How autoformers work?

[thanhh]

Hi, could someone please tell me how this works? How does it affect the sound? The reason I'm asking is I found out that 1 supplier used these on a pair of Magnepan 1.7 speakers at Melbourne Hifi Show on Oct 2019 (it's in Australia ). The general consensus on StereoNet is everyone loves how they sound. The description below sounds reasonable but I'm not sure if I can trust anything in manufactures' description. TIA.

"It is well understood the importance of getting a well matched amplifier for your speakers, or vice versa; getting the proper speakers for your amplifier. Now you can make virtually any amp/speaker combination work well together with the ZEROs.

The ZEROs are the simplest type of transformer called an auto transformer or autoformer. They are used to multiply the impedance of any speaker so that it "feels" like the optimum load for the amplifier being used. They are very helpful in matching speakers to amplifiers. By adjusting the speaker's impedance, both the damping factor and the maximum power transfer of the amp/speaker can be tailored for best sound. Almost all amplifiers sound better when driving a higher impedance speaker, simply because amplifiers produce less distortion when driving less current.

Made of the same original toroidal autoformer; has the ability to multiply a speakers impedance by 2x, 3x, or 4x. For example, the ZERO can transform a 4 ohm speaker into an 8 ohm, 12 ohm, or 16 ohm speaker depending on which two of four leads/connections are connected to the amplifier. They are very helpful in matching speakers to amplifiers, even amplifiers that already have a variety of output taps available realise benefits."

 

[Sir Sanders Zingmore]

there's a thread on StereoNet about this

https://www.stereo.net.au/forums/to...e-of-speakers/?do=findComment&comment=3750377

 

[RayDunzl]

https://www.communitypro.com/sites/default/files/Autoformer Tech Note_v2.pdf

https://www.plitron.com/custom-toroidal-transformers/custom-autoformers/

https://www.electronics-tutorials.ws/transformer/auto-transformer.html

 

[thanhh]

I read through the post and not much clear explanation on how it affects the sound. Some said it's ok for low impedance speakers only. I'm just curious why lots of people were impressed with that setup regarding sound while most of them didn't know autoformers being used.

 

[RayDunzl]

It's an impedance matching device.

Not so much a magical sound producing device.

If well designed, I wouldn't expect a change in sound, other than the amplifier and speaker can operate within their separate, and possibly otherwise mismatched, limits.

Lowering the output voltage relative to the input would create the potential for higher current, if that is what is needed for a low impedance speaker.

Increasing the output voltage relative to the input would decrease the potential output current, but a high-impedance speaker may want more voltage.

 

[Sir Sanders Zingmore]

I read through the post and not much clear explanation on how it affects the sound. Some said it's ok for low impedance speakers only. I'm just curious why lots of people were impressed with that setup regarding sound while most of them didn't know autoformers being used.

Bill Mclean, who is the Maggie distributor in Australia always has an impressive setup. He treats the room (as much as you can in those tiny hotel rooms) and often uses a DEQX for digital room correction.

Given that people are listening to unfamiliar equipment in an unfamiliar room I'm always puzzled that they can say things like "that autoformer sounded good".

 

[thanhh]

Thanks @RayDunzl Do they only work with low impendance speakers or it doesn't matter? It sounds like a good companion for my Maggies to run on couple of vintage amplifiers that I have.

 

[thanhh]

Bill Mclean, who is the Maggie distributor in Australia always has an impressive setup. He treats the room (as much as you can in those tiny hotel rooms) and often uses a DEQX for digital room correction.

Given that people are listening to unfamiliar equipment in an unfamiliar room I'm always puzzled that they can say things like "that autoformer sounded good".

Hi, I don't think they said that autoformers sounded good. Sorry I didn't make it clear. It's just veryone being impressed with Bill's setup and some didn't even know the autoformers were there. That's why I'm curious to know if the autoformers had any roles in it. Also. I don't think Bill used DEQX last time on that show.

 

[RayDunzl]

Thanks @RayDunzl Do they only work with low impendance speakers or it doesn't matter? It sounds like a good companion for my Maggies to run on couple of vintage amplifiers that I have.

What is the problem you are trying to solve?

 

[thanhh]

I have a few vintage amps that rated for 8 and 6Ohm only. So I think I cannot use it with my Maggies.
EDIT: I also want to know if I can use them on my Kef Q900 as well.

