Fosi PH-05 Headphone Distribution Amplifier

[AdamG]

This is a review and measurements of the Fosi Audio FH-05 five (5) channel analog headphone distribution amplifier. It was kindly sent to me by a member and costs US $49.
View attachment 396490
The package is extraordinarily nice given the price. Controls feel nice and having five outputs at once each with their own volume control is more than one could ask for. A tiny power supply powers the unit in the back. Note that I have tilted it up. Normally sits flat.

So it is clear what the device does, you feed it one analog stereo input using 3.5 mm jack, and then have five outputs of the same signal, each with their own volume trim. And then a master volume control.

Fosi Audio FH05 Headphone Distribution Amplifier Measurements
To have a realistic situation, I opted to drive the FH05 using a high-performance headphone amplifier, the Topping A90:
View attachment 396491

I then fed the output of A90 to FH05. Trying to get 4 volts out caused clipping so I backed off on the input to FH05 and adjusted the output to avoid clipping:

View attachment 396492

So we loose good bit of performance. Let's measure to see how much power we have at 300 and 32 ohm:
View attachment 396493
View attachment 396494

Sadly we don't have much power and what we have is in dongle adapter category, albeit a more powerful one.

Conclusions
Fosi nails the functionality and look/feel of the unit with FH05. Hard to imagine you can get anything close to that for $49. Alas, compromises had to be made to have not one, but five stereo headphone amplifiers here. Both in power and noise+distortion. I love to see Fosi build a higher end one with more powerful and lower distortion amplifiers, at least for one channel.

I can't recommend the Fosi Audio FH05 from overall performance point of view. That said, I could not produce a better product and sell it so cheap!
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As always, questions, comments, recommendations, etc. are welcome.

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Hi Boss,

Just an FYI. I think the product name has a typo. Fosi’s webpage has it listed as the “PH05”. But the title is possibly incorrect in multiple locations Sir:

Fosi Audio PH05 5-Channel Headphone Splitter Amplifier

The SK02 employs a minimalist and stylish design language. Despite its small size, it boasts mighty features. It supports DSD256 and PCM 32bit/384kHz high-resolution decoding, along with 3.5mm single-ended and 4.4mm balanced headphone outputs.

fosiaudio.com

 

[Nathan Raymond]

What in the world is this for?

I use something similar in my home with my AV receiver. I have two little kids and if I want to watch a movie with a group of adults and not have the home theater wake the kids it's useful. I run a long 1/4" cable from the headphone out of my receiver (which enables a headphone surround mode) to the headphone amp box and each person has their own volume control.

 

[TNT]

Silent disco ;-D

//

 

[phoenixdogfan]

Silent disco ;-D

//

This ain't no Mudd Club or CBGB's
I ain't got time for that now!

 

[phoenixsong]

I voted it "Fair" as I can definitely see it having its uses while not busting the bank, being quite an affordable solution. However, one will have to reign in their audiophile/measurement connoisseur expectations of quality audio (which kind of is what this site is all about so that's where the divergence in opinions may stem from)

 

[kelesh]

What in the world is this for?

Headphone distribution amplifier. Similar units have been used in pro audio for decades. Or you could compare headphones.

 

[TheWalkman]

Like many other ASR members, with all of the headphones in my collection, I could easily fill all of the jacks, but instead of adding to my pile of gadgets, I’m going to take a pass.

 

[vkvedam]

So we loose good bit of performance.

Nitpicking @amirm, 'lose'

 

[Fosi Audio]

Thank you all for your attention to the PH05. The PH05 is an audio splitter and headphone amp with independant volume control, which is especially useful for real-time monitoring in music production, podcasting, and audio-sharing scenarios. Below are some demonstration scenes. It is not considered a HiFi audio device. Its performance parameters are not yet optimal, and we are working on ways to improve it.

 

[SCR]

In a studio recording environment you usually get your own mix though?

 

[Joachim Herbert]

I owned such a device decades ago. Made by Fostex for studio use, where several listeners would use headphones to listen to one source at a volume of there liking. This was before headphone amps as we know them were a thing, though some (expensive ones) did exist at that time.

I bought it back then because it was the cheapest headphone amplifier I could find.

 

[mc.god]

This thing can be considered as a better featured and probably better quality competitor of the even cheaper Behringer HA400, so I rate it fine for the intended use case.

 

[pseudoid]

I am the guilty-party for buying this FOSI PH05 on a whim.

I baited @amirm to test it, because I was going back to strictly 2-channel audio and walled-away from multi-channel A/V system hook-ups.

