kgst

[Laowei]

KGST PCBs in da house. They look great. Thanks Headinclouds!

[meeskees]

What are those pins on the right part of the PCB? (Servo) The op27 is not inserted, so what is the use of the pins?

Perhaps Birgit is willing to explain.

Has someone already made a new BOM?

[UFN]

I believe the pins are a jumper to enable/disable the DC servo.

 

//UFN

[spritzer]

Yup and on the KGDT it's used to change the current on the CCS. 

[chiguy]

What voltage rating should the 1uF and 0.1uF capacitors be?  (On the right side of the amp board.)  I didn't see them marked on the silkscreen.  

The 1uf cap has to be 25V+ so anything with 15mm lead spacing will work.  I use 250V Panasonic caps which fit perfectly into the footprint.  Kevin posted the part number either here or in the KGSSHV thread.

 

The 100nf caps should be rated to handle the B+/B- plus a bit of headroom.  We've normally used 1000V caps here but 630V also works.

 

So I didn't notice there were two types of 0.1uF caps on the amp PCB.   I meant to ask about the 0.1uF capacitors by the servo.  The BOM says 50V will be sufficient.  Is this still true?

Edited August 18, 2014 by chiguy

[spritzer]

They are being driven off the +/-15V rails so anything above 25V works just fine. 

[meeskees]

Yup and on the KGDT it's used to change the current on the CCS.

What is the name of these parts? I can't find them in the Mouser catalogue.

I presume they are open with normal use. Sorry for these dumb questions, but I am no technician.

[meeskees]

Hi, Birger, how is the Bárðarbunga, at the moment?

[spritzer]

They are just DIP jumpers and can be found everywhere.  The ones I used I got off ebay some years ago but Mouser should have something like that. 

 

It could be years or it could be tomorrow when we see some action there but the aftermath can be pretty bad when the flash flood comes from under the glacier.  That particular volcano last went active in 1996 and I visited the result of the flash flood to the south side of the island.  Icebergs the size of houses scattered around a huge region with most of the infrastructure washed away.  Nobody lives there though and all the roads, bridges and power lines are designed to break away and be replaced quickly. 

[meeskees]

My wife's grandson lives in Reykjavik, so we follow the news there.

About the DIP jumpers. Perhaps I have to try harder, but I found this 571-826646-2 and this one 517-9691020000DA in the Mouser catalogue. Will this do? I can't see in the picture of your boards weather they are open or closed.

[wink]

Got the boards today.

 

Thanks Headinclouds.....

[PICaudio]

I think there is an error in the BOOM of this thread, in the "KGST-New" label the 3K5 resistor should be 1K5?

[Laowei]

I think there is an error in the BOOM of this thread, in the "KGST-New" label the 3K5 resistor should be 1K5?

The KGST is an evolving work in progress, so there is no one single BOM. Use the value printed on the PCB (1K5). That is correct for the revision the board was made to.

[spritzer]

Indeed and this also changes with the actual tubes used.  1k5 with a 1K pot should work for most tubes but at +/-400V you might need to go lower.  1k37 is what I use in my amps. 

 

My wife's grandson lives in Reykjavik, so we follow the news there.

About the DIP jumpers. Perhaps I have to try harder, but I found this 571-826646-2 and this one 517-9691020000DA in the Mouser catalogue. Will this do? I can't see in the picture of your boards weather they are open or closed.

 

Those jumpers will work just fine and we are far away from an volcanic activity so it will be fine. 

[wokstarr26]

Received boards and parts in good order.

Thanks for the group buy Headinclouds.

[chiguy]

PCBs received.  Thanks for an awesome group buy!

 

So I have been requesting quotes from different vendors for transformers using the specs posted earlier in this thread. 

