i'm on a roll... the kgsshv

[kevin gilmore]

this is closer now, assumes the on board heatsinks

http://gilmore.chem.northwestern.edu/kgsshv.xlsx

[rille]

I already ordered a hifi2000 case with external heatsink, but it was an horror, impossible to drill it. In addition, if you want to attach a component, you must completely cross (if you succeed) the heatsink and put a nut on the outside.

What did you do? It's possible This was done with a cordless electric screwdriver and a hand thread cutter. It's a Pesante Dissipante 2U:

[Pars]

This is why GOD invented centering drills.

Even with my NC machines good for .0005 inch positioning,

without using the centering drills first, the wander is horrible

even when clamped to within about .5 inch of the end of the drill bit.

The problem with manual methods is first you have to use the

centering drill on all the holes, then go back and actually drill them.

Without a DRO, this takes a lot more time because you have to change

the centering drill and the real drill bit for every hole unless you

are confident enough in your positioning.

By centering drill, do you mean something like this?

My link

Edited May 7, 2011 by Pars

[kevin gilmore]

Thats the things. Even better in carbide.

Just about impossible to get those things to walk.

[Craig Sawyers]

Thats the things. Even better in carbide.

Just about impossible to get those things to walk.

I used those back in the dim and distant when using a metal turning lathe, either to make a feature for a tailstock centre, or prior to drilling a centre hole. I'd forgotten about them until now, and must get a few sizes for my drill press.

To use such a lathe now I'd have to take a remedial course - too many decades have passed.

[charlo89]

@livewire what stax plug do you use for your kgsshv ? On the picture, this is not the plug that I usually see in DIY.

[livewire]

Hi charlo89, nice to see you are taking on KG's build, love your case design.

The connectors I used are a discontinued 6 pin female mil-spec microphone connector made by Amphenol.

The part number is 91-PC6F. The number when encountered, may be prefixed with "WPI" or "CNA".

These are available through some electrical surplus resellers.

Kevin Gilmore used this connector in his first prototype KGSS amplifier.

You can see it on his HeadWize website which also has much useful information about the KGSS amp.

Allied Electronics also carries a plastic version of this connector without the chrome outer shell.

It is a WPI design now distributed by Cooper Interconnect.

EDIT:

Hmmmm, just did a search. It seems that Cooper still makes them.

Newark or Element 14 part number: 38F1544 ~$26 each

Come and get em! Only 11 pieces in stock.

Surplus houses sell them cheaper. Just sayin.

+

2 pieces on ebay @ $20 each plus shipping. Auction # 350113117987

Edited May 9, 2011 by livewire

[wink]

To use such a lathe now I'd have to take a remedial course - too many decades have passed

I know the feeling.

Haven't used a lathe since the late 60's.

[livewire]

Yeah? But can you drill or mill?

[wink]

In my days as an apprentice electrical fitter/mechanic in the NSWGR, we had to learn how to use drilling machines, lathes, shapers, linishers, etc.

Milling machines were just out of reach.

We used to drill and tap blind holes in all sorts of material.

For aluminium we used kerosene.

For most other metals it was machine oil or soluble oil.

CNC's didn't exist as small hobby machines.

Edited May 9, 2011 by wink

[kevin gilmore]

The chrome jacks have to be machined down a bit otherwise the

plug won't fit in all the way. Pictures were posted many moons

ago. They are still slightly off size.

My jacks are the exact right size, i will have to make more

in the future.

here is the print should someone want to make a bunch of them

http://gilmore.chem.northwestern.edu/staxout3.pdf

[charlo89]

I bought his plug for 11 USD + 19 USD for the shipping to France

http://cgi.ebay.fr/6-PIN-FEMALE-Amphenol-MICROPHONE-CONNECTOR-91-PC6F-/350113117987?pt=LH_DefaultDomain_0&hash=item51845e3723#ht_1666wt_1139

Thanks livewire

If the plug is not perfect, I will machined it.

[livewire]

That is the one!

If you notice in the ebay pic, plastic part is recessed in front.

KG was referring to machining the threaded chrome shell down until it is even with the plastic.

This will insure that the Stax plug will enter completely.

[wink]

They're US$20 now with US$18.95 shipping...

