i'm on a roll... the kgsshv

[DefQon]

Slightly bit off topic long before I got into Stax but was sort of familiar with Dr.Gilmore's designs from Headwize, I use to think the KGSSHV was short for Kevin Gilmore's Super Sexy High Voltage amplifier. 

[kevin gilmore]

more like KGSSSic

[spritzer]

That's a lot of S's.... 

[wink]

S sir, 'spose it is.

[Sherwood]

more like KGSSSic

 

Super Sexy Silicon integrated circuit?

 

EDIT: Did my own research.  Cree SiC mosfets.

Edited July 11, 2014 by Sherwood

[nopants]

SiCKGSS

[eggil]

Gilmoretron

[kevin gilmore]

it used to be that Disney would sue anyone with anything with the word "tron" in it.

[wink]

Gilmoretran as opposed to Gilmoretube

 

Also does this mean the Megatron should be changed to Megatube?

Edited July 12, 2014 by wink

[astrostar59]

Prototype nr. 2 of the tiny HV up and running. 

 

 

Different output devices, pcb's mounted closer to the sinks, different assembly technique, new chassis feet plus a lot of holes drilled into the bottom plate to see how much cooler inside is.  It isn't SRM-T2 hot but then again the T2 didn't have electrolytic caps inside the amp section.  I'll send the first prototype to the US next week to see how it plays in a warmer climate and for some measurements. 

 

These small amps seem to be multiplying like rabbits though...

 

 

It is Easter after all.   Speaking of Easter, it marks the anniversary of me giving up on making new offboard PCB's for the HV so to celebrate I've started work on them again.   Glutton for punishment here... 

Birgir, I like it a lot! The new cases are top notch. How did you manage to get the (hot) KGSShv into such a small Stax sized case. Remarkable.

 

Good luck with the new amps, and if I can help you with any web pages. I could help you get a Wordpress site up that you can put your photos and specs up on if it will help your cause. 

[kh90123]

I need a bit of help trying to find a good quad volume pot for my build, that's not too expensive.

 

Justin from Headamp has the Alps RK50, but at $800 a piece it's a bit steep. What's the consensus on the RK27 quad from eBay Germany? That's a motorized version, but I think the DC motor can be removed easily.

 

Is the Khozmo really worth the money? (http://www.partsconnexion.com/KHOZMO-74888.html). The thread on HF seems to suggest that a few people has had problems with it (http://www.head-fi.org/t/440942/how-is-khozmo-stepped-attenuators/390).

 

There is also the very expensive DACT pot: http://www.partsconnexion.com/product1195.html

 

So what's the consensus on cheap and good audio pots, could anyone guild me on where to buy those? I saw Birgir using Alpha pots in his builds, does anyone have extra Alpha quad pot to spare? 

 

And must the volume pot be 50kohm? What will happen if I use a 100kohm pot?

[spritzer]

Birgir, I like it a lot! The new cases are top notch. How did you manage to get the (hot) KGSShv into such a small Stax sized case. Remarkable.

 

Good luck with the new amps, and if I can help you with any web pages. I could help you get a Wordpress site up that you can put your photos and specs up on if it will help your cause. 

 

It's quite cramped, that's how.    Here is the latest version:

 

 

 

Only major change is the voltage selector PCB which makes the AC wiring all neat and tidy.  Nearly every centimeter is used now and I'm up to 9 pcb's per amp. 

 

The bigger changes are outside as I changed the layout a bit from the one above:

 

 

 

It's very hard to photograph the chassis as it's so reflective... 

 

Thanks for the offer but I do have a Wordpress site up and running but it appears to be down now.  My friend hosts it and he's been having some issues due to some of the other stuff being hosted there.  It's mjolnir-audio.com and .net when ever it is up again.  Haven't done a whole lot with it yet but I need to add all the DIY stuff and what stuff I have in stock. 

Edited July 13, 2014 by spritzer

[kevin gilmore]

The khozmo is a massive piece of crap. I have 2 on my desk that after repeated

tries, cannot be made reliable. wiper made out of material without enough spring

and eventually it goes intermittent and noisy.

