Group Buy for KG's Boards (2nd)

[charlo89]

Yes I have sent a PM to Tran, but no answer

[nopants]

He could be busy, should probably relax a little

[charlo89]

I'm in no hurry, I participated in the first and GB and Tran was perfect. There I have no answer, I hope everything okay on his side.

I just want to reicived the board before June 2014 (I think it will be good  ) I will have the resources and skills to build it after that date.

[insanity]

I recently tried to reach lil knight via PM to ask for my tracking number. But he didn't answer. I hope he is alright. My boards arrived a few days later. 

[mvwvm]

Hello,

 

I've added myself to the spreadsheet for 1x dynahi set. Hope there are still some boards left.

 

Thanks.

[RiStaR]

While waiting for my transformers for the megatron, I've completed the Squarewave with KG's help on the Krell power supply. Just tested it single-ended with the lone transformer that I had.

It's definitely worth the build... Not too expensive and makes my HD650 sound big. Gonna go try to find another amp to compare it with, but I'm liking what I'm hearing

[GeorgeP]

Sounds great! Pictures please!

[kevin gilmore]

I finished my singlepower squarewaves last night. pictures when I get home.

 

really sounds nice with hd800.

[chiguy]

While waiting for my transformers for the megatron, I've completed the Squarewave with KG's help on the Krell power supply. Just tested it single-ended with the lone transformer that I had.

It's definitely worth the build... Not too expensive and makes my HD650 sound big. Gonna go try to find another amp to compare it with, but I'm liking what I'm hearing

If you don't mind me asking, what are the specs on the transformers that you're using for the Megatron?

[RiStaR]

If you don't mind me asking, what are the specs on the transformers that you're using for the Megatron?

 

I kind of went overkill on it...

 

HV

420V 430mA x 2

17-0-17 1.2A

 

6.3vdc power supply

9v 30VA

 

6.3vac filaments

Using 3 (2x 30VA; 1x50VA)

 

For the PS board I'm using 2222A instead of 3904 and have changed the 15R to 10R so hopefully I won't have a problem with current. The PSU currently powers up fine without load. Waiting on the lv transformers to power up the amp board. Fingers crossed I get music on a flick of the switch

 

Just checked my squarewave amp boards and I have some issues I can't get the DC voltage down... two of the boards are -2v and the other two are like 1.6-1.9v ... will have some time to debug over the weekend. Not quite sure where to look, yet

Edited September 27, 2013 by RiStaR

[spritzer]

430ma??!!?? 

[RiStaR]

430ma??!!?? 

 

I know... But I thought you'd be the first to approve!

 

I'll take a pic of the EI core when everything comes together. Took me a while to find a case that'll fit all the bits I need inside the power supply. Waiting is always the hardest part with this hobby. I'm gonna turn in for the night. Have a good day the rest of you!

[kevin gilmore]

If you are using the central semiconductor metal can fets on the square wave boards

They have to be flipped from the plastic parts so put them in backwards.

And the servo does not work and will need to be rewired so pull the opamp and you

Should get about 200 to 300 mv of offset. Fix coming.

[nopants]

Where did you pick up a transformer like that, torodiy? Maybe you can hook up a kgsshv out the back while you're at it

 

I know... But I thought you'd be the first to approve!

 

I'll take a pic of the EI core when everything comes together. Took me a while to find a case that'll fit all the bits I need inside the power supply. Waiting is always the hardest part with this hobby. I'm gonna turn in for the night. Have a good day the rest of you!

[kevin gilmore]

what I had to do is add an extra inverter on top of the servo to get it to work right, shades of sijosae

with that inverter

http://gilmore.chem.northwestern.edu/sqwave1-1.jpg

http://gilmore.chem.northwestern.edu/sqwave1-2.jpg

http://gilmore.chem.northwestern.edu/sqwave1-3.jpg

 

updated schematic

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

Edited September 27, 2013 by kevin gilmore

[RiStaR]

what I had to do is add an extra inverter on top of the servo to get it to work right, shades of sijosae

with that inverter

http://gilmore.chem.northwestern.edu/sqwave1-1.jpg

http://gilmore.chem.northwestern.edu/sqwave1-2.jpg

http://gilmore.chem.northwestern.edu/sqwave1-3.jpg

updated schematic

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

Thanks making this easy! I did flip the FETs when I put them in because of the pinout. Will work on this today and tomorrow. My wife thought the sound was amazing through the realiser then I told her that was just with the radio as a source! Can't wait to get this working properly. Have a plan to get it stacked on the 8channel ess9018 DAC that I'm also waiting on parts for.

EDIT: never,ind the schematic is updated now... Pulling the opa134s did bring the offset down

Edited September 28, 2013 by RiStaR

[RiStaR]

Where did you pick up a transformer like that, torodiy? Maybe you can hook up a kgsshv out the back while you're at it

I had it custom made locally because toroidy was having issues shipping over... Thing is on the day I got back from ordering it toroidy came back and said ok. Would have worked out cheaper and much smaller too!

To be honest 430mA didn't seem excessive when I thought of it... I read 27mA per EL34 and some smaller values for the other 4. I figured with our usual 1.5 to 2 times for margin it was pretty close. Add in all the transformer issues people were having when having transformers so close to the actual rating of the kgsshv in the past, I thought going a 'tad' over would be ok.

That is until the EI transformer came in measuring 134 x 110 x 115...

Must have missed this out when I lost my post last night. I got the ideas for the change in resistors from talking to Victor. (15R to 10R for PSU and 1.5k to 1k on the amp board).

[cetoole]

How is the regulation of that transformer?

[RiStaR]

How is the regulation of that transformer?

I don't have a dummy load for testing around. And sharing that the readings never changed/fluctuate plugging the transformer to the kgsshv ps board isn't useful the transformer was at room temperature for the 10-15 mins I left it running.

FWIW, a couple of local niche hifi shops do use his services (which is pretty high cost for something very plain looking). I got his contact from one of those stores. Cetoole: way to go to make me calm my own fears

[kevin gilmore]

With pot at minimum bias is 120 ma with pot at max it's 200 ma

Probably should cut 75k resistor to 50k

And 1 meg resistor to 100k.

Servo takes 2 minutes to go from 200 mv to .2 mv with 1meg resistor.

Thd and noise below baseline of my meter. Slew rate which is already

Limited by input filter is very fast. Just great with hd800.

Going to add pads to measure bias on next board rev

[RiStaR]

With pot at minimum bias is 120 ma with pot at max it's 200 ma

Probably should cut 75k resistor to 50k

And 1 meg resistor to 100k.

Servo takes 2 minutes to go from 200 mv to .2 mv with 1meg resistor.

Thd and noise below baseline of my meter. Slew rate which is already

Limited by input filter is very fast. Just great with hd800.

Going to add pads to measure bias on next board rev

 

 

Thanks Kevin.

 

Will be picking up those resistors - have stacked the opamps per your schematic and pictures.

[RiStaR]

Have changed the resistors... The 50k resistors help to adjust bias very finely but I encountered some problems with two of the boards. I'm using 1% resistors but it seems the tolerance isn't good enough.

One of the boards refused to go above 30mA with the 50k resistor... Swapping back to the 75k one worked perfect. Probably my 34.8k resistors giving me grief...(can't access the schematic at the moment so I hope I remembered it right)

The other problem board jumps from 140ma to 200ma with a very fine touch... Not able to set anything in between and fluctuates a lot once i get there. Not sure if its the pot acting up or what not. I intend to swap the resistor to 75k as well to see how that works.

With the 50k resistor on the two "good boards" bias start at 60-80ma with the pot at minimum on my boards. With the 75k it starts at 128ma

The opamp stacking worked very well with the 100k resistor.... On the good boards they never go above 0.8mv and mostly stay around 0.1mv. Even on the "bad boards" it stays below 2mv.

I intend to run at 150ma for now since I fked up and got the smaller heat sinks (should have used a smaller depth and I'd have gotten the taller ones appearing on mouser ><). The sinks are just warm to touch at this setting.

Overall, this has been a simple fun build even with the minor problems on this revision Sounds good, too - I understand why singlepower was that popular in the day now.

[kevin gilmore]

strange both of my boards go smooth from 120 to 200ma with the 75k resistor and the pot.

have not tried the lower value resistor yet. kind of busy.

 

northwestern network down for most of the day due to dns issues.

[RodrigoRocha.RJ]

Any predictions on when there will be another group of purchases?
Why we recommend the use of AMB Sigma22 and not using the PSU Dynahi onbord in Dynahi Balanced?

[RiStaR]

strange both of my boards go smooth from 120 to 200ma with the 75k resistor and the pot.

have not tried the lower value resistor yet. kind of busy.

 

northwestern network down for most of the day due to dns issues.

It's probably my resistors and capacitors... Tried to go local on this low voltage stuff.

All the boards go smoothly except for the one that goes from 80 to 130+ smoothly then just jumps to 200 with a touch... Anything less and it jumps around. I'll swap the 50k to 75k to eliminate the pot being a possible factor I guess. At this stage it's done and has kept me occupied while waiting on transformers for the Megatron.

Thanks for the quick support! I'm happy with this