Thanks!
I will check the values of those when I return.
C6 is .1 400v
(Though I think the Oblgato cap I used is 600v)
I have a few of the .1’s on hand. Bought a lot of the when that line was discontinued. Will measure the value of that, and R9
I did check all values prior to assembly and went over the board not too long ago, and all values were as they were supposed to be.
But will happily check them again!
I will check the values of those when I return.
C6 is .1 400v
(Though I think the Oblgato cap I used is 600v)
I have a few of the .1’s on hand. Bought a lot of the when that line was discontinued. Will measure the value of that, and R9
I did check all values prior to assembly and went over the board not too long ago, and all values were as they were supposed to be.
But will happily check them again!
I still think you probably have a ground loop somewhere. That board is so tricky if you don't don't use their prefabbed case. I assume you've tried cheater plugs for your amp or amps. I wish I had documented how I finally got mine quiet. I used a Kohzmo stereo ladder attrenuator for the master volume, and there was a thing about snipping the bridged ground connection that solved a lot of the problem, also grounding the case of the attenuator to the board. Since you're using the little stepped attenuators and have grounded the plate that holds them I don't know if that's relevant. I know you'll get it solved eventually.
Do you knopw, or have you mentioned, the frequency of the hum? If it's 60Hz it's a ground loop, if it's 120Hz it could be a lack of PS noise cancellation, or hum from the regulated heaters.
Do you knopw, or have you mentioned, the frequency of the hum? If it's 60Hz it's a ground loop, if it's 120Hz it could be a lack of PS noise cancellation, or hum from the regulated heaters.
Post 102 has clues. He hasn’t hooked it up to a scope yet. But there seems to be a fair amount of 60Hz and 120Hz noise from the in room RTA measurement. More > 100Hz noise.
Earlier in the thread, he had measured AC values in the main B+ supply, heater supply, etc…using a Fluke RMS DMM.
Right now, on each of the preamp outputs, we have about 1.3mV RMS AC. That in my experience is too high for a preamp circuit but it’s also highly dependent on how sensitive your speakers are and how much gain there is in the power amps he is using. Certainly not for headphones!
In any case, your mentioning of the hum cancellation circuit within the Aikido circuit itself has me thinking. The PSRR of the Aikido as published by Broskie isn’t really that high, i.e. about -30dB from what I recall. So it still needs a decently cobbled, well filtered B+ power supply and DC filament supply. Clearly, placement of the toroids, shielding of power transformers and proper wiring should make a difference.
I know I’ll be building my own version, but it will be demonstrably different from anything presented in the SP14.
Scanning through my Aikido document, it appears that with 6SN7 tubes, the recommendations for C6, R15 and R16 are:
C6 = 0.047uF to 0.22 uF (must exceed the B+ voltage for rating)
R15 = 83.3K (or thereabouts since that’s an unusual value)
R16 = 100K
Best,
Anand.
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One would hope, that when a kit is provided, and all the parts shiped, match the parts on the BOM, and all the parts measure as they are supposed to and are finally put in the correct spot for that part, that the amp should function as it should.
Will individual 6SN7’s vary so much that values of the supporting parts on the board need to be adjusted for different brands of tubes?
So much for tube rolling…
Will individual 6SN7’s vary so much that values of the supporting parts on the board need to be adjusted for different brands of tubes?
So much for tube rolling…
Here is the first AIKIDO that I completed in 2017. Chinese PCB from Aliexpress for 6N3P tubes. Tried 6N3P-EV, 5670, 6CC42 and similar, even 6922/E88CC/6N23P-EV with adapters. I had to rework it a lot by adding a new HV power supply and timers for heating, high voltage and output mute. For the R9 (or R10?) I put a 200k trimmer to adjust the value for the various tubes. The GND on the board was miswired, and I chopped and reworked that. After that there were a few more changes. 
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Nice
All metal chassis.
I can’t help but think, my noise is because of the grounding between the front, top and rear panels.
Combined with a steel top plate and it’s proximity to the transformers.
Prior to grounding the top plate, the noise was profound! I mean, really loud.
98% of the noise disappeared after grounding the top. Left channel is all but gone.
Lot to consider.
All metal chassis.
I can’t help but think, my noise is because of the grounding between the front, top and rear panels.
Combined with a steel top plate and it’s proximity to the transformers.
Prior to grounding the top plate, the noise was profound! I mean, really loud.
98% of the noise disappeared after grounding the top. Left channel is all but gone.
Lot to consider.
This is the last one I made, for my sister. AIKIDO Cathode Follower. Point to point. Aliexpress box, later laser engraved text front and back. On that box, due to the anodization, the panel contact was not good, I put serrated washers everywhere so that everything was connected to GND.
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Yeah
Still hums
Checked the amp, with no input and it’s dead quiet.
I checked all the solder joints on the right channel. Reflowed a couple of things even though it didn’t need it just to be safe.
This is what I’m seeing out of the Cornwalls with the mic on my phone right against the right driver
Still hums
Checked the amp, with no input and it’s dead quiet.
I checked all the solder joints on the right channel. Reflowed a couple of things even though it didn’t need it just to be safe.
This is what I’m seeing out of the Cornwalls with the mic on my phone right against the right driver
