continue to use China factories to assemble their products.

OK then, if American companies are the ones selling products made in China (but built to American specs) and American consumers keep buying them...why is there a basis for a complaint against Chinese manufacturers?

heiney9 · February 2012

headrott wrote: »

Brock, I've been "parroting" this about Chinese made goods for about 20 years now. The reason American companies still use Chinese factories to produce thier products is because:
1) They make a bigger profit from them
2) People keep buying them even though they are (in general) made pooer and fail sooner. But, with the cheaper price people are apparently willing to buy another one to replace the one that failed.

If you make a bigger first sale profit and also end up selling more of the item due to a higher failure rate, plus people keep buying them of course American companies will continue to use China factories to assemble their products.

Greg

I have bought a lot of various items over the years for general use and I have rarely had anything flat out fail. I also am acutely aware you get what you pay for. I can't think of a single thing that failed before its expected life cycle. My last computer (A Dell) lasted 7 years of being on 24/7 before the power supply gave out. I bought a new power supply and that's now my secondary computer. I've had toasters, coffee makers, electric toothbrushes, lights, power tools, yard equipment, blenders, refrigerators, electric outdoor grills, window air conditioners, space heaters, point and shoot camera's, external hard drives, a host of other common items all assembled/made in China or Taiwan and I can't think of one time where it failed, caught fire, was dangerous, etc.

Again, I'm sure it happens but I don't think the blame is always because of the Country of origin. Sometimes the design is flawed.....the American design and spec is flawed.

Again, not trying to start a flame war............but in my experience I just don't see it as an issue. Now morally or politically that's a different story.

H9

headrott · February 2012

DarqueKnight wrote: »

OK then, if American companies are the ones selling products made in China (but built to American specs) and American consumers keep buying them...why is there a basis for a complaint against Chinese manufacturers?

Ray, I am blaming BOTH US companies and the Chinese manufacturers. IMO, they are both responsible. I agree completely that it's the US companies contracting the Chinese factories to manufacture their products that are ultimately responsible for the quality of product that is sold to customers. No question that is the case. But, it doesn't change the fact that Chinese made products are ultimately inferior to USA, Japan, German, and English made ones (in general, but not absolutely)and are produced by the Chinese manufacturing plants. Therefore, it is also the Chinese manufacturing plants that are paid to make products that are of usable quality for reasonable amount of time. That is what they are being paid for. My motive in saying don't buy Chinese made products doesn't come from trying to place blame soley on China for the outcome of producing a poorly made product. That is simply the result.

Ultimately it doesn't matter who is to blame for the inferior product, it's a matter of whether the product sells and how much it sells. If the product has poor quality but still sells in the millions that is the problem. It's also the consumers' fault for buying the poorly made products and then continuing to buy poorly made products after they fail quickly. If they sell, both the US and Chinese companies win and the looser is the consumer. Ideally, consumers would not purchase something unless it was well manufactured and consistantly (both diversity of products and quantity of products) lasted a reasonable amount of time.

Greg

headrott · February 2012

Sorry for the derail of the thread, not my intent. To get back on topic:

I recieved a reply from TCM (actually two because I forgot to ask about the purity of the copper and where it is sourced from). Here are the replies regarding part number: 782.1202.

Ming at TCM gave the following specs for the part:

DC resistance: Primaries in parallel: "will be about 0.27 ohms" Secondaries in parallel: "is about 0.413 ohms"
Winding inductance: "We do not measure the winding inductance. My guess is they are more than 10mH."
"The output current with both winding in parallel is 7A. By the way, higher current will not saturate the core. but will increase the temperature of the winding."
"The transformer can be wired to have 1:1 ratio under load."
The copper purity is: "But I know the copper purity will be over 99.5% or 99.9%."

I am still waiting for a reply as to who manufactures the copper wire for the toroid. I will post a reply when I recieve a response.

Greg

Schurkey · February 2012

headrott wrote: »

"The transformer can be wired to have 1:1 ratio under load."

Exactly the problem. Their idea of load is to plug the primary into house current, and run an electrical device--a motor or heating element or some such--from the secondary. The inefficiency of the transformer will result in less voltage on the secondary side, so they add a few windings to bring the voltage back up.

Used the way WE need, this would result in minor channel imbalance.

The figure I have for a certain non-toroid transformer is 1:1.04. MAYBE that's insignificant...

headrott · February 2012

Yeah, can't answer for sure if it's insignificant. To my ears I can hear a slight SDA imbalance to the left channel. Not sure if it's the transformer (although Ray said using a meter and listening in mono he couldn't see/hear any imbalance). As Jesse brought up, it could be due to mixing biased towards the left channel or some other factor. Whatever is causing the imbalance to the left channel is only very slight. I think it may be due to mixing as with some albums I don't notice the SDA imbalance as much.

I recieved another e-mail from Ming at TCM and he responded who makes the copper wire for the transformer saying "The manufacturer of the wire Superior Essex."

I also asked about the inductance of the transformer, but he responded "We do not have anything in stock right now. We can measure the inductance for you after your piece is made. Inductance of each transformer is not same."

So, huy if you already ordered a transformer from TCM can you have them measure the inductance before they ship it out to you?

Greg

huy · February 2012

Thank you Greg for all your valuable information. I will ask them.

The AI-1 Dreadnought Project Pt.1

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