KINKI Headphone Amplifier Repair (Vision THR-1)

Mark takes a look at a rather high end Headphone Amplifier, from Kinki Studio in China. It was made in 2019, but has no output after 5 years. What went wrong?
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[@ralphalder14]

If Kinki Audio ever teamed up with Schiit Audio they’d have a fantastic opportunity for a new brand name !! 😅😅😅

[@FrankWoodPhotography]

😂

[@wollaminfaetter]

😂😂😂😂

[@tjtreinen7381]

🤣🤣🤣🤣🤣🤣🤣🤣🤣

[@rillloudmother]

at least they would sell a lot of bumper stickers in certain parts of the usa...

[@potassiumchloride6968]

inki pinky ponki💀💀

[@bobgrob4]

70K subs and climbing. We need to get Mark up to about 5 Mil

[@pabloluchi3595]

Burnt mosfets, overheathed PCB .. and there is no ventilation holes in that chassis.. My guess,, It will happen again soon. Anyways.. Great repair on this, Mark!

[@edmaster3147]

Mark has the spares on the shelf ;)

[@RedShift5]

I think in this case on FET failed and then cooked the others resulting in total failure

[@absurdengineering]

Last thing I’d have ever expected to see that is a headphone amp lol.

[@petercornell2002]

That amp is SERIOUSLY over-engineered. Something like 2 x 15w for headphones? I love it! Good to see you back Mark.

[@borlibaer]

Yes, overengineered at the wrong Place. Massive enclosure, pippi heatsink plate 😂

[@mattparker8747]

Yep, it's audiophile quality 🙂 The clue is in the word audiophile. Someone who loves listening to music is a musicophile. Audiophile just means lover of sound - they just listen to their system....

[@csm0881]

​@@borlibaerĺpp

[@peterlarkin762]

The output spec is there to accommodate very power hungry headphones. Some fancy headphones need a LOT (maybe not quite this much). The sad thing is the case itself would have worked as a heatsink far better. The engineer should know better.

[@edmaster3147]

@@peterlarkin762 I kida get the idea that they tried to engineer the mosfets as 'tube' devices, hence the high voltages, which are for headphone output uncommon. FET's often sound nice when warm -70 degrees centigrade und up-. A more common solution is just an arrangement of good op-amps for headphone use, which drastically reduces the amount of components and more importantly, coupling over caps and worse, resistors. Yet, I have never designed an headphone amp nor do I like headphones, so I can be very wrong. In general I would stay away from hard to drive headphones, the same for non-efficient loudspeakers, though there are always many reasons to oppose that.

[@Mihail_K.]

Such a chunky aluminium enclosure and they put the transistors on that little slab, I guess you could say that's a little... kinki, isn't it.

[@radicalaudiodesign]

That heatsink connects to toplid when screwed down so not so little slab anymore.

[@Mihail_K.]

@@radicalaudiodesign I doubt it makes good contact thermally. And the lack of vent holes... Those transistors shouldn't be getting really hot to begin with but still, it just looks dodgy.

[@Tokaisho1]

I'd say there's an air gap@@radicalaudiodesign

[@SusanAmberBruce]

An improvement would be a thicker longer block of aluminium that gets screwed to the lid and with the mosfets wider apart.

[@andrea.dalessandro]

@@radicalaudiodesign kapton tape instead of thermal paste is an indicator of someone who was asleep at school that day when they explained how to make heat sinks.

[@T0pBaNaNa]

I literally threw my hands in the air when i got the notification 😂....Haven't even watched it yet 🤗

[@bobgrob4]

I know...Mark is the best. Love these videos.

[@jeremywh7]

Great video as always! Regarding those power transistors; Kapton tape has poor thermal conductivity vs thermal pads - perhaps the root failure was from someone trying to use this as a regular speaker amplifier, overheating to short? But as @pantelisEVs noted, using the chassis seems like a much better idea too (with thermal pads 🐱).

[@sw6188]

You're dead right - Kapton tape isn't designed as a thermal conductor. No way would I use it in place of silicone pads or thermal grease. It's the sort of cheap-ass shortcut that I see in china stuff all the time and just another reason I tell people not to buy this stuff.

[@mactheweld]

thats what i thought and possibly wrong impedance speakers . made that mistake myself used my bi amp speakers (paralleled 🙄) on my rotel 931 amp , like a divi and cooked the o/p transistors

[@maksqwe1]

Just got out of the shower, got in bed and thought let’s watch a few videos before bed.. and Marks video pops up!!!

