spritzer

Yup, and they sure can rock. Bass has that slight reverb to it which suits rock perfectly. I'll reserve final judgement until I've plugged the ports and played with the pads. This is a bloody good start though...

An hour or so ago I got a brand new SR-007Mk2 delivered to me serial SZ3-2029. First impressions are positive, the fit out of the box is good and the midrange issues I had with the older Mk2.5 are gone now. The bass is a joke as is to be expected from a ported design but it is at least mostly controlled and only falls apart at a limited range. The top end is not as smooth as it should be but it might just be due to the earpad position. More updates coming and we'll see how long I'll last until I've ripped them apart to mod.

More than half of my SumR transformers buzzed and about a quarter are simply unusable. One of them melted through the insulation and shorted to the chassis... I've had some up and downs with Toroidy but they are mostly good.

I just want some large film caps right on the rails.

I don't think there is anybody who will match these for you. The amp will work just fine with unmatched ones though

The transformers are over spec so line fluctuation should never be a problem.

Poly caps always beat ceramic in my book so go for it. As for the 4.7uf caps, I can't find the layput files here for this board but I'm pretty sure they are the bypass caps I wanted Kevin to put in. Any value that fits is fine there but moar is moar bettah!!!

Indeed!!!!

Should be ok at lower voltages.

Been there, done that. It's a waste of money in this circuit.

It can be wired as both 117V and 230V but why would you order a transformer like that. You need a switch to wire them either in series or parallel but no simple solution springs to mind. Nothing wrong with doing this but watch the phase. I had to do this on the KGDT's that I'm working on and used this transformer: 553-FS36-350 with these custom PCB's: It was the neatest way of doing it. I have some spare PCB's listed on my site if anybody needs one.

The 21K is to drop the +450V down to +300V to power the front end. There is no attenuation anywhere so either wrong parts somewhere or the tubes are bad.

Indeed, doesn't make any sense.

100V zeners back to back and 1N4007's is what I used.

It would be very Rudistor though. He had "silver reinforced" traces...

I think the only reason why my T2 arced through the bushing into the screw is because of the hole on the 3675's isn't quite large enough so I had to force them. Might have damaged one in the process.

Yup

It's fine to keep C108 but put it before R104.

I use M3 standoffs instead of nuts. Less chance of the thread stripping.

On none at all and just a plastic washer.

Nope, I haven't had any for a few years now.

You need a special bushing for the ceramic insulators. Can't remember the part name though...

The non engineer will chime in then. We don't specify HV resistors except where they are actually needed. I for one don't count the Vishay/Dales as a high voltage type even though they are good for 500V. The ballast resistor should be a 1000V unit and the output resistors should be 500V or more. The thicker traces aren't needed per se but they also don't hurt. Kevin and I use larger traces than is usual so making those thicker will only help with the thermal performance of the boards i.e. when soldering and as is the case with DIY stuff... desoldering. Ceramic insulators are simply the end result of lessons learned the hard way. The thinner insulators can and will be damaged. For instance when using the IXYS ccs on the KGSSHV the tab of the transistor will see a lot of voltage so why not go into overkill mode. I wouldn't really call this over engineering in any way, this is the sensible sort not driven by any cost factor. Overkill is to use a 400VA transformer where a 100VA would suffice and drive the pass transistors in the psu into oblivion.

Yup. Stax finally stopped doing this as it will damage the diaphragms. King Sound still thinks this is a good idea though...

Any strong glue will work for the drivers. Polyurethane is what is commonly used as it is very strong and stable but with a long cure time. Martin Logan use tape but they also use it as spacers. You can use poly to attach the driver to the baffle but it is very strong so odds of removing them ever again, are slim. Better use double sided tape as that's what Stax use. Now theirs is crap so any strong glue that doesn't leave a lot of residue works. I bought once everything I could find locally and some Tesa carpet glue worked very well. Two different kinds though, the transparent one which is reinforced with some twine is the best one. Ditto for the earpads, double sided tape there too. Now with the dust cover compromised you can expect some squealing. How much is impossible to tell.