i'm on a roll... the kgsshv

[kevin gilmore]

Ksa1156 from mouser

Current part

[justin]

Ironically enough I'm having trouble sourcing the 1156 for the blue hawaii

 

i have plenty of authentic 2sa1486 if you need any

[kevin gilmore]

2sa1486 moar better anyway

[nopants]

So those are a direct drop-in replacement then? I think I have some extra 1486 lying around from a bdent splurge.

[spritzer]

The KSA1156 is a direct replacement for the 2SA1156. 

[Emooze]

So I haven't received my replacement 10m90s yet and I called Mouser again. Turns out the first CS rep I spoke to never put the order in to ship me the new parts. It's been well over 2 year since I first bought the boards for this amp. Maybe it's just not for me...

[wink]

Keep on trucking.... It,s worth the trouble.

[spritzer]

Keep at it but bear in mind that the high voltage really wants to escape to that lovely ground plane.  When in doubt, lift the component up. 

[palchiu]

Still waiting for 420VAC tranformer.

 

I've 450VAC transformer in hand right now, is use with 450V power board setting will too hot? (too much voltage waste?)

 

Or any parts needs spec upgrade?

 

Thanks!

 

Pal

[spritzer]

That's a lot of energy to burn off in the pass transistors so I wouldn't do it. 

[palchiu]

That's a lot of energy to burn off in the pass transistors so I wouldn't do it. 

 

Hi spritzer, thanks!  that's accurate I'm afraid.

 

Best

 

Pal

[insanity]

I fired up my kgsshv today and it didn't blow!! After a bit of troubleshooting with the psu it works fine. I now have 2 questions.

 

1. When watching temps with my IR meter I noticed the temp of the high wattage resistors is around 65-70C (with only one amp board connected). Is this alright? Output voltage is fine around 450V. Maybe if I connect two board and draw more power the tranformer output voltage will go down a bit and cause the resistors to dissipate less heat?

 

2. On one amp board I cannot get the offset lower than around 10-15V. I have not yet used the servo. Do I need to change the 2k resistor to another value or is 15V still ok? When I get the opamp for the servo in standard config, this should be able to regulate another 15. So it would be around 0V. I don't know if its good for the servo to work that hard all the time. 

Edited September 29, 2013 by insanity

[kevin gilmore]

1) with both boards connected the temps will drop a bit

 

2) you should change the 2k resistor to get the voltage to zero before you add the servo

[insanity]

Thanks Kevin. 

 

Would a 1k resistor be fine?

 

I did a test with both boards still quite warm resistors but I think ok. 

 

During testing I had an error on the board that was adjusted to about 0V offset and balance. Everything was up and running. Before I connect anything to the inputs, I wanted to be sure it is safe and I measured the voltage between GND and I+/I-. The inputs were not connected to anything and I measured around 0V from one input to ground and surprisingly 50vdc from the other to gnd. During and after these measurements I noticed a hissing sound to occur from somewhere on the board (no sparking). I cut power and turned it on again. The hissing was gone and then after maybe a minute R17 (20k) got really hot and started smoking. I immediately turned everything off. 

 

I removed the 20k resistor, which still measures 20k when off the board. I am unsure what else I should replace. Maybe Q9 and Q10?

Should I not have measured what I did, or did this problem occur independently of what I describe?

Since the inputs are "grounded" through the onboard 500k resistors I thought it was alright to leave them floating.

[kevin gilmore]

depends on which end the pot is at.  1.8k or 2.2k

 

the 500k resistors are really a safety thing. best to simulate the pot for real, but they are ok, just a bit noisy.

[insanity]

I now replaced Q1 Q2 Q9 and Q10 which I think were all damaged. I am uncertain if I replaced everything I need to. 

 

What cause this?

 

Shall I connect I+ and I- to gnd when I power up next time?

 

Could a faulty LSK389 be the cause of this?

Edited September 29, 2013 by insanity

[Remolon]

I plan to use this PSU to obtain +/-350VDC and the 580VDC for the bias.

 

 

The Zener DZ and the resistor R3 define the current which pass through R3, R4 and R5, and, obviously, the output voltage.

[spritzer]

Don't use those zeners on the bias.  Just adds noise and it is already adjustable. 

[Remolon]

The bias Zener are 3x200volts just in case the voltage get to high for the specified 580VDC. The bias will be regulated with the trimmer RVB.

 

Your comment make me to consider the option of moving the connection of the trimmer to the V+ output, more stable. Thanks

[spritzer]

Using the regulated output is a good idea and what I did in the Liquid Lightning.  The zeners will just add noise though. 

[TMoney]

With the help of a friend I swapped out a long-malfunctioning Khozmo pot in my HV for an RK50 over the weekend.

 

 

For the longest time I put up with clicks/pops/random volume cut-outs and blasts at max volume from the Khozmo pot seen here.

 

 

A couple of weeks ago my friend and I decided to take the Khozmo apart and see if we could find the source of the problems and potentially repair it.

 

 

What we found was kind of shocking. On one of the four channels of the Khozmo there is clear signs that someone goofed up during the manufacturing process. If you look closely at the picture, you can see that something sharp had cut some of the traces on PCB. Look at the traces coming from pads 3 and 4 and you'll see the scratch. Also, if you look very closely you can see that pads 3 and 4 have been bridged.

 

 

For reference, here is a photo of one of the (presumably) fully functioning channels. Unlike the channel above there is no scratch on the PCB, all the traces appear to be fine, and none of the pads are bridged.

 

 

Judge for yourself whether this kind of workmanship from Khozmo is acceptable on a nearly $300 part.

 

In any case, I figured in order to avoid any more problems with the pot I might as well go for the gold (literally) and throw in an RK50 purchased from Justin as a replacement. Thankfully my friend and I were able to borrow a drill because the volume control post on the RK50 is friggin massive. Not only is it 8mm thick (10mm at the base), it also is quite a bit longer (30mm) than the Khozmo (20mm).

 

 

Drilling the front panel went smoothly and the RK50 mounted nicely. However the volume knob ended up being a bit more of an issue. The knob I was using was (A) for 6mm shaft, and (  only 21mm deep. We ended up having to drill out the knob to within a mm or two of drilling all the way through to get the thing to mount without a large gap between the edges of the knob and the front panel. It still doesn't look perfect, but it will work for now.

 

 

I'm happy to say that the amp is now back up and running and fully functional. I'm not sure the RK50 is worth the extreme cost, but it really tracks well. The sound is beautiful and there are no more pops/clicks/etc. Mission accomplished.

 

[insanity]

Today I finally had the balls to test my freshly built KGSSHV with a source and phones AND THERE WAS MUSIC. Great neutral music and dead quiet! Gotta buy a case and a pot/stepper, box it up and have fun.

 

I wonder. Do you guys have some kind of ground loop breakers in your boxes?

[GeorgeP]

Some do, I didn't. If it is silent you shouldn't need one, but wait to see if it is still quiet after you wire your pot/stepper and input connectors.

[RiStaR]

Gratz Insanity

 

There are also some tweaks in the thread (suggested by Justin) for if you have some noise once you add the stepper/pot. If I remember right, and I've seen it in pictures by a number of the folks here, it involves 100ohm resistors just after the pot (do verify).

[s_r]

Most likely for my build. At extreme left I got some ground hum, so justin suggested putting in 100ohm resistors after the pot. Dead silent at both extremes now so no complaints.
 
Might put up a pic of my kgsshv's inside a few days from now, since I reworked the wiring a bit since the last pic I have up here.

Edit: Here's that pic

Edited October 4, 2013 by s_r