AKG Perception Capsule Swap Tutorial
This tutorial explains how to replace the capsule in the following single-pattern (Cardioid) AKG Perception microphones. The microphones pictured in the tutorial are the P220 and older Perception 220, but the instructions apply to all of these models:
- AKG Perception 100
- AKG Perception 200
- AKG P220
We no longer recommend this mod for the AKG's 3-pattern Perception mics (the Perception 400, Perception 420, and P420), because we do not have appropriate documentation. Should you choose to install the RK-87 capsule into one of these models, proceed at your own risk. (The general procedure is to duplicate exactly the installation of the original capsule wires; beyond that, we cannot offer support on the three three-pattern models.)
Note: The Perception 120 is not compatible with the RK-87 capsule, nor with any true condenser capsule. This tutorial applies only to microphones with externally-polarized capsules, listed above.
How to open the AKG Perception Condenser Microphone
Warning! Opening the microphone will void your warranty. Proceed at your own risk.
Locate the threaded ring on the bottom of the microphone.
Insert the tips of a pair of needle-nose pliers into the two notches in the ring. Spin the ring counter-clockwise and remove it. Caution: take care to avoid pinching your hand within the mechanism of the pliers.
Remove AKG Perception Microphone Circuit Boards
Locate the circuit board with the transformer on it (labelled "1045" in this photo). Remove the two screws holding the PCB to the chassis. Set the screws aside where they won't be lost.
Grip the transformer; use it to gently pull this circuit board away from the chassis.
If the board does not lift relatively easily, you can very carefully pry up one corner of the board with a small flat-blade screwdriver. Do not pry with so much force that the blade slips, as that will almost certainly destroy the circuit board.
The transformer circuit board remains attached to the chassis, via the XLR wires. These can remain in place.
Inspect the six brass pins on the back side of the transformer circuit board. If any are bent, straighten them gently with a needle-nose pliers. The microphone will be difficult to reassemble if these pins are not straight.
Remove the two screws holding the second circuit board to the back side of the microphone chassis. Set them aside with the screws from the transformer circuit board.
This circuit board is connected to the switch PCB via a pin connector. To remove the board, first swing the bottom edge away from the microphone chassis. Once it has cleared the XLR housing, tug the board toward the bottom of the housing to slide the pin connector apart.
As with the transformer circuit board, inspect the pins on this connector to ensure that they are straight.
Remove the five indicated screws. These mount the switch PCB to the chassis, and the chassis to the headbasket. Set all five screws aside where they will not be lost.
Note the style and length of each of these screws. The one with a built-in washer goes into the narrow end of the switch PCB. The four remaining screws are two different lengths; the longer pair goes through the circuit board, while the shorter pair goes into the chassis directly.
Remove the AKG Microphone Capsule
Find the wire indicated in the photo. (In the photo, the wire is black, but your microphone might be different.)
Remove the screw that attaches this wire to the capsule's backplate. Also remove the other screw pictured, which mounts the capsule to its plastic saddle.
Note: never unscrew a wire from the center of the diaphragm, as this will likely destroy the diaphragm and render the capsule useless.
After the backplate wire has been unscrewed from the capsule, you will be able to position the switch PCB as pictured. Find where the 2 or 3 capsule wires are soldered to the circuit board, and label them:
- "FR" for Front Diaphragm
- "BP" for Backplate
- "RD" for Rear Diaphragm (used on multipattern microphones only)
Note: Cardioid-only microphones such as the P220/Perception 220 will have only 2 capsule wires, as pictured here. Multipattern microphones like the Perception 420 will use 3 wires.
Desolder these 2 or 3 wires from the switch PCB.
The backplate wire is now free at both ends, and can be removed from the microphone.
The one or two diaphragm wires should stay attached to the capsule if you ever hope to use this capsule again. Pull the wires through the holes in the mount, from the capsule side of the mount. This step is easier if you clip off 3–5mm of the free end of the wire, to remove any leftover solder that might prevent the wire from fitting through the narrow holes in the capsule mount.
Remove the indicated screw, to release the capsule from its saddle.
Set the capsule aside for use in another mod project. (It is not a bad capsule, but arguably needs more corrective EQ than the Perception circuit provides.)
Upgrade the AKG Perception Capsule
Remove the screw holding the saddle to the capsule's mounting post. Then remove the saddle.
Install the "supersaddle" that came with your RK-87 capsule. Add a drop of thread locker to the mounting post first, so that the saddle does not come loose in a session.
Mount the RK-87 to the supersaddle using two M1.6x4mm machine screws (included). Tighten these screws until they are snug, but do not overtighten. If you stripping the threads in the backplate, or break the head off of the screw, it will be very difficult to install the capsule securely.
Bend a clipped component lead (e.g., the leg of a resistor) around the tip of a needlenose pliers, to form it into a small (~3mm diameter) loop. Insert a 2mm panhead M1.6 machine screw (included) through this loop, into the RK-87 backplate, as pictured.
