Physical very large PP caps are used instead of small 10uF E-Caps?
These large PP caps could pickup hum?
These large PP caps could pickup hum?
Will order some nylon screws for the Korg thank you. I wonder why they made it that way, with gnd around the screws in the corners.
After listening to the Preamp hooked up to my VFET 2 I have to thank Mr. Pass for this gorgeous preamp... definitely in the top 3 of preamps!
That's an example of an installation where one can reasonably expect little or no issues with line frequency hum when tying audio and chassis ground together. The previous setup is slightly more complex. While that does not guarantee issues with audio and chassis ground, it is one of the first places I would look. 6L6 proposes a methodical approach to learning the source of the hum, which is also recommended.
Yes mine is much more complex. Separate power supply for each Aleph 1.7 etc. I have shorted the negative fase for input to ground on each Aleph. Maybe I should use a resistor between negative and ground? I will follow 6L6 instructions. I Will isolate Korg from chassis as a start. Then a common gnd somewhere.
Followup
So I had zero noise or hum with the JT-11P-1 transformers added to my inputs UNTIL I plugged something into it. Even a stand alone high quality CD player created a low level hum. This was with isolated RCA input jacks mounted to the chassis and the reversed transformer primaries connected only to them.
So I ended up running a ground wire between the L and R RCA shell (negative) connections and to circuit ground. Yes, it gets rid of some of the theoretical advantages of transformer isolated input but now everything is dead quiet. Success!
If I ever add balanced XLR connections, I will add a DPDT switch to add or defeat the circuit grounding as a "balanced/unbalanced" switch.
So I had zero noise or hum with the JT-11P-1 transformers added to my inputs UNTIL I plugged something into it. Even a stand alone high quality CD player created a low level hum. This was with isolated RCA input jacks mounted to the chassis and the reversed transformer primaries connected only to them.
So I ended up running a ground wire between the L and R RCA shell (negative) connections and to circuit ground. Yes, it gets rid of some of the theoretical advantages of transformer isolated input but now everything is dead quiet. Success!
If I ever add balanced XLR connections, I will add a DPDT switch to add or defeat the circuit grounding as a "balanced/unbalanced" switch.
Killed a NuTube in 1.5 hours!
Put my Nutube from DIY store together with the DIY store board, store NuTube with the matched J113 jfets, using a Meanwell set to 23.75v. Followed Nelson’s excellent setup instructions, all test points were spot on, two beautiful blue lights. Let it burn in and adjusted T8 and T7 to a perfectly stable 9.5v. The left channel played perfectly, the right channel had an intermittent static and flutter sound, but otherwise sounded fine. I shut it down and reflowed all solder joints, cheched all test points, which were stilll perfect, hooked it back up, and same thing. I put it back on my bench and looked at all of the solder joints under a large magnifier and all looked good. I also went back and verified the values of all board components, and could not find any errors. I hooked the board back to the powersupply and the right channel on the Nutube flickered and failed, followed by the right channel a few minutes later. All test points are perfect except T8 and T7 which no longer respond to turning the 2 10k pots. I attached pictures, any ideas?
Put my Nutube from DIY store together with the DIY store board, store NuTube with the matched J113 jfets, using a Meanwell set to 23.75v. Followed Nelson’s excellent setup instructions, all test points were spot on, two beautiful blue lights. Let it burn in and adjusted T8 and T7 to a perfectly stable 9.5v. The left channel played perfectly, the right channel had an intermittent static and flutter sound, but otherwise sounded fine. I shut it down and reflowed all solder joints, cheched all test points, which were stilll perfect, hooked it back up, and same thing. I put it back on my bench and looked at all of the solder joints under a large magnifier and all looked good. I also went back and verified the values of all board components, and could not find any errors. I hooked the board back to the powersupply and the right channel on the Nutube flickered and failed, followed by the right channel a few minutes later. All test points are perfect except T8 and T7 which no longer respond to turning the 2 10k pots. I attached pictures, any ideas?
Attachments
When I encountered a similar partial situation with my nooby booby solders, it turned out to be intermittent connector on one of the 10K trim pots.
I see this board is version 1. Did you add the jumper to the bottom of the board in the correct location?
12 and .5v. She sure sounded awesome on the one channel before she died! Thanks for everything you do here Nelson!
I had something similar happen when I built a Millett Nuhybrid. Double check the solder points on the nutube itself confirming no cold solders or bridges. I had not properly soldered a couple pins on one of the nutube channels. Once fixed, it worked great.
Checked with high magnification, looked good, reflowed all joints anyway, checked again, looked good, reflowed all joints on the board again, rechecked with magnification, no joy, both channels are inoperable, no blue lights.