Apex 460 capacitor change?

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mbrebes said:
C6 can be considered to be in the signal path, since it directly responds to the signal path passing through the tube circuit. If you put an oscilloscope on the cathode, you would see the signal that is being fed to the grid. The cathode resistor sets the DC offset of the tube stage, to try to get positive and negative clipping to occur at the same time. Unfortunately, it also lowers the gain of the stage. The capacitor (C6) brings back the gain by passing all the higher frequencies.

So if you were to remove C6, the gain would drop?
 
amzavareei,

Thanks for that link. I'm surprised to see that the Black Gates are electrolytic caps. People raved about these, but I thought we were supposed to use mylars. The more I learn about all this the confused I get.

PhilGood,

From everything I've read, yes the gain will drop, but that's supposed to add to the headroom and clarity. I believe that's how Dave Thomas now upgrades his mics. Sure is easier to just remove parts instead of replacing them.

Lucio
 
LDT2 said:
amzavareei,

Thanks for that link. I'm surprised to see that the Black Gates are electrolytic caps. People raved about these, but I thought we were supposed to use mylars. The more I learn about all this the confused I get.

PhilGood,

From everything I've read, yes the gain will drop, but that's supposed to add to the headroom and clarity. I believe that's how Dave Thomas now upgrades his mics. Sure is easier to just remove parts instead of replacing them.

Lucio

In my mind it will also increase the noise floor. I'm glad I bought a Black Gate to replace C6!
 
PhilGood,

Is your Black Gate a mylar or is it electrolytic?

amzavareei's link has Black Gate caps, but they're all electrolytic. I imagine it's just what's left of there stock, but on the outside chance....

Actually, I've found a couple sites that still have Black Gates, but they are all electrolytic caps.

What series should I get?

Lucio
 
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LDT2 said:
PhilGood,

Is your Black Gate a mylar or is it electrolytic?

amzavareei's link has Black Gate caps, but they're all electrolytic. I imagine it's just what's left of there stock, but on the outside chance....

Actually, I've found a couple sites that still have Black Gates, but they are all electrolytic caps.

What series should I get?

Lucio

Electrolytic.

Black Gate had a secret recipie for making electros with outstanding quality and linearity. They had more of the qualities of film caps. That's why the are so highly prized. Very good for signal path!
 
The NX series is what you should probably get. Or some people leave out C6 altogether it seems.

I finally fixed mine last night! Burning in at the moment. I'll test it tonight.

I've got a Mullard 12AT7 CV4024 in now. I think it might be a military version. What's the story with this GE 5 Star? That's supposed to be the best for this?
 
GE five star is the tube picked by AKG for the Ela M and C12 mics. Very low noise, low chance of microphonics, high durability, high sound quality. Better than a JAN tube (Joint Army Navy military spec tubes).
 
The only thing close that I can find is an N series 100uf 50v Black Gate. I realize that the voltage indicates the maximum the cap can handle and I know that some dropped the voltage from 400v down to 250v for C8, but will it be a problem using 50v when C6 was originally 25v?

Also, would there be any advantage to putting Black Gates at C1 and C2? I know that Marik had mentioned possibly raising the values on C1 & C2 and I read about someone putting 100uf in place of the 1uf's, but in the process dropped the voltage to 25v from 400v! That's why I'm a bit unclear as to how loose these values are.

Thanks again,

Lucio
 
Yeah, I think that's the cap I used. I know it was N series. The only problem in using a higher voltage caps, as far as I know, is the physical size. My Ansar 1uf and the Black gate both barely fit, and I had to move a couple resistors to the back of the board. C1 and C2 aren't really in the signal path, so I don't THINK that Black Gates would be cost effective. Where did you read about the C1 and C2 and the 100uf/1uf change? What are they supposed to do?

So I tested out my mic last night, and it seemed good in some ways. I paired it with a U87 on a 12 string, both in figure 8. I tried to get them real close, but I think the placement had a lot to do with the sounds I got. The 87 had a nice body, but was a llittle dull on top. I think it was pointing more towards the sound hole though. The "apex" had a very defined and shimmery top, but the lows seemed lacking. I think that it was closer to the 12th fret. I don't have much experience with the 87, but I THINK it was just the placement. The "apex" needed some cut around 12k, it definitely had a rise up there. Maybe that is something that could be fixed? I'm using a peluso CK12 and a Cinemag 2480, BTW. But also for some reason, the gain seemed really low. I had to crank the gain on my Octane. But the gain would change radically, it seemed depending on the pattern. Omni was so quiet, I forget if cardiod or 8 had more. When I originally had it connected to my VTB-1 on the bench, it had TONS of gain. What happened between there and the Octane, I wonder? Could this be a symptom of one of the capsule sides coming loose? Anyway, I'll have to check more thoroughly later. And then male vocals through a 421, then a modded 57 through my customized BOGEN tube "mixer" pre. Anywho, the mix with the 2 condenser mics sounded about perfect, but the u87 is just a loaner, so I won't have that luxury much longer, so I'm really trying to get the "apex" in top shape. Thanks!
 