[@Rob1972Gem]

Without doubt the best electronic fixing channel on KZbin please please longer videos I have learnt so much from watching your videos please keep the vids coming

[@PrimeHiFi]

All the thermal mass of the over-built chassis and they choose to mount TO-3P lateral mosfets which are no doubt biased into class A to a tiny piece of metal as a heatsink! You can tell they’ve been getting excessively hot by the board discoloration. Even the cases of the MOSFETs have discolored. And scraped part numbers on the components! This amp is over-engineered except for where it counts. Good for the warranty period and then will give you a bunch of trouble afterward. The company scraping part numbers and not providing even a simplified schematic screams stay away… Great work on the repair, Mark 👍🏼

[@nevillegoddard4966]

@@PrimeHiFi ...And yet I wonder if the manufacturer even has a repairs department if miracle Mike wasn't there to mend it? I'll bet not! I just HATE it when manufacturers scrape off part numbers!😠😡🤬🤬! It seems almost CRIMINAL!

[@LeifES]

Came here just to see the electroshock in the intro again. Haha no, great video!

[@DavidFRhodes]

the best part for sure

[@AG-cg7lk]

Companies that grind labels off of components or cover them in goop need a slap.

[@UnCoolDad]

Where is part 3 of the AIWA?

[@artsimannisto5659]

Yes mee soo eagerly waiting,Hungryfor that.But,sadly,Mark hates cassdecks....

[@batmandestroys1978]

Good point! Mark needs a rest on that one, but will suddenly strike back with it repaired in another video! I cannot wait for that one!

[@darrenmurphy6251]

wonder if someone ran high impedance mode into low impedance headphones = loads of heat then eventually mosfet failure i dont think that was a heatsink but just a way of thermally ballancing the high and low side mosfet pairs , like those little alluminium twin to92 clamps for input differencial pairs we used to see in the 90,s i didnt see any switching relay to select a lower rail voltage by selecting a lower voltage secondary winding just a protect relay for high and low impedance modes

[@trickyd499]

Best electronics channel, keep it up Mark!

[@pantelisEVs]

WOW. Thats the definition of an overkill output stage for headphones! Notes: -These power MOSes could be mounted and take advantage of this chunky bottom plane. -Is this high impedance mode protected in case someone plugs low impedance headphones or overcurrent and damage to the output devices Really interesting design anyway!

[@gibbogle]

Using the bottom plane looks like a no-brainer.

[@thesleepstate]

This unit is £1199 street

[@SusanAmberBruce]

@@thesleepstate Really, I knew it would be expensive, but that's mental!

[@JPDESS]

Hi, some micas and thermal paste should work better to dissipate the heat than capton tape on those mosfet, it is not suppose to break.

[@danhorton6182]

Interesting you saying the MOSFETs not needing a heatsink considering how hot they’ve clearly gotten. Excellent video.

[@edmaster3147]

4 mosfets for a device with has an output of just a few watts, the FETS should stay extremely cold, yet they decided to large packets, I'd suppose at least.

[@danhorton6182]

@@edmaster3147 well then in reality they could have used TO220 devices then, regardless they don’t look like they’re staying too cold.

[@paulb4661]

@@edmaster3147 These lateral FETs have their Rds on the high side and benefit from sensible thermal arrangement, especially that they should ideally be run with high DC bias.

[@marjon1703]

Yay!... new 'Mend it Mark' Vid... Happy, Happy, Joy, Joy!

[@colin4850]

Another great video Mark, could the damage have been caused by some piece of external equipment being connected wrongly, I guess we will never know. Looking forward to next video , keep up the good work.

[@baronofgreymatter14]

Great to see you Electronic Zen Master

[@SuperHyperExtra]

Balanced but not balanced... Is this acceptable practice or kind of a scam?

[@sw6188]

It's typical china 'cheat' - use 3-pin XLR sockets so you think you are getting balanced audio, but skimp on the circuitry inside and just make it unbalanced. The whole unit is one big design flaw aimed at extracting money from audiophools.

[@RJ-qh2px]

Do you think anyone that buys this device will actually notice?

[@ibrahimkocaalioglu]

We missed you. Nice quick fix.

[@DarrenMossAU]

Nice repair. I wasn't expecting that amp to be so well made. Really good workmanship on everything, even the case!

