spritzer

Have you quadruple checked all the parts? Same fault on both boards is either PSU related or the wrong part on both boards.

The new HVk PSU board? It is 6.92" by 6.56 and the distance from the back of the transistor to the edge is 0.563014" give or take... So both boards are like this?

Using the BH transformer requirements would be a good idea with this one. I will be using one of my spare BH transformers so only +/-400V but for 450V use a ca. 400VAC transformer.

Glad this was sorted.

Happy Birthday!!

There should be a schematic in the "now for something different thread" or I could just be imagining things. I'm sure Kevin sent me a link to it at some time or I can try and find the simulation files...

So no more Analickus? Such a shame... How will we find out more about the plankton?

Yes that's how the rating works. I believe Belden also rate their wires when you bundle them and then they are 1000V+ for the 600V PTFE.

They claim 450V but who knows what the drivers will actually handle.

Who let the HF shortbus in?

283-2.0-RC should work just fine.

You are talking about the production amp here then? Doesn't matter really as it is the same case with all amps that feature multiple outputs, there are just two channels in the amp so power will be shared. Matching is better but it should work just fine with no matching at all.

Try them on Pro bias and report back. They should be just fine unless you given them the full volume of the BH.

The blue caps are probably the WIMA FKP's so that could be 470pf/2000V. Still, those are kinda important... I'm also wondering what's lurking underneath the boards. Could be the missing resistors from the board as thick films bonded to the sinks.

There is a newer version too with a full size PSU so they can be stacked. So pretty much a WES which isn't terrible...

I'd rather have gone with "in Russia, amp listens to you"...

So, who wants to see the Russian Blue Hawaii? http://fluxlab-acoustics.com/Products/11 Looks kinda nice but they are using the old parts so sourcing them must be an utter pain.

The L-2 fully balanced would be very complex and defeat the point of the circuit IMO. I did tell Doug to just put an XLR output and be done with it though. That felt paper stuff they use on the surface of the tweeter panels. That felt is utter overkill but these were also nearfield monitors.

I agree here, these mods went too far which is why removed them all after a while. Subtle surface treatment is all you need sane as you get around tweeters.

It's the first of the two designs they published in 1968 for DIY use. The second, which is at the bottom of the page (you can just make out the tube types), is the SRX. This design fits with just one rectifier and the low voltage rating of the tubes used. They could have used a voltage doubler after the rectifier but it makes little sense since the EL84's really don't like 300V or more. There are also just 8 tube sections in those 6 tubes and only two ways to go about it. Either you use this setup with a two stage phase splitter into the output tubes or a diffamp on the input which provides enough gain and uses one tube for each channel. The small amp I built with the Ikea bowl over the transformer is essentially just that, this circuit with a differential amp input to make it fully balanced but run at +300/+600V.

It is a good idea to never rely on the insulation actually insulating. As somebody on HF found out, the shell of the caps is connected to the negative terminal which is fine in a simple B+ setup (where the negative is always grounded) but here it is prolematic. If the cap is sitting on the PCB then just the thin shrink wrap is all that sits between 650VDC and ground. Even 1mm of clearance is enough for 1kV or more at high humidity so that makes sense.

The new ones? Shouldn't be necessary with the increased tolerances. Edit: Also won't help with this since it's trace to ground plane, not something that's on top of the board.

Well we should never have to rely on the solder resist for insulation. It's very thin on the boards Tran has made though

Anybody want to bet that this is the basis of the M-20 amp?

This is a PCB issue but whether it's the design or the fabhouse that gets the blame is the bigger question. Those traces are seeing upwards of 650VDC but the insulation should be adequate on the boards and more than double what is needed. There is not a whole lot of room for error though which is why we more than doubled the clearance on the mini boards. I usually have my own boards made and I haven't had this problem even with my mini boards which are the same spec as the older boards. As for grounding, simply connecting the XLR to the chassis assumes that the chassis is a perfect conductor when most are far from that. The real culprit is humidity and temperature extremes when shipping something. These have metal stators so freeze them in the cargo hold and then bring them back to room temp or even far more in high humidity will cause problems. The resistive coating traps the static generated and voila... imbalance. Now ship something like this on land at it is much less of an issue.