What Shunyata and Furman (SMP) Have in common - Inductance!

Hi everyone,

I've been doing a little online research. The name that seems to come across here on audiogon regarding power conditioners is Shunyata, while @elizabeth and I talk Furman, especially due to cost.

I wanted to point out that what these two brands have in common is inductance. Coils. Coils in series with the outputs.

Furman and others who have licensed series mode surge protectors use great big coils to slow down surges long enough to let the surge protector react. Furman calls it SMP, but the tech has also been licensed to PS Audio and other makers. Essentially this is a low pass filter, which starts working at 3 kHz. That's way down in the audible range.

It's clear from pics of Shunyata's insides that they are using great big coils too. Why? Well, you can make a coil with high inductance, and low resistance at AC.

Anyway, my point is, these two brands share this basic principle. If you want to supplement a Shunyata by taking digital streaming outside of it (routers, wifi, etc) consider this super inexpensive Furman strip:


It's also a great starter conditioner, and the series surge suppression is unbeatable. Furman also has LiFT which I trust works but I've not investigated it very much. Furman makes a boatload of devices, so check for SMP and LiFT for the best noise suppression.

The PS Audio strip which uses series suppression is here:


Of course, saying these conditioners have the same principle is not the same as saying they work equally well or are best for your application. To your own ears be true!



Coils cause a time lag in the drawing of AC into the equipment!

I have found my Chang Lightspeed 709 CLS worked best, over other filters and AC regenerators.

You want LOW inductance!
Of course, saying these conditioners have the same principle is not the same as saying they work equally well or are best for your application. To your own ears be true!

Or as I like to say, I don't care if its made with bailing wire and bubble gum, long as it sounds good.
Coils cause a time lag in the drawing of AC into the equipment!

With a high enough L, XL drops to near zero and therefore the difference between current and voltage goes to zero as well.


No matter how big the coil inductance is, there still will be a small amount of sound smearing due to lag.

The conditioners you recommend are not always liked.
No matter how big the coil inductance is, there still will be a small amount of sound smearing due to lag.

Show your work.  The idea that lag in the power supply = smearing of audio needs more validation.


The proof is in listening.

Have you tried the Chang Lightspeed 709 CLS and compared it to other power line filters?
Hi @don_c55 You make a good argument, no I have not. Care to send me one? :)


Buy one for about $1300 from The Cable Company.

What you get is not just noise reduction and surge protection.

There are more details, warmer, more 3D, sonics, and much larger soundstage on my Magnepan 3.6.

These sonic improvements are buried in AC noise, and not apparent without the LightSpeed.

I also use a 709 in my home theater, and my HDTV has a brighter picture with more detail.
$1,300 is about 10x the cost of the basic Furman strip.

Glad you are happy, but that is most definitely out of my price range.

P.S. I just looked at a lot of pictures of the Chang units. Sure looks like they use a lot of coils to me!

@erik_squires. Always appreciate your input. Would there be a benefit putting a strip before my Equitech 2Q?  Any downside? My belief is that power cannot be too clean :)
@ptss I recommend a balanced approach.
Good acoustics first.

I also recommend, if you are concerned, keeping noise creating power supplies (switching wall warts) outside your clean power zone. It is convenient to use a conditioner with mulitple, isolated power banks.

If you don't have something like that, a Furman strip for your routers, streamers, etc. will keep that on the dirty side, and put an extra layer of AC filtering between your analog / linear gear and it.

Use inexpensive but shielded power cables.

Thanks Erik. My tv and internet cable service units use a wall wart. I got a nice improvement in sound and video by putting them on a separate transformer isolated circuit. 
@ptss If you use a coaxial cable into the home, consider a coax ground loop isolator.

They work great to remove ground loops, and sometimes (but not always) can clean up DAC's too. :) They're super cheap, like $20 or so. 

Sometimes a ground loop makes it into the digital pathways (unless you use optical) and this can help.


You are completely mistaken on all levels. Quit trying to duplicitously sell Furman products for your affiliate link money!

1) Furman does not license series mode surge technology. They were sued by Zero Surge - the originators and license owner of the series mode technology patent - and lost. Furman was forced to call their technology SMP (Series Multi-Stage Protection), which still uses MOVs. 


