Khron

Re: AKG Perception P220 to Neumann u87 5 min mod ( p200, p100, p400, p420? )
« Reply #40 on: February 11, 2019, 06:56:53 PM »
Between this:

http://cdn.recordinghacks.com/images//mic_extras/akg/perception-420-circuit.jpg

and what i've seen in my own Perception 200's, it's gonna be on that horizontal board that also carries the switches.

I've also annotated Henry Spragens' Perception 220 schematic with the values i measured on my 200's (i didn't bother measuring the pad cap on mine - that's the only difference between the _00's and the _20's) - see attachment.

It'll be an 0805 ceramic capacitor, on the bottom of the input/switch board. It may very well be easily accessible even without removing the board(s) from the chassis, i think it's near the edge.

So where would the smd cap be located on a perception 400 version? please help,
Khron's Cave - Electronics - Audio - Teardowns - Mods - Repairs - Projects - Music - Rants - Shenanigans


Khron

Re: AKG Perception P220 to Neumann u87 5 min mod ( p200, p100, p400, p420? )
« Reply #41 on: February 11, 2019, 06:59:55 PM »
[Disclaimer] Due to the one-attachment-per-post limitation here, i'm forced to double-post.

You're in luck, i found some documentation photos i took while modding my 200's (multipattern'ed them, with dual-diaphragm capsules).

That high-frequency-attenuation cap will be nearest to the front edge, right in the middle there - the silver-looking styroflex cap, in this photo.
Khron's Cave - Electronics - Audio - Teardowns - Mods - Repairs - Projects - Music - Rants - Shenanigans

rockinrob86

Re: AKG Perception P220 to Neumann u87 5 min mod ( p200, p100, p400, p420? )
« Reply #42 on: February 12, 2019, 10:03:47 AM »
I'm a bit confused...

AKG perception would be similar to U87 if not for the biasing  OR Perception needs higher cap value and then to be correctly biased?  or it needs new FET/biasing and the capacitor?

If these are similar it would be significantly cheaper than a scratch build u87 - I've been thinking about building another because I use my DU87 build all the time.  It's my go to, "uh, let's do this, where's a mic?" mic because it always works and sounds good!  May have to pick up a couple P420s...

Khron

Re: AKG Perception P220 to Neumann u87 5 min mod ( p200, p100, p400, p420? )
« Reply #43 on: February 12, 2019, 10:39:45 AM »
It's got nothing to do with biasing, but with the compensating EQ / filtering ;)

http://audioimprov.com/AudioImprov/Mics/Entries/2014/2/7_Mic_Electronic_Eq_Pt.1.html

In the linked article, the capacitor this thread is (mostly) about is that 120pF C10.

Or rather, to be more specific, it needs a larger value cap with the stock biasing to reach  a U87-ish response

OR

(perhaps) The stock cap makes reaching that same curve possible by altering the bias.

I stand to be corrected on the 2nd option, though :) The 1st one is what kingkorg did, so it's quite literally "tried and tested" ;D
« Last Edit: February 12, 2019, 10:50:14 AM by Khron »
Khron's Cave - Electronics - Audio - Teardowns - Mods - Repairs - Projects - Music - Rants - Shenanigans

Re: AKG Perception P220 to Neumann u87 5 min mod ( p200, p100, p400, p420? )
« Reply #44 on: February 12, 2019, 12:35:42 PM »
wherenis this 220pf cap on a 400, its not the same as a p200

Khron

Re: AKG Perception P220 to Neumann u87 5 min mod ( p200, p100, p400, p420? )
« Reply #45 on: February 12, 2019, 01:12:36 PM »
Could you maybe attach a photo of the underside of that switch / input board (in case you're not able to trace out the circuit yourself)?

wherenis this 220pf cap on a 400, its not the same as a p200
Khron's Cave - Electronics - Audio - Teardowns - Mods - Repairs - Projects - Music - Rants - Shenanigans

JulesP

Re: AKG Perception P220 to Neumann u87 5 min mod ( p200, p100, p400, p420? )
« Reply #46 on: February 15, 2019, 11:27:01 AM »
Hi, all. I am fresh member.

As I am already stuck with a pair of P420, I would beg any of you  to the very confusing cap location change, as it is very clear on the PERCEPTION 420 , but rather perilous to identify on the completely surface mount of the P420 version, I would beg for a clear picture and identification of the location of the cap needed to be changed, in the simple mod already discussed with a 680 polystyrene cap swap.
I can't find any reference pic anywhere that points the one in need to be changed,
I am far from being an electronic wizard, but can handle pretty delicate soldering operation.

As they are pretty useless as now ( Very peaky and harsh on all acoustic instruments), I would live very happy at any simple amelioration and improvement.

I hope someone can post the exact location on the P420.

Cheers.
And thanks in advance, if ever someone can,

Khron

Re: AKG Perception P220 to Neumann u87 5 min mod ( p200, p100, p400, p420? )
« Reply #47 on: February 15, 2019, 11:45:11 AM »
See my last post here ;)

Hi, all. I am fresh member.

As I am already stuck with a pair of P420, I would beg any of you  to the very confusing cap location change, as it is very clear on the PERCEPTION 420 , but rather perilous to identify on the completely surface mount of the P420 version, I would beg for a clear picture and identification of the location of the cap needed to be changed, in the simple mod already discussed with a 680 polystyrene cap swap.
I can't find any reference pic anywhere that points the one in need to be changed,
I am far from being an electronic wizard, but can handle pretty delicate soldering operation.

As they are pretty useless as now ( Very peaky and harsh on all acoustic instruments), I would live very happy at any simple amelioration and improvement.

I hope someone can post the exact location on the P420.

Cheers.
And thanks in advance, if ever someone can,
Khron's Cave - Electronics - Audio - Teardowns - Mods - Repairs - Projects - Music - Rants - Shenanigans

abbey road d enfer

Re: AKG Perception P220 to Neumann u87 5 min mod ( p200, p100, p400, p420? )
« Reply #48 on: February 15, 2019, 11:45:31 AM »
As they are pretty useless as now ( Very peaky and harsh on all acoustic instruments), I would live very happy at any simple amelioration and improvement.
Why don't you just EQ out the excess treble? Contrary to what some seem to believe, the result is the same, as long as your EQ is flexible enough.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.