KGSSHV Carbon Build Thread

[GeorgeP]

1 hour ago, gepardcv said:

Thanks, Kevin. In light of this, any concerns with keeping headphones plugged in while turning the amp off?

They all do it, including the T2. Its normal.

[gepardcv]

Sweet. Thanks for the explanation about the voltage jump, guys!

Pictures attached to this post.

This was my first time working with external heatsinks. I underestimated the difficulty, and ruined one sink trying to hand-drill it. Total fail. Luckily, I discovered that a colleague owns a Tormach PCNC 1100, and he was kind enough to invite me to his workshop and let me use the machine. A gorgeous device, let me tell you. It made short work of all the drilling. Then I hand-tapped all the holes (I think the Tormach machine can tap holes, but I wasn't sure how to keep the oil flowing and the taps clear of gunk for this operation).

The heatsinks themselves took some finding. They are Fischers, 10mm high by 300mm long, with 40mm fins, part SK 56 100 SA. High quality, and hard to find in the US. With 10mm standoffs, the entire amp fits nicely into an enclosure just slightly larger than 2.5U. (I also tried sinks with identical dimensions from HS Marston, and they sucked: all extrusions I received were crooked, and there was no way I could have bolted angle brackets to them.)

The rest of the chassis was done by FPE. In retrospect, I wish I extended the top and bottom panels to overlap the sharp edges of the heatsink fins, with large rectangular cutouts so air could still circulate. Still, I'm happy with how the case turned out. If anyone cares, I'm happy to share the .fpd files. Because FPE does not do anodizing, I had to have the panels made in two steps: one run before getting the pieces to an anodizer, and one run after.

The circuit itself was easy to assemble and adjust. No trouble from the Toroidy transformer. Overall, the amp runs a little warm to the touch (at 20mA output): cooler than either my KGST or mini-KGSSHV, though we'll see how it fares after more than an hour (all I've listened so far).

Many thanks to @mwl168 for the group buys and build notes, @sorenb and @jdineshk for the capacitor group buy and help, @vilts for making the spectacular titanium knob, everyone else who answered questions and provided inspiration, and many many thanks to Birgir and Kevin for making all this possible in the first place.

[GeorgeP]

Wow, looks awesome!

[Parbaked]

Your titanium knob just gave me wood!

Cheers...

[Kerry]

Congrats! Enjoy

[johnwmclean]

Awesome build.

I like how you have the panels now, not being extended... that’s just me.

 

[wink]

Note, John, he has 2 (count 'em) sockets....  

[johnwmclean]

With these voltages I would consider not using those terminal blocks for earth grounding as they tend to relax and loosin over time, I don't hold much confidence in there ability for this purpose.

[kevin gilmore]

great build

 

not sure where to put this (because i'm lazy) but congo5 figured out what was wrong with his grounded grid dht amp.

hint:   4.7M resistors replacing the 5.1k output resistors do all sorts of bad things to the sound. (unless you are a severe bass head)

 

anyone know somebody that will make me a couple of metal knobs?

I will supply the material.  warning: toxic, and slightly radioactive

 

 

Edited June 27, 2016 by kevin gilmore

[spritzer]

4M7 output resistors....yeah that will cause issues...   

[wink]

On 27/06/2016 at 8:08 PM, kevin gilmore said:

9snip)

anyone know somebody that will make me a couple of metal knobs?

I will supply the material.  warning: toxic, and slightly radioactive

 

 

Go Plutonium, or go home. Think of it as doubling up as a night light.  Gotta love atomic power....   

 

Edited June 29, 2016 by wink
fixed youtube linky

[kevin gilmore]

The depleted uranium and the beryllium are enough thank you

A tungsten knob would be nice. Almost as hard as the uranium

[joehpj]

what was @congo5 building? I thought it was GG not GG DHT?

[purk]

Gotta love the Carbon guys!  What an awesome sounding amp!

[wink]

10 hours ago, kevin gilmore said:

The depleted uranium and the beryllium are enough thank you

A tungsten knob would be nice. Almost as hard as the uranium

How about a lustrous Cobalt knob..?

... and it only has a hardness of 5.

[kevin gilmore]

5 hours ago, joehpj said:

what was @congo5 building? I thought it was GG not GG DHT?

actually it was the GG

hard to keep track of who is building what.

[joehpj]

3 hours ago, kevin gilmore said:

actually it was the GG

hard to keep track of who is building what.

Thanks. I had a plan to build a GG before I knew the problem of frequency response congo5 met. It's time to restart the project. 

One more question. What's the influence if I increase/ decrease the value of the resistors connecting the tube's G1 to G2 and G4 to G5? I had read from somewhere I could not remember which said the value of the resistors needed by EL34 and 6CA7 were different because of the internal structure difference between beam-tetrode and pentode.

Edit: and outout resistors? Should I just copy the settings of T2?

Edited June 28, 2016 by joehpj

[mwl168]

On 6/26/2016 at 1:56 PM, gepardcv said:

I have music! Pretty obvious this is something special. It was pretty easy to adjust, and the circuit seems fairly stable so far.

Still, something strange is going on: when I turn the amp off, all offsets jump to >250V, and then slowly down to 0. It's looks like the HV rails short to the output. I don't think this happens with my KGST and KGSSHV builds. Is this expected, or did I fuck something up while wiring the amp?

I am fairly certain I've measured similar effect of my Carbon which I have been listening to on and off for months without issue.

I do disconnect my headphone before power on and off.

[JoaMat]

Seems Stax used a Low Signal Relay in their SRM-T2. Anyone like to try it?

[spritzer]

1 hour ago, mwl168 said:

I am fairly certain I've measured similar effect of my Carbon which I have been listening to on and off for months without issue.

I do disconnect my headphone before power on and off.

It think this is a quirk of the CCS or something like that as my Carbon's don't do this. 

15 minutes ago, JoaMat said:

Seems Stax used a Low Signal Relay in their SRM-T2. Anyone like to try it?

Stax still use it to this day in the 727.  It's long been out of production though. 

[JoaMat]

Thanks for info, Birgir.

I’ve been thinking about the possibility to use some kind of relay in a future T2. Not sure that Omron G6A equivalent is the one to use, but if Stax can - I could try...

[kevin gilmore]

on srm717/727 only I think stax used this relay with a detect circuit that opened the relay if either of the + outputs exceeded + or -400V  or the difference between the + and - power supply exceeded +/-30V.  which is why that fucking idiot over there who thinks he was gods gift to modifying stax amplifiers had all sorts of trouble.

on the T2 pretty sure it was a delay circuit only. will look later.

Edited June 28, 2016 by kevin gilmore

[spritzer]

I think it is tied to the servo but I can't be sure.  Too lazy to look for the schematics...   

[Skooby]

Another Carbon powered up.  The chassis a tad bit long/deep but too lazy to chop 2-3 inches off to size.  A phase splitter sits on top of the trafo for SE input (a power switch off when use balanced).  Going cheap with Alps R27; will upgrade later.  Thanks, Dr. Gilmore and everyone else for designing the Carbon.  Thanks to sorenb for organizing the group buy! 

 

[spritzer]

Why are you using the phase splitter?  This isn't a Cavalli amp, there is no need for it.