[@eddieMurphy11111]

that's is a superb job, nice to watch somebody who knows what they are doing ,thank you for the video

[@paulb4661]

Hi Mark, these fabulous fets based on Renesas J162/K1058 have unusual pin-out; the beads actually went on the gate and drain.

[@exiledscouser919]

Excellent as ever, it’s our pleasure to see you work through the problems and get them fixed. Thank you as always.

[@AMByram]

On holiday with my wife in Puerto Rico. She's taking a nap and I'm sipping a gin and tonic watching your vids and listening to the waves. Does it get better?

[@francomarianardini681]

good to see you back, Mark! ciao from Italy!

[@NoobCannon1234]

Another great video. I wish you posted more often but always a treat when you do. Thanks

[@D.Hozzie]

You’ve been missed Mark. Thanks!

[@blindbob4115]

I love listening to the sound of you working ❤️❤️❤️ great channel

[@Mickey-Knox]

I love these retro Phil Collins videos!

[@mistersunny3636]

🤣

[@AnthonyBarry-q1i]

All done as usual with the efficiency, finesse, and as usual the astounding knowledge you bring to this channel.

[@vintagehifirestoration6515]

Hi Mark I look with great pleasure at your videos they are very inspirational and I think I will made my own videos in audio repair soon, I learned a lot from you. Thank you!

[@rayofcreation3996]

Mark there you go again. Its an absolute joy watching you perform. Thanks and lots of love. 🎉

[@andrewwturner]

Excellent as always Mark. Please dont keep us waiting as long for the next one! 😊

[@neilosullivan8216]

I'm surprised you didn't run it under load for a while and test it for hot spots with your thermal camera - perhaps if it returns in the future? 😊

[@fantummenelkinstruments1959]

Happy days when there's a new vid from Mark! Top notch work once again!

[@TheMteok]

Hi Mark: The balanced OUTS are moste likely Impedance Balanced This is the type of output is notable for only driving the +leg (XLR pin 2) with audio. When measured on the bench, because of the absence of audio on the -leg (XLR pin 3) this circuit gives the appearance that it is an unbalanced output. In fact it is designed to provide a very good impedance balance. It gives correct level into an unbalanced input without needing special cables or wiring and it gives correct level when driving a cable with pin 1 & 3 connected, audio level or frequency response will not be affected.

[@bobrose7900]

Quality balanced connectors possibly the reason they are used but it does seem strange. Nice unit, made in China! It would have been nice to have done a performance test, i.e. frequency sweep at various gains and THD to see if it was worth the money... Great video at usual, thoroughly enjoy them but this was a bit short!

[@darrenmurphy6251]

i love mosfets in audio output they often blow up a little more gracefully than bipolar fire mongers and the usual 100r gate resistors protect the driver stages (usually)

[@sw6188]

The trouble with MOSFETs in audio output stages is that 30 years after the unit was made and you need to change out some transistors, they are obsolete and impossible to obtain. A good example are the 2SK1058 and 2SJ162 pairs. Used in many amps, they are now obsolete. BJT transistors are much easier to find - I have large stocks of genuine ones, many more than the MOSFET stocks that I have.

[@darrenmurphy6251]

Yes iam running genuine hitachi 2sj50, 2sk135 and some of my spares will be fakes 😢

[@sw6188]

@@darrenmurphy6251 The Hitachi 2SJ and 2SK series MOSFETs are pretty much bulletproof. I had an amp come in for service that the owner replaced the fuses with nails and drove the thing to max - yet the MOSFETs didn't die. In fact, in the past 40 years I have only replace ONE of these Hitachi devices. They just don't fail. I have good stocks of them.

[@Starcraftowns99]

Mark great video as always. I might be a bit sleepy, but I thought the second from left Exicon was loose in the part where you were installing the beads. Maybe it was deliberate to aid alignment of the pins to the board… if not. It needs to be tightened 😅

[@sw6188]

I saw that as well. Hopefully he caught it in time.

[@mattsan70]

Capton tape is terrible as transferring heat. No wonder they cooked themselves - Mark get it back and put some mica or silpads in do a proper job

[@twobob]

0.1 to 0.3 W/m•K ish versus 400 ish. Nah... be fine...what's several orders of magnitude between friends...

[@eolhcytoos]

I was wandering about that! Not being an engineer I assumed Mark knew best and let it go. Thanks for the info.

[@cesio25]

Another great video from most positive technician on YT. Pure pleasure to watch your content Mark

[@richardbrobeck2384]

nice repair !!

