A headphone amp with mystery features you might love - Fosi Audio SK02

I explore the features of this fascinating and fun headphone amp and test it with headphones that are known to be very difficult to drive.
My review of the Verum 1 - • I test the Verum 1 Pla...
CREDITS
Roberts radio - www.robertsradio.com/en-gb
AudioQuest Diamond - www.audioquest.com/cables/dig...
Parallel connectors - Shieldforyoureyes CC BY-SA 3.0
Tales from Topographic Oceans amzn.to/3ucLgWC
DAVID MELLOR'S MUSIC
David Mellor's music on Bandcamp - davidmellor.bandcamp.com/
David Mellor's music on Spotify - open.spotify.com/artist/6OkaD...
Available on all good streaming services
EQUIPMENT USED TO MAKE AUDIO MASTERCLASS VIDEOS
CAMERA - Sony Alpha A6600 amzn.to/3uj7Dtq
COMPUTER - Apple Mac Mini M2 Pro amzn.to/47tW6Wg
MICROPHONE - Sennheiser MKH 416 amzn.to/3QWWvuO
ALTERNATIVE MICROPHONE - AKG C414 amzn.to/3SLqCad
BUDGET MICROPHONE CHOICE - Rode shotgun amzn.to/3G0ni36
MICROPHONE PREAMPLIFIER - Comica LinkFlex AD2 amzn.to/40SMHFT
TELEPROMPTER - Padcaster Parrot alternatives amzn.to/40A55TJ
TELEPROMPTER SOFTWARE - PromptSmart Pro promptsmart.com/
AUDIO INTERFACE - Behringer UMC202HD amzn.to/3ugj6db
HEADPHONES - Sony wired amzn.to/3sEjlht
SPEAKER CABLE - KabelDirekt amzn.to/3ucgQ6T
POWER AMPLIFIER - Fosi V3 amzn.to/3vRumNH
KEYLIGHT- Amaran 100d amzn.to/40A5Gor
FILL LIGHTS - Switti RGB amzn.to/3ufhOPu
SOFTBOX Phot-R alternatives amzn.to/3QGoTjJ
LIGHTING STANDS Phot-R alternatives amzn.to/3QWXOKe
MONITOR - Samsung UJ59 amzn.to/3MEoBsk
MONITOR ARM - Invision alternatives amzn.to/40SLqi5
MIC ARM - Neewer amzn.to/49Ob0sD
TRIPOD - Velbon alternatives amzn.to/46gu2oa
GREEN SCREEN - Elgato alternatives amzn.to/3SG2F3L
DESK - FlexiSpot E7 Pro amzn.to/3QVIWvS
VIDEO EDITING - Apple Final Cut Pro www.apple.com/final-cut-pro/
IMAGE EDITING - Adobe Photoshop amzn.to/3FZ7Ww0
AUDIO EDITING - Avid Pro Tools amzn.to/3QA5Wz7
NOTEBOOK - Leuchturm 1917 hardback amzn.to/47zonKX
PEN - Sakura Pigma archival pen Sakura Pigma archival pen amzn.to/47zz3cP
OSCILLOSCOPE - Hameg HM 203 alternatives amzn.to/47tWN1O
GROOMING - Philips 3000 nose hair trimmer amzn.to/40BdLJo
GROOMING - Nose plier amzn.to/41IOZaR
HAIR COLOUR - Just For Men amzn.to/475OgS1
HAIR CONDITIONER - TRESemmé Silky & Smooth amzn.to/41AdWFd
Disclaimer: Videos on this channel may include affiliate links and may feature software that has been received free of charge with an NFR (not for resale) licence, equipment that has been loaned or donated by a manufacturer or distributer, or equipment that has been bought for less than full retail price.

[@rienpost3145]

I love the subtle undercurrent of sarcasm in your videos.

[@thefloop2813]

Subtle?

[@rienpost3145]

@@thefloop2813 That whas sarcasm from my side.

[@thefloop2813]

@@rienpost3145 Yea def seems pretty obvious now. I was probably drinking, does tend to be when i make the poor choice to enter youtube comment threads lmao. Generally if there's a beer in my hand im on youtube talking shit about something instead of just listening to or making music like i should be doing

[@davespagnol8847]

I guess the biggest fun with Toslink is getting the connector from Poundland for .... a pound, and finding that it sounds no different to a £300 one.

