Ok...I'm doing this from memory...Pin one is 160v
pin 2 is 6.something volts, pin 3 is 0-120v...

Now, when I took readings before the high value resistor, the capsule was seeing 76v. The tube was seeing about 160.

This is what I don't get about the 56v zener thing. This cuts the power down to pins 1 and 3 about 40%? Ok. Maybe I'm missing something, wouldn't mean that the capsule is seeing like 44v? and the tube is seeing about 110v or so. I think that's the motivation for the 56v mod, that the tube is seeing the same voltage as a vintage C12 saw. But the voltage to the capsule is seemingly totally wrong. Peluso told me that his capsule sort of wants to see 60-64v. Changing the voltage to the capsule totally effects the sound of the mic way more than changing the voltage to the tube, IMO.

So, that's why I changed the value to the 82v zeners, it's about an 18% change which gets the capsule sort of right where you'd want it to get the proper C12 response. The higher, about 132v, to the tube, isn't a bad thing and doesn't effect tone/frequency that much IMO. It does effect the mics ability to handle higher dynamics and it also effects the output. To me whether in a guitar amp or other tube circuit higher voltage generally sounds better and more "alive", too high voltage can make for a bit of a sterile sound.

Did you put back R8 and reattach pin5 of the tube? Maybe if you posted a checklist of what you put back one of us will notice the error you made?

Michael

Yup,

Put R8 back in. Reattatched 5.

The problem I'm thinking has something to do with putting in a new tube socket. The reason i did this was that my mic came w/ the tube soldered to the board. But I was able to fashion a standard plastic socket to go in this spot.

When I removed the cathode follower I actually cut the socket tabs on 5-8 and grounded them. Which rendered them unusable when i wanted to re-attatch the follower. So I did the same thing again w/ another socket.

Anyway, I'm getting the 6 volts to the heaters. (pins 4 and 5 right?) Also, I think 2 has 6 something.

But I'm unable to get readings for pin 3 or 6, 7, 8 or 9. I forget what 1 was.

Am I doing it right? Black lead on the board (ground) and red lead down in whichever socket pin I'm measuring?

honkyjonk,

One thing to remember is the numbers count chronologically on the actual tube socket. On the schematic it counts 1,2,3,4,5,8,7,6.

Lucio

Okay,

I understand the schematic pins look different than the socket pins. On the socket (looking down into it) it's 1-9 counterclockwise starting at the gap.

I measured the voltages on the pins. This is what I'm getting:

1. 6.6V
2. nothing
3. nothing
4. 6.7
5. 6.7
6. 6.7
7. 6.6
8. nothing
9. nothing

I can see that for pin 9 I should be getting nothing, as it's grounded directly to the main ground.

Pins 3 and 8 are the cathodes no? So something is definately wrong if I'm not getting voltage to those pins?

I'm not sure what 2 is.

But anyway, does anybody have any idea what the hell I could have done?

Hmmm

1,4,5,6,7 should have juice, but I think 1,6&7 should be more like 100 something volts (depending on you zeners) because that's the plate supply.

The one thing I noticed with my 1050 is that it is wired clockwise. My Apex is wired counterclockwise. This looking from the top of the socket, not where the tube plugs in.

Looking from the front of the 1050 circuit board;
-1&7 are tied together. 1 goes to R2-(1st connection top right corner)
-2 goes to R6/C4-(isolated junction on right side of C4)
-3 goes to R7-(2nd connection from top right corner)
-4&5(heaters) are also tied together.-(5 goes to -3rd connection from top right corner)
-6 goes to R4-(3rd connection from top left corner)
-8 goes to C8-(2nd from top left corner)
-9 goes to 1st connection at top left corner.

Maybe this will help somehow?

Lucio

Thanks guys.
I'll probably just start harwiring the questionable pins on the tube and see where that gets me.

We'll see.

Hey guys,

Thanks for the help so far. Now I think it's not the tube socket at all. I went and manually wired all the pins correctly and still havn't fixed it.

