Royer mod. finished!!

HI
After long,long time :grin: I finished assembling.
I agree sugestions from Gus and grid connections to capsule I dislocated of board.
Also I used Zebra schematic with 1G grid to ground and 100uF cap bypassed with 750 ohm cathode resistor.
After 1K bleeder I saw 98,7V. On plate after 100K is 36,8V, but after 2,2M and 3,3M I saw only 26V. I expected about 50-60V from voltage divider formula.
I replace both but voltage stay same. On cathode I have only 0,47V.
I expected about 1-1,5V.
Does anyone measure all voltage and what is right voltages?


Thanks to Lampas (Vili, moj brat), Gus, Zebra and other guys who help me.
Duka

Microphone works :grin:
Its very good sound :grin:
Also I make Neuman style omni switch and it works very good.
Any answers :?:
Thanks in advance :thumb:
Duka

Hi Duka, looks good & am happy to hear that it's working.

[quote author="dukasound"]
Also I used Zebra schematic with 1G grid to ground and 100uF cap bypassed with 750 ohm cathode resistor.
[/quote]

OK. I have used the circuit with and without the bypass cap. They sound a little different - neither is 'better', just different - so see which you like best. Make sure the bypass cap is of very best quality.

[quote author="dukasound"]
After 1K bleeder I saw 98,7V. On plate after 100K is 36,8V,
On cathode I have only 0,47V.
[/quote]

Sound about right to me, IIRC

[quote author="dukasound"]
but after 2,2M and 3,3M I saw only 26V. I expected about 50-60V from voltage divider formula.
[/quote]

It sounds like you are taking the polarisation from AFTER the 100K reisitot, bot from B+. Check the voltage at the high voltage end of the 2.2M (?) and see if it is about 100V.

Hope that helps.
Stewart

Hi Stewart
I check again.
B+ voltage -99,6V
After 1K - 98,8V
On plate - 37V
On point 2,2M, 3,3M and 33M -26V
On cathode -0,4V
Did you have this voltages?
Best
Duka

Looks great Duka :!: :thumb:

Regards

ju

Duka the meter is loading down the voltage at the 2.2 3.3 junction. Like Stewart posted what is the voltage at the "top" of the capsule voltage divider. Then do some simple math.

The voltage at the "top" should be close to 100V divided by 5.5 meg give the current.

That current times the 3.3meg is close to the capsule voltage assuming low leakage paths.

In the old days using an anolog meter we had to calculate the loading due to the meter into the measurement .

What is the input spec of your meter when measuring voltage? How may ohms load?

I calculate the capsule voltage but I first measure the resistors out of circuit, don't use you fingers to hold the meter leads to the resistor it will add you skin resistance to the resistor and give a bad reading when measuring high value resistors.

Very nice, Duka! :thumb:

Is that a MXL V93 or V77? If so, then you are the first to "Royer" mod one of the MXL 3-micron mics (unless someone did and I just missed it...). Glad to hear that it sounds good.

The V93 was a silver version of the 2003 that MXL made for Mars Music. I love the silver finish on those things. It's a shame MXL no longer makes the '93 or '77.

Hi Gus
I have bad english but I tried
If I have 98,8V divided with 5,5M (2,2M + 3,3M divider) I have about 18mA.
Than, 18mA x 3,3M give 59,4V. Is it right?
I havent special meter. Its digital. In spec. I saw 1M load.
Why I measured voltage on other mikes without problem. I suppose there was lower value of resistors in divider. On Ela and G7 are 470K and on C800 are 180K and 47K.
What about 5840 cathode biasing? I expected higher voltage
I make some math and I find current is: 98,7V-35,8V=63V divided with 100K plate resistor is 0,63mA.
Than 0,63mA x 750ohm I got 0,4V. Is it OK.
Thanks
Duka

Well, on second look, the new MXL 909 appears to be the same body and silver color (champagne?) as the '93 and '77. Doesn't use the 797 3-micron capaule, though. :sad:

[quote author="Flatpicker"]Very nice, Duka! :thumb:

Is that a MXL V93 or V77? If so, then you are the first to "Royer" mod one of the MXL 3-micron mics (unless someone did and I just missed it...). Glad to hear that it sounds good.