[@gustavehenry]

One of the major advantage of optical is the quality of the signal. Because, an optical signal can't have interference. (It light, not electrons). Therefore the only thing that could go bad in a optical cable is... if you break it. The only potential problem of your dollar (pound, euro, who cares) cable, is that it might be too fragile. But event that... if you don't try to hang yourself after figuring out that the 300x more expensive version that you bought first is no better, there is little chance that you would damage it if you care ^^

[@apigge8723]

Thanks for emphasizing "fun" here. I believe it's always good to take some time out for that!

[@markphilpot8734]

You spoke of fun in your review. Sarcasm seems to be your fun and why not. Cheers !

[@nicc5122]

Optical eliminates ground loops. That's why I favour it PARTICULARLY from laptops which have inherently noisy power supplies (especially HP...) I've several transformer balanced humblocks too but can introduce more problems and you need to part with a lot of money for good transformers.

[@artysanmobile]

A decent Toslink cable should cost you $10 or so. Note I said decent. The reason being it is optical and as a result is a go/no-go proposition. There is no ‘quality’ involved. It either works to absolute perfection or it is dead silent. I have many of these cables left over from a project with Yamaha consoles. Audiophiles are welcome to them for the ‘nephew’ price of $200 apiece. I’ll mark them North and South to make installation more special for them.

[@steverobertsbbc]

"I abstain." No sh*t, Sherlock! :D

[@dmikelyn]

Nothing subtle about this gentleman’s sarcasm and innuendo. It certainly speaks to my jaded audio soul! So I say “More of the same Good Sir!” if you please. :-)

[@shipsahoy1793]

I am not using the optical output on my TV either. I use the HDMI connections on my TV, just for the bloody FUN of it!🥁

[@artysanmobile]

Macintosh computers have used a dual function 3.5mm audio out jack for many years. It has a tip-ring-sleeve construction just like you’d expect but also, way in there, an optical transmitter exactly suited to the Toslink Mini plug you’ve shown. I don’t know 3 people who realize it’s there.

[@MrAdopado]

The optical is not there any more ... in fact it's been a few years since they (unfortunately) dropped the optical out that was combined with the 3.5 socket.

[@artysanmobile]

@@MrAdopado I knew it was no longer, but it was such a secret in the first place I didn’t expect an announcement. Probably 2015 or so.

[@JHDundrum]

An Asus Xonar DS 7.1 PCI sound card I bought in 2011 had this feature too and even came with a Toslink-mini to standard adapter. The Google Chromecast Audio had the same 3.5 mm copper / Toslink-mini dual purpose socket.

[@gustavehenry]

Tos-link sends a digital signal, therefore, there is no way to amplify it. That is a major disadvantage of using it as audio output from a tv, you can't use the tv volume control for your volume any more. You have to change the volume on the receiver. The advantage, is that it's a 1 thin cable, 5.1 signal with no interference possible. (therefore, you'll only fear interference from the 10+ other cables linking your speakers and other devices....)

[@user-le8ho1ml5b]

Very interesting device. Strangely enough, it reminds me about (almost) similar on functionality and internal parts DAC/phone amplifier Fiio K3 new. Not sure about the prices' comparison.

[@obsprisma]

Great video sir. Could you give a link where you can order this Fosi SK02? I can't find it on Amazon yet.

[@AudioMasterclass]

I think it's going to be on general release in February. Perhaps Fosi could advise you.

[@mathumphreys]

You reminded me that I have had a couple of laptops that had 3.2mm optical out. I never used it though.

[@danrussell9357]

Hope to see a DSD video!

[@MrBenherrmann]

Can this thing be used as a preamp also - or is it just a Head Amp? I have an SK01 and enjoy it, and as you know it is both a head amp and a preamp (albeit a preamp out with only a 3.5 MM). I like the added DAC feature also.

[@Kevin-sh1sx]

It looks like this can be used in conjunction with SK02.

[@MrBenherrmann]

@@Kevin-sh1sxWhen I got it, I immediately saw that it can be used as a Preamp, with a 3.5 output. Attached to both the V3 and ZA3, I found the combinations to be outstanding. This is a really good DAC and I prefer it over my iFi ZenDac Mk II and some of my Schiit gear.

[@simonegleton1790]

Thank you for this; am wondering if you, or any followers, know what the retail price will be?

[@AudioMasterclass]

No idea but I wouldn't expect it to break the bank.