 

I'm still waiting on a few vendors but so far SumR wants $94 and Toroidy quoted:

Audio grade transformers with mounting pads:
TS 150VA PRI: 2x 117V SEC:
> 2x 280V @0.18A
> 15 - 0 - 15V @0.5A
> 2x [email protected]
cost: 75,80 EUR/pc
 

Audio Supreme version:
TS 150VA PRI: 2x 117V SEC:
> 2x 280V @0.18A
> 15 - 0 - 15V @0.5A
> 2x [email protected]
cost: 112,70 EUR/pc
 

In audio grade, noiseless transformer price You'll get transformer wound on high inductive, selected and measured core. 
Core and all the windings will be impregnated. Transformer will also has electric and electromagnetic shields, epoxy 
filled interior and mounting pads in price.

Audio SUPREME version is fully epoxy resinged in stainless steel box:
http://www.toroidy.pl/s783/57ad94c01a056094fc22ba3ecded9a40.jpg

Will using 150VA as quoted be okay or should I stick to 120VA?  Also, is the Audio SUPREME version worth it?

[chiguy]

Avel Lindberg quotes me as follows.  Any thoughts?

This  request for an extremely high end Audio Transformer and  as “mechanically silent”, heavier wire gauges”, Static Shield”, 
Magnetic Shield” are standard requests that will always improve a transformers operational quality. However the offered dimensions 
of 100mm Dia x 50mm Ht are restrictive to the design relating to performance. In addition the rating of this transformer is nearer 
135VA than the 120VA stated in the request which also affects the design parameters. The is the best 135VA possible that we can 
offer within the 100mm Dia x 50mm Ht dimensions given.

Description         Toroidal Transformer.
Primary               117v + 117v   50/60Hz
Secondary 1        280v @ 0.18A rms.
Secondary 2        280v @ 0.18A rms.
Secondary 3       15v-0-15v @ 0.5A rms.
Secondary 4        6.3v @ 1.5A rms.
Secondary 5       6.3v @ 1.5A rms.
Total Rating        135va approx.   
Int. Shielding      Pri-Sec Static Shield.
Ext. Shielding     External GOSS “Magnetic” Band Fitted
Mounting            Dish Mounting kit supplied.
Finish                     Polyester Tape
Leadouts              300mm Flexible Style.
Size                        100mm O.D x 50mm Ht approx.
Weight                 1.54Kg approx.
HIPOT 4000VDC PRI-SEC

$209.75

[spritzer]

You can lower the HT current a bit down to 140mA.  That is already overkill so no need for the extra headroom. 

 

The audio supreme transformer is just a bit silly so I wouldn't go for it unless it is some very sensitive piece of kit. 

[Laowei]

FYI

Power transformer with shipping quotes I received to the same specs as above:

SumR: $94.00 plus $30.00 shipping to US

Toroidy: €75,80 plus €45 shipping to US.

Shipping is a killer for me with Toroidy.

Edited August 21, 2014 by Laowei

[headinclouds]

Iceland watchers, the Iceland Symphony Orchestra makes its BBC Prom debut tonight beginning with, aptly enough,  "Magma"

 

You can listen online

 

 

http://www.bbc.co.uk/programmes/b04dqhf5

[kevin gilmore]

headinclouds has his kgst working now, I assume he will post pictures.

had to decrease the cathode resistor to 1.1k  and is running 10ma

to the tubes.

[Laowei]

That's the resistor marked 1k5 on the boards (3k5 on previous virtual versions) next the 1k offset trimpot?

[headinclouds]

Yes that's the one. (edit; of course that doesn't mean that everyone should be fitting that value, just note you might have to adjust this)

 

Public thank-you to Kevin and Birgir for the design and pcb layout for this very nice project.

 

Birgir's and Kerry's comments encouraged  me to build it and I'm pleased I did.  The SQ is excellent.

 

Mine is on a piece of plywood at the mo.

 

To encourage those who have just got their pcbs;

Edited August 23, 2014 by headinclouds

[Aive]

That's awesome. Must be good feeling to finish a project

[insanity]

Beautiful! Looking forward to seeing mine.