[@lumbo101]

Thank you Mark for another highly entertaining video, so well produced. When that resistor measured 3.9 Ohms I thought you were going to find out it was one of those chokes that looks like a resistor! I’ve been in power electronics for 35 years and not seen a resistor fail short either!

[@johnmarchington3146]

Nice one, Mark. Interesting that the XLRs were not truly balanced. I also wonder if the owner inadvertently shorted one of the outputs. The overheating of the PC board didn't look good either.

[@enoz.j3506]

People are saying why have a large piece of thick aluminium as a case, and not fit the power transistors to it, well i will explain, the transistors collector is live,+- 80volts ,and your relying on a piece of very thin kapton tape,just think of the shock risks,if the tape broke down,swarf etc,the case would be sitting at 80 od volts (enough to give a shock) ,its that simple,it wouldnt meet the safety specs,even though its made in China.

[@nevillegoddard4966]

@@enoz.j3506 We just used the regular mica washers & silicon grease under our power transistors that have 1200V on them with no problems! The pcb should NEVER get so hot that it discolours like this one did. It will eventually become conductive. The uniform discolouration under all the mosfets means they've ALL been overheating. $1000 for a piece of 💩 that just looks good, feels heavy, but WILL fail! Kinky CRAP!

[@enoz.j3506]

@@nevillegoddard4966Yes ,as a qualified electronics engineer,for 40+ years,mica washers and silicon grease was & still is, widly used,mica withstands 1000 deg c,Kapton 260 degs c,big difference,got to look at worse case cenarios,to blue the legs on those fets,i dont know ,as you say the fact that the pcb is burnt means,bad designe & will conduct eventually. I dont know why they didnt use insulated fets,then bolting to chassis would be the way to go.Its made in China,nuff said.Make it look good and it will sell.

[@Bigbluevwvan]

Another great fix and Kinki look great build quailty :)

[@MonguzTea]

An electronics engineer would laugh his ass off looking at that thing. The case is impressive the rest not so much.

[@nickk6109]

love the metal back to the mosfet, with a metal screw into a combined metal heatsink.. (I have a set of these same fets). I'd probably want insulating inserts or plastic screws..

[@chezsnailez]

By the time you were able to afford this sort of kit your hearing has deteriorated to the point a 1990s Aiwa all-in-one would suffice...

[@barrybradfordlocksport]

Great, but not enough uploads mark we love your content

[@gordonm2821]

You would think if they were throwing that amount of money at it you would have transformers feeding the XLR outs. Also I think it’s a bit overkill sanding off the component text. I think if someone was looking to copy the idea they would not copy this design!

[@sw6188]

A good balanced output stage can be done cheaply and well with op-amps but yes, for the money this thing costs I would expect to see transformers in it!

[@skypittman9303]

Call me an oddball but I think all videos of the unscrewing fast forwards would make a good ASMR compilation. Another great video Mark, it made my day after work to relax and watch. Cheers future watchers and enjoy.

[@adalbertus777]

Good to see you're back Mark! You've set the bar very, very high when it comes to electronic repair videos. Different camera angles, zoom-ins, lightening, post-production and so on. I wonder how much time did you spend making this, relatively short one. ;)

[@edmaster3147]

hear hear, Mark does a great job, smart and capable guy

[@wirdy1]

Those that know, know how much thought & time this takes.

[@mactheweld]

great vids mark . would be nice to listen to the repaired equipment operating in real world use

[@Trucam2020]

Thanks Mark, I always enjoy your videos

[@michaelcarey]

I'm not sure Kapton tape is a good thermal conductor. It has fantastic thermal stability and a great electrical insulator, but I don't think it is a good thermal conductor. This could be part of the failure mode, if heat can't be removed from the semiconductors it will hasten their demise.

[@MendItMark]

You're right, but kept it to the audiophile factory spec. There is such a high voltage across those transistors, it wouldn't take much current to get them toasty!

[@DominicClifton]

I use kapton tape to STOP heat transfer. Does the kapton tape behind the mosfets actually stop the heatsink from acting like a heatsink? That'd be my guess why it failed.

[@sw6188]

For sure, that tape should not be used in that application but also those transistors shouldn't get anywhere near hot enough to fail even without decent heatsinking.

[@kevinmothers904]

Mend it Mark notification. Ah! the parts have arrived for the AIWA tape deck. Nope, we've gone all KINKI from China.

