[The analog thread.]

I have been ripping my vinyls into digital files (96K/24bits). I found that they easily beat the CD version of those albums in terms of sound quality.

You will probably need a high quality A to D converter to get the best results. I am using a Lynx Hilo with thunderbolt output which goes into my Mac. I have also used a PS Audio Nuwave Phono Converter. The PS Audio is currently collecting dust. The Lynx Hilo accepts XLR input. You can order a UBS output too if you do not want Thunderbolt. 

The software I use to rip the file is VinylStudio. 

Hope this help. 

[kgst]

Hi CrowDaddy,

Thank you for the encouragements. I will send you the BOM I used. 

I think its a personal choice on whether to use an EI or toroid transformer. It's a matter of availability for me. I have since replaced the transformer with one that can also supply the 15-0-15V and removed the smaller LV transformer.

 

[kgst]

After almost three and a half months, the KGST is finally in operation, and is sounding great. Thanks to all who have responded to my questions and given guidance. I am really surprised at  how good the 40 year old headphone sounds with this amp. 

Special thanks also to Bigir and Dr. Gilmore for such wonder contributions to the community. 

 

[kgst]

11 hours ago, jamesmking said:

how is the voltage O- to ground does it behave and vary similarly to the O+? 

are both channels approximately the same?

Yes, both O+ and O- behave similarly, and both channels behave similarly too. For the balance i manage to get it down to around 100mv or less. 

I will do more testing and run it longer to see how they go. Right now I feel better knowing its should be ok. 

Thanks for the guidance. 

[kgst]

What should be the upper limit of the off-set  ( between O+ and ground). It fluctuates from a couple of voltages to 100 mV range. This is after the amp has been running for about half an hour. When its so unstable, does it mean something is not quite right. One of my friends told me that the off-set should be in the 10s of mV range. 

[kgst]

This is the schematics I downloaded from the web. On the board, I think the D12 anode is connected to the cathode of D1. So the board is correct, but the schematics may have an error (at least on this version that I managed to lay my hands on).

[kgst]

Love that warm glow of the tubes.

[kgst]

Hi JoaMat, I followed your advice and I have been able to set the bias to 230V. Thank you so much.

For the balance and off-set, I have been able to set them to around 1V, but it fluctuates quite a bit. I think that should be ok. 

 

[kgst]

I could not adjust the bias down to 230V (for my normal bias Lambda). The lowest I could adjust is 333V.  How should I modify the voltage divider circuit to all the voltage to go down further. 

[kgst]

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. 

[kgst]

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

[kgst]

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.

 

[kgst]

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.

[kgst]

Thanks. That's the plan.

[kgst]

Thanks, mwl168.

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

 

[kgst]

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.

[kgst]

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

[kgst]

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.

 

[kgst]

Thank you, UFN and mwl168.

 

[kgst]

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.

[kgst]

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. 

[kgst]

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.

[kgst]

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.

[kgst]

5 hours ago, kevin gilmore said:

nope that is not the psu for that board.  much simpler, 10m90 feeds zener string, drives single pass transistor

Hi Kevin, Is the PSU schematics stored somewhere that I can go search? Thanks.

 

[kgst]

24 minutes ago, valve5425 said:

Just had a hunt through my files and I've got Gerbers, but don't have the PSU schematic, so can't help with that.

Thanks. Hope others can provide a pointer.