Addiction

September 2, 2021

5 hours ago, spritzer said:

Here is something that has been cooking for a while but I've been just too busy to do anything about it. So JR Audio out of China have been building our amp designs for a while now and I started to hear horror stories almost immediately. They naturally have no right to use our designs and work in their crappy products but since when has that stopped anybody... I have been looking for one of these amps for a while now as I want to rip it apart and well... one owner contacted me. I'm going to ask him to come here and tell his story which is quite the tale. Let's just say Caveat emptor...

So here is the amp and it arrived dead which will soon be clear. It is the KGSSHV version and well... it doesn't resemble my amp in any way... 🙄

One funny thing is that the Stax socket is made from nylon so the quality starts there. 😉

Nothing remarkable here but that voltage marking is directly lifted from my amps. Completely identical...

Here is where I started laughing, this thing uses clone versions of old PCB's I made back in the day. The amplifier board (as can be seen by the date which they also copied) was in some of the older KGSSHV mini amp but this one is quite a bit bigger. Same goes for the PSU which was in the first KGSSHV minis but this one is 2.5cm wider and 1cm taller. All the components are in the same spots... it's just a bit bigger.

Now here is whats wrong with it, see the bridge rectifier in the middle. That larger chunk of plastic shouldn't be sticking out of it.

Here is one amplifier section and I just find it hilarious that they do a direct copy of my 7 year old PCB but manage to completely fuck it up while doing it. So all of those resistors are 1/4W units and that is a big no-no. Most are well shy of that power level (though not all) but the voltage ratings for many of those resistors is well below safe levels. It also annoys me (Kevin even more) that they have removed all values off the boards and replaced them with generic labels. We have always pushed for proper markings on all boards so they can be serviced at any time.

Another thing clear in that picture are the 10M90's on that small heatsink on the PSU. They have a lot of voltage sitting on the metal tab so they naturally use a silpad and metal screw. Fucking amateur hour here.

Another picture of the damage and one more of the underside:

One nice attention to detail... or lack thereof is no thermal paste or silpad on the PSU pass transistors. Nothing at all and since the chassis is powerder coated, it has a hard time passing heat through the thin metal below. It's a shame I don't have any of these old PCB's in stock just to show how much of a blatant rip off they are. I'm tempted to order some (as I have the Gerbers for everything) just to show off what they are up to.

Now what happens to this amp, well it belongs to me so I'm going throw out the PSU and the transformer plus replace all the necessary resistor on the amplifier boards to make this safe. Then I'll just keep it for shits and giggles. I'll update the thread when I do some more work on this clusterfuck.