[Driftwood]

My jacks are the exact right size, i will have to make more

in the future.

here is the print should someone want to make a bunch of them

http://gilmore.chem.northwestern.edu/staxout3.pdf

If you (or anyone) decides they want to make a bunch, I'd take about dozen

[charlo89]

There is a question I did not think. The Kgss is better than the kgsshv?

[livewire]

I've never heard the KGSS, so Doctor G would have to answer that after listening to both.

I've heard that the KGSS has plenty of power for driving electrostatic headphones, I would guess that

the extra headroom afforded by the KGSSHV's higher voltage rating is a good thing to have for the harder to drive models.

On paper, the KGSSHV is the higher power modernized version of the (12 year old?) KGSS design.

450 volt vs 350 volt rails, it also has a newly designed very low noise, current limited power supply.

The design of the KGSSHV amp boards is very similar to the KGSS. Compared to the original design

the KGSSHV has higher voltage withstanding output transistors and the option to use high voltage mosfets

for the current source. The dual input fet (lsk389) is also a newer, very low drift design.

[kevin gilmore]

That is a pretty accurate description of the differences.

[charlo89]

I was not expecting to have such a good response. Big thank you

[spritzer]

The other big change is also how the third stage is handled as it has a CCS now and not resistors as the original used. This is also what Stax did with their newer amps (323/727).

[livewire]

Been kind of quiet around here. Anybody else finish their kgsshv yet?

Welp, last night I was immersed in a four hour listening session with my kgsshv.

Did I ever mention how good this thing sounds? Had the bass a-thumpin on the ESP-950's.

Was listening to a lot of vintage Allen Parsons Project. Heavenly!

This morning I turned on the kgsshv, and nothing. Blew a fuse.

Put in another fuse and it fired right up.......with a faint buzzing coming from the transformer.

Then the smell of magic smoke accompanied with substantial heat rising from the toroid.

Seems like my SumR piece of shit has a short.

Oh well, I have yet to tear into it and form a plan of action.

I'll just fire up my itty-bitty Stax amp and experience bliss without the bass.

FWIW, Previously I did order from SumR, the beefier (100ma?) trafo spec that Spritzer mentioned.

I think that I may head to ebay and pick up a cheap Hammond dual 500 volt job and be done with it.

I have a 15VDC Sola brick (ala the original kgss) that I will be using in addition for the low-v stuff.

[wink]

This morning I turned on the kgsshv, and nothing. Blew a fuse.

Put in another fuse and it fired right up.......with a faint buzzing coming from the transformer.

Then the smell of magic smoke accompanied with substantial heat rising from the toroid.

Almost brings tears to the optical orbs................

[Horio]

I'm hoping to get going on a KGSSHV build soon. Just waiting for a board run to get going. Would be cool to give the case mounted heatsink build a shot.

Sorry to hear about the transformer problems. I have ordered several transformers from Sumr and I haven't had any issues (knock on wood). People posting problems with the Sumr units on this thread and the T2 thread have me a bit weary...

[ujamerstand]

Sorry to hear about the transformer woes jim. I guess some sort of soft start circuit would help here?

[livewire]

Sorry to hear about the transformer woes jim. I guess some sort of soft start circuit would help here?

That and a bigger trafo? I dunno.

The start-up surge on this thing is quite intense.

A loud buzz/thump can be heard, while the livingroom lights go dim for a second.

I mentioned this earlier during the build, another more experienced board member dismissed it

saying that he wouldnt worry about it, or something to that effect.

So I figured why bother and didnt implement a soft start. I will now.

BTW, the trafo never ran really hot, it was just warm to the touch with the amp turned on for an extended period.

I couldnt find any cheap Hammond trafos on ebay, usually they have them for about $50.

New, they are $105 on up, so I'm not going that route for an older, noisier design.

This fried SumR toroid only cost ~$100 with the core band insulation added.

Craig Sawyers talked of some super-duper trafo that has every turn layer insulated

which he sourced for his T2 build, I might look into that as well as a fully encapsulated unit.

So it's back to SumR? Makes me cringe, although I will spec something a bit more substantial this time around.

I have room for it in this chassis.

EDIT: Another thing. I'm not actually blaming SumR here due to the fact that

I had previously shorted the power supply twice in the past,

possibly weakening the trafo insulation in the process.

I am aware that they are getting a rep for "donut fail".

Since I dont have a failure analysis lab at my disposal,

nor want to pay to have that done, I can only guess.

Edited May 18, 2011 by livewire