Sonoma Model One electrostatic headphone system

[mulder01]

Power consumption and output power are two different things. For example, the Schiit Magni 2 Uber can output up to 1.2W RMS per channel at 50 ohms, but its power consumption is 5W.

Electrostatic headphones use hundreds of volts, but very little current, so maximum output voltage instead of output power is listed for the amps. They also usually list the power consumption.

Here are some of those specs, for reference. The thread links are for voltage and output stage current. The specs I list under that are power consumption.

Note that the voltage specs on that thread are listed peak to peak rather than RMS. It's important to know which spec you're looking at, since they can differ based on that. (For example, the STAX SRM-T8000's maximum output voltage is 470Vrms or 1330V p-p.)

https://www.head-fi.org/threads/electrostatic-amplifiers-voltage-ratings.582518
https://www.head-fi.org/threads/electrostatic-amplifiers-voltage-ratings.582518/#post-7925458

HeadAmp Blue Hawaii Special Edition: 180W
Woo WES: 118W
STAX SRM-T8000: 95W
HeadAmp Aristaeus: 60W
STAX SRM-007tII: 55W
STAX SRM-006tS: 49W
STAX SRM-727II: 46W
STAX SRM-353X: 30W
STAX SRM-252S: 4W

Yeah that was my point - that power consumption is not the same as power output so knowing it has a 60va power supply doesn't really tell you the output. Was still curious as to the actual power consumption of the headphones though.

Jim seems like he might be onto it but. That's a fair bit of juice!

 

[Music Alchemist]

Yeah that was my point - that power consumption is not the same as power output so knowing it has a 60va power supply doesn't really tell you the output. Was still curious as to the actual power consumption of the headphones though.

Jim seems like he might be onto it but. That's a fair bit of juice!

I think the term "power consumption" should be avoided when referring to what can be sent into the headphones, since that term usually refers to something else.

Anyway, their site tells you the spec:

https://www.sonomaacoustics.com/US/technology/

The drive signal has a maximum amplitude of 145 V (rms), which is superimposed on the 1350 V DC bias. Despite operating at low current levels, the high voltages in use translate to significant power (for a headphone amplifier) at the output of the amplifier. Consequently, high quality devices are used throughout which are designed to cope with the power levels.

This in itself doesn't tell you much unless you understand the other factors, such as the impedance, sensitivity, and design of the headphones, specs of other amps, etc. Even the weakest STAX amp in production (not counting the portable one) is 280V RMS. (And the bias voltage for modern STAX is 580V.) These are different systems, so glancing at the specs won't tell you how they compare. But everyone is saying the M1 either can't get very loud or distorts badly at higher volumes, so for those seeking high fidelity (including reproducing the instruments at their original volume), it's going to be limited by the amp in many cases.

 

[Muinarc]

I figured someone was just eco conscious and wanted to know how much the whole setup would use. I didn't think we were asking how many W the amp's rating on the headphone output was. I've never even seen an electrostatic measured that way so the thought didn't cross my mind. They're always spec'd at p2p voltage swing.

One test I like to do with all headphone amps traditional or electrostatic, is turn it up until I can't keep the headphones on my head at all due to pain threshold (not great for your ears but we're talking about turning it up and pulling them off in a 5 second span so it's not bad). If I can actually leave the headphones on my head then there's not enough power even if it's not normal listening level. Is this scientific? Not at all, but dynamics are important to me and my personal belief is amps need lots of headroom to better express dynamics.

All that being said, the Sonoma that I heard was not even that loud at max volume. I'm not sure if a source with higher voltage output would change this with the Model One's ADC setup but it might so it could just be what they had at the show that day. My comfortable listening level was at maybe between 11 (quiet listening) and 2 (rockin' out listening) o'clock and all the way up was at 5 o'clock and wasn't exponentially louder. The amp definitely ran out of steam *(in that particular setup).

