Royer MXL 2001 mod HUMMMMM.....

[lowbujit]

Ok I did it. Cant honestly say it made any difference. The hum was already so low that as soon as the heater warmed up after turning on the power supply that the hum is quickly overwhelmed by room noise coming in the mic. I can actually get rid of more hum by placing the mic in a different position in the room. That thing is an EMF magnet. There MAY have been a very slight difference in the very small hum that was there. But as I said before I have to have the preamp gain at max, the channel fader gain at max, the channel fader at max and the headphone volume at max to hear it. Theres probably more electronic hiss than anything else. At normal recording levels the hum is inaudible as it was before the re-routing of this ground trace. Anyway if it works for you great, and if anyone else is having hum problems you can try this and see if it works for you. Thanks B3groover for your continued support in this area.

[b3groover]

Just to show I'm not crazy, here are some samples of what I'm hearing. Let's start with our "control", the Royer PSU.

NOTE: The following samples were recorded with the mic I made from your kit. The same audio and power cables were used for all power supplies, with the same gain settings, and the mic in the same location. The preamp is a channel of my Topaz, cranked all the way, with the fader all the way up, going into a Presonus Firepod (line level) and into Cubase. No processing of any kind other than creating an mp3.

Okay, without further ado:

Sample 1: Royer PSU

Sample 2: Un-modified lowbujit PSU

Sample 3: Same lowbujit PSU with the trace mod


This time I did not change the grounding scheme at all. All I did between Sample 2 and Sample 3 was the trace mod.

Comparing Sample 3 with Sample 1, there is still just an ever-so-slight hum, but it is really far down in the noise floor. Still, it begs the question: How did Royer get his supply so clean? Maybe it's that big-ass ground plane on his PCBs.

Sorry for the walking noise in Sample 3. My wife came home just as I was finishing this test.

[wilder]

FWIW, I built mine with the lowbujit PSU and didn't make any changes. I don't experience this hum as in example 2. Mine sounds like example 3...minus the footsteps. I wonder if there's some other difference that your mod manages to compensate for?

[b3groover]

Not sure. How did you wire your grounds?

[b3groover]

Here is the trace mod if anyone is interested:



Step 1 - Cut the trace between negative leads of C1 and C6

Step 2 - Remove some of the screening on the trace between the negative leads of C2 and C3 (easy to do with a razor blade). Solder one end of a short piece of wire to the exposed trace.

Step 3 - Remove some of the screening on the trace between the negative leads of C6 and C7. Solder the other end of the wire to this exposed trace.


It solved my hum problem with these boards. That's all I can tell you.

[kywoman]

worked like a charm - thanks for the super-clear explanation!

[marktokach]

Are there any more boards available?

[Brian Brock]

I would love it if you could explain what you changed electronically speaking. Maybe you already mentioned this, I'll look back, but a clear explanation of what on the schematic you clipped and what you connected together would be cool as a starting point for me to look at this thing again.

I have the same hum, but made my own boards from the schematic.

Thanks.

Brian

[bluezplaya]

Can anyone recommend an inexpensive cable for the 5 pin?

Thanks,
Adam