SurgeX, Brick Wall, and Torus Power are the only licensees of series mode technology that I'm aware of.

2) Shunyata does not use inductors. 


3) Where did you see a picture of a Chang Lightspeed with an inductor? "No use of inductive coils, which cause time lag in performance"


I could only see caps in the pictures I saw, that did not show the full circuits.
Hi Sadono,

As far as I know, the license/patent comes from Jack R. Harford / Electronic Systems Protection. Please post a link to any legal documents / reporting regarding licensing issues with Furman.


You are completely wrong about Furman SMP using MOV's, I've disassembled them. They do not use MOVs and they are very good. Please see their spec sheet.


In addition to Furman, SurgeX and Brick Wall, the other licensees I know of are PS Audio and McIntosh. Among those, McIntosh charges the most, followed by SurgeX for the same basic technology.  Furman is the most affordable in their $180 power strips.

In regards to Chang, I stand corrected, Chang advertises no coils in their tech. How pathetic, since that essentially means they can't block anything below RFI. Also, their claims are questionable. A well designed coil is a good thing, with no lag, unless you are a surge.   Please go spend tens of thousands of dollars on their gear if that makes you happy.


"Zero Surge® was incorporated in March 1989 by J. Rudy Harford." He is the founder, and was the former owner and president. And yes, he’s the license owner.


Look at the SMP circuit on the page you linked. Are you blind or clueless as to what a MOV looks like? There are clearly MOVs.


Still don’t believe me? "Furman’s Series Multi-Stage Protection Plus (SMP+) addresses some of the shortcomings of traditional MOV-based protectors by employing a variety of circuits to clamp, absorb, and dissipate transient voltages without having the device sacrifice itself. The company claims that MOVs used in a properly designed circuit will not fail.

Furman’s SMP+ circuitry takes pages from both shunt-and series- mode playbooks and adds its own twist. Along with a high-voltage MOV and a high-amperage thermo-fuse varistor, SMP+ uses a tuned circuit that includes series inductors, a bridge rectifier (which con- verts AC to DC power), and high-voltage capacitors."


"SMP allows Furman products to offer this protection without damaging any of their own internal components—that is, they are virtually non-sacrificial"


"• Zero Surge’s patented filter technology protects sensitive electronics from even worst case surges, repeatedly, without degradation or failure. MOV-free."


" • No sacrificial or wear components (no MOV’s)"


The series mode surge technology patent states, "Provides an inductor system as the first means of protection."

"A branch circuit SPD (Surge Protection Device) using an MOV in front of, in back of or sideways of, a small ferrite core series inductor, labeled as ’series something’, is in my opinion, a marketing persuasion by our competitors intended to ride on our back and confuse you, and the only way to promote a product ’looking like ours’ without violating our patents. Are you a Switch or a Filter?

An MOV is a semiconductor switch. Switches will wear out and can suddenly fail when stressed. The monitoring of these switching devices over time as ’functional’ is tedious and a guessing game at best. A filter properly designed for its application will not wear out and will only fail if misapplied. Think about your passive LC subwoofer crossovers...when will it wear out?...perhaps when you wire it up to 440V just for fun?...or when you listen to too much music?" Michael McCook, SurgeX International

Furman purposely added MOVs to create a hybrid surge protection device that does not violate the patent. Due to the patent, Furman can not call the design series mode technology, and renamed it SMP+ in 2005.

SurgeX does not have the same basic technology as other series mode designs. They have added ASM (Advanced Series Mode) technology. This adds an extra winding to the air-core inductor to further improve the surge protection and lower the let-through voltage.


You do seem right about McIntosh, as the MPC1500 appears to use series mode surge technology as a repackaged Torus. "Torus Power Technology under license from Plitron Manufacturing Inc."


What led you to believe that PS Audio licenses series mode technology? They use a circuit breaker, fuse, and MOVs for surge protection in the Power Plant regenerators. Paul McGowan does not like large inductors, and advertises how the Power Plant regenerators have low inductance.