[@mtinhk]

Isn't the "Optical In" useful if you want to use the SK02's own DAC/AMP without coloration by previous DSP? Whether or not all DAC chips sound the same, a "DAC" is usually more than the DAC chip itself, isn't it? For example, I have my projector connected via optical output to my SMSL SU-1 and can get better sound out of this combination (even if at fixed volume, and even if I lose Dolby Atmos) than I could get out of the projector's own 3.5mm analog output. In another use case, I don't want to use the "DAC" of the HDMI extractor connected to my Roku to have sound DSPd by the extractor itself before it reaches my SMSL DL200. As in the previous case, I am assuming that the converstion from digital to optical does not alter the sound in the ways that convertion to analog + amping would. I do agree that one's levels of interest in very high sample rates might be directly proportional to the seriousness of their ADHD, but other functions here may have their use cases even if one is not a flamboyant audiophile, isn't it? I would have been more interested in learning how the SK02 sounds. For example, I have the Fosi Audio DS1. Does the SK02 sound similar to it?

[@AudioMasterclass]

I have a feeling that people often get overexcited about DACs. Having said that, I've just had two sent to me for review. Maybe I'll change my mind.

[@JustLearning]

I may have missed it but did you provide a link for the Fosi Audio SK02? You had loads of links to everything but the SK02?

[@AudioMasterclass]

I got my spreadsheet in a twist and released the video too early. From what I've been told so far, the SK02 will be released in February.

[@Bizzle65]

I had a quick look and from what I can gather it’s still at the Kickstarter stage. I just backed the project for £65!!

[@slinkman79]

4:07

[@kevinmcgrath3591]

I do like their good stuff (rare but great) but this album is a prog rock car crash of the worst kind imaginable so I totally get his remark. Im old enough to remember when it was released and being stunned by its meandering, soul less dreadfulness compared to the preceding 'close to the edge' , a wonderful LP in 1972

[@rhodaborrocks1654]

@@kevinmcgrath3591 I couldn't agree more, I bought a copy when it was released on the strength of their previous records but could not figure it out .. I eventually gave it to my sister, because I didn't like her.

[@slinkman79]

@@kevinmcgrath3591 Indeed! I don't rememeber being able to listen to a single side of this double LP in one seat, I always get bored... As for "Close to the Edge", it remains one of my favourite album of all times.

[@williamobrien6936]

Many modern TV's can transmit audio through their USB ports. The SK02 could be used as a preamp.

[@JHDundrum]

"TOSLINK is a trademark of Toshiba Corp." Toshiba is the Tokyo Shibaura Electric Co., Ltd., therefore I go with a pronunciation starting with a word sounding like "toss". Now, if anyone can outline why Tesla is pronounced tezla, I'd be ever so etc. : )

[@IncognitoChild]

The only thing I ever remember seeing a mini toslink on was Sony Mini disc portables..... But now I think of it, I've seen it on Sony TVs as well for headphone/optical connection.

[@MrAdopado]

Apple had it for years ... but then unfortunately dropped it in 2016.

[@IncognitoChild]

@@MrAdopadothey only started using it in 2006, strange how they dropped it so quickly. I only used Mac's in the 80s, so I don't know the Apple consumer products. It was sold as "surround out" - did HDMI replace it?

[@MrAdopado]

@@IncognitoChild Apple used many different ways of delivering a digital output over the years that could be used for high quality audio. Early days was SCSI then Firewire 400, Firewire 800, Ethernet, USB versions 1,2,3, A,B and C variants, Mini DisplayPort, Thunderbolt versions 1,2,3,4, HDMI ... I may have missed a few! ... so Optical was just one of them. Presumably they found that the optical option wasn't frequently used by their customers so decided to drop it (like they dropped many of the previous standards when they became less in demand). Keeping optical for 10 years is a long time in the computer world ... and you can still do it with a "dongle" of course. Optical is still often used for domestic audio (TVs and Amps) and my own TV has no other method for me to easily get a discrete audio out to my amplifier.

[@timf-tinkering]

Not just Sony. Pretty-much all portable Minidisc recorders had a combined 3.5mm analogue / optical digital input connector.

