Tube Mic Royer Mod Build Thread

[tchgtr]

OK, gotta fit all this stuff in the ammo can...

 

[tchgtr]

Success!
The pattern knob is from an old Mutron pedal. Will check it later using a 12VAC wall wart, and see if everything comes out around a 10th of the value it should be. It worked before I put it all in the can, so the outlook is good.

 

[tchgtr]

Say hello to the Audi Nova microphone.
  The idea was to throw together a bunch of parts that were just lying around from various builds. The capsule is from a Nady 1050, in which I put a group-buy C12 clone, and now like very much.
  It should be obvious where the body came from. The Nova has a crappy circuit, but the body/grill are very solid and make a good platform. I put it's 47-style capsule in a MXL 9000, which greatly improved the sound of it (I just don't like those Chinese 67-style capsules), and used the circuit board, 1G resistors, and 7:1 transformer from the Nova for this build.
  The PSU is based on the info that PRR gave earlier in this thread (and the Gyraf and Big Ugly schemos), and I used three 5K resistors, two 22uf and two 180uf caps for the B+, which comes out at a whopping 140V. I know the capsule can handle that based on the 1050 specs, and that falls within the 5840 tube specs, tho I'm not sure it's the best voltage for that tube. Maybe I should have used four 5ks...
    Most of the other parts came from All Electronics, my favorite adult toy store.
  It took me a few days to find some problems with the initial build (bad 5k adjuster pot in the PSU, wiring mistake on pin 1 of the tube), but I'm proud to have figured it out on my own without asking the forum. I was afraid there might have been problems from using the Novas circuit board for this build (hidden traces and such), but it seems to have worked quite well.
  It sounds good. Better than this capsule sounded in the 1050. I used the Gyraf pattern scheme (just 3 choices; omni, cardioid, figure eight), and can't get over how well that worked. It may end up with a dual-sided 47-style Chinese capsule, but for now it's got the more 67-ish sound, which will match my other cardioid Royer build quite well for some MS experiments. It seems both sides match in figure-8 better than they did in the 1050...
  There is a bit of noise, a buzzing that can be heard floating around the noise floor, so I guess I have a bit more troubleshooting to do, but the posts above have a few guidelines to help me along.
  As always, this place is a wealth of info, and I'm grateful for the constructive atmosphere here.
Thanks to all...

 

[Blue Jinn]

Would love to see some internal shots too of the mic!

 

[tchgtr]

Here's a shot of the tube side of the PCB. I'll be the first to admit it's not pretty.
You can see the other side in an earlier post, before it was installed in the mic, but I'll be happy to throw up a shot of it now, if you want. It's not pretty either, but I have the two capsule connections floating above the PCB on the extended leads from the white cap you can see in this photo.
Nice things about working from the original PCB are that it fits the mic well, there are connections for xformer and such that go pretty much where you want 'em, and I didn't have to unsolder the two 1G resistors or the 1n capsule input cap. There's always the fear that you missed a via or something, and have a short, but the few times I've done it, I have not had that problem.

 

[funkymonksf]

This looks like a cool project and I'm fortunate to have most of the parts in my shelves. I am however confused with the PSU layout. What exactly is the 250k pattern selector pot all about? I read it is more of a rotary switch w/ 11 positions, but on the schematic it says 10 step potentiometer. Does anyone have a part # and/or pictures of their Multi pattern PSU build? I would love to build one of these completely point to point since I'm financially forced to sell my IOaudio mk47 kit.

Thanks for any advice in advance,
Brice

 

[tchgtr]

  This was discussed a bit earlier in the thread, and there are many ways to skin this cat.
  It seems to be generally agreed that the 11-way switch is the most reliable, as it will give repeatable results, whereas, if you use a 250K pot, it might be hard to get it in exactly the same spot every time.
  Personally, I just went a 3rd way, and used the scheme from the Gyraf mic, with a 3-position switch, giving only omni, cardioid, and figure-8. It works great, and I can easily replace it with more steps later, if I decide I just gotta have it. I also prepared a 5-step switch that I had on hand, but never used it. Maybe I'll pop it in there some day...
  Sorry to hear about the mk47 sale, Wish I could afford it.

 

[funkymonksf]

For the 3 pos pattern switch did you use the same resistor values as listed on Gyraf's schematic? Or is this a equation to figure it out. I've been searching for a resource on simple PSU for tube mics. Any suggestions? The meta came up empty handed

 

[tchgtr]

  I split the 250K value for the Big Ugly/Royer schematic in half and used 125K per resistor. Works very well.
The G7 PSU is about as generic as one can get for a plate-out head amp circuit, and it's a good starting point for any tube PSU IMHO, since it has a pattern switch, and a way to adjust the heater voltage. Probably why Big Ugly used it for this project.
  Unless you need a higher polarization voltage or B+, it seems to work very well, and I'm still intrigued by the original use of two AC transformers to get the proper voltages, as opposed to the voltage tripler that Royer used.
  There's a bit of info about it in the META to read, and it seems to be a very forgiving circuit in terms of the range of values one can use for the PSU capacitors, as long as the voltage ratings are good.

 

[Enchilada]

In case anyone else comes across this thread and has the same question, I used a voltage divider and a 3 position switch for pattern selection. I soldered two 470K resistors between pins 1 & 2 and pins 2 & 3. Connected ground to pin 1 and B+ to pin 3. The pole is the output voltage. Pos 1 = 0V, pos 2 = 1/2 B+ and pos 3 = B+.