Funny thing. Tell me if this sounds like a problem:
I was measuring the voltage coming out of the power supply. Pin 1 of the power supply is putting out 110V when not connected to the mic (this seems correct considering the zeners I have in there). When I connect the mic, the voltage drops down to 6V.
I have the cable to the mic opened up and I'm measuring on pin 1 of the cable just like I was without the mic connected and all the sudden it's at 6V when the mic is connected to the p.s.

I wonder if I put the wrong resistor in for R8. Would this have this sort of effect?

Also, what if I just leave r8 out for testing purposes? What will that do?

R8 should be 270k. I've read in other forums where they dropped this to 20k to increase low freq, so I tried it and the output dropped significantly. I would imagine that not having a resistor there could make the gain extremely low to not there at all.

Do you know how to read the colors on a resistor?

Try here and click on calculators. Then scroll down and you'll find different resistor band code calculators.
Maybe that will help.

Lucio

Yeah,

I put in a 2.7K resistor in instead of a 270K resistor.

So, now I've switched back, but still nothing. This is crazy.

Anybody have an idea as to whether those voltages I measured are correct?

Okay.

Figured it out finally. I had a solder bridge between pins 5 and 6 UNDERNEATHE the tube socket. Man was that annoying. Took hours to figure out. That plus putting in the wrong resistor really had me confused.

Back to business.

Glad to hear it.....I hate it when it's something like that!!

How do you get the tube out of a DT modded 460? I opened up mine, and it looks like you have to remove 8 screws and move the mic base/xlr connector down in order to get the tube out of the socket. Is this right?
Makes me appreciate my Charter Oaks 538b, which has the tube mounted sideways. (very wide mic body) Swapping tubes in that puppy takes about 30 seconds.

I can change a tube out of my 460 without removing any screws.....can't you just push the tube up a little which releases it from the rubber shock thing?? That's how I do it.

Michael

It doesn't look like there's room to go up with the tube before it hits the white pastic cone, which looks like it's holding the red rubber bumper. Does the white plastic cone come out? I must be missing something (like, my brain.)

I pop out the cone or at least the little rubber piece, then you can push the tube "up" slightly towards the capsule as well.

I remove the tube easily by pulling the tube downward, which compresses the spring loaded cone, while holding the socket, which will separate the tube from the socket a bit. I then, while still slowly separating the tube from the socket, angle the two in the same direction, to the side opposite the tube side with the spaced pin. There is enough stretch to the rubber that holds the socket to allow you to separate the tube from the socket without the need for tools. I hope that is clear.

O.K. I've been trying alot of different parts out on both mics and have come to some conclusions. Here are some schematics that I've made up that show the mods that I've done to each mic. I have 2 for the 1050, one with the cathode follower and one without (which is how I have it at this time). The schematics also show voltages at different points for reference. The voltages change quite a bit depending on which resistors you use at different points. I'll update them as I finalize my mics, but I'm pretty much done at this point and plan to use them like this for awhile and see how they work.


This is as close to the C24 schematic as I could get, but with R6 and R10 with the C12 values and I left C1 and C2 in as they just filter AC from the circuit and are present in the C12VR. Removing R1 and changing R3&R4 to 499k's opened up the highs. Removing R5 made it a bit thin but removing C3 filled things back out. Think of C3 as a bypass to add highs back. So is C7, which I also removed because it's not present in the AKG's. Dropping R7 to 2.49k (**now 1.82k like the M251) adds bottom extension and C6 controls how much you want to actually hear. The stock 100uf adds alot of bottom and also gain. The 2.49k(**182k) adds the gain and fills out the mic without too much bottom, like the originals. C5 also acts like a bypass and by dropping to .0047uf it opened up the "air" and clarity nicely. I'm really liking this mic as the open, clear yet full mic in my collection. I have the original zeners in the PSU, two 1N4761(75v each 150ish total)(**dropped one zener to a 56v for 131v total, dropping the capsule voltage from 62v to 50v).