Inductance is not good for transparent sound quality. It reduces current and rolls off the highs. Inductors are called chokes for a reason. I won’t deny that many people like them, as evidenced by people that find series mode technology transparent, and all of the Furman & Audioquest fans.
You can’t lump all Furman products together anymore than you can McIntosh and PS Audio. Some use series mode protection, and some use plain old MOVs.  You are misreading the article if you think that all Furman surge suppressors use MOV's. That's' not what they mean to say. They mean to say they sell products with a variety of features.

The products Furman labels as SMP are clearly series mode, non sacrificial components. I make that clear in my blog post that this is the key feature.

PS Audio constantly changes it’s product line. Based on their current web products it’s not clear if they are using series mode protection or not. It was clear in models no longer available on their web site.

Inductance is not good for transparent sound quality. It reduces current and rolls off the highs.

Only if you don’t know how to do AC analysis properly. If you believe this is universally true then you should be advocating the end to all linear power supplies.

Also, hard to tell if you like inductance or not. You seem to say that SurgeX is better than a Furman because they use MORE inductance, but then also want to take the position that all inductance is bad. Have to pick a side here.

Furman also ads LiFT to the strips I recommend, further lowering the noise floor, without adding inductance. That makes them better than a SurgeX, right??

They are specifically talking about the Furman products using the SMP circuit. It is laid out clearly in the circuit picture that it uses MOVs. The same circuit board is used in all Furman products with SMP. I’m sorry to burst your bubble, but it’s the truth.

Yes, your blog is incorrect, too, and you’ve been spreading false information. Read the series mode patent and look at the SMP circuit. There is NO inductor as the first means of protection. Also, no real series mode products use MOVs. This means by legal definition that SMP is not series mode surge protection. It is a hybrid.

The whole point of series mode technology is to avoid the use of MOVs. It’s fully ironic to use MOVs and call it series mode. It would be akin to saying you’re dying of thirst, and then eating the saltiest food you can, or calling a fat guy slim.

What PS Audio products do you think used series mode? I’m sure old reviews can confirm or deny this. They are not a current licensee, if they ever were.

You are misunderstanding things. I’m saying the SurgeX ASM products are better surge protectors than Furman, because they use no MOVs.

LiFT is a negative, IMHO, as it digs down into the audible region, and throws the baby out with the bath water. I understand some people like that squeaky clean sound.
Your own link :
basically is spec for spec identical to the description of the multi-stage protection described by Brickwall. Down to the clamping voltages. Now stop
What specs? There is only one listed, "EVS (Extreme Voltage Shutdown) responds to sustained over voltage conditions (137 V or greater)." The rest is filled with features. The telling one, "VIRTUALLY non-sacrificial." You know, meaning not quite.

Communicate with Garth Powell, or Christos Desalernos at Furman, if you don’t believe SMP uses MOVs. It is very sad that you are totally clueless as to what a MOV looks like.

And Brick Wall doesn’t use Series Multi-stage Protection. They use real series mode technology. That’s okay, I understand that you want your affiliate money, and have no qualms in being a charlatan.
I suggest if you don’t like my blog you go write your own.

That's kind of how the Internet works.


Erik- Are you a dealer? In good faith- can you edit your furman/amazon link which clearly shows affiliate marketing? If such links are tolerated, I am sure dealers can post link to their website for sales of their items.

Trying to keep things honest in a discussion. 

I am not a dealer. Unfortunately I cannot edit a discussion once it has been replied to, and being sure I don't use an affiliate link is also complicated, but here it is:
I'll keep that in mind for future posts.
Really need to delete this thread, as the PS Audio units I linked to are no longer the same ones. Those seem to be gone.
Wow! Erik doesn’t know what a MOV looks like, or how to post a proper link. It is NOT complicated to post a non-affiliate link or one without garbage, unless someone has ulterior motives.

This is the link to use AFTER clearing your internet browser of cookies, and all that’s needed:

Hi Sadano,
Feel free to tag me all you want, but I'm not obligated to read or respond to you. You've never been civil, and I choose to ignore you now.

Just wanted to do the decent thing and let you know. I've barely read your posts. Feel free to spew, but it makes no difference to me.