If you do not have any surplus component leads available, any short piece of bare wire will suffice.
Insert a second M1.6x2mm screw through the eyelet in one of the blue wires included with the RK-87. Screw it part way into the other half of the RK-87 backplate, adjacent to the bent component lead.
Bend the component lead around the shaft of the second screw, as pictured.
Tighten both screws, then trim off the excess lead.
Note: the point of this step is to connect the two backplate halves together. The RK-87 ships with insulated backplates, but the Perception mics do not need a 4-wire capsule. Therefore we must connect the two backplate halves together externally.
Thread all three capsule wires through the holes in the pedestal of the capsule mounting post, then through the holes in the switch PCB.
If you are working on a Cardioid microphone, the rear diaphragm's white wire is not needed. Cover the bare end of the wire with a piece of electrical tape. It is best to leave this wire intact, rather than clip it off.
Cover the capsule with a plastic bag, to protect the diaphragms from damage during soldering.
Solder the backplate wire (which is blue) to the joint previously marked "BP."
Solder the front diaphragm wire (which is white) to the joint previously marked "FD." Note: the front of the microphone is the side with the switches on it. You will see that the switch PCB only fits the chassis in one orientation.
If you are working on a multipattern microphone, solder the rear diaphragm wire to the joint marked "RD."
We recommend cleaning these joints with 99% Isopropyl alcohol, or flux cleaner. Caution: do not allow solvents to come anywhere near the capsule, as they will likely damage the capsule diaphragms. Do not use aerosol flux cleaner near the capsule.
If you have "conformal coating," painting these joints with it will help prevent contamination.
Upgrade the AKG Perception's Input Coupling Capacitor
If your Perception mic has a ceramic coupling capacitor, we recommend replacing it with polystyrene. To do so, first remove as much solder as possible from the two indicated joints.
The input cap's leads extend several millimeters into these joints, making the cap difficult to remove. Try heating the joint with one hand while tugging on the capacitor with a pair of pliers in the other hand. Or, as a last resort, clip the capacitor body off of its leads.
During desoldering, it would be helpful to clip a copper heatsink to the JFET gate pin (which connects the JFET to the coupling cap), to prevent the JFET from overheating.
Form the leads of the styrene cap as pictured.
Position the styrene cap as pictured, so that its leads sit on top of the two insulated terminals without being under tension. Use a small piece of tape to hold the capacitor in place.
Attach a copper heatsink to one leg of the capacitor. Solder the joint on that side of the capacitor. Be sure the solder joint encompasses the styrene cap's lead, the 1KM (aka 1G) resistor lead, and the gate pin of the JFET. This joint must be shiny and smooth, once cooled; if it is cracked, dull, milky, or has divots or craters, remove the solder and reform the joint.
Move the copper clip to the other side of the styrene cap. Then solder the remaining joint, following the guidelines above.
Clean both joints with 99% Isopropyl alcohol, or commercial flux cleaner. Caution: solvents will destroy the polystyrene capacitor. Clean the solder joints without splashing solvent on the input cap or the capsule.
AKG Perception - Microphone Reassembly
- Make sure the trim ring is installed on the headbasket.
- Restore the small fabric tabs onto the switches. These are difficult to install after the grille is attached to the body.
- If you covered the capsule during soldering, remove the covering.
- Hold the headbasket against the table, open end up. Carefully invert the microphone. Insert the capsule into the headbasket. Be sure the front diaphragm faces the front of the microphone. Tuck in the fabric switch covers prior to fully seating the chassis into the headbasket.
- Position the switch PCB against the underside the capsule deck. Reinstall the five screws that hold this assembly together.
- Verify that the capsule wires are securely soldered to the switch PCB. If you are working on a Cardioid microphone, tape its free end to the underside of the switch PCB so that it cannot make electrical contact with the circuit.
- Locate the circuit board with the 5-pin socket at its top end. Position it against the rear of the microphone chassis. Slide its socket onto the pins that protrude from the switch PCB. Snug it firmly against the chassis, and screw it into place.
- Line up the transformer circuit board so that the two sets of 3 pins on its back side match the sockets on the rear circuit board. It is possible to reinstall this board without all the pins and sockets engaging properly, so we recommend working slowly and verifying visually that the pins are connecting with their corresponding sockets.
- Install the two remaining screws, to attach the transformer circuit board to the chassis.
- Reinstall the microphone body and the nut at the bottom of the microphone.
Perform an audio test to ensure that the microphone is functioning as expected.
Neither the new capsule nor the input capacitor need "breaking in." Your microphone is ready to use immediately.
- Verify that all the pin/socket connectors are properly aligned and completely engaged.
- Verify that the capsule wires were soldered to the proper joints.
- Inspect all circuit boards to verify that components were not burned or otherwise damaged during the modification process.