The V93 was a silver version of the 2003 that MXL made for Mars Music. I love the silver finish on those things. It's a shame MXL no longer makes the '93 or '77.[/quote]
Hi
Its Behringer B2-Pro. Jensen JT-DB-EU(nfortunately) :evil: and RCA 5840.
Polys are Wima, Elna elco, resistors 1/4W metal film and high ohmage 1G from board in B2-Pro. Also I made omni switch like U47.
Duka

[quote author="dukasound"]Its Behringer B2-Pro...[/quote]Hey, nothing wrong with that. The B2 uses a 797 6-micron dual capsule, and of all the Chinese capsules, Gus (who's modified them all) seems to like this one best. If I were going to put any significant amount of work into a mic modification, I'd pick one that used a 797 capsule.

I never realized that the Behringer B2 used the same body as the V93. At least it looks the same from your pictures.

Nice work Duka!

Duka

The 1 meg DMM will load the capsule voltage to much.

I tried to hint at low voltage operation of tubes in microphones in the past here. This is were you can get a "tube" sound because of the low B+ (about 100V).

You need to look at some tube curves.

To get more current to flow you need to use less negative voltage at the grid. So I think Dave Royer set the tube in a a good spot at the B+ used.

Notice he used a 12:1 transformer this gives less voltage output: however it has more current drive. The current in your circuit is the 98.8V - the plate 37V lets call it 100V -40V for about 60V. 60V in a 100K is .6ma

Then you want the plate R to be >= Rp of the tube

take .6ma times the cathode R and you get the cathode voltage.

Now at Voltages like in this circuit you are often on a more curved part of the curves. So maybe the stock circuit not using a cathode bypass cap is to help a little with some negative feedback, You lose a little gain and maybe have a little more noise but are a little more linear.

Its all about maximizing the operating points for the "sound" you are after.

You can make a tube so clean you can't tell it from clean solid state if you want.

Hi
Some guys asked for pdf of my board.
A three type on pcb, for uncased and cased and all of three mirrored.
http://www.cankar.net/duka/Royer_JT_boards.pdf
Here is a layout for Zebra and original Royer style.
http://www.cankar.net/duka/Royer_JT_Parts2.pdf
Duka

Duka, whay dou you have and elctrolytic cap and extra resistor on the mic in the Royer mod?

I'm doing the original MOD which does not have this, please tell me what you have done and why.

I think I take some of the blame for this. I was experimenting some time ago and a schematic got circulated with some extra 'optional' parts that make it closer to the G7 circuit in some ways - look at the G7 circuit and compare to the Royer circuit.

The extra parts give local filtering of the B+ supply which may reduce noise.

And also there is a cathode bypass cap. This subtly alters the sound - you may or may not prefer it. The cap must be good quality as it is in the signal chain.

Treat these as optional and do some experimentation if you like, but the original Royer circuit is fine.

Stewart

Hi
Many microphones have grid to ground resistor (like U47 or U49, etc,etc) which is Royer modification "younger brother". Also U47 have additional filtering and many microphones have elco bypassed to cathode resistor.
Taste and choose what kind of circuit you prefer. I am satisfied with sound like on Stewart but I will test without this extra parts.
Also I will test with capacitor to heater voltage.
Duka

hi everyone,

i'm new here, only came across this forum a few weeks ago.
I'm doing the Royer mod on my Behringer B2. I was wondering
whether you guys had any luck getting around the connectors in the mic
as i'd love to get rid of them and have a more direct way of hooking up the capsule with the board? And Duka, did you leave the connectors in
and did you keep the switches that are already installed to use them for the omni and pad functions??

any help would be much appreciated

cheers Neal

hi all,

just wanted to say that i finished the my Royerised B2 a few weeks ago
and really like it. I did modify the switches in order to keep the pad option,
as well as the omni mode.
I used the recommended (forgot the number) sowter transformer.........
but it doesn't look as pretty as Duka's insider
I quite like the look of the power supply, whose case i took from a cmputer power supply.....

anyway, thanks for the help

cheers Neal