Perception 200 Polarization Voltage

[Aaronrash]

Hello Everyone


I've been having some fun modding my Perception 200. The schematic on it is the same as the Vintage U87. I put the RK-7 capsule on it and it made a huge difference. I also removed the NFB circuit with seemed to introduce noise so I'm going to put it back and see how it sounds with such a dark capsule.

However, the RK-7 is a 6 micron thick capsule and it likes a much higher voltage than the 46V I'm measuring off of mine. Is it possible to change some resistors or mod the circuit to get the voltage up to 60V or even 70V.

I've attached the schematic

 

[gary o]

does the Perception have same schematic as U87 ? ....You might need to build little DC DC converter circuit ...... I tried adding batteries to a mic works good for me

 

[RuudNL]

If there is no DC/DC converter, 48 v phantom power is all you have...
So 46 V is the maximum you can have as polarisation voltage!.

By the way: The fact that a RK-7 capsule can withstand a (maximum!) polarisation voltage of 70 volts, does not mean you have to use 70 volts.

 

[HellfireStudios]

I modded my Perception 200 with the Royer LDC tube mod. I pulled the original surface-mount circuit, and did a point-to-point Royer circuit on perfboard, but that utilizes the original 67-type capsule. Check out that mod to see if the 47-type capsule sounds good with the circuit. A Cinemag CM-2480 (10:1 ratio) is small enough to be glued into the mic. I believe the power supply gives a proper 60 volt polarisation voltage.

-James-

P.S.- Paying clients love tube mics. Don't ask me why, but they love to hear that a valve is involved in their sound.

 

[Khron]

Actually, the Perception 200 schematic is a copy of the U87Ai - one of the three PCB's inside the mic is actually the DC-DC converter

http://www.audioimprov.com/AudioImprov/Mics/Entries/2013/2/26_AKG_Perception_220.html

The only difference between the 200 and the 220 is the value of the pad-capacitor (which gives a -10dB pad on the 200, and -20dB on the 220).

 

[gary o]

How interesting the Percetion in U87 copy ...... then does it not sound good stock .....

 

[gary o]

Hmm according to mr Lolly it doesnt have de emphasis like U87 ....

http://www.oktavamodshop.com/product_info.php?cPath=1_46&products_id=164

 

[Khron]

"Of course" it (supposedly) doesn't have U87-like de-emphasis - otherwise, what reasons would Mr. Joly have, to "push" his own capsules?

""Neumann-esque" timbre requires either a K67-type capsule followed by a HF attenuation circuit (like the U 67 or U 87), or a K47-type capsule feeding a flat response circuit (like the U 47). The MJE-K47 mod takes the second approach."

Yeah, because modding the electronics (which would be the obviously cheaper way) doesn't really make any $$$ for him Why do i have a strong hunch he hasn't even bothered with tracing out the circuit? Unlike the gentleman from the link i posted earlier...

 

[Aaronrash]

Yes I can confirm the P200 does have a NFB circuit and is actually a pretty awesome sounding mic stock. I've already spoke with Hennry at audioimprov. He's the guy that helped me find the NFB cap in the first place.

He did say it was possible to up the voltage by changing some components and he was gonna get back to me on it but I didn't want to bug him so I thought I would post here.

On his perception he's measuring 44V I'm measuring 46V on mine. The RK-7 can handle up to 80V but I don't want it that sensitive. After removing the NFB cab there's allot of modulation noise so I'm trying to solder it back on but it seems since it's all SMD I ripped one of the pads off and there's no way to solder back on. Looks like I'm stuck with a noisy P200. Other than the noise the tone sounds awesome.

 

[Khron]

Mmm... Is there no length of track going off the ripped-off pad, that's accessible? If there is, you could scrape off a few mm of the soldermask, (carefully) tin the now-exposed track, and maybe "coax" the cap to stay there, with one end on the "healthy" pad, and one end on the tinned track A photo might help, as well.

 

[gary o]

Sounds like a good plan to fix that board hope it works must be a way .....

Great news about this mic then ......it must sound very dark after the jolly mod then, flat capsule de emphed ? ........seem like a great mic, lots of guys here falling over themselfs to built a U87 from scratch & this is already done & has the DC DC thrown in....

Talking about th DC DC converter shouldnt that be supplying 60V for the capsule isnt that why its there, I just built a KM83/84 46V for capsule no DC DC converter, what is capsule polar voltage in U87 60V ?

 

[Aaronrash]

Here's the cool little paint job I gave mine

 

[Aaronrash]

And here is the horrid pcb

Both pads are gone. On the left pad you can see the pcb trace is peeling up but I found where it goes to so I'm not worried about this pad. However the right pad, I'm completely clueless on where it ties into. I checked everywhere for continuity and I'm guessing since the pad is messed up if probably why I'm not getting continuity anywhere. I know it looks like that middle trace goes to it but it actually curves off and goes to the resistor above it. If I can find out where it goes I could just wire it.

 

[HellfireStudios]

I painted mine the same color. I also painted the shockmount to match. It looks cool that way. One day, I'll paint the grill black to complete its "tuxedo" look.

-James-

 

[Aaronrash]

Lol yeah looks good!


So a little update. I was able to find the traces and replaced the NFB 0.47uf with a film cap. The result was much darker then I would have liked and the same hiss noise was still there. It's not very noticeable unless you're doing super intimate stuff but still... I'm obsessive about mic noise. I took the NFB cap back out of circuit, it just sounds better that way with a dark capsule.


Not sure where the noise is coming from but it wasn't the NFB cap.

 

[Marik]

Actually, the Perception 200 schematic is a copy of the U87Ai

Here is the quote from the link you provided:

The output stage is on one PCB, containing the output emitter follower...

I don't remember U87Ai (or any its modification) having an emitter follower.

Best, M

 

[Aaronrash]

To me it seems like a U87 circuit especially since my polarization voltage is 46V if it were a Ai it seems the DC coupler circuit would be populated and I would have around 60V It's there just not populated.

 

[gary o]

I have been reaching for my wallet to buy one of these mics if it were a U87 circuit BUT Im guessing its just similar as Marik says U87 doesnt have emitter follower it seems like the MXLV67 u87ish circuit where they add the emitter folower so they can use cheaper lower ratio op transformer

So the DC DC board not populated with components that makes sense leaving you with 46V for capsule ..... so I wonder if that is populated in another AKG mic model .......& can we finf a schematic so you can re populate

What FET is in the mic bet its not 2N3819 ......

Makes sense that will sound good with flat darker than K67 capsule with de emphasis disconnected...... makes me worry about M Jolly not noticing de emphasis is present & then adding a flat capsule & then the usual wow its sounds just like a U blah blah blah

I still think this seems a great little mic & for not much money......

Im very interested in this & similar circuits as I have been experimenting with the very simple neumann KM83/84 circuit have been toying with adding external power for th capsule & even batteries ( the higher 60V polarisation voltage didnt make a huge difference in my case).... be interesting for me to add de emphasis & a cheap K67, so am think about buying this mic....

 

[Khron]

A couple months ago, i got a dead one off fleabay - turned out that one leg of one of the 1G resistors was partially broken off. No capsule polarisation => no signal. Fortunately, i had one to spare (from a previous mod i did on an Alctron LDC), and voila' - it lived again

Bad part is, i didn't have too much time to fiddle around with it any further, 'cause a friend was interested in buying it, so i "had to" let it go

I *CAN* confirm that the DC-DC converter PCB was indeed fully-stuffed, although i don't remember measuring any voltages on it.

 

[gary o]

That is very interesting about the DC DC board surely it must supply more than 46V for capsule no point it being stuffed otherwise ....