KGSSHV Carbon Build Thread

[JoaMat]

Nor sure where to post this. Sorry for polluting.

4 x 2SC4686, 2 x 2SA1968 and 2 x 2SA1486. Rest of the parts from Mouser except LSK389. Two trimmers, no servos. Does it work? – that is to be seen, or heard.

[Blueman2]

@JoaMat, what is it for?

[JoaMat]

I would say it’s a modified KGSShv or Carbon with T2 style current sources at outputs. My intention is +/-400V but +/-450V will be OK as 2SA1968 is a 900V device (I think). Schematically it looks like this.

 

I’ve saved the old, now hard to find, transistors from my first built electrostatic amplifier - an onboard heat sinks KGSShv.

 

Edited March 23, 2021 by JoaMat

[Blueman2]

Nice.  

Edited March 15, 2021 by Blueman2

[JoaMat]

Seems R21 – R23 string is upside down. Lucky I discovered it before milling/etching boards.

[Blueman2]

6 hours ago, JoaMat said:

Seems R21 – R23 string is upside down. Lucky I discovered it before milling/etching boards.

What is your setup for creating boards?  Do you use a small CNC router?

Edited March 19, 2021 by Blueman2

[JoaMat]

Yes, I use a small CNC machine. Just made a file for the CNC machine for top side of the board. Below you can see the route (red lines) for a 15th or 0.38 mm end mill.

I’ll try to make a board in the next few days -  if no unexpected happens…

[JoaMat]

Milling process went smooth. 

Here is the board populated with components I had at hand and it works alright I would say.

It is playing in pair with a Carbon I built three years ago.

The Carbon to the left but its actually the right channel. Amplifier is upside down. I put the trimmer on bottom side – I forgot that this isn’t a tube amplifier with none component side facing upwards.

In schematic posted earlier there is a couple of 2SA1486 but I took a pair of KSA1156 instead which is OK as HV is +/-400V.
 

[JoaMat]

Schematic a few posts up is updated and now reflects what I’ve built. Changes: R21 – R23 and Q3,Q4.

 
Picture from top. Carbon board to the right with ceramic insulators. New thing to the left. All transistors (2SA1968 and 2SA4686) on bracket are insulated and don’t need ceramic insulators.

[JoaMat]

This is probably pushing it too far. Changed ksc2690 for 2sc3324. Board size now 99mm x 112mm or 3.95in x 4.44in. Looking at the 3D visualizer it seems doable.

I've found a way to lay down the transistors flat but not how to bend the legs. Anyhow it’s fun working in Proteus. You can create the most odd things. 

 

Edited March 24, 2021 by JoaMat

[JoaMat]

We all know what KGSSHV Carbon is. But why was it baptized Carbon?

[judo]

From Silicon Carbide. Spritzer's invention, the name too AFAIK.

 

[JoaMat]

Today I made a couple of “adapter” boards with small smd transistor 2sc3324and replaced ksc2690 Q8 and Q11. So far it seems to work…

bad picture by a usb microscope

[Blueman2]

1 hour ago, JoaMat said:

Today I made a couple of “adapter” boards with small smd transistor 2sc3324and replaced ksc2690 Q8 and Q11. So far it seems to work…

Whaaat?  Did you hack apart a TO-247 casing to put that SMD into it?  Insane.  😄

Edited March 25, 2021 by Blueman2

[JoaMat]

No, I didn’t hack anything.  I made small pcb 8mm x 10mm with my CNC router. Maybe the USB microscope picture fooled you a bit, but the piece on the right is the small PCB I milled with a 2sc3324 and three leads from a power resistor.

[Blueman2]

Ah.  Very ingenious!  

[JoaMat]

Just completed the work with another board (right in picture below) and it is now up and playing.

Yesterday I milled board similar to one just done. But unfortunately I forgot to correct the resistor string mentioned here...

On 3/19/2021 at 11:05 AM, JoaMat said:

Seems R21 – R23 string is upside down. Lucky I discovered it before milling/etching boards.

...so it died in thunder and lightning. Made a new corrected board today and moved the good parts from the faulty board. Also had to fix the PSU. Due to all earlier disasters I know which parts that need to be replaced…

[JoaMat]

I’m working all week around. Today I milled left channel board similar to the right side done yesterday. Here it is.

For some reason the holes of big pads aren’t centered. Grrrrr.

Three round  tanned pads close to offset trimmer are test points. Measure voltage cross 100R resistors R25 and R31 and you get an idea of current through output stages. I got 1.014V and 1.007V so approximately 10mA.

