Bias set to 20mV! Running fine with music. Sounds very good. The hum is not audible >2ft away. With no input, there’s 40mVAC at the outputs. 1mV with input shorted.
I’ll have to experiment with different setups for DC protection and delay to stay safe.
If I’m lucky I will conquer the likely grounding hum, but I could live with it at this level.
I’ll have to experiment with different setups for DC protection and delay to stay safe.
If I’m lucky I will conquer the likely grounding hum, but I could live with it at this level.
Last edited:
Have you experimented with moving the amp away fro the power supply and changing wire routing? This would give you an indication if the hum is coming in through the power supply or is being induced into the circuitry. SMPS can be tricky!
You should have only one ground wire running between the input and output boards. Running two can set you up for a ground loop, causing hum.
Good points, thank you. I have not experimented yet with separating the amp and smps further and changing wire routing. I will see if that affects the hum. Later today!
Thank you both for your help!
Edit: I’ll remove the redundant ground wire first.
Thank you both for your help!
Edit: I’ll remove the redundant ground wire first.
I was just looking at your connection diagram PDF. GND1 should connect directly to the power supply, not through the wire to the input end of the board. Speaker returns should also go directly to the power supply. The input end should either connect to the output end of the board or the power supply directly, one or the other but not both.
Grounding is very important to eliminate hum. It can be tricky to get right.
Grounding is very important to eliminate hum. It can be tricky to get right.
Last edited:
Thanks for the extra picture and this point. I will experiment with lifting the PE connection, too.
I also have MicroAudio (Cresnet) SMPS-600 supplies to test with the amp.
Many variables. 😀
Please see the PM ))
I mentioned 44mV across 2 source resistors there - 20mV is also no problem, you can try moving between those values and see if you notice some difference.
I mentioned 44mV across 2 source resistors there - 20mV is also no problem, you can try moving between those values and see if you notice some difference.
Yet another PCB...
Happy new year to all of you guys
I started to prepare for a "Full Enchilada"-Build - TubSuMo + NS-OPS. The PCBs provided so far are a masterpiece of layout work - anyway I need to redraw them to fit some of my requirements. I started with TubSuMo IPS, which I wanted to be designed in a way that you can watch illuminated tubes through the enclosure's front panel 😀 In addition, I took the chance to give some options for the caps - I plan to assemble cheap SMD caps for first test and replace them with Nichicon KZs and Silver Micas for the final setup. Here's a screenshot of how my idea looks like - still a lot of checking and refinement to do:
I take the chance to thank Valery, Jeff and all the other guys to lead a great idea to an idiot-proof design. Once I finished IPS I'm going to start NS-OPS sim + layout with 4 pairs of 2SC3263/2SA1294 - it seems to be quite impossible to catch 2SC2922/2SA1216 these days 😡
Will keep you up to date with my progress (as long as sbd. is interested and has some patience)...
Prost!
Holgi
Happy new year to all of you guys
I started to prepare for a "Full Enchilada"-Build - TubSuMo + NS-OPS. The PCBs provided so far are a masterpiece of layout work - anyway I need to redraw them to fit some of my requirements. I started with TubSuMo IPS, which I wanted to be designed in a way that you can watch illuminated tubes through the enclosure's front panel 😀 In addition, I took the chance to give some options for the caps - I plan to assemble cheap SMD caps for first test and replace them with Nichicon KZs and Silver Micas for the final setup. Here's a screenshot of how my idea looks like - still a lot of checking and refinement to do:
I take the chance to thank Valery, Jeff and all the other guys to lead a great idea to an idiot-proof design. Once I finished IPS I'm going to start NS-OPS sim + layout with 4 pairs of 2SC3263/2SA1294 - it seems to be quite impossible to catch 2SC2922/2SA1216 these days 😡
Will keep you up to date with my progress (as long as sbd. is interested and has some patience)...
Prost!
Holgi
Maybe - 10 pairs of 2SC3263/2SA1294 are ~50€ and seem to share the die inside, though 2SC2922/2SA1216 in MT-200 are way more sexy... have to think and will come back to you in case 🙂
Prost!
Holgi
Prost!
Holgi
That looks like a nice layout! Sounds like a neat design with the tubes showing through the front.
We've switched to MJL4281/4302 output devices. They're double die devices for extra current handling, but they aren't as hard to kill as the Sanken MT-200s.
We've switched to MJL4281/4302 output devices. They're double die devices for extra current handling, but they aren't as hard to kill as the Sanken MT-200s.
Thanks, Jeff 🙂 Yep, I noticed the change to the Onsemi devices, but I'm curious about the impact on sound signature - did anyone ever compare the well-known smooth/warm Sanken sound to the Onsemis? I will try to find out and maybe I build both versions for 1:1 comparison with my sources and speakers - at least for me that's what counts 😀
Same applies for the tube selection, I have some old 12AU7 at hand and ordered some matched/selected for comparison. This is going to be fun!
By the way: Is there a condign SMT replacement for A992/C1845 available? I found SOT-23 variants (MMBT) for some MPSA TO-92 devices, but nothing for the Fairchild semis...
Prost!
Holgi
Same applies for the tube selection, I have some old 12AU7 at hand and ordered some matched/selected for comparison. This is going to be fun!
By the way: Is there a condign SMT replacement for A992/C1845 available? I found SOT-23 variants (MMBT) for some MPSA TO-92 devices, but nothing for the Fairchild semis...
Prost!
Holgi
Thank you! Will modify my layout accordingly - next step is to find an SMT 12AU7 😉
Prost!
Holgi
Prost!
Holgi
I've never heard any difference between the On Semi or the Sanken output devices, the distortion is so low in these amps it would be hard to hear any difference in output stages. You need to pay attention when first warming up the On Semi output devices though. They will blow if you let them run away, while the Sankens would just blow the fuse.
We've been using the FJV versions of 992/3324 as Rick suggests.
We've been using the FJV versions of 992/3324 as Rick suggests.