i'm on a roll... the kgsshv

[s_r]

Yea, I'm probably just being overly cautious. I'd rather that than not cautious enough and have things blow up in my face, though.

[jwzhan]

I just realized that there are some changes to the v0.6 board...

Can someone explain to me what these changes are for?

Edited February 21, 2013 by jwzhan

[spritzer]

Local and global feedback.  Pick which you want. 

[jwzhan]

That clears everything up. I was just wondering what the L and G stood for. Thanks.

[s_r]

Is there an updated schematic for this amp revision floating around? I assume I use a jumper between which feedback I want and the middle pin (and solder the 100k into the appropriate spot). How much does the difference between the two matter?

[kevin gilmore]

You populate all the resistors, there should actually be 2 more

(I will look later)

And then 2 x 3pin jumper blocks.

Then you can switch between the two

(not with the power on)

There might be a schematic

[s_r]

Yea there are six 100k resistors on this board total. I'll probably just make another smaller order with mouser after some more resistor stuffing (since I foolishly forgot to order two of each of the balance/offset pots). So, could I put a 3pin switch over the global/local jumper pads? Also, I assume mixing local on one set and global on another would be bad news right?

[Victor Chew]

Nice idea for the local and global feedback choice. Are there any sockets that can be used for the acitive parts so that when things blow its just a matter of unplugging and replacing? And perhaps aslo for higher current choices as well.  

[kevin gilmore]

schematic

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

 

you definitely want global on both, or local on both.

and the output dc will drift a bit.

 

i would use the jumper block you typically find on pc motherboards.

.1 inch spacing. There should be miniature switches for pc mount that

would also work. (remembering that the pointer works in the other direction)

make sure they can handle 500 volts.

[SoupRKnowva]

In case anyone was wanting to build one of these bad boys, i have since moved and now have room for speakers so i dont have any reason to build it anymore. I have the majority of the parts needed, no case or transformer, and i didnt get some of the power supply caps yet. But i did get all of the hard to find sand ahead of time. Just trying to get some of my money back on the purchases

http://www.head-fi.org/t/652453/kgsshv-parts-most-of-the-parts-needed-to-build-including-boards-no-case-or-transformer

[s_r]

Are those 5pF caps on the amp boards necessary? I'll order some of those when I get the rest of the parts I need if so.

 

Nevermind, found some among the pile of parts I have.

[spritzer]

Don't run the amp without those caps. 

[RiStaR]

Like Jwzhan, I just received my board and noticing some things different from the BOM I followed. I do notice more things that are different on the onboard version, though.

 

 

 

https://www.dropbox.com/s/xh5hy0ai28mccfo/Ampboard.jpg <Can't seem to get the other link to work>

 

Can I check if the extra parts are needed for the top and bottom of the board? I couldn't find any discussion on op amps and servos so I hope I'm not asking something that's already been discussed. Can I also ask what they are for?

 

Looking for suggestions for jumpers. They seem rather far apart for the PC motherboard type?

 

Best

[Victor Chew]

Looks to me like, the new additions are feedback and a servo. Additional parts should be for both these items. You should be able to get the parts from Mouser.

I believe the jumper is to give you the option to use the servo or not.

You can choose either local or global feedback. The terminators give you the opportunity to try out both.

Edited February 23, 2013 by Victor Chew

[RiStaR]

Looks to me like, the new additions are feedback and a servo. Additional parts should be for both these items. You should be able to get the parts from Mouser.

I believe the jumper is to give you the option to use the servo or not.

You can choose either local or global feedback. The terminators give you the opportunity to try out both.

 

 

Hi Victor,

 

I got that part, but I guess my question was would it run if I just jumpered it for global? Just realized I didn't order enough spares for the 100k resistors so ordering the additional parts from mouser isn't the worst thing, I suppose. I'm assuming this op amp 595-OPA227U will work?

 

Edit: Nevermind. Figured out "servo" = jumper

[kevin gilmore]

updated schematic with servo

 

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

[s_r]

Hmm, I don't see that servo section on my amp boards. I assume it's because of the limited space on the offboard amp boards though. Which of the jumper spots are necessary to fill in if I intend on using the 1968 CCS? Also I need a wire from that single point above the 5pF cap to the 20k resistor right? The 175k resistors below the t-block are a bit in the way, but it shouldn't be too much of a problem.

 

Anyway, I've done all I can at the moment until I get more parts or the replacement PSU boards in.

 

[jwzhan]

not really getting what you are saying about the cap and 20K, but I don't believe any wires are needed. The small pads above the caps are through plated so the top and bottom layers of traces can connect, and it should serve no other purposes.

 

CCS choice has nothing to do with Global or Local feedback, so nothing needs to be changed. Just jump G or L (which ever you desire) to the center pad. Or use quick connect method, so you can switch between G and L if you so desire.

 

Just wondering.. what benefit does the servo provide in this case?

I'm sure off-board with servo is coming some time, because there are still plenty of unused space on the PCB to cram in additional circuit!

[Victor Chew]

As far as I am aware, it responds to dc voltage errors and corrects them when the signal is inputted. Its a more accurate way of correcting the dc offset than shorting to ground, which is an unatural way, and not in use this way during normal use. 

 

Technically speaking, with the dc at zero all the time, it should therefore, make the sound better.

[eggil]

Nothing to calibrate?

[Victor Chew]

You still callibrate so that the servo works less hard. To calibrate I believe, you will need to remove the opa27, then power up and get both the dc offset and balance near to zero. After that, power off and put the opa27 back in.

I am not sure if the servo will be able to correct a dc offset that is way off.

Edited February 24, 2013 by Victor Chew

[s_r]

not really getting what you are saying about the cap and 20K, but I don't believe any wires are needed.

 

Here's the bit I mean:

 

 

As far as I can tell it's just another bit to connect the traces on the bottom.

[livewire]

Yup, that would be a pass through trace.

[spritzer]

We strive to put all traces on the back side but often it just isn't possible, hence jumpers such as that one. 

[s_r]

Makes sense. My original confusion came from seeing other peoples amp boards with those jumper spots empty. For example this one (I grabbed this from this thread but I forgot whose board it is, sorry):