Also could be a USB problem, see https://www.diyaudio.com/community/threads/audio-and-chassis-grounding.427613/page-2#post-8012211 .
THANKS
That is a true "Inside The Box" thinking while many of us were trying to solve the issue "Outside The Box".. I just took a look at my Zenductors... about five feet from my left hand, with their really HOT stacked heatsinks.
Hmm... another project.
Ideas...
For bias.. how about drilling a couple of 1 inch holes on the top lid above the pots? That way you could adjust the bias with the lid off? You could also drive the bias test points to the test points to the outside and use a DMM... this is how my B1K is built. I can adjust and measure the bias from the outside.
Power supplies.... you went to a bigger power supply?
Oh, the back panel is confusing. I'm trying to make sense out of all the connectors. I figured it would have two low level inputs (2 jack), four posts for the speakers and one for the power supply.... but I see more..... I guess I don't understand that... is that to provide power ON/OFF from the front panel?
That is a true "Inside The Box" thinking while many of us were trying to solve the issue "Outside The Box".. I just took a look at my Zenductors... about five feet from my left hand, with their really HOT stacked heatsinks.
Hmm... another project.
Ideas...
For bias.. how about drilling a couple of 1 inch holes on the top lid above the pots? That way you could adjust the bias with the lid off? You could also drive the bias test points to the test points to the outside and use a DMM... this is how my B1K is built. I can adjust and measure the bias from the outside.
Power supplies.... you went to a bigger power supply?
Oh, the back panel is confusing. I'm trying to make sense out of all the connectors. I figured it would have two low level inputs (2 jack), four posts for the speakers and one for the power supply.... but I see more..... I guess I don't understand that... is that to provide power ON/OFF from the front panel?
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Thanks for the suggestions, Tony. I could move the power supplies inside the chassis, but then I'd want a proper power inlet with fuse and filter and switch; I like the small DC jacks, and the external supplies are not too much of a hassle.
Regarding bias: I think I'm pretty close to picking a 'final' setting, and will use the built-in DVMs just for monitoring warmup and stability.
I am though going to replace the original 7/8" 6-32 metal standoffs with 20mm M3 nylon ones, to gain a tiny bit (2mm) of clearance between the top lid and the inductors (currently touching, with a kapton strip in between), and I might redo some of the internal DC wiring with RG316 cable. But before I do any rewiring I am going to try the effects of a USB isolator and of a galvanic separation transformer (both of which I already have, but forgot about....) on the noise and distortion measurements. Those bumps and spikes just look very suspicious.
Regarding bias: I think I'm pretty close to picking a 'final' setting, and will use the built-in DVMs just for monitoring warmup and stability.
I am though going to replace the original 7/8" 6-32 metal standoffs with 20mm M3 nylon ones, to gain a tiny bit (2mm) of clearance between the top lid and the inductors (currently touching, with a kapton strip in between), and I might redo some of the internal DC wiring with RG316 cable. But before I do any rewiring I am going to try the effects of a USB isolator and of a galvanic separation transformer (both of which I already have, but forgot about....) on the noise and distortion measurements. Those bumps and spikes just look very suspicious.
Also, regarding 'outside the box': I did and do like the look of the naked amplifiers. Somebody should try a conformal coating and test how that holds up to everyday use, dusting and handling. There are no high voltages here. With a standard coating (25 micron or higher thickness) one probably wants to mask the heatsinks. At work at some point we were thinking about parylene coating of whole modules, but then gave up on it (too hard to get a good estimate on long-term effects and reliability for a large number of devices); that can be done in the sub-micron to tens of micron range, and there are no solvents involved. But most people or even labs don't have a parylene coating reactor/chamber. There are companies that offer it as a service.