 

[Sir Sanders Zingmore]

Hi, I don't think they said that autoformers sounded good. Sorry I didn't make it clear. It's just veryone being impressed with Bill's setup and some didn't even know the autoformers were there. That's why I'm curious to know if the autoformers had any roles in it. Also. I don't think Bill used DEQX last time on that show.

Understood

Hard to know what the autoformers added/took away from the sound.

But people are always impressed with Bill's setup - every year. DEQX or not, he takes a great deal of care setting up his room - I'm pretty sure he measures for optimal positioning.
His music choice is great, he's a very friendly chap. It all adds up to a good experience.

In your situation, maybe he can lend you some autoformers to try?
However, I suspect a better option would be to get an amp that is more suitable

 

[Blumlein 88]

These were a fad for awhile used with ESLs. Made it more amplifier friendly. I never used any. I've used McIntosh amps with autoformers. Those allow you to pick a tap for the speaker impedance and get the same power (more or less) out of the amp for any load while optimizing the amps happiness.

I think they'd work for Maggies for the OP's purpose. Of course Maggies being mostly resistive it is quite possible his vintage amps though not rated for 4 ohms would be okay with Maggies.

Care to be more specific about your vintage amps @thanhh

I thought it was humorous that a common customer was an Atmosphere OTL owner. What makes an OTL work, well making it no longer transformerless. I agree the Atmo-Sphere OTLs have no real current capability, and these are just the ticket.

But these are genuine useful products. Not some snake oil high end product. Autoformers do work.

Of course people don't like my idea of feeding OTLs or SET's into the input of beefy transparent SS amps to get the sound of these other amps to your speakers. But it works really well.

 

[thanhh]

Thanks @Blumlein 88 I have an Yamaha CA 810. To me it sounds just as good as my other vintage Sony TA F555ESX (Japanese version of F800ES). The only thing is it’s not recommended for 4ohm speakers. Both my Maggies and Kef are recommended to use with 4ohm amps. I just like the Yamaha better because it has VU meter
I’ve also got a Crown XLS 2002 to drive the Maggies daily. If these autoformers can help the Yamaha to drive my speakers without affecting the sound then it would be great.

 

[RayDunzl]

I have an Yamaha CA 810.

Just don't push it real hard, you should be fine.

It has A and B speaker outputs. If using two pair of 8ohm speakers that would be a 4 ohm load.

Manual attached below.

 

[thanhh]

I tried the Yamaha amp with the Maggies and it sounds dull and flat (not in FR but almost like no sound stage). It sounds worse than the Maggies on my 30W Cayin tube amp. I asked the previous owner who is a retired tube amp tech, he told me that he found the Yamaha got a weird impedance characteristic when using with 4omh required speakers. He did not elaborate on that so that's a far as I know about this amp.

 

[restorer-john]

I have an Yamaha CA 810. To me it sounds just as good as my other vintage Sony TA F555ESX (Japanese version of F800ES).

The CA-810 and the TAF-555esX couldn't be more different in terms of ability into low impedances.

The Sony (I've got several of that series 333esR/730es/444esXII/555esX) will absolutely obliterate the CA-810 into 4 and even 2 ohms. Last time I tested the 333esR it achieved 312W/ch (single channel driven) into 2 ohms. Yes, 2 ohms continuous. Around 195W/ch @4R both channels driven and over 120w/ch @8R continuous. Your 555 is essentially the same topology with a bigger transformer.

The Yamaha really struggles into low impedances due to very aggressive current limiting. Which is due to there simply not being enough SOAR in silicon. Lovely amplifier to look at, but it rolls off by design at each end of the spectrum.

The Sony is ruler flat, fast and powerful- the Yamaha CA-810 is the opposite.

Took the opportunity to do a subtle conversion to LEDs as the original Yamaha illumination is and was always dreadful and only gets worse with age.

 

[ajawamnet]

Hi, could someone please tell me how this works? How does it affect the sound? The reason I'm asking is I found out that 1 supplier used these on a pair of Magnepan 1.7 speakers at Melbourne Hifi Show on Oct 2019 (it's in Australia ). The general consensus on StereoNet is everyone loves how they sound. The description below sounds reasonable but I'm not sure if I can trust anything in manufactures' description. TIA.

