kgst

[Laowei]

Built it to 350V like you did. It settles in at +349 and -358. The non symmetry does not bother me as the tubes cathodes are sitting around 23V off the negative rail anyway.

Edited November 9, 2014 by Laowei

[insanity]

Look how beautiful it is   Just listening to Beethoven's Waldstein. 

 

Edited November 9, 2014 by insanity

[nopants]

anyone have a part number for the 1M trimpot? I bought one which I can no longer find, and even then it had the trim screw on the side of the package

[Laowei]

http://www.mouser.com/Search/ProductDetail.aspx?R=T93YA105KT20virtualkey61330000virtualkey72-T93YA-1M

T93YA is what you need. Trim screw on top, and pins in a row on the bottom.

[chiguy]

http://www.mouser.com/Search/ProductDetail.aspx?R=PV36W105C01B00virtualkey64800000virtualkey81-PV36W105C01B00

[gepardcv]

Thanks to some kind souls here, I now have KGST boards (yay!) from headinclouds' group buy. Very happy about that. Now I have a question about the PSU board: which Gerber file package on KG's site does it correspond to? There's kgstpsu21.rar, but it's marked "Modified Blue Hawaii PSU v3.0", whereas the PSU board I have is simply marked "Version 1.0", with no mention of the amp it's meant for. The two boards look different in general, including 350V vs 400V labels (though I did not compare the parts component-by-component yet).

[headinclouds]

The group buy used kgbhultraminipsV4 as at 21 July.

Edited November 12, 2014 by headinclouds

[nopants]

I got a KGST up and running last night, haven't tested it with music yet. I'll probably have to swap out the tail resistor in series with the pot, getting 10~30V offset for each channel. This has happened to me on the KGSSHV as well, might be a good idea in the future to leave the tail resistor in a spot where it can be swapped more easily. 

 

That is, if we stick to the 1k trimpot

Edited November 13, 2014 by nopants

[luvdunhill]

Like, on the bottom side? You only have yourself to blame for that

[nopants]

the worst part is I still had to process the genius of that after I read it

 

I hope my tears of frustration don't short the board

[spritzer]

No way to move that resistor, just look at how cramped the PCB is.  The boards keep getting smaller but the circuits more complicated.  The stereo KGSSHV board takes this to the n-th level. 

[nopants]

I was trawling the thread but I couldn't find anything. hat should the voltage rating on the .1u servo caps be? I have some 50v c0g lying around but I wanted to make sure.

[insanity]

50V is fine and recommended in the BOM. 

[nopants]

Thanks insanity. Haven't populated the servo yet, but I'll get around to it eventually. Seems pretty stable without it already.

 

I was able to zero the offset by populating a 1.2k in the tail.

 

There's some low level hum in only one of the channels which is sort of annoying... aside from that it sounds very good. Keeping it in prototype form makes for some nice handwarmers this time of year. Slightly different vocal imaging compared to BHSE, more forward.

 

I might have to swap the Megatron for this at the office.

[spritzer]

Did you tightly twist the heater wiring all the way from the transformer to the board?  That is the most likely source of hum...  You can also try swapping the wires and see if that helps. 

[nopants]

The heaters are straight shots over atm, I'll give that a try when I can stop listening to it

[insanity]

Although I don't have that problem, I was wondering if the heater current could be rectified to prevent such a problem. Is there any negative effect of using DC for tube heating? Obviously there is the cost for an additional rectifier, but capacitors could probably be omitted. 

Edited November 16, 2014 by insanity

[spritzer]

Just rectifying the heaters won't do and will cause a lot of problems.  You need to regulate it and doing so while it floats at -350V is problematic. 

[Laowei]

From the experience on my past tube amps, by habit on my KGST build, I tightly twisted all paired wires. The result is it is dead quiet operation.

Now I am wondering how best to dress the wires between amp PCBs outputs to the Stax jack. Not sure what is best practice driving e-stats. Right now on my build they are twisted too, which would minimize capacitance in the pair. Scatter wired pairs would maximize capacitance. Maybe paralleled wires like the Stax cord would be the theoretical best?

[s_r]

I finished my KGST recently. The fit was pretty tight in this 2U/330mm/280mm case. Had to reduce the 1.5kOhm resistor to get the offset to 0V though. Spritzer did mention a case this small would need a lot of ventilation, so I went with a pretty open top cover. Dead silent operation too.

 

[JoaMat]

Beautiful. Like that top cover.

[Kerry]

Nicely done

[gepardcv]

That looks great! I just ordered the Modushop Galaxy 330x280x80 case for my KGST build, is that what you used? I got one with a fully-vented top and hope to fit the tubes without the dedicated openings.

[s_r]

Yea, the modushop case is what I used. I used 6mm standoffs for the boards too, so the tubes don't really stick out of their openings. You could probably get away without dedicated holes if you select short tubes.

[nopants]

What version of the PSU board is that? I like the spots for bigger LV caps