 

[JimL11]

Yeah, I used the wattage rating of the power supply (60VA) and what Sonoma said on its website to calculate the power consumption of the amplifier. This allows you to calculate the maximum theoretical output of the amplifiers (approx 2 watts). One can calculate the max theoretical output of the Stax and KG amps in a similar fashion, which I did for comparison's sake, but again, it doesn't have that much to do with power consumption - other than that the power consumption is ALWAYS much greater than the maximum power output (the rest of the power is wasted as heat).

The amount of power it takes to actually drive the headphones is unknown because we don't know the efficiency or the impedance. As I mentioned, Kevin Gilmore measured the SR-007s as consuming around 1 watt peak at presumably a pretty high level, but again he just gave that one number and no other details. That wattage is at least a reasonable order of magnitude estimate for most electrostatic headphones, because they tend to present a similar load.

 

[JimL11]

I figured someone was just eco conscious and wanted to know how much the whole setup would use. I didn't think we were asking how many W the amp's rating on the headphone output was. I've never even seen an electrostatic measured that way so the thought didn't cross my mind. They're always spec'd at p2p voltage swing.
.

Well, power consumption (wastage) is a separate concern, but yeah, you can use the power consumption to calculate the maximum power output. Although electrostatic headphones resemble capacitors, and are sometimes modeled as such, in fact they use power, unlike capacitors - in a pure capacitor, the voltage are current are 90 degrees out of phase, so if you do a power calculation, a capacitor uses no power. OTOH, an electrostatic headphone HAS to consume power, because it makes NOISE, which is a form of energy, so by the law of conservation of energy, it has to consume energy/power. That's why voltage swing is only a part of the picture - for example, the commercial headphone amp with the largest voltage swing is the Koss E/90 (+/-600 volt PS), but it doesn't run very hot because it only has a couple mA of current in the output stage. That amp's sound quality is limited due to current limiting, not voltage swing.

If you think about it, 1 watt peak for the SR-007 (2 watts if it's per channel) using a BHSE at 180 watts power consumption is overkill. As I recall the DIY T2 is around 200 watts, so 198 -200 watts of that is heat, in fact, since there is no music that is at peak values all the time, pretty much all the power of any electrostatic headphone amp (or any other headphone amp for that matter, since dynamic headphones play pretty loud with a few milliwatts) is wasted as heat.

 

[mulder01]

Hmm 200w of heat is pretty ridiculous. I remember trying out a friend's Ragnarok (75w consumption) and the heat coming from the thing put me off owning one regardless of sound. I think I saw a picture the other day of a guy's house who owned a T2. You can almost see where he has it sitting...

I suppose it is difficult to tell power consumed by the headphones as it's not something normally discussed with estats by the sounds of it. I only asked because someone said the amp didn't put out enough power - hence the question "well how much power DOES it put out" - I mean there is a certain amount of electrical energy required to produce the kinetic energy of the diaphragm moving... normally expressed in watts... ah well.

It wouldn't bother me if the thing can't get to the threshold of pain - I would listen louder than normal in shop conditions and louder again in show conditions so I'm not really deterred by people saying that they weren't extra loud in show conditions. It would probably suffice for home listening at sensible volumes. You would think. Otherwise it wouldn't be viable as a product.

It also doesn't really bother me that the response of the driver is corrected by the amp. Due to the physical restrictions of vinyl as a media, music is stored on vinyl in a way that exaggerates higher frequencies and this is corrected by the phono stage. There are no audio purists crying blasphemy at that, so I don't see this as being SUPER different. For all I know the Orpheus has something weird going on with the electronics in the earcups... Doesn't really matter as long as it sounds good.

 

[Pokemonn]

we need a lot of nuke power plants to drive T2s

 

[Music Alchemist]

Hmm 200w of heat is pretty ridiculous. I remember trying out a friend's Ragnarok (75w consumption) and the heat coming from the thing put me off owning one regardless of sound. I think I saw a picture the other day of a guy's house who owned a T2. You can almost see where he has it sitting...