View attachment 42294
"It is well understood the importance of getting a well matched amplifier for your speakers, or vice versa; getting the proper speakers for your amplifier. Now you can make virtually any amp/speaker combination work well together with the ZEROs.

The ZEROs are the simplest type of transformer called an auto transformer or autoformer. They are used to multiply the impedance of any speaker so that it "feels" like the optimum load for the amplifier being used. They are very helpful in matching speakers to amplifiers. By adjusting the speaker's impedance, both the damping factor and the maximum power transfer of the amp/speaker can be tailored for best sound. Almost all amplifiers sound better when driving a higher impedance speaker, simply because amplifiers produce less distortion when driving less current.

Made of the same original toroidal autoformer; has the ability to multiply a speakers impedance by 2x, 3x, or 4x. For example, the ZERO can transform a 4 ohm speaker into an 8 ohm, 12 ohm, or 16 ohm speaker depending on which two of four leads/connections are connected to the amplifier. They are very helpful in matching speakers to amplifiers, even amplifiers that already have a variety of output taps available realise benefits."

https://en.wikipedia.org/wiki/Autotransformer

Where it states:
"In audio applications, tapped autotransformers are used to adapt speakers to constant-voltage audio distribution systems ..."

is the only time I ever used them for speakers was for running reentrant horns:

up and down the Allegheny River for the Three Rivers Regatta. We needed to get the amp outputs some silly distance to a ton of these. Worked well.

Also, at the bottom of the wiki thing:

used these on FM transmitters for filament voltages:

And used the variac as a bench tech for bringing up gear slowly; tho a lot of stuff really didn't dig that so much - why we also used lightbulb feeding an AC outlet. Still do the later - you can see them on a vid I did when testing an audio interface - they're up at the right hand corner:

 

[thanhh]

The CA-810 and the TAF-555esX couldn't be more different in terms of ability into low impedances.

The Sony (I've got several of that series 333esR/730es/444esXII/555esX) will absolutely obliterate the CA-810 into 4 and even 2 ohms. Last time I tested the 333esR it achieved 312W/ch (single channel driven) into 2 ohms. Yes, 2 ohms continuous. Around 195W/ch @4R both channels driven and over 120w/ch @8R continuous. Your 555 is essentially the same topology with a bigger transformer.

The Yamaha really struggles into low impedances due to very aggressive current limiting. Which is due to there simply not being enough SOAR in silicon. Lovely amplifier to look at, but it rolls off by design at each end of the spectrum.

The Sony is ruler flat, fast and powerful- the Yamaha CA-810 is the opposite.

Took the opportunity to do a subtle conversion to LEDs as the original Yamaha illumination is and was always dreadful and only gets worse with age.

Thanks so much @restorer-john for the information. It's just the Sony has been having this weird problem lately. 1 channel gets quieter the more I turn up the volume. At 12 o'clock volume, 2 channels sound the same, but at 4 o'clock volume, I have to turn the balance pot to 2 o'clock to get the same volume both channels. Anything I should look at first before taking this heavy thing to the amp tech. I hate to move this amp, too heavy for me

 

[OldJong]

My understanding is that Autoformers like the Zero( not those used by McIntosh) help tube amps deal with difficult speaker loads that have low impedance.

Would love for someone to send Amir a couple of Zeroes

 

[Tom C]

These were a fad for awhile used with ESLs. Made it more amplifier friendly. I never used any. I've used McIntosh amps with autoformers. Those allow you to pick a tap for the speaker impedance and get the same power (more or less) out of the amp for any load while optimizing the amps happiness.

I think they'd work for Maggies for the OP's purpose. Of course Maggies being mostly resistive it is quite possible his vintage amps though not rated for 4 ohms would be okay with Maggies.

Care to be more specific about your vintage amps @thanhh

I thought it was humorous that a common customer was an Atmosphere OTL owner. What makes an OTL work, well making it no longer transformerless. I agree the Atmo-Sphere OTLs have no real current capability, and these are just the ticket.

But these are genuine useful products. Not some snake oil high end product. Autoformers do work.

Of course people don't like my idea of feeding OTLs or SET's into the input of beefy transparent SS amps to get the sound of these other amps to your speakers. But it works really well.

Interesting notion, that I never thought or heard of before. Might be fun!