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SMSL HO100 Review (Headphone Amp)

Rate this headphone amplifier:

  • 1. Poor (headless panther)

    Votes: 1 0.6%
  • 2. Not terrible (postman panther)

    Votes: 5 3.2%
  • 3. Fine (happy panther

    Votes: 32 20.4%
  • 4. Great (golfing panther)

    Votes: 119 75.8%

  • Total voters
    157

solderdude

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How is such a sharp cutoff at exactly 14 Hz possible?

Amir explained this already, it went in protection so there was no output below 14Hz. This is (very likely) caused by a (too) fast acting DC protection.
At lower levels I am sure the frequency response will be down to DC or at least well below 1Hz.
 

AudioSceptic

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This is a review and detailed measurements of the SMSL HO100 balanced (input) stereo headphone amplifier. It was sent to me by Aoshida Audio and costs US $149.
View attachment 208728

The HO100 matches its companion DO100 DAC. Switches feel nice and so does the volume control. While 4.4mm penticon connector is provided, its output is no more than 1/4 HP jack (so it is for convenience, not power).

What is unusual and welcome at this price point is inclusion of AC adapter and XLR inputs:

View attachment 208729

As with other SMSL products I have tested, it comes with regulator and safety certification:

View attachment 208730

SMSL HO100 Measurements
As usual we start with 4 volts in (for XLR input) and adjust the output to get 4 volts out. This meant using medium gain at max volume. Output is the same with either HP connection:

View attachment 208731

The only artifact visible is at -130 dB (15 dB below threshold of hearing) so definitely transparent to the source. This lands the HO100 in our top 10 best headphone amplifiers ever measured:

View attachment 208734

Noise performance is excellent at max level of 4 volts and near that at 50 mv out:
View attachment 208735


View attachment 208736

I tested the frequency response with the amplifier with 4 volts in/out with load of 600 ohm. This caused an odd muting at 14 Hz:
View attachment 208737

I tested it at 2 volts out and it did not do this. I am assuming it is the protection circuit kicking in.

Multitone test shows impressively low intermodulation distortion:
View attachment 208738

Sweeping at all frequencies we likewise get excellent performance:
View attachment 208739

Power is one of the most important measurements of the headphone amp so let's see what we have at 300 ohm:
View attachment 208740

My minimum requirement for desktop amps is 100 milliwatts and the HO100 clears that mark. It also delivers over 1 watt at 32 ohm:
View attachment 208741

Notice how the noise penalty is marginal for medium gain yet you get a lot more power than low gain. So that would be the setting I would use instead of low.

Sweeping for a range of loads we get sable and nice performance:
View attachment 208742

Finally channel matching is excellent as I adjust the volume but your sample may not be as good:
View attachment 208743

SMSL HO100 Listening Tests
I started in reverse order of my usual testing with Dan Clark Stealth. This is a very difficult and power hungry headphone to drive. HO100 could only drive it to medium volume before getting distorted. Switching to Drop Ether CX bettered performance where I could get to ear bleeding levels before I could hear distortion. Best performance was with the Sennheiser HD650 where the HO100 drove it with authority to any volume level you wanted. Dynamic rand and detail was superb as is the case when the amplifier is not the bottleneck.

Conclusions
The SMSL HO100 delivers on three of my favorite features: balanced input, included AC adapter and low cost. Distortion and noise performance are excellent landing near the top of the class at any price. Power output though is good to excellent depending on your headphone impedance, leaving room for pricier offerings from SMSL and others. The only odd thing in the measurements is the muting at subsonic frequencies (which I could not force with music content with very deep bass).

I am happy to give a recommendation to SMSL HO100.

---------
As always, questions, comments, recommendations, etc. are welcome.

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You've described the output at both 300 and 33 Ω as "excellent", yet it cannot drive the Dan Clark Stealth to high volume. Wouldn't "good" be more accurate?

Just what does it take to drive the Stealth?

One other thing, you say "included AC adapter". I find that confusing: wouldn't "built-in power supply" be more meaningful?

Sorry about the nitpicking!
 

AudioSceptic

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Excellent review @amirm.

It looks to be a great value (AUD$199 on Amazon) HPA and nicely made if the interior shots on their site are representative.

It could be a decent line level preamp with noise levels that low.
Apart from the reduced number of inputs, what is the difference between a HP amp and a pre-amp, if we exclude the need to drive very inefficient HPs?
 

