#### JanesJr1

##### Addicted to Fun and Learning
Hi, I'm trying to understand how the power ratings work.

The review says the S9 reaches 110 mW with 32 ohm headphones. But for example I'm looking at a headphone (ES R-10) that has a sensitivity of 103dB/mW. 103 dB sounds about as loud as I'd even want to listen to headphones.

So does that mean that the S9's output is 110 times more powerful than what I would need for those headphones?

There's gotta be something I'm misunderstanding.

Thanks
I'm not an electronics expert, but maybe because of that I can explain it easier. There are apples and oranges to understand.

Let's use a water analogy, water coming out of a pipe to turn a waterwheel.

The amount of water per second drives how fast the waterwheel turns. The amount of water is the same as amps, the amount of electrons flowing through a wire.. The water pressure is the same as volts. You need both water and pressure or the water won't go through the pipe to turn the water wheel. When you have both water (amps) and pressure (volts), you end up with a flow of water to the waterwheel (watts).

However, we've left out another variable that tells us how much water will reach the water wheel each second. The size of the water pipe determines how much resistance (impedance) the pipe will offer to your flow of water (amps).

So, if the water (amps) is flowing through a big sewer pipe, it can flow pretty freely and the amount of water reaching the waterwheel is based on how much water (amps) you flow into the big pipe. In the same way, a low-impedance headphone will provide a big pipe for your amps, and amps are the important variable to powering those phones. But if you're driving your water (amps) through a pipette, clearly you're going to need a helluva lot more pressure (volts) to overcome the resistance (impedance = ohms) of the tiny pipette. So the crucial variable for your high-impedance headphone, with its tiny pipe is the combination of BOTH water volume (amps) and pressure (volts); i.e. watts.

So we've identified how much water per second (watts) are going to your waterwheel (headphones), but that doesn't tell you how fast the water wheel will spin (how loud the headphones will be). The waterwheel will either be efficient or inefficient in spinning based on the diameter of the impeller, the shape of its blades and its turning resistance. In the same way, your headphones will be louder or softer based on their sensitivity, which is the dB of sound volume per watt of power.

So you've got four variables that determine how loud your headphones will get: (1) volts; (2) amps/current [(1) x (2) = power or watts]; (3) impedance/ohms; and (4) headphone sensitivity.

Now let's go back to your original questions. The sensitivity of your headphones is how loud they'll get per watt (1,000 mW) of power coming in. It's not a measure of the power coming in, or how loud your headphones will be without also knowing watts and impedance. Headphone sensitivity is a characteristic of your headphones, not a power rating for your amp. Three variables, apples and oranges and kumquats, that in combination tell you SPL into your ears.

If you're referring to Amir's review, that was of an earlier version of the S9. The current version of the S9 Pro has 100 mW (single-ended) into 32 ohms impedance. It also has a current-limiter at 90 amps, so that is your maximum amperage. I don't know what headphones you're looking at, but if you know their rated sensitivity and impedance, you can go to the "headphone power calculator" (google that phrase and it should take you there at Headphonesty). Enter the headphone sensitivity dB(1vrms) and impedance, and then enter possible target SPL's until you see where either the required amps go above 90 or the required milliwatts are greater than your headphone's rated mW at that impedance. That should be a rough estimate of the max undistorted SPL you'll get from the Hidizs. Note: if you use the balanced connector instead, the mW will be doubled (except that for very low impedance headphones and/or amps required >90, you'll hit a speed limit).

(That said, some of these specs are estimates or are calculated by manufacturers using non-standard methods. It's nice to get good third party measurements (like Amir's reviews) before you draw any final conclusions.

Last edited:

#### Astojab

##### Member
Also, is the Hidizs S9 dongle (and presumably its S9 Pro successor) audibly indistinguishable from something like a Topping DX3 Pro+ or even a DX5?

If so, are the only reasons to get one of those the following?
• Extra features (screen/knob/remote control/etc.)
• You have some obscure, super hard-to-drive pair of headphones
Thanks
I have the Topping DX3Pro+ and the A50s and in a Blind test roughly volume matched I couldn't determin the difference to a S9 pro. For Desktop use I don't like the s9 Pro for desktop because you have to use the Windows Volume and I rather want a physical button.

BTW I compared it with 2 IEMS and my Sundara with a balanced cable.

#### JanesJr1

##### Addicted to Fun and Learning
Also, is the Hidizs S9 dongle (and presumably its S9 Pro successor) audibly indistinguishable from something like a Topping DX3 Pro+ or even a DX5?

If so, are the only reasons to get one of those the following?
• Extra features (screen/knob/remote control/etc.)
• You have some obscure, super hard-to-drive pair of headphones
Thanks
The max SPL for the Hidizs is lower than my desktop Topping. I can cause transient clipping that is inaudible to me if I crank things pretty loud. Others might define "Loud" differently, and different headphones might have different results.