 

The dact is also a piece of crud. At least it stays reliable for a significant period

of time.

 

The rk50, penny&giles, and constant impedance digital attenuators are the only

things that work correctly forever.

[kh90123]

The RK50 is rather expensive...what about the RK-27 quad?

 

Mr. Birgir do you have any extra Alpha quad pot which you can sell?

 

Oooh, from the picture above the part # for the pot is 3RP/2142GSA1A50k. So it's a 21mm quad pot. If no one has extra to spare, I will try to get a quote from Alpha myself. If not I will go with the RK-27.

 

Thanks.

[kevin gilmore]

i'm using 10k quad rk27 for testing the preamp. its ok.

if you can find the noble, those are better.

minimum order from alpha is 50 pieces i believe

[kh90123]

eBay has one seller selling the Noble 25kohm quad pot, but it's linear. 

 

What about TKD pots?

[kevin gilmore]

our current mini board is for rk27 and tkd pots.

 

if you think about it, the shorter the resitive path, the

more mismatching you are going to have. So a bigger

pot should always be better.

[kh90123]

I read somewhere saying that pot with too high resistance (>100kohm) will interact with the capacitance it sees and form a low pass filter, and this will limit your bandwidth. Is this true? Or does the resistance need to be much higher than this before it becomes a concern?

[kevin gilmore]

yep. and I never use pots >25k

 

even if there is no external low pass filter, jfet and tube inputs

have a specific capacitance which will form a low pass filter

anyway

 

for my system I could use 50 ohms if I wanted to.

Edited July 13, 2014 by kevin gilmore

[UFN]

I am in the process of gathering parts for a KGSSHV build and came across some 2SC4686a's at a reasonable price. Now, not the best picture in the world, but what do you think – are these genuine?

 

 

Pin connections are consistent with the data sheet and hfe seems to be in range as well. Unfortunately I have no way of measuring the breakdown voltage.

 

There’s no bar under the batch/lot number so either they are very old (pre-RoHS) or they have been remarked.

 

Thanks,

 

//UFN

[kh90123]

Hello again, Toroidy has sent me the specs and the pricing for the transformer.

 

100VA

Triple primaries: 100V, 115V, 230V

Secondary: 2x 450V/130mA, 16V-0-16V/500mA.

 

Then there's the 150VA that goes up to 160mA for the 450V, and 700mA for the 16V rail.

 

There's audio grade, then there's Supreme version: http://www.toroidy.pl/s783/57ad94c01a056094fc22ba3ecded9a40.jpg

 

It's cased in such pretty stainless steel shell. Is the shell important to prevent interference?

 

What's you guys' opinion on this? I really feel like getting the supreme stuff, but 160 dollars for the 150W transformer is not cheap too.

[spritzer]

The audio grade transformers are already shielded so not a whole lot of benefits to be gained from the can. 

 

I am in the process of gathering parts for a KGSSHV build and came across some 2SC4686a's at a reasonable price. Now, not the best picture in the world, but what do you think – are these genuine?

 

Pin connections are consistent with the data sheet and hfe seems to be in range as well. Unfortunately I have no way of measuring the breakdown voltage.

 

There’s no bar under the batch/lot number so either they are very old (pre-RoHS) or they have been remarked.

 

Thanks,

 

//UFN

 

Looks real to me. 

[astrostar59]

Another subject line but still KGSShv. Is it ok for the 580v bias to be around 594v? I don't want to blow my

009s. If this is not good, can it be lowered to 580v easily?

 

Thanks in advance guys.

[kevin gilmore]

I have not measured in a while, but the zeners keep it pretty close to 580 +/-5%

 

600V bias won't hurt the headphones, once in a while you might hear

whooshing noises. Also depends on humidity.

Edited July 14, 2014 by kevin gilmore

[astrostar59]

Thanks Kevin, I am at 102.5% so ok then - great.

 

BTW I love the KGSShv, it seems a perfect match with my 009s.