DMill

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Another great review @amirm
thank you for mentioning the AC adapter on both this and the previously reviewed DAC. A brick filling up three slots in my power adapter seems like a minor inconvenience but I find it very annoying. Looks like a good product at a more than fair price.
 

kchap

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I often use an AC extension cord for these. The brick can be located away from the wall socket.
Instead of oversized "wall warts" I wonder why the manufacturers do not ship SMPS units that have an IEC C7 power receptacle on on on one side and DC power outlet on the other. Not only are wall warts inconvenient they must be more expensive as multiple versions are needed to suit the different standards for AC outlets.
 

solderdude

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I wonder why the manufacturers do not ship SMPS units that have an IEC C7 power receptacle on on on one side and DC power outlet on the other.

The larger power bricks often do. With different types of AC inlets b.t.w. and supply a mains cord.
The small ones (wall warts) are cheaper to make a in a few different enclosures than 1 'universal' one with various adapters for different outlets.
This amp has a built-in (wide range) power supply so no bricks or wallwarts.
 

Steamrolly

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While the HO100 is very good, it's not as flawless as the DO100 and will not be a "perfect" amp for the "perfect" DAC.
Amir pushes these companies that hard that we become so spoiled with great performance on the cheap…
My thought is that the DO100 is the perfect companion for an AO200. I find the performance I am getting with this combo is quite amazing for the price. I am not convinced that one would benefit too much going to the DO200 or SU-9 etc. at close to twice the price. (using an AO200 or similar amp).
 

kchap

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The larger power bricks often do. With different types of AC inlets b.t.w. and supply a mains cord.
Agree, but the manufacturers do still make strange decisions. I have a Topping L50 which has an external 230V to 15V transformer. You would think the L50 would be an ideal candidate for an external power brick. Instead I have a very bulky and hot wallwart. A modern SMPS is lighter, smaller and more efficient than the equivalent transformer.

The small ones (wall warts) are cheaper to make a in a few different enclosures than 1 'universal' one with various adapters for different outlets.
This must be true. Companies are are not known for spending money when there is no need. However I think there must be a chicken and egg problem here; if the production of a universal unit started to get as high as wallwarts it would be cheaper than the ten or so wallwarts needed for a world market. Plug & Socket Types

This amp has a built-in (wide range) power supply so no bricks or wallwart
I wish more manufacturers did this but it seems most do not. I forget the actual thread but @boxem-audio pointed out that in some regions the certification of devices with an internal PSU is relatively expensive. In many cases it is a lot cheaper to select an off the shelf external PSU that has already been certified.
 

Atanasi

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I have a Topping L50 which has an external 230V to 15V transformer. You would think the L50 would be an ideal candidate for an external power brick. Instead I have a very bulky and hot wallwart. A modern SMPS is lighter, smaller and more efficient than the equivalent transformer.
Topping's L series is designed around a transformer and changing the design to an SMPS would require significant changes. Other models make other choices. Apparently commonly available transformers are bulky wallwarts and making a customized transformer is expensive.
 

solderdude

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I have a Topping L50 which has an external 230V to 15V transformer.

The reason is lower leakage currents and some people also still think linear power supplies sound better as well. For the topping the reasoning was leakage current though.

The advantage of an external power supply can be:
Smaller enclosure, easier to get lower hum (no need for internal screening), heat build up, saving of parts and certification.

SMPS (the cheap ones) have a shorter lifespan but are smaller, cheaper, wide range and are stabilized. There is a lot to be said for SMPS.
 

dib

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My thought is that the DO100 is the perfect companion for an AO200. I find the performance I am getting with this combo is quite amazing for the price. I am not convinced that one would benefit too much going to the DO200 or SU-9 etc. at close to twice the price. (using an AO200 or similar amp).
The AO200 is an all in one combo that includes a built in DAC. You can connect it to your phone thru USB or Bluetooth and speakers.
Anyway, you are right about the small to non existent difference between a cheap excellent DAC and an expensive excellent DAC, yet finding yourself spending much more just to have a physical match between the components. The companies knows that too...
 

Steamrolly

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The AO200 is an all in one combo that includes a built in DAC.
No, it is primarily a Class D integrated power amplifier. The on board DAC is more of a bonus feature which SMSL will not even provide information on. It only allows for USB A input (no coaxial or optical); I agree it is useful if you want to use USB prior to getting an external DAC. This makes it a great amp to start your system with however the on board DAC performance is very far from the performance you get when adding an external balanced DAC such as the DO100. The AO200 is not the same as a Topping MX5 which is a true DAC amp combo unit.
 
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