[@Choralone422]

Time to get KINKI with Mark! Let's do it!

[@rhkavli]

As usual, the Chinese doesn't know how to spell. But I was surprised by the build quality and the component selection. At least the ones that survived the anonymisation process.

[@zuvinrat4155]

Youre back , great episode Mark!

[@MrTurboturbine]

I love the 555 timer in it's heavily guarded isolation 2:54

[@andyfish4821]

Wow, tidy bit of kit....Nice to see you back mark 👏

[@kjbunnyboiler]

Excellent as always👍👍

[@sjqideez6626]

Wow Mark, awesome stuff. Thank you

[@brianhoskins1979]

I don't understand the use of kapton tape on the heatsink. Is it a good conductor of heat? I always thought it was a _bad_ conductor of heat, and hence why it is used to cover components where a hot-air gun will be used. I'd have used thermal pads on those FETs instead.

[@JonnyMac351]

My thoughts too.

[@edmaster3147]

Excellent Mark; not truely balanced. That was really funny :) They made it look so impressive, kinda wondering if the elektrons don't get lost, in all that copper. Were the little diodes in series with the stoppers?

[@robinandreasson4911]

Ahh great content, thanks Mark

[@Fanan67]

Mark can you make a video on testing balanced outputs on the oscilloscope ?

[@alialmahanawi8409]

Excellent job Mark thanks for sharing 🙏

[@artsimannisto5659]

well,aiwa is ,i think, way pain ina ass. HOPE THAT we see that soon enough,thumbs up. Thanks,Mark,top guy in repair business.

[@hw4527]

Thank you for posting 👍👍

[@andrea.dalessandro]

I'd say "underengineered" (in the sense "designed by someone who was not a real engineer"): 4 large mosfet for an amp needing few milliwatt (they managed to get fried anyway); kapton tape (an heat insulator) instead of thermal grease between the mosfets and the heatsink; a 30VA transformer for stand-by function, paired with another toroidal transformer, etc. etc. 🙄

[@sw6188]

It's typical china 'bling' - made to look the part but what's under the hood isn't that great. Designed to extract money from audiophools mostly.

[@andrea.dalessandro]

@@sw6188 exactly. I despise them (both the audiophools and those who exploit them).

[@andygardiner6526]

I really appreciate the quality of that unit but, at some point during manufacture, the question must have been "Are we designing this box to survive re-entry from orbit?" :-)

[@janinapalmer8368]

It's made like a PS Audio amp ... I'd like to know what actually caused this thing to fail and if Mark did find ALL of the damage too, quite often things like this will work ok after you replace the obviously damaged parts but all too often there are other components too that have been knocked about a bit too that are only just hanging in there and may well fail in the future . I am guessing this headphone amp was used to drive some 4ohm speakers ..!

[@fichambawelby2632]

Nice to see you again, Mark!

[@batmandestroys1978]

I Always buy Japanese products, whether they are are vintage or brand new! I have vintage Japanese audio going back to the 70s and 80s which has never failed! The only works I have carried out to them, is replacing the capacitors, a few transistors, few resistors and update the speaker terminals and RCAs! Chinese amplifiers look nice, but they use very cheap components, is grossly over engineered, and very poorly ventilated! The same fault will occur due to poor ventilation! The customer should work with Mark, to fit a fan on the outside, and make some vent holes in the casing, because Mark is an exceptional, wonderful, talented gifted engineer!

[@zokxzoranovski5255]

As usual, Mark is the best.. :)

[@quadmods]

Kapton tape is very insulting for heat transfer. Just saying… cheers, I enjoy your videos. 👍

[@cesio25]

Exactly, I think kapton tape suppose to be used as thermal isolation fx when solderind, desoldering SMD

[@quadmods]

@@cesio25 ask me how I know 😂 wrapped a little video transmitter in it to keep it clean, would constantly over heat, removed it and was good for months…

[@cesio25]

@@quadmods so this little Amp will come back to Mark with the same issue🤷

[@keithneal5369]

Talk about overkill. Just shows what extremes some people will go to just to listen through headphones. God knows why you need so much power. As always your video's are educational and entertaining.

I guess it cooked itself as it lacks even pasive cooling like venting holes. I guess a slab of aluminium block with kapton tape is not enough for these mosfets.

[@nicodenhaak3961]

Great channel, one of my favorites. Just one observation: Mark, when you did put the four fets back together, mounted on that aluminium plate, one of them seemed to turn and shift. Second one from the left. Like it wasn't torqued down? Worth checking the video possibly.

