Royer MXL 2001 mod HUMMMMM.....

phantom power · Post by **phantom power** » Tue Nov 27, 2007 3:35 pm

Lowbujit,

Thanks for the pics. I was starting to feel a little anxiety about diving in on this. The pics calmed me down in some weird way.

I was gonna wait 'til you guys found the PSU hum to start my mod, but I decided go ahead and populate my PCBs in the meantime.

Here's my question: What do I do with R4 on the PSU PCB? There's a spot for it on the board, but no part on the BOM included with the boards.

Oh yeah, I know nothing about electronics, so I may be putting my foot in my mouth here, but if I end up with the hum and can't get rid of it, would something like this work?

http://ebtechaudio.com/humxdes.html

Thanks again -AE

tubemonkey35 · Post by **tubemonkey35** » Tue Nov 27, 2007 4:57 pm

lowbujit, bdstrate is a good friend of mine down here in San Diego. He knows his electronics well!

I have been lame as of late completeing the PSU, holes are drilled forthe AMMO cases, but sometimes wife intervenes...

lowbujit · Post by **lowbujit** » Tue Nov 27, 2007 5:03 pm

phantom power wrote:Lowbujit,

Thanks for the pics. I was starting to feel a little anxiety about diving in on this. The pics calmed me down in some weird way.

I was gonna wait 'til you guys found the PSU hum to start my mod, but I decided go ahead and populate my PCBs in the meantime.

Here's my question: What do I do with R4 on the PSU PCB? There's a spot for it on the board, but no part on the BOM included with the boards.

Oh yeah, I know nothing about electronics, so I may be putting my foot in my mouth here, but if I end up with the hum and can't get rid of it, would something like this work?

http://ebtechaudio.com/humxdes.html

Thanks again -AE

oops, you're right there isnt a R4 on the parts list for the power supply. I'ts the same as R3, a 4.7k (4,700 ohm) 1/2 watt resistor. My bad. Thanks for pointing that out.

bstrate · Post by **bstrate** » Tue Nov 27, 2007 6:15 pm

Bugit,
I built my own supply.
I used a toroid transformer with two seperate ouputs, 4-wires. Just what I had laying around. Since then I bought a few more. My schematics and mics are at the studio, 20miles away, so I'm going from my bad memory.
This weekend I'll take a look at the scematics and the board layout etc.
I used a quadrupler diode configuration to get more voltage on the bias. I think I used a safety bleed resistor at the end, and I grounded the case & mic (three, prong). I used a few extra capacitors and large wattage resistors to get extra smooth DC. I also made sure I had enough current to power up the heaters. I didn't use a voltage regulator chip or anything like that. I used a different tube 6205, Plesuo capsules (u67, and the c12), mogami wire. Hand wired on a protoboard. I think I used solid silver wire for the capsule wires, (more current, for the same diameter wire as copper). I used that same case you are for my first project (cast aluminum), but its tight. I now use a aluminum military radio box, not the ammo ones (steel). Aluminum is better conductivity, you can tell what you have by using a magnet. If the magnet sticks, not aluminum. I also have a small AC/RF filter on the input to the box. You can get those cheap. This is where the three prong plug fits into.
I thing that is it, hope this help in the future.
p.s. you need to drill out the opening to the 2001 head larger for the plesule capsules, but its worth it, you will get ride of some of that sibilence you hear. The MXL capsules are small 3/4" I think. You want a 1".

??????? · Post by **???????** » Tue Nov 27, 2007 10:55 pm

I was thinking about/planning on going for one of the Peluso capsules as well, if I like what the mod does to the mic.

bstrate · Post by **bstrate** » Wed Nov 28, 2007 8:38 pm

lowbugit,
Did you find the humm?
Brian

lowbujit · Post by **lowbujit** » Wed Nov 28, 2007 8:57 pm

No I really havent been looking that hard lately. The only time I can really hear it is when I've got the gain all the way up on the preamp and on the fader. Also the fact that I live really close to an AM radio tower may have something to do with it. I'm waiting for someone else to build one to see how it works for them. I wish I had one of the original Royer boards to compare with.

bstrate · Post by **bstrate** » Thu Nov 29, 2007 8:45 am

I don't think the AM radio station will affect you since all your gear is balanced.( I would still put a RF filter on the AC input to your box. What type of mixing board or preamp are you sending the signal too? Also how loud is loud, when you have it up? After you have it up for like five minutes, then turn the power supply off to the mic. Can you hear the sound of the tube move as it is cooling down (tink,tink type of sound) through the speakers. The tube should still stay on for a while depending on your RC discarge time constant.
What I'm getting at is, maybe the humm is normal (small) if you have it cranked so loud. THese mics are quite but not like a solidstate mic.
Brian

bstrate · Post by **bstrate** » Thu Nov 29, 2007 8:48 am

p.s.
Radio Frequencys are too high for what you hear. This is a problem with 60Hz, 120Hz etc depending on you diode rectification configuration. THis all comes from your source AC and Gnd.
Brian

??????? · Post by **???????** » Thu Nov 29, 2007 10:19 am

just a thought... have you picked the power supply up and rotated it around with the gain cranked to see if the hum goes away/changes? What about the mic itself? Maybe there's a huge transformer outside of your house that's inducing hum? Who knows.

??????? · Post by **???????** » Thu Nov 29, 2007 12:41 pm

Additionally, here are some things to consider purchasing that are not listed in the bill of materials, but that you will probably need anyway:

Lamp holder
Lamp
Jewel
Switch (carling or similar)
Hammond 1590E or similar enclosure
Standoffs (4)
3pin XLR Male panel mount
Fuse holder
IEC power connector
Power cord
5 pin XLR male
5 pin XLR female panel mount
rubber feet

??????? · Post by **???????** » Wed Dec 05, 2007 12:03 pm

possible "Eureka" moment:

When looking at the pictures of lowbujt's power supply, I noticed that he has the power switch and pilot lamp on the same end of the box as the xlr connectors!

Royer SPECIFICALLY states to put those things at the opposite end of the enclosure. Is this for noise/hum reasons? It certainly stands to reason that the AC going to the power switch and lamp could be capacitively coupled to the signal wires, especially if they run parallel to one another.

This is the reason heater wires in amplifiers are run at right angles to signal wires and are as far away from them as possible.

Could this be the cause of the slight hum problem?

Food for thought anyway!!

tubemonkey35 · Post by **tubemonkey35** » Thu Dec 06, 2007 2:18 pm

I have completed the Royer mod using Lowbujits PSU/MIC and I CAN REPORT THERE IS NO HUMM!

FWIW: In my point to point version of the PSU, all switches, fuse and connectors were on the same side, and I had no hum or noise.

??????? · Post by **???????** » Thu Dec 06, 2007 2:36 pm

that's good news.

I got my jensen tranny in the mail today as well as most of my other parts. I'm still waiting on my tube (WTF?) and my panel mount XLRs and tube mic cable (something happened to my order at redco and I had to place it again) but other than that I'm just waiting on the paint to dry on my enclosure and mic body so I can put it all together (hammerite paint takes 48 hrs to cure).

phantom power · Post by **phantom power** » Thu Dec 06, 2007 4:35 pm

Wow! That's great news Tubemonkey.

I'm just sourcing a few more parts, then I'll be firing mine up. Did you use the the Jensen or the Cinemag? Is it the same tranny as your other mic?

Thanks -AE

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