[@IncognitoChild]

@@timf-tinkering yeah, you're right I should have said not exclusively limited to. Although they were the first (I only ever bought Sony)👍😎

[@gregwmanning]

I used duplex (tx/Rx) "single mode" optical fibre patch cords at work (telecommunication) of varying lengths upto 30m, that carry a 10Gb signal, (some patch cords even carry dozens of 10Gb wavelengths or "colours"). Some of my equipment have 100Gb ports. The patch cords cost depends on their length. I dont see the invoices now days, but previously they were about $20-$100. In my industry stuff get cheaper and better (and faster) as time passes. My short investigations of Toslink, says it is a multimode optic fibre system. Manufacturing tolerances required for multimode fibre are a lot lower than single mode, so therefore should be cheaper. Is it possible audio fibre systems, is marketing hype over substance?

[@chrisbartram3034]

It's the pricey Toslink cables that are hype over substance, plenty for under a tenner on Amazon, and TBH, it's either going to work or not.

[@georgebliss964]

I am not sure why Fosi chose Toslink over SPDIF which is more popular and user friendly.

[@Wuppie62]

​​@@chrisbartram3034 I'm using a very affordable Amazon toslink cable between my TV-mediabox and an external DAC for TV-audio, and it works perfectly. Why? Because all the other ports on my external DAC are already occupied by other digital sources, my amp has only one unbalanced audio input (which is connected to my DAC's audio out), and I also prefer the sound of my external DAC over the TV-mediabox' internal DAC.

[@davidkclayton]

They have been using encoders in audio equipment for quite some time now. I have not yet seen a system that doesn't remember it's settings. If that's the case in this piece I think that's an oversight.🤨

[@billmankin6204]

Wow. >$700 for a TOSLINK is _criminal_. Any computer engineer

[@dangerzone007]

It doesn't sound like any more fun than a regular DAC amp. Nowhere near as much fun as a Mojo 2 with its EQ and crossfeed features. And then there's trying to remember what the lights do.

[@Kevin-sh1sx]

Oh, 650$

[@mortenjohansen4120]

Why don’t you use thr headphones they use in studios, AKG k240 or Behringer hps 3000???

[@AudioMasterclass]

Wot? Behringer HPS3000 for $15? Sure you don't mean Beyerdynamic DT100? Anyway, here's my affiliate link for the Behringers. Buy, buy, buy - amzn.to/3HXox4n

[@PeTroL420]

I don't understand. Wouldn't a balanced output be mono? On a mixer's XLR inputs, you have to run two balanced cables and have a two channel capable DI box or use two DI boxes to achieve stereo.

[@Wuppie62]

A standard XLR cable is wired in a certain way that it transports 1 signal. But with (mini-)jack plugs you have variants like TR, TRS, and TRRS, where T stands for Tip, R for Ring, and S for Sleeve. Therefor a jack plug can be mono, stereo, unbalanced or balanced.

[@PeTroL420]

@@Wuppie62 I don't think you understand what I'm saying. TS, TRS and TRRS are all unbalanced. TS is mono, TRS is stereo left/right and TRRS is stereo left/right plus mic. A stereo balanced plug would need something like a TRRRS because you'll need two positives, two negatives and a ground to get the signals balanced.

[@Wuppie62]

@@PeTroL420 6.3mm jack plugs cables can be used for one channel (mono) Balanced. Just like XLR. I have them and use them as such. TS jack plug is unbalanced mono. Bytheway, search for and look for instance at " iFi Audio 4.4mm to XLR cable ".

[@peters7949]

Headphones, being a relatively high signal level & low impedance (like loudspeakers) do not need a screen, just 2 wires per driver (ear) so an XLR with 4 or more pins would be ideal, preferably wired so the output is on a socket, and. The head phones on the plug, so it’s not possible to touch the ‘live’ contacts when not plugged in. The voltage is almost certainly not large enough to cause harm, but shorting the pins might damage the headphone amplifier.

[@thefloop2813]

Your unboxing music might indeed be absolutely abysmally horrible. It does sound really good though, especially for a youtube video. P.s. Ill poke my nose into the cable and capacitor issues whenever i get the chance, but i just like to chuckle from the sidelines when it comes to the whole usb/coaxial/optical thing. Gotta choose your battles, ya know? And SCSI? Why did you have to remind me, the night terrors are gonna come back now.

[@middleearthltd]

I Heart stick up the arse Brits who love to hear themselves talk I would rate this sarcasm at SK02 level

[@ac81017]

As an Audiophile DSD is useless unless you like classical music. Last time I checked there was only 1000 odd albums in DSD.

