Just wonder if Kerry may make them tighter, and put them in chassis like densen's amp will looking cool .

 

url.jpg

 

b_330_alb_f-980x450.jpg

 

Looks interesting.  I was going for a small footprint so it would fit on my night table.

 

I've just ordered the amp boards and should have them within a couple of weeks.  Looking forward to testing the boards.

So I'm trying to track down some buzz/hum I'm getting in just the left channel of my recently acquired HV. The level of the buzz doesn't change with volume level at all. Here is a diagram of the grounds in the amp

 

 

The wire connecting the power supply to the star ground goes around behind the transformer, and when I move that wire around the buzzing changes, but it is weird that its only buzzing in the left channel during all of this.

 

Also of note is that this is my first/only stat amp, and I only have one brand new pair of Stax, 307s, that got to me from Price Japan with a channel imbalance issue. So I can't test other amps/cans.

 

Any advice is appreciated guys

So...

 

Add two wires from input and pot to star ground?

 

 

Hope this can solve.

Also of note is that this is my first/only stat amp, and I only have one brand new pair of Stax, 307s, that got to me from Price Japan with a channel imbalance issue. So I can't test other amps/cans.

 

Now, if it makes you feel better, my 307s also had a significant channel imbalance. What's up with Stax quality control?

Now, if it makes you feel better, my 307s also had a significant channel imbalance. What's up with Stax quality control?

 

heh, now I have to deal with shipping them back to Price Japan and then waiting for warranty repair and then to ship them back. I guess even though they arrived essentially dead on arrival, they don't do exchanges of any kind...I'm starting to think the buzzing in the left channel might be related to the imbalance as well, since the amp was silent before it got shipped to me.

 

Palchiu, thanks for the advice, but something I left out is that the pot is grounded to the chassis already, and adding those two wires seems like it would make a literal ground "loop" of wire, which doesn't seem like a good idea?

Now, if it makes you feel better, my 307s also had a significant channel imbalance. What's up with Stax quality control?

 

This happens during shipping so it's not a Stax QC issue.  Just an annoying quirk of electrostatics. 

This happens during shipping so it's not a Stax QC issue.  Just an annoying quirk of electrostatics. 

 

Is like the normal periodic channel imbalance issues that crop up? Do you think it will go away after playing music for 2 weeks? Or is it something that we need to send them back to get fixed?

 

I feel like it was packaged pretty well though

This happens during shipping so it's not a Stax QC issue.  Just an annoying quirk of electrostatics.

Ok, maybe not QC at end of production line, but they - stax, the importers and the retailers - should either package the earphones well enough so it does not happen or design the product so it can withstand the treatment from the shipping companies. When you buy eggs at the supermarket, you expect them to be fresh and without cracks!

SoupRKnowva, did you ground pin 1 to chassis at entry point?

SoupRKnowva, did you ground pin 1 to chassis at entry point?

 

Uh...to quote GeorgeP, who I bought the amp from "The input grounds are grounded in accordance with the Rane standard which is the proper way to ground xlr - ie through the shield", pin 1 from the XLRs goes the the ground pad on the pcb for the pot, which is grounded to the chassis through contact.

My power supply board was making popping sounds yesterday.  A close look showed that there were two short circuit spots.  One underneath a capacitor and the other one near the diode.

 

 

 

I think the insulation varnish on the PCB is too thin for 500VDC or the copper traces are too close to the ground plain.  

 

I clean the spots up, cover them with nail clear coat, and now it's working fine.

Pin 1 should be grounded on the panel by one of the mounting screws which hold the socket to the chassis.

Make sure the panels are grounded to the base by removing any paint, powdercoating etc.

Edited August 3, 201313 yr by wink

So I'm trying to track down some buzz/hum I'm getting in just the left channel of my recently acquired HV. The level of the buzz doesn't change with volume level at all. Here is a diagram of the grounds in the amp

 

 

The wire connecting the power supply to the star ground goes around behind the transformer, and when I move that wire around the buzzing changes, but it is weird that its only buzzing in the left channel during all of this.

 

Also of note is that this is my first/only stat amp, and I only have one brand new pair of Stax, 307s, that got to me from Price Japan with a channel imbalance issue. So I can't test other amps/cans.

 

Any advice is appreciated guys

 

Run a search in this thread for "star ground". It has been discussed at length.

My KGSSHV has zero discernable noise, never did. It just blows up all of the time.

Another common theme with this amp. I hope your trafo is robust enough

and that the large HV lytics on the PSU are stood-off or insulated with kapton tape!

Well... at last I wasn't the only guy with the problem.... Mine only shorted once tho, and it was more like BOOM than popping, but it didn't look that bad.

 

I followed Birgir's advice to star ground everything on the PSU board. (IEC ground to PSU; AMP to PSU; Case to PSU, Input and pot to PSU) It doesn't have any noise whatsoever. The problem tho is finding enough place to ground on the PSU.

KGSSHV's are a'popping!

the shorts look more like a circuit board problem than a capacitor insulation problem?

Well... at last I wasn't the only guy with the problem.... Mine only shorted once tho, and it was more like BOOM than popping, but it didn't look that bad.

 

I followed Birgir's advice to star ground everything on the PSU board. (IEC ground to PSU; AMP to PSU; Case to PSU, Input and pot to PSU) It doesn't have any noise whatsoever. The problem tho is finding enough place to ground on the PSU.

 

I was thinking the same thing, how would I fit all those ground wires into that one little ground spot on the terminal block on the Power Supply...I was thinking I would star ground everything to the bolt attached to the bottom of the chassis

the shorts look more like a circuit board problem than a capacitor insulation problem?

 

Now come to look at it, yes, it does look more like that than shorting via the cap.... That didn't come to mind first tho, because it seemed more unlikely to me since I presume that the traces are laid out in similar fashion to the normal version just more compated and no one has reported (or I haven't seen any) that the traces are directly shorting to ground without a potential path.

 

If that is the case.... it might not be good... since there are quite a few traces that are carrying similar voltage. And if it happens to one board, it might very well happen to other boards...

By the way, right after the diode bridge, it's more like close to 700V than 500V.

The problem doesn't tend to manifest itself when the above mentioned precautions are taken.

The caps seem to act as a bridge to accomodate the short path when in contact with the pcb.

It does look like that the +/- traces are way too close together to handle these high voltages.

Hopefully the new "mini" boards will be an improvement.

My power supply board was making popping sounds yesterday.  A close look showed that there were two short circuit spots.  One underneath a capacitor and the other one near the diode.

 

 

 

I think the insulation varnish on the PCB is too thin for 500VDC or the copper traces are too close to the ground plain.  

 

I clean the spots up, cover them with nail clear coat, and now it's working fine.

 

how many hours did this run before the problem?

how many hours did this run before the problem?

Just about 2-3 hours.

I really don't think it's the cap problem. I think it's PCB problem.

Wachara C.

Is your offboard version still running fine?

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. 

 

Ok, maybe not QC at end of production line, but they - stax, the importers and the retailers - should either package the earphones well enough so it does not happen or design the product so it can withstand the treatment from the shipping companies. When you buy eggs at the supermarket, you expect them to be fresh and without cracks!

 

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. 

Edited August 3, 201313 yr by spritzer

Wachara, I am glad that it has been fixed. Looking at your first picture, the short looks like it was caused a cut in the pcb. My guess is that when the amp gets hot and the cap expands and if soldered near the pcb, the cap's sleeve could have cut the solder resist. 

The off-board one is running fine.  It's possible that I had a little cut on the insulation paint over those spot and overtime they shorted. 

 

Thicker insulation paint would help a lot, IMO.