Just reflowed v111/112 and it didn't make any difference. I see v111/112 are getting 0.6v BE
Do
Do
Please stop searching... Issue has been found...
First, I would like to apologize for wasting everyone's time trying to help me find this issue... And yes, it was a rookie issue...
So... On the Mosfet buffer PCB, I had the diode in the wrong orientation for the N Channel!
I was going through every components at a time and measuring what could be measured on board and checking schematic to make sure everything was properly installed... Then on the buffer PCB of the N channel, I had the cathode pointing to Source... Yes, that did screw everything up...
So, for someone else building this PCB, double check this.
I just checked a nice sine wave and it is all beautiful!
Question... between BD140 and KSA992 for position v131, technically, which one would be best, or it does not make a difference?
Thanks
Do
First, I would like to apologize for wasting everyone's time trying to help me find this issue... And yes, it was a rookie issue...
So... On the Mosfet buffer PCB, I had the diode in the wrong orientation for the N Channel!
I was going through every components at a time and measuring what could be measured on board and checking schematic to make sure everything was properly installed... Then on the buffer PCB of the N channel, I had the cathode pointing to Source... Yes, that did screw everything up...
So, for someone else building this PCB, double check this.
I just checked a nice sine wave and it is all beautiful!
Question... between BD140 and KSA992 for position v131, technically, which one would be best, or it does not make a difference?
Thanks
Do
Do,
Good to know that you found the root cause, and now everything is working as it should be. 🙂
Good to know that you found the root cause, and now everything is working as it should be. 🙂
Yippee!! We were all waiting with baited breath! Good that the solution was simple ;-)
Best,
Anand.
Best,
Anand.
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Thanks for the positiveness! This is greatly appreciated!
Thanks Anand for this buffer board schematic. On my side, I just soldered everything without thinking of looking at Hugh schematic, I mean, it was all there... I just got distracted I guess...
Thanks
Do
Thanks Anand for this buffer board schematic. On my side, I just soldered everything without thinking of looking at Hugh schematic, I mean, it was all there... I just got distracted I guess...
Thanks
Do
Congratulations Do!! Excellent sleuthing 😉
I have to apologize Do, When I saw you’re picture of the snubber boards, it brought back a memory from when X posted a picture of his snubber boards and the orientation of the diodes I wanted to alert you but got sidetracked and forgot 🙁
Let the listening begin!!
Cheers.
I have to apologize Do, When I saw you’re picture of the snubber boards, it brought back a memory from when X posted a picture of his snubber boards and the orientation of the diodes I wanted to alert you but got sidetracked and forgot 🙁
Let the listening begin!!
Cheers.
R141, 142 (0R12 5w) gets pretty toasty... Around 55-60 Celsius... Maybe I should stack 2x 0R24 each 5W and spread the heat? Hopefully it is not oscillating... I was checking the scope and I was not seeing any oscillation, I'll check again on square wave output.
As far as DC offset goes, with trimmer at max, I'm getting ~4mV of offset. If removing the 200R trimmer and adding a 500R trimmer, at max, I'm getting 0.5mV DC offset.
Also if anyone could answer the BD140 vs KSA992 question a few post above
Thanks
Do
As far as DC offset goes, with trimmer at max, I'm getting ~4mV of offset. If removing the 200R trimmer and adding a 500R trimmer, at max, I'm getting 0.5mV DC offset.
Also if anyone could answer the BD140 vs KSA992 question a few post above
Thanks
Do
Congrats Do! I forgot all about the diode on the snubber too. I don’t think it matters which for the BD140 vs KSA992. The latter has faster response but not sure it’s that important here. 55C on the resistors is normal. Those can take much higher temperatures. If you are running 3A bias current then power dissipated would be about 1.5W and well below the 3W rating.
If you look hard enough you can see the orientation of the diodes. From Post 1.
If you look hard enough you can see the orientation of the diodes. From Post 1.
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Congrats, Do.
There was a hint and I ignored it too.........
The voltage between gate and source of the nmos.
Good find. These are not easy to find, diagnosis is an art/hunch.
Hugh
There was a hint and I ignored it too.........
The voltage between gate and source of the nmos.
Good find. These are not easy to find, diagnosis is an art/hunch.
Hugh
Bravo! How does it sound? Two channels yet?
I can't wait for the cold days to arrive to fire mine!
BD140 or KSA992
Do,
That is the question......
I believe best would be BD140, to make it slow. The Vbe of this transistor should be close to constant but the collector should hike up and down to drive the p mosfet currents, which should vary from about -3.9V to -4.2V, a narrow range. It must be slow for the audio, but not too fast which encourages the high transconductance p mosfet to oscillate.
A smaller KSA992 is much smaller and lightly to be more skittish.........
Please give us your SQ thoughts after a couple of good listening sessions!
Hugh
Do,
That is the question......
I believe best would be BD140, to make it slow. The Vbe of this transistor should be close to constant but the collector should hike up and down to drive the p mosfet currents, which should vary from about -3.9V to -4.2V, a narrow range. It must be slow for the audio, but not too fast which encourages the high transconductance p mosfet to oscillate.
A smaller KSA992 is much smaller and lightly to be more skittish.........
Please give us your SQ thoughts after a couple of good listening sessions!
Hugh
@jacques antoine
I can’t really tell about the sound with just one channel tested on a cheap speaker, but I’ll be working nights this week to try and finish the second channel. I also need to add speaker protection to the amplifier. No matter how reliable an amplifier is, I never trust any amplifiers without protection on the speakers. This is my paranoia I guess… LOL!
@AKSA
Thanks Hugh for the help, information and recommandations. I’ll change the KSA992 for BD140 shortly.
@XRK
Thanks for your support, it’s really appreciated.
Also everyone else who chimed in to help!
Do
I can’t really tell about the sound with just one channel tested on a cheap speaker, but I’ll be working nights this week to try and finish the second channel. I also need to add speaker protection to the amplifier. No matter how reliable an amplifier is, I never trust any amplifiers without protection on the speakers. This is my paranoia I guess… LOL!
@AKSA
Thanks Hugh for the help, information and recommandations. I’ll change the KSA992 for BD140 shortly.
@XRK
Thanks for your support, it’s really appreciated.
Also everyone else who chimed in to help!
Do
Hi Do,
Looking forward to hearing your impressions in stereo. Do you still have enough SSR speaker protection boards?
Looking forward to hearing your impressions in stereo. Do you still have enough SSR speaker protection boards?
Hi X,
I’ve got a set of first generation available. I’ll be salvaging it from another build. I might need more in the near future though.
Thanks
Do
I’ve got a set of first generation available. I’ll be salvaging it from another build. I might need more in the near future though.
Thanks
Do
Wow! this thing has got some impressive bottom end punch, I mean on my test speaker it goes really deep. Can't wait to have the second channel up!
There's still a lot of work to do but it's coming along!
Do
There's still a lot of work to do but it's coming along!
Do
Thanks Vunce! 🙂
Chassis is Chinese made, so partly DIY (assembling and drilling/tapping).
Thanks
Do
Chassis is Chinese made, so partly DIY (assembling and drilling/tapping).
Thanks
Do