I was also planning to replace all of my current multi-channel Rotel A/V separates-based system to one that does not strictly rely on a software/update driven monstrosity that I feel most current A/V systems have become.
I figured that I can feed four (4) separate zones in the house for music from/to a variety of audio sources that we have access to: PCs, Server, NAS, DAP, mobile, SXM, cable, streaming, and mobile... using a shared/hybrid local (PoE/Cat6+) Dante network and adapters.
I have been using the Dante network for a few years, and it truly outshines the rest of my network hardware/software for uptime. Even when the rest of the network is down, the Dante I/F nodes continue to perform.

I also decided that this revised audio system will be balanced (XLR) interfaces to the maximum extent possible.
It also had to be based on stereo hardware which were small, dirt-cheap but w/2024 level of competency in technical performance.
After seeing the performance and test results of this FOSI PH05, I decided that it will NOT work for its originally intended task.
I need to feed a stereo-pair of RCAs (single-ended) audio simultaneously to two (2) different 2-channel loads that are now XLR inputs (balanced).
A 4-channel Direct Box.
I did not like the idea of a 'y-splitter' cable and/or "2in-4out" transformer-coupling and this PH05 does not match the performance and features I desire.

I am considering the purchase of either the RadialEng'g J+4 or the HenryEng'g Matchbox HD which are more costly than the SMSL D100Pro or FOSI ZD3 and ZA3, that they maybe be used with.
I also don't see any ART boxes which provide an active L/R RCA input with dual-L/R XLR outputs. ART is more inline with my budget.

Any suggestions for other such active DI boxes would be much appreciated.

 

[Cbdb2]

In a studio recording environment you usually get your own mix though?

View attachment 396688

Yes those are common now but that gets expensive and complicated if you need 20 of them.

 

[DavidK442]

This thing can be considered as a better featured and probably better quality competitor of the even cheaper Behringer HA400, so I rate it fine for the intended use case.

I use that Behringer for watching movies out in the yard with the family. Tried to go wireless but could not find a low latency option that didn’t crackle intermittently. Shudder to think how the $40 HA400 would measure but it is good enough for our purpose. This Fosi unit looks like a nicer option for about the same price.
I have so many pairs of old wired headphones that I could daisy chain a few of these things and invite the whole neighborhood. Then there would be no need for headphones anyway.

 

[AnalogSteph]

@amirm can you measure the output resistance ?

Going by the delta in maximum output power, it seems to be roughly 23.4 ohms (maybe 22?), so nothing super high.

Noise floor is pretty mediocre at about 46 µV (that's only a 95 dB SNR, clearly failing spec), driving abilities seem semi-decent.

What do you expect from a $49 distribution amp, I guess.

 

[solderdude]

Possibly, could also be caused by current limiting (80mA) in the output op-amps (so still be near 0 ohm).
The way clipping occurs is a bit puzzling as it is similar yet in 300ohm there will be no current limiting, it may be that the input op-amp is doing the clipping here before the output op-amp.
Usually these circuits have some output resistor in it and 22 ohm is a likely value but could also be a value an output resistance could have been set to if the output is just a pot in series.

The low price indeed suggests simple cheap circuits have been used and in bulk op-amps cost very little.

It appears to be an improvement over the PH-04 which has 80ohm output R

 

[Mr Vinyl]

What in the world is this for?

For studio work when different musicians need to hear what they've recorded at the same time. But there are already many alternatives for this type of usage aimed at recording artists.

 

[pseudoid]

For studio work when different musicians need to hear what they've recorded at the same time. But there are already many alternatives for this type of usage aimed at recording artists.

I imagine starving artists bunched up in a home bedroom-studio, trying to make a demo... and they have that Italian social disease, called the Fundsalow!

 

[Mr Vinyl]

I imagine starving artists bunched up in a home bedroom-studio, trying to make a demo... and they have that Italian social disease, called the Fundsalow!

Well, all great artists - including the Beatles - started with cheap equipment. In fact, one of them still uses an 'ordinary' but iconic instrument. That said, maybe Fosi is trying to diversify. Most consumers are familiar with Fosi for good inexpensive audio peripherals, so it may be the 'wrong' place to have this reviewed. The again, one never knows. From Fosi's site: ''One-In-Five-Out headphone splitter, effortless multi-user audio sharing catering to various scenarios such as professional music production, podcast broadcasting, teaching sessions, and everyday use. It's your perfect companion for audio-distribution tasks.''