[@Jacob1451_Kapnobatai]

Honestly, after 124kpbs, I realistically can't tell objective sound quality differences. I still wonder what the benefits of all the extra file size of hi-res files actually is for the listener. Far as I can tell it at best, mostly benefits producers making music

[@tinetannies4637]

​@@Jacob1451_KapnobataiWhen you get older, wealthier, more able to afford high end audio equipment, and your own high end hearing simultaneously fades away, you'll appreciate having those larger higher res files. Wait a sec.....

[@Jacob1451_Kapnobatai]

@tinetannies4637 Oh yeah, I got 2 DAPS, 3 DACS, and balanced cables already too. Slowly building up a decent song library. Loving this journey 🤟🤟🤟🤟

[@Synthematix]

Toshiba Link

[@nicc5122]

Hang on, there's no 32kHz sample decode? More optical comments. I use a DAC on a laptop to generate an OPTICAL output (electrically isolated) then feed it into a DAC, so USB in and optical out does make sense (just digital pass through)

[@AudioMasterclass]

At some point someone is going to say they like the sound of optical.

[@deejayiwan7]

Fun fact: older Mac Book Pro models had optical out in headphone combo out

[@AudioMasterclass]

I try to learn something new every day. I can relax now.

[@chefsteve8381]

Balanced will stop ground loops.

[@PeTroL420]

Not all the time. You can still get a buzz with balanced cables.

[@marcbegine]

Toshiba link (Toslink)

[@SparK17299]

It's toslink, not tozlink. Toshiba invented it and the term stands for toshiba link

[@AudioMasterclass]

Aha, toshlink then.

[@SparK17299]

@@AudioMasterclass 😂

[@kristianlarsen7694]

Ere we go again, facing endless amounts of rewievers, producing avalanches of statements and verdicts of this, they may believe is a new thing. Its not new, you made a balanced output yourself, and i as a very practical amateur did with the xlr output of my Lynx one soundcard. I had a pair of sennheiser 410 that were 600 ohm. They had cable for each side into 6,5 mm jack. I cut it and soldered each side + and - to xlr, and plugged it into the output of my soundcard. Used it for tracking. I may not be the only one to do that. It was in use until microsoft with an "upgrade" of their OS turned the sound card obsolete. I am glad that microsoft OS is not part of my car. Is it correct that noise mostly hits high impedance connections? Headphones with 32 ohms are low impedance, so is there a problem to fix? As the saying goes. If it aint broke, dont fix it. There is allways a fair amount of trolling in your videos just 0,0001 mm below the surface. Thanks for the fun.

[@edwarddodge7937]

Too bad there are no PCM multiples of 44.1kHz

[@peters7949]

Whilst not common they do exist, 88.2kHz, 176.4kHz. Although I can’t see the point of the, in this day & age. In the dim & distant past down conversion from 88.2 to 44.1 was much easier, but with modern sample rate converters this is no longer a problem.

[@Kevin-sh1sx]

It seems to include, but there is no separate light display, classified as adjacent lights, for example, 88.2KHz will be placed in the 96KHz light.

[@chaoticsystem2211]

what?? 4?

[@AudioMasterclass]

Correct. You're the first and only to answer so far.

[@chaoticsystem2211]

@@AudioMasterclass But how? The only way i can think of, is to use separate transformers for each channel. Without common 0V, you could save one wire. But does that even work?

[@AudioMasterclass]

@@chaoticsystem2211 I didn't use transformers, I used two op-amps. Each side of the headphones is connected across the outputs of the two op amps (one is inverted). Two pins x two channels = a four-pin XLR.

[@chaoticsystem2211]

@@AudioMasterclass i see... thanks. analog circuits are like magic to me anyway :D

[@D1N02]

too bad I can't read lips

[@jimhines5145]

While your reviews are extremely good and well thought out, I liked your channel better before you started this...review thing. Sure free stuff is always great to get, but this is really cheap stuff. Don't get me wrong, some cheap stuff is great quality and I do have a few Fosi audio components myself. I just feel like you had a great channel before you started doing equipment reviews. Please don't do many of them and get back to your original ideas, which are great videos.

[@AudioMasterclass]

My secret plan is to work up from cheap gear to high-end. I don't know whether the high-end manufacturers will dare though.

[@amcluesent]

Not sure if this was meant to be humorous, but satirising your core audience doesn't seem the smartest of moves.

[@hansfijlstra5932]

What do you think his core audience is?

[@Smithy225]

Oh chill out

[@peters7949]

I’m with Dave on this one, satirise away.

[@ChrisStoneinator]

I don't think you're his core audience mate. Sorry. And yes, it's hilarious actually.