I read about that here . I've been asking questions there, too and the guy that did that mod,craigmorris74, just said that it was a typo and corrected it to 100uf 250v for C1 and C2. Earlier in this thread Marik and mbrebes said that C1 and C2 are filter caps.

As far as comparing your 460 with a U87, they not gonna sound similar. The CEK12 is designed to sound like a AKG C12, which is a brighter mic than a U87. The rise at 12k is supposed to be there. I believe the Peluso capsule that would be more U87ish would be the CEK89, which has been used to recreate a U67 type mic and the U67 and U87 used the same capsule from Neumann.

As for the gain difference, that I don't know. It could be what you said, check and see. I know that C6 is supposed to add gain to the circuit, maybe it's loose?

Thanks for your help,

Lucio
 
Well, I wasn't really hoping for them to sound similar. I've got a C12VR at work I might A/B it to at some point though. I just was stating that some of the difference was probably from placement. It wasn't the most ideal test. It went from me wanting to A/B them, to my 2 roomies wanting to make a song, which turned out for the better, since I won't have that 87 much longer.

So is the C12 called a C12 because of it's rise at 12K?

Did anyone notice that the Peluso CEK-12 capsules have doubled in price?! That's some crapola. The 89s still seem reasonable though.

I'll check C6 later, thanks!
 
Sorry, I misunderstood. Comparing the C12 and U87 are kinda like apples and oranges. It's not so much 12k as it is just brighter and more transparent.

That's cool that you have access to a C12VR to compare with. I'd love to hear what you think when you do that comparison as would many others I'm sure.

Man, you scared me for a moment there. The Peluso CEK12 and CEK367 used to cost $175.00, so it went up $20.00 to $195.00. The other capsules went up around the same, give or take $5 to $10 dollars or so. I hope they don't go up too much more although it's still cheaper than paying $2000.00 to $5000.00 for a mic.

Thanks again,

Lucio
 
amzavareei,

What did you do at C6 and C7. I wonder if that has anything to do with missing low end?
 
Oh crap! I thought I got the CEK-12, but I forgot, it was the CEK-89. Just checked my old email receipt. Is that supposed to have a 12k rise too? Is it supposed to be the more U87ish capsule? What do people think of the differences between these 2 capsules?

I actually have a C12 capsule that was in one of my bosses mics that fell over, and they had replaced. One side looks pristine, but the other has few very tiny little scuffs. Maybe it will be worth trying out, and if I like it better, could save the 89 for another project. Should that capsule be better suited for this circuit? I've got the basket too, but it's banged up, and too small anyway.

C6 is a Black Gate N series, and I left C7 alone. What does that have to do with the low end?
 
I'm in the process of doing this mod, but I've done ALOT of research on it.

From what I understand, C8 is the key to the low end. The higher the value the more low freq extension. Dave initially used a 2.2uf 400v. Later used 1.5uf. I've even read about someone using a 10uf with a .001uf in parallel, which added 7db at 100Hz! PhilGood said that a 3.3uf was used in the ELAM 251 circuit.

I know that I'll at least use a 2.2uf 'cuz I know others in this thread have wanted more low end when using a 1uf.

Lucio
 
amzavareei,

The CEK89 would be the one to have for that Neumann U67/U87ish sound, so you're good. Now remember, the U87 does not have a tube and circuit would be different, so that will make a difference in the response. It will probably sound closer to a U67 as that mic also had a tube.

Lucio
 
So the gain is MUCH lower in Omni than in Cardioid or Figure 8. But it goes gradually up or down several seconds after switching it. If it was just a capsule side not being connected, I figure it would be something more concrete. There must be cap somehow involded storing a charge for a few seconds. Anyone got any bright ideas about THAT? Thanks!
 
Peluso makes 2 versions of the CEK89, one is dual sided and one is single sided. I think that the dual is for multipattern and single is for cardiod only.

Which one did you get? That might explain the problem, if you have the single sided capsule. I don't know why they used the same name on both.

Lucio
 
Correction: The CEK367 is the capsule that is closer to a U67/87. The CEK89 is actually more like a U89, the capsule only 32mm in diameter versus 34mm for the CEK12 and CEK367, and the same size as the original capsule for the 460. They are going to sound quite different. Don't expect the 89 capsule to sound like a 67/87.

C6 can also play a part in the bass response.
 
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