That said, I'm driving the S9 pro into very low impedance phones (12-13 ohms). There's some debate on Hidizs S9 specs, but StaticV3 gives a good estimate of about 98 db max undistorted SPL for my hard-to-drive phones, and in practice it is very hard for me to distinguish the Hidizs from the Topping because that is pretty darn loud. The Topping desktop amp accepts multiple inputs and can also act as a pre-amp for active speakers. It has more headroom against clipping. But the Hidizs sounds awfully good to me, and in combination with my compact Noires, I take full headphones with me (hard-to-drive ones) twice a day and no longer listen to IEM's most of the time.

I listen with a PC as source, if you want to listen using a cell phone and also want to EQ, consider the Qudelix 5k. The E1DA 9038s G3 with balanced cables may also have even more power.

#### JanesJr1

##### Addicted to Fun and Learning
I have the Topping DX3Pro+ and the A50s and in a Blind test roughly volume matched I couldn't determin the difference to a S9 pro. For Desktop use I don't like the s9 Pro for desktop because you have to use the Windows Volume and I rather want a physical button.

BTW I compared it with 2 IEMS and my Sundara with a balanced cable.
I hadn't thought of this. The PC brands I usually buy have physical volume buttons and I'd forgotten some PC's don't. Good for future reference,

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Interesting~

#### chi2

##### Active Member
Forum Donor
What devilish device is that in #666?

#### staticV3

##### Master Contributor
What devilish device is that in #666?
That's most likely the soon-to-be released successor to the Topping NX4 DSD.
It's a battery-powered, portable DAC+Headphone Amp.

#### Jimbob54

##### Grand Contributor
Forum Donor
That's most likely the soon-to-be released successor to the Topping NX4 DSD.
It's a battery-powered, portable DAC+Headphone Amp.
A Mojo murderer!

#### Veri

##### Master Contributor
A Mojo murderer!
Mojo2 has some (kind of weird) built-in EQ though

#### Jimbob54

##### Grand Contributor
Forum Donor
Mojo2 has some (kind of weird) built-in EQ though
It's the best eq ever devised. Apparently.

#### Veri

##### Master Contributor
It's the best eq ever devised. Apparently.
I'm sure once you hear the -130 -140dB Chord intricacies, you simultaneously become capable of hearing it EQ better. somehow.

#### Jazz

##### Active Member
I am thinking of repurposing an S9 v.1 to be a DAC for my older car. Just 3.5 mm to head unit.
I could place it in the glove compartment. The 3.5 comes into there from head unit (was an add on board in back of it). Then USB adaptor to a USB to Lightning line out side of compartment door to my phone.
The question is: Would the DAC melt in my glove compartment parked on hot days? It does get very hot on its own. So I suspect it is pretty heat resistant.
So far, the small Apple Lighting DAC has been superb and, I leave that plugged in all the time. It just rests on the passenger footwell floor when parked.
I mostly play HE-AAC while driving so, there might not be any advantage to this idea. BTW: HE-AAC is pretty amazing!
For longer trips, ALAC from iPhone.
We do occasionally have car break ins. They politely use spoofers and are only into cash (drug money). But, my remote is now in a metal box when I am not driving…
But I could mount the S9 on the back side of the glove box not too hard. Like many, it drops for air filter access. It would be unseen. Just a freaky Lighting wire hanging out on floor.

#### Mulder

##### Addicted to Fun and Learning
Forum Donor
I am thinking of repurposing an S9 v.1 to be a DAC for my older car. Just 3.5 mm to head unit.
I could place it in the glove compartment. The 3.5 comes into there from head unit (was an add on board in back of it). Then USB adaptor to a USB to Lightning line out side of compartment door to my phone.
The question is: Would the DAC melt in my glove compartment parked on hot days? It does get very hot on its own. So I suspect it is pretty heat resistant.
So far, the small Apple Lighting DAC has been superb and, I leave that plugged in all the time. It just rests on the passenger footwell floor when parked.
I mostly play HE-AAC while driving so, there might not be any advantage to this idea. BTW: HE-AAC is pretty amazing!
For longer trips, ALAC from iPhone.
We do occasionally have car break ins. They politely use spoofers and are only into cash (drug money). But, my remote is now in a metal box when I am not driving…
But I could mount the S9 on the back side of the glove box not too hard. Like many, it drops for air filter access. It would be unseen. Just a freaky Lighting wire hanging out on floor.
Why? The noise floor in a car must be far worse than the noise floor of the Apple dongle?

#### RobSmith

##### New Member
So for a newbie to this site, what are the top 3 under \$1000?

#### Jimbob54

##### Grand Contributor
Forum Donor
So for a newbie to this site, what are the top 3 under \$1000?
Top 3 what?

#### Jazz

##### Active Member
Why? The noise floor in a car must be far worse than the noise floor of the Apple dongle?
This is right!

#### Absurdityinaudio

##### New Member
Hi!

The device seems to be working and turn on green light, but:

1. Unable to find on Mac outputs.
2. Doesn't work with iPhone and otg cable.

Thank you.

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