Unfortunately, I sold and shipped off the other set yesterday

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Unfortunately, I sold and shipped off the other set yesterday

 

Yes, I was an hour too late sending my message.

 

Anyone else have a set left over from the group buy? Failing that, is there any interest in another group buy?

A 3U unit has a lot of air in it so you should be fine without a fully vented bottom.  I hate those inner bases and my bottom panels always look perfect.  :´) 

 

Can you please post a photo of the bottom of one of your builds? Do you use countersunk screws to secure the offsets?

Yes I want to see Birgir’s bottom as well. 

  or      can you it?    

This thread took a different turn... 

 

Anyway, my only KGST is in use right now so I just grabbed the nearest plate to my desk, a mini HV:

 

 

A few of the holes are crooked but they are all there for airflow so I'm not that bothered. 

Would vent holes on the sides of the case work?  I'm using a Par-Metal 20 series case that has a column of vent holes on the left and right side of the bottom plate and top panel, and a row of vent holes towards the bottom for the side panels.  Picture here: http://par-metal.com/product-ttp-20series.php

 

I'm getting a top panel made with more vent holes and was wondering if an additional row of vent holes on the side panels would help. 

Edited October 31, 201411 yr by chiguy

What is the recommended thermistor to serve as an inrush current protection for the KGST and KGSSHV? When I built my KGSSHV I used one that was listed in a BOM, without giving it much thought. 

 

When using 230VAC mains, would you put one in series with the primary?

I never use one. 

With 230V I would put it "between" the two primaries, if you have dual primaries and in series otherwise.

Edited November 3, 201411 yr by luvdunhill

Yes that is a very good idea to put it "between" the dual primaries (I know what you mean). My question was also how to calculate the optimal value for it?

 

I happen to have 10ohm thermistors. I this a good fit, or would you recommend another value?

This depends on the inrush current which is a function of the VA of the transformer and the amount of capacitance in the PSU.

My speculation, is that Spritzer oversizes his fuses a bit to not need a thermistor. I use VA/line * 1.33 to size the fuse. Then choose slo-blo. If this works, leave it without a thermistor. If it doesn't, use something like a CL60 for a 300VA or so transformer and adjust up or down from here depending on what sort of capacitance you have. It's a rule of thumb.

I like fuse ratings as absolutely small as possible. Some people just keep increasing the size until it works. YMMV.

Why not use a soft-start module?

Why not use a soft-start module?

Complication. Why involve a relay when you don't really need to? If we want to talk about a power amp with a 1kV toroid and mF of capacitance, sure lets talk. That's not what we have here.

Edited November 4, 201411 yr by luvdunhill

It's starting to look like no one has KGST boards available. So I started researching getting my own made. I've never ordered PCBs before, so I could use some advice.

 

The cheapest thing I found is a $33/board deal from 4pcb.com, with a minimum of 4 (http://www.4pcb.com/33-each-pcbs/index.html). It ends up being $99 per set of three boards, with a minimum order of 4 for a total of around $400 (guess I'll just make more amps or have extras available for the next interested person). I'm worried about the specs. Is the 1-oz copper enough? What about the 0.062" thickness?

 

For small runs of boards, which manufacturers do you guys use? Are there better deals around?

I've used Bay Area Circuits (http://store.bayareacircuits.com/) for a number of projects and have been more than happy.  They also have an online viewer so you can see what the boards will look like.

 

Me

/

Edited November 11, 201510 yr by JoaMat

Wow!  Nice!

 

Are you using T2 PSU for the KGST?

Are you using a filament and HV switch instead of a delay?

/

 

Edited November 11, 201510 yr by JoaMat

It's starting to look like no one has KGST boards available. So I started researching getting my own made. I've never ordered PCBs before, so I could use some advice.

 

The cheapest thing I found is a $33/board deal from 4pcb.com, with a minimum of 4 (http://www.4pcb.com/33-each-pcbs/index.html). It ends up being $99 per set of three boards, with a minimum order of 4 for a total of around $400 (guess I'll just make more amps or have extras available for the next interested person). I'm worried about the specs. Is the 1-oz copper enough? What about the 0.062" thickness?

 

For small runs of boards, which manufacturers do you guys use? Are there better deals around?

The board run I did was for 2 oz copper, 1.6mm FR4 HASL.

My KGST is finished, only the frontpanel is missing. I must say I am really impressed. Have not had time yet to do a 1 on 1 with the KGSSHV (IXYS parts), but it sound really really good. I'd say there is something special to it, the KGSSHV doesn't have. May be the secret lies in the tubes? It's my first tube amp. It sounds sooo good, it give me a chill all the time. 

 

What do you think about the difference between the KGST and the KGSSHV? My memory tells me that in the KGSSHV the difference between the sa4686 and ixys parts is really minor. Can someone confirm? 

 

Edited November 9, 201411 yr by insanity

Congrats on the nice build, Insanity!

ATM long term temperature monitoring mine while listening. The heatsinks opposite side of the CCS are running 130-134F. I'll probably go with a cutout in the top plate and screen mesh insert above the tubes and heatsinks and see how that works out.

Agree that the KGST is a very special amp. Can't turn it off if I start listening.

Many thanks again to Kevin and Birgir for the original design and development. And to Geoff for the PCB group buy.

134f doesn't seem that much to me, although i agree that there should be some venting. Did you build the 350v or the 400v version?