 

[funkymonksf]

After reading all I can on the royer mod, I find myself still unsure how I'm going to pull of the PSU , which I'd like to p2p. 2 questions:

1.) wouldn't IOaudio mk-47 PSU schematic work for the B+ (105v), ground, pattern?

http://www.groupdiy.com/index.php?topic=41379.0

2.) If I did use that schematic I'd still need 6.3v for heaters, couldn't I simply wire 6.3v from power transformer (AC) or should I filter it like gyrafs G7 schematic?

Thanks for any advice.
Also have any off you used a Samar mic transformer before? Any thoughts?


Brice

 

[dissonantstring]

hi brice,
the original royer mod psu is pretty simple to p2p, just do it that way for the most simple solution.  there will be additional trouble if you want to use the MK47 psu and you'll need to adjust the resistor values anyway as current draw is different.  i was about to go this exact route as well, but stopped myself as using the G7 type psu (which the big ugly psu is derived from) with additional filtering as suggested by PRR seemed less expensive and just easier.

i ended up using big ugly's (james) design on the psu pcb that we got from blue jinn but changed resistor values and added some additional RC filtering and pattern voltage divider resistors on perfboard mounted next to the pcb.  very quite psu (i have not actually measured the noise through an analyzer - only through monitors and with about 30dB of preamplification) - no noise, very little hiss...maybe i got lucky on the first crack, but was pretty simple. 

best,
grant

 

[tchgtr]

Hi Brice,
  At the top of this page is a photo of my P2P PSU using the Big Ugly schemo and the advice given by PRR earlier in this thread. I just used some caps I had on hand, and it is implied on the G7 schemo that almost any value caps will work, as long as they can handle the voltages. B+ came out almost exactly at 120v under load. The adjustable heater voltage works great.
  I'm lucky to have a good surplus store locally (allelectronics.com), and most of the parts came from there, including the blank pcb, the power transformers, and spacers, and such. For me the hardest part of the build is making the case for the PSU----drilling holes, bruising fingers, ...etc.
  The mic sounds great, and will probably be upgraded with a Cinemag transformer soon, and perhaps a much better capsule in the future. I learned much from building it (especially about pattern voltages using the G7 info), and they get a bit easier with each build.
  Haven't used any of the SAMAR stuff, but after years of seeing his posts, I'm sure it's all top-notch.

 

[dmp]

Also have any off you used a Samar mic transformer before? Any thoughts?

I have a pair of ribbon mics with Samar transformers and they are outstanding. I haven't tried the tube outputs, but definitely want to in the future.
And dealing with Marik is great - highly recommended.

 

[funkymonksf]

I appreciate all the advice, however from what I understand I could use 120ac sec tranny to
Get the necasassry voltages for B+, I just need to filter it  rcrcrcrc till I get the right voltage, but for 6.3v...? Do I rely need to filter it at all or could I send it directly to heaters? Can anyo e post their PSU layouts mixing both PRR and/or bigugly & Gyrafs G7?

Thanks guys/gals

 

[funkymonksf]

And I still do not understand the pattern switch equation... So assuming I want a 3way switch w/ omni cardiod & figure 8.., which values would I use for the resistors? (1. The same as Gyrafs g7, spitting up 250k either 2or 3 ways or what?) I'm just lost figuring out the multiple pattern switch and I want to use just a 3 way like the g7 and mk47. So I guess in looking around for the easier circuit to use for that. One that provides 100-120v B+, 6.3+-.3v heater and a 3 way pattern option.

Also I've found some affordable transformer for the PSU, but before I buy, what is the amp values needed for the b+ and heaters? From what I've read on the 5840 spec sheet is b+=7.5ma and heater=150ma. Is that all I need for current draw for the royer multi pattern design?

Thank you!

 

[tchgtr]

Brice,
    I just used two 125ohm resistors, and wired it like the G7 schemo. Was amazed at how ell it worked. Don't forget, it shouldn't be too much trouble to replace this switch at a later time with a 9 position switch, should you decide you have to have more choices. All you would do then is divide the 250 ohm figure by nine (or is it 8?), and make it so that the highest position has 250 ohms, and the rest go down in a nice progression with the halfway point being at 125 ohms, and the first at 0 ohms. You could even do a 5 pos. switch with 75 ohm resistors. I used my voltmeter to find the closest match between the two resistors I used.
  As to the PSU caps, I really just faked it, and it came out great. This circuit is designed to be simple for folks like you and me getting our feet wet in this stuff.  If mine worked as well as it does, it must be almost fool-proof! I ended up with two 180uf caps with two 22uf caps between them, and three 5 ohm resistors, one between each cap.
  For the 6.3 volt heater supply, use the BU/Gyraf scheme, as you can then adjust to get the ideal voltage.
  My mike is a bit bright, as I used a cheap capsule and leftover OP transformer. but it sounds good/clean/quiet enough that I will upgrade over time.
  If you jump in, and double-check all your work well, it should come out great.
  I assumed that the PSU transformers should handle about 1 amp, based on the original Royer schemo, and so far it has worked fine. Will let you know if it blows up....but have checked it for warmth many times and it seems to stay nice and cool.

 

[funkymonksf]

I'm confused with your resistor values... Do you mean 250k instead of 250ohm? Either way I get your idea and totally appreciate your advice

Thanks
Brice

 

[Enchilada]

Doesn't really matter as long as the values are identical (check with a multi).

+1 on bigugly's PSU, I've built three of them.

 

[tchgtr]

Brice,
  Yes, exactly. 125k ohm... See what I mean. If a fathead like me can build one of these, you can do it, too.
Jump in!