[@mrrootytooty5797]

Mark is my hero ❤

[@faps7283]

tuyệt vời,những kinh nghiệm và máy móc sửa chữa kinh điển

[@gibbogle]

For all the thick alloy of the case, there is minimal heat sinking on the power transistors. Very crappy design, IMO. They will overheat and blow again unless some extra heatsink is added.

[@paulanderson7796]

Driving cans? We're talking milliwatts here.

[@prairiedawg792]

It could be a Class A amp which still consumes full power even at quiescent

[@paulanderson7796]

@@prairiedawg792With pairs of output transistors and no output decoupling that's unlikely.

[@gibbogle]

@@paulanderson7796 How do you account for the heat discoloration on the circuit board?

[@paulanderson7796]

@@gibbogle I am thinking that it's possibly a symptom of the fault itself.

[@profpep]

I wonder if one of those MOSFETs had gone unstable? In earlier days of MOSFET power amps Ihad a few go like that. They can osciliate in the GHz region, too, so you see nothing on your scope. The ferrite beads on the legs are a hint that it might be an issue. With one brand of power amp in the 80s, I resorted to the old radio amateurs leak testing trick of a wire loop with a PIN diode and a small bulb to see if the power amp I was looking at had turned into a transmitter.

[@acj2789]

Is it possible that the amplifier has been used with loudspeakers connected to the low-impedance outputs? With 65 V rails either side of the 0 V line, the output swing of the voltage could be enough to give a decent power output to the loudspeakers, for which the heatsink would be inadequate.

[@adriangreen6462]

Hi mark , love your channel, you are very talented, can you tell me where you get your components from, especially caps, as a lot of components on the internet arnt very good, your advice would be appreciated, thanks ade Sheffield

[@יהודהנטף]

Like always, great work!

[@utp216]

That’s one chunky chassis! I hope it sounds good on the output side!

[@johnfitzpatrick2469]

G,day Mark from Sydney Australia. That is a quality amp. The burn marking on the PCB is a strong indicator of short circuits? * Also running the output to the oscilloscope to check the sine wave frequency. 🌏🇦🇺

[@hugeshows]

Great repair as usual, but I'm afraid I'll have to ding you one point for not cleaning the carbon from the burnt resistor off the circuit board!

[@matthewhaddon599]

I have an Allnic preamp which certainly looks good and works well, but when you actually look at the way it's been made, you find issues, such as you discovered with this Kinki not being balanced.

[@sw6188]

China is all about 'look' and not about 'form'. They often produce products like this that have the appearance of 'expensive' but they cut corners.

[@jimfarrell4635]

​​@@sw6188 Allnic is a small Korean family firm who, for example, hand wind their own transformers. They are not associated with shoddy workmanship although their design choices can be unorthodox. Also, not Chinese.

[@McGyver0479]

Curiosity. Mark are you a model maker? Helicopters or Planes? Complimenti!

[@jimbobroon-wj4qx]

Superb !!! As always😁👍

[@dumitrubaluta7058]

so much aluminium on the chase and so tiny heatsink

[@homolupus1]

What are the output protections? This failure mode is quite common if there's no robust output protection block (and doesn't look like there's one) and someone yanks out TRS plug while amp is driving some reasonable signal.

[@arenaengineering8070]

This headphone amplifier have a big aluminium case, but output trasistor mounted on little heatsink. Case can be a good heatsink.

[@jamescollins6085]

I would take advantage of that huge bottom plate and mount them onto there.

[@arenaengineering8070]

In this amplifier, you can simply place the output transistors on the bottom side of the printed circuit board, bending the leads and fixing them directly to the bottom of the case. The main thing is to use an insulating thermal pad. As is done, for example, in the Burson Soloist HA160 amplifier.

[@jamescollins6085]

@@arenaengineering8070 The Kapton tape used here seems like a bad idea, seeing as it's best known for its thermal insulating properties. A thermal pad would definitely be better. What's the reason for the transistors being unable to make direct contact with the chassis?

[@arenaengineering8070]

@@jamescollins6085 The case of the used output transistors is not insulated and in direct contact with the aluminum chassis a short circuit will occur between the + and - power supply. Kapton tape is used in this amplifier more as an insulator.

[@jamescollins6085]

@@arenaengineering8070 Thank you for the explanation.