My power amp can output up to 750 watts into 8 ohms in bridge mode (that's more than twelve times as much as the Ragnarok, which is 60W at 8 ohms and 100W at 4 ohms...although mine normally only outputs up to 200 watts into 8 ohms) and doesn't even get warm thanks to the (not quiet at all) cooling system. I'm not sure what its power consumption spec is, since it doesn't seem to be listed anywhere. The Ragnarok's power consumption is listed as "75W quiescent, 500W max"...and going from data on other amps, it would appear that power amps generally consume even more power than they can put out. At any rate, power consumption is separate from (but obviously related to) how hot the unit gets, since that depends on more than one factor.

 

[JimL11]

... it would appear that power amps generally consume even more power than they can put out.

Yeah, there's actually a basic concept in physics involved here, the law of conservation of energy, which basically states you can't get more out than you put in. In fact, you always get less out than you put in, or in other words, the output power is always less than the power that is drawn from the AC line - the remainder generally is wasted as heat.

 

[mulder01]

My power amp can output up to 750 watts into 8 ohms in bridge mode (that's more than twelve times as much as the Ragnarok, which is 60W at 8 ohms and 100W at 4 ohms...although mine normally only outputs up to 200 watts into 8 ohms) and doesn't even get warm thanks to the (not quiet at all) cooling system. I'm not sure what its power consumption spec is, since it doesn't seem to be listed anywhere. The Ragnarok's power consumption is listed as "75W quiescent, 500W max"...and going from data on other amps, it would appear that power amps generally consume even more power than they can put out. At any rate, power consumption is separate from (but obviously related to) how hot the unit gets, since that depends on more than one factor.

Oh yeah of course there are different designs - but the Rag sitting there just being switched on got very hot. The amp I used to use for my speakers seemed like it got hotter when it wasn't in use than when it was as well - If I had the music cranked up for a while it would only be warm, but if I just switched it on and forgot about it, a short while later the cooling fan would be working overtime. It was like whatever power you use don't use in outputting to the speakers, that power got used as heat or something. I've had another amp that gets hotter the harder you drive it (which makes more sense to me) so I guess there are many ways to design an amp. Perhaps the T2 does not actually consume 200w idle, but only at full output. Which is still a bloody lot for a pair of headphones...

I remember a couple of people who tried the Viva Egoista a while ago (powering probably less than a watt into the headphones) got so hot that the temperature of the chassis exceeded what is considered to be safe and legal to be sold in Australia...

But I suppose this has gone pretty far off topic from the power output of the Model 1 now...

 

[JimL11]

Oh yeah of course there are different designs - but the Rag sitting there just being switched on got very hot. The amp I used to use for my speakers seemed like it got hotter when it wasn't in use than when it was as well - If I had the music cranked up for a while it would only be warm, but if I just switched it on and forgot about it, a short while later the cooling fan would be working overtime. It was like whatever power you use don't use in outputting to the speakers, that power got used as heat or something. I've had another amp that gets hotter the harder you drive it (which makes more sense to me) so I guess there are many ways to design an amp. Perhaps the T2 does not actually consume 200w idle, but only at full output. Which is still a bloody lot for a pair of headphones...

I remember a couple of people who tried the Viva Egoista a while ago (powering probably less than a watt into the headphones) got so hot that the temperature of the chassis exceeded what is considered to be safe and legal to be sold in Australia...

So, class AB amps (most speaker amps) pull more current as they make music, so they get hotter as you play louder (the hottest they get is if you are running a sine wave output at 1/3rd of full power, which was a complaint by some amp manufacturer when the FTC came out with its amp rating system a few decades ago). On the other hand, class A amps run a bit cooler when you play louder because some of the energy is going to driving the speakers/headphones rather than heating up the room. The T2 is class A, as are pretty much all electrostatic headphone amps, so it runs 200 watts all the time. The Sonoma amp is single-ended class A so its current draw is constant and continuous as long as it is on.

 

[MacedonianHero]

In case anyone is interested, my review is now live on Headphone.Guru.

 

[wink]

Who is this Headphone Guru of which you speak...?

 

[Music Alchemist]

Who is this Headphone Guru of which you speak...?

Assuming your post is not a joke: http://headphone.guru/the-sonoma-acoustics-model-one-the-new-kid-on-the-block

 

[wink]

Thanks.