 

Edited March 28, 2021 by JoaMat

[chinsettawong]

How much smaller are these boards compared to the originals?

[JoaMat]

The first board is 120mm x 60mm / 4.72in 2.37in while this latest is 99mm x 56mm / 3.92in x 2.22in.

 Here they are together with a mini T2 for comparison.

[JoaMat]

Here is a version with FJPF2145 in stead of 2SC4686 and 01N100D replacing 2SA1968. The file name is xxx_Mouser to indicate components are available at Mouser.

 

Yesterday I completed the left side board and I’m listen to it this very minute. I’m very pleased with the outcome.

[sweetleaf]

Joachim never sleeps, if he isn't climbing the Keb, he's grinding out PCB's  I have some Fjallraven Keb trousers, they are awesome.

Just saying hello and announcing my up-coming Carbon build using Joachim's older compact SMD version of the Carbon layout. I might be the first to use these but Joachim gave his blessing so I'm sure everything will be fine. These left/right mirrored boards use the discrete servo by Kerry, seen prior to Kevin's offset opto circuit.

Several reasons why I chose these older boards; they are beautifully compact allowing me to work inside a 200mm inside width case, I love SMD  and the left / right layout is genius, this should be done more.

The PSU is the kgsshvpssicfetsmall3.zip V1.4 all in one, single PCB. This will be a two box amp with an custom R-Core by James Transformers, same as Bigir uses in the CC edition. The R-Core is the size of a small car so will need a 80mm high case.

No SiC Fets available until next month unfortunately but PCB parts are arriving soon and Bigir helped with the 5 pin pro jack. I have LSK389 on hand and MPSA65 from a guy on DIYA, everything will be to original spec.

Big thanks to Joachim, Kerry and Kevin for all the work, advice and putting up with the questions.

Keep it going Mafia.

[JoaMat]

Great, this is the first time I see them boards, even if it’s just on photo. I want to add that one name is missing on the boards – Kevin Gilmore. Kevin added a few things like trimmers to set output current, test points to measure it, terminal blocks, part values, labels etc. etc.. During the work with the boards he taught me how to quickly make a mirrored (as far as possible) board from the first one. Thank you, Kevin.

Welcome to Head-Case, Rich (sweetleaf)!

[sweetleaf]

Thank you Joachim, it's great the forum is back up and we can meet on the spiritual home ground of the amplifier. Hell of a community this Mafia crew.

You might see two of these Carbon's being made, another member expressed an interest in the SMD version PCB's so it would be great to have a companion on the journey. I have three pairs of SMD Carbon boards left and three HV PSU boards if anyone else is keen.

Also picked up the newer version 6 Carbon PCBs with top ground plane and the Grounded Grid PCB's as deep down I have a softness for tubes. But that's a rabbit hole I need to stay away from  

[sweetleaf]

A few people have asked for built and tested SMD carbon amp boards. I can do this.

So I am offering a tiny group buy for the four remaining pairs of SMD boards in my possession. Maybe more can be made later.

Out of the four pairs left, I think sebtdi and icarium and  are interested so three pairs available unless someone just wants a blank pair of boards.

It looks like the Mouser BOM alone will cost just over £100 plus taxes for one pair, this does not include 2 x LKS389 / MPSA65 and I will need to buy, drill and fit L-brackets.

The board set and obsolete parts come to £50 before adding the Mouser BOM, add £10 for brackets and a little something for the work and we are around £200 for a pair of built and tested SMD Carbon boards. It's a pricey project.

My BOM uses high end parts, for important projects I use 0.1% Susumu resistors, some cost can be shaved by using 1% MELFs etc. (I FORGOT TO INCLUDE CERAMIC INSULATORS - they will need to come from Digikey)

The boards will have pluggable Molex MiniFit Jr connectors for signal which adds a few dollars but makes things very easy  They have gold plating and are very good. I can supply pre-made crimped signal connectors using Mogami wire to custom length.

To be clear - 

I am offering one pair of built and tested Carbon boards, the PSU is up to you. The Carbons will only be tested electrically to spec, I cannot audition all pairs it means connecting to heatsinks. If mine sounds ok then they will all work.

This will take a few weeks. Parts are out of stock until next month.

You will need to buy and build the PSU yourself, order the transformer now if you are keen, contact Spritzer for the 5 pin jacks (($41 shipped).

 

KGSSHVCARBON_SMD_BOM.xls