It's caused by trapped air trying to escape to equalize the pressure. Put the earphones on and with music playing, press them gently towards the head... I don't recommend doing this with the HE90, it's a bit unnerving...
Fair point but swapping in another tube type changes a lot of other things besides just the output power. I take it no adjustment is done to the amp besides changing the tubes?
Well ideally I'd want to fit an amp like that with an active cooling system. Think amp with a freezer attached...
It's the only way to get silly power levels from Class A. All the electricity here is green and renewable so I can waste it at will.
One must remeber one thing about BNC, that there isn't just one standard out there. There is also a 50 ohm version which most of the higher end connectors seem to be designed for...
That basically covers it but Toslink has its own problems but not the more advanced optical systems. I for one just use a transformer coupled BNC system with a true 75ohm coax.
Yeah, the fuse blew for a reason. Meets and B22's don't mix well so taking pix of the amp boards for use to see could be a good move. Look for charred parts next to the large heatsinks...
Hmmm I could go all Rudistor and attach power resistors to the chassis fed off a spare filament transformer controlled by a thermostat... "Forget preheating the valves, I preheat the chassis!!!"
One thing computers do very poorly is ground plus noise and other garbage riding on the power rails. I for one have a unit that offers the ability to use a separate PSU and there might be a small difference compared to powering it off the USB bus. Now my PSU cost me absolutely nothing (old Iomega Zip power brick) so why not use it...
That's one of the reasons why this is a prototype. The heat has an easy route up and away from the boards but the main heatsinks might be a different matter. There is also the issue of warmup as this massive billet might take a while to heat up...
I do have access to some crazy expensive thermal camera if I ask nicely enough quite frankly I'm not too worried about the thermal properties of this thing. We'll see when I get the boards mounted though.
As you might have spotted already, that riser in the side of the chassis doesn't work to fix the transistors in place. I'll have to a spreader and then mount that to the chassis.
The rated sensitivity of the transducers tells you everything about how much real power they need to reach a certain volume level. This naturally doesn't account for wild changes in impedance and the crap that goes with it.
I also hate the crap about this amp can drive full size cans just because it is loud enough. Fucking retarded idiots have no idea what they are talking about...