Look ma! No Tube
FAR FET 47
The APEX 480 FET microphone can be made to sound fantastic with some careful electronic component changes and a new K47 capsule
Ok I know you are dissappointed but listen I think they might be on to something with these transistor thingys. They don't get very hot, they use a lot less power and you can make really fast accurate amplifiers with them.
We spent some time working on the APEX 480 and we can do a lot to improve this mic but even out the box the internal electronics are very good.
The circuit uses a 2SK170 low noise Field Effect Transistor (FET) coupled to a low noise PNP transistor in an emitter follower (EF) configuration. The EF stage drives a transformer to give things that vintage sound. The amp is flat +/- 0.5 dB form 30Hz to 30KHz!
APEX 480 internal Preamp response Stock
Keep the Original Capsule?
Acoustically the response shows the typical curves of a 32mm chinese capsule. We show in this mod how to EQ the mic internally in an inexpensive way. This is the same technique used in the u67 and u87 microphones, but of course they do it a lot fancier, using negative feedback.
APEX 480 stock response at 0.5 metres from the source
EQ Improves the Response
Below you can see the difference between the stock electronics and our little EQ addition. It warms up the sound quite well.
FAR FET 47 response at 0.5 M with 32mm capsule
New!! CEK47 Capsule Results (Oct 1, 2010)
Actual FAR Fet 47 response with Peluso CEK47 capsule at 0.5 M
We recently purchased a CEK47 capsule and tweeked the internal preamp to create the response shown above. It only takes one small capacitor to fine tune the response!
This is now a very nice microphone. The CEK47 capsule is not a real replica of real u47 capsule. It uses a more AKG type of drill pattern in the back plate. This causes it to rise 7 dB at 10Khz! But by carefully adjusting the response of the preamp it can be tamed.
Listen to this FAR FET 47 in a Podcast
( Gibson SJ-200 plays at the end of the track)
You can see the typical u47 double hump response above matches the u47 pretty closely. It is a real 34mm capsule and with the larger diapghram it begins to roll off after 10KHz, like a u47. This makes a smooth sound with a mid-range lift that makes a voice cut through the mix.
u47 Cardiod response from a 1958 brochure. Scale is 40Hz to 15Khz
NEW! RK47 Capsule Available
We have found a supplier of lower price K47 capsule that performs like a champ. To be very honest for the price point we see great attention to detail and a backplate hole pattern that looks very much like a K47 capsule.
The response on the high is a pretty good replica of the K47. The bottom end has a little lift (1dB) that we do not see with a more expensive capsule but that is not a problem. In fact some of the great mics by David Bock have a similar low end response. If your budget is tight ask for the RK47 capsule in your upgrade and it will take your price down by $150 !
Executive Decision Required
While working through the details on this microphone we had to make a decision. We had to decide is excellent signal to noise more important than a Figure 8 polar pattern feature.
We voted for excellent signal to noise. Low noise microphones create that transparency that makes all the details in the sound come through. So the FAR FET 47 is modified to have the front end circuitry mimic the original FET 47.
Why no Figure 8?
To properly do a multi pattern microphone, you need a minimum of a 110 volt power supply for the back capsule so you can get at least 55 volts for the front capsule.
The APEX DC board can only generate 80 volts max which would mean a very low 40 volts on the front capsule.
So we said no to Figure 8. This way we were free to use a healthier 65 volt polarizing voltage like a real u47. This improves the output signal of the capsule and therefore better S/N.
So for this upgrade you get Cardiod and Omni-directional polar patterns, like a Neumann FET 47.
You have Four options with this one
- You do the work yourself from the drawings we provide.
- You let us modify the electronics so it sounds great without changing the capsule.
- We upgrade the electronics for you and put in a slightly less expensive Peluso CEK47 capsule and it sounds really great.
- We go for it and do the full upgrade, put in a Peluso K47 capsule and this mic ROCKS!
Do it yourself instructions
We have updated this Audio board Schematic. The previous one had an error. Apologies
Audio Board Schematic with Mods Rev 3.1
DC to DC converter Board Schematic with MOD Rev 2
BF Notes:
You can experiment with your own ears. Match the EQ capacitor, shown in the schematics, to make your capsule sound best. For the CEK47 capsule, we used a 1000pF polystyrene cap. For a 32mm Pelsuso CEK89, we found it only needed 100pF. Use your ears to make it sound best for you. That's all that really matters.
Remember if you replace the capsule with a flat response capsule like a K47 type capsule remove the EQ cap completely. The K47 capsule is designed for a flat preamp circuit.
If you prefer us to do the work send us a note at: