kgst

[azrael3000]

I did a quick drawing from the boards. If anyone spots a mistake please let me know.

Valve: Thanks for the notes, much appreciated.

[matthew-levi]

Hi Arno,

I found this PSU schematics and I think this is very close to the one that is on the board, except for some values in the components.

[matthew-levi]

just received most of the components and parts for this build....will be busy for the next few weeks. Probably will have lots of questions when I do testing.

[HemiSam]

It is a great amp.  May not be as sophisticated as some of the newer designs, but it is exceptional in my humble opinion.

Best of luck.

HS

[matthew-levi]

13 hours ago, HemiSam said:

It is a great amp.  May not be as sophisticated as some of the newer designs, but it is exceptional in my humble opinion.

Best of luck.

HS

Thank you, HemiSam. Sometimes simple is good too.  Looking forward to it. 

[azrael3000]

Looks nice Matthew, still waiting for my parts but they should be here any time now. Have fun with the soldering 🧙‍♂️

[matthew-levi]

Need some advice on mounting the 8N80C onto the heatsink. The version of 8N80C I've got has a plastic tab at the back, unlike the usual TO-220 package with a metal tab. I wonder whether I still need to use a plastic washer on the tab before I put the screw through. The problem is the hole on the tab is too small for the regular TO-220 plastic washer and I dont want to enlarge the hole with a drill bit. Please advice.

[mwl168]

May be better to post a picture to be sure but if the 8N80C you have are encapsulated then there is no need to use an insulator/plastic washer when mounting to the heatsink.

 

[UFN]

11 hours ago, matthew-levi said:

Need some advice on mounting the 8N80C onto the heatsink. The version of 8N80C I've got has a plastic tab at the back, unlike the usual TO-220 package with a metal tab. I wonder whether I still need to use a plastic washer on the tab before I put the screw through. The problem is the hole on the tab is too small for the regular TO-220 plastic washer and I dont want to enlarge the hole with a drill bit. Please advice.

Isolated semis you normally just mount with a bit of thermal compound between the package and the heatsink and a metal screw. That's the benefit of the full-isolated package - faster mounting (the downside is poorer thermal performance compared to a regular TO-220).

[matthew-levi]

Thank you, UFN and mwl168.

 

[matthew-levi]

Can anyone tell me how I can delete the photos in my media storage on this forum. It seems that I only have 500mb of storage, and my previous photos has taken up most of the space. How can I delete my previous photos to make space for new photos I want to post.

 

[n_maher]

16 hours ago, matthew-levi said:

Can anyone tell me how I can delete the photos in my media storage on this forum. It seems that I only have 500mb of storage, and my previous photos has taken up most of the space. How can I delete my previous photos to make space for new photos I want to post.

As far as I know there is no way for users to do this, only Admin's have rights to manage attachments.  I'll look into it a bit further but honestly, just get yourself some photo hosting space for cheap and don't pile stuff onto Todd's server. Something like https://pbase.com/pricing.html will run you $23 a year for 3000MB of storage.

[Fitz]

Or just upload them to imgur and link them.

[matthew-levi]

Thanks for the advice. I will try linking my photos to a photo site to see how it would work.

[matthew-levi]

I am trying a mod layout of my KGST build. Any comments or suggestions would be appeared. I am using two stereo stepped attenuator for the balanced input.

[mwl168]

Looks good to me counselor. No need to appear!

[matthew-levi]

Thanks, mwl168.

I just hate auto correct. Yeah, no need to appear. But I appreciate your comment(s).

 

[mwl168]

This is probably stating the obvious, I would also position the input connectors to the opposite side of where the mains AC connector is and route the input signal wires along the chassis wall, far away from the transformers.

[matthew-levi]

Thanks. That's the plan.

[matthew-levi]

I am almost ready to test. The power supply seems to be working ok. With no load, the HT voltages are 368V and -370V. The low voltages are 15.07V and -15.09V. The terminal blocks will only be used for power to the boards, signal leads will be soldered directly to the input and output pins.

I want to proceed to testing the amp boards without the servos. On the earlier posts in this forum, ppl mentioned about a jumper to connect the servo. But I dont see any jumper on this board. Can I just not install the op amp to disable the servo. I have put sockets for the op amps.

[Pars]

Just a couple of comments:

1. The sockets you used for the opamps are shit. Machined pin sockets such as Mill-Max 110-93-308-41-001000 are greatly preferred for reliability.
2. The terminal blocks look suspect. Normally, Phoenix Contact terminal blocks are used. Did you check the voltage ratings on the ones you used, compared to what you are running through them?

[matthew-levi]

The terminal blocks on the boards are all from Mousser and they are Pheonix brand. I will check on the op amp sockets and see if I can order the ones you suggested.

To all, I would still like to get an advice on no putting on the op amps to do testing. I actually could not see the op amp on the schematics that I found. Is the op amp optional in the operational of the amp assuming I can balance the DC offsets through the trimmer pots.

 

[valve5425]

13 hours ago, matthew-levi said:

To all, I would still like to get an advice on no putting on the op amps to do testing.

Page 4 of the Addendum I posted July 15.

Edited September 30, 2020 by valve5425
clarification

[matthew-levi]

@Valve5425, thanks for the reminder about your addendum, I should have checked that first. 

[matthew-levi]

Just want to report that the amp seems to be working, at least I can adjust the off-set and balance the O+/O-.

I will let it run ahwile and remeasure/re-balance. The next is put together the case work and also connect the headphone connector and some music. I will report further once everything is up and running.