I ultimately wound up removing the cathode follower because I have other mics that sounded about the same so I decided to try it without the CF and now it has a different character than my other mics. I must say that I'm not sure if this will be it's final configuration until I try it with some other voices to see if it fills a void in my collection. I actually tried a 3M and 2M at R3 and R4 respectively, which is the size used in the U47, but it dropped the voltage to around 45v at the capsule (before R10), so I stuck with the 499k's (*I've put the 2M and 3M back in because the parts have broken in and sound really open this way and the 45v(**now 30v with zener change)at the capsule doesn't drop the gain. I talked to John Peluso and he said that voltage is fine, it just rolls a bit more of the highs off to sound more vintage). I added R5 back as it thickened up the mic where before it was too close in sound to the Apex for me (*I have since removed R5 because once the parts were broken in it thickened up fine). I'm thinking about trying a 30ohm resistor at R7, which is what the U47 uses, just to see(**tried it and it drops the cathode voltage to 0. John Peluso said this was used specifically for the VF14). The PSU originally had one 1N4764(100v) and one 1N4762(82v) zener, which was too high so I kept the 1N4764 and changed the other to a 1N4758(56v) for a 158v.(**Now using a 75v zener with the 56v for 135v total).



This actually sounded very good but, as I said above, I have other mics that sounded pretty much the same. You could put R5 back in if you're looking for a more U47ish response (*see above, R5 won't be necessary once the parts break in completely). You can also add a 1000pf cap where R2 connects to tube pin 1 and this softens the highs more if you want something even darker. Zeners are the same as the other 1050 schematic.

Overall observations are that;

R1&R2-control voltage to tube pin 1 and 3.
R3&R4-control voltage to the capsule.
R5,R10&R6-effect the sound of the capsule-smaller=darker, larger=add highs.
C4-effects the sound of the capsule also-larger=favor lows, smaller=add highs.
R7-effects the low freq extension-smaller=more bottom.
C6-effects low end depending on size-larger=more bottom. Also adds gain.
C7&C3-bypass to add highs.
C5-effects high end depending on size-larger=more bottom.
C8-effects low freq extension-Larger values=more bottom.
R8-smaller value adds bottom but loses gain.
R9-only part I haven't changed.

Hope this proves useful. (*Check edits made on 08/05/08)(**Edits made on 11/19/08)

Lucio

Really nice summary of your work. I'll use these as a reference if I pick up another of these on the cheap.

Lucio,

What voltages are you ending up getting (w/ the various mics) to the tube and capsule w/ the different resistors in R1-R4?

Seems to me these might be the keys to getting the voltage proper to BOTH the capsule and the tube, whereas folks have speculated on modding the power supply to do so in the past.

Thanks so much for all the work you've done and info you've given on these!

honkyjonk,

Thanks, just trying to help out. I agree with you about this, here are some examples that I experienced;

-with R3&4 at the original 270k I had 78v to the capsule in the 1050. With those raised to 3M and 2M respectively I had around 45v.

-with R1 removed in the 1050, as it is, I had 100v at tube pin 1 and it also raised the cathode tube pin 3 to 4v.

Changing the tube also changes the tube voltage slightly to 90v with an 12AY7 vs 88v with 12AT7 at pin 1 and 1.8v vs 2v at pin 3.

One thing I've noticed looking at the original schematics is that the C12 had 120v at B+ and 66v at the tube. The U47 had 105v at B+ and 36v at the tube (but it's a different kind of tube so I think we should stick with AKG voltages).

If I mix and match zeners I can get down to 131v with what I have and I'm thinking of trying this just to see.

Does anyone know the ideal voltage for the 12A*7 tubes? It looks like maybe around 70v?

Lucio

quote:

Originally posted by honkyjonk:
Whoa!!!!!!!!

I just had the wierdest thing happen. I was recording some acoustic guitar with my 1050 and the polarity of the capsule changed right in the middle of the recording. Crazy.

There is a big pop and then all of a sudden the acoustic becomes very distant sounding (because it's now on the backside of the capsule! [had it in cardiod])

Anybody have an idea what could cause this?

The same thing happened to me, although not in the middle of a recording. The front diaphragm on my 1050 became detached in one spot on the capsule, it must have been loose from the factory. Anyway, I took the grille off and the gold sputtered mylar film was touching the back plate so there was a direct short. I sent the mic back to Nady and it was replaced no questions asked. Makes you wonder about the quality though.

Cheers,

J.J.