SCA N72 & Shure KSM32 combination not working??

GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

imloggedin

Well-known member
Joined
Dec 17, 2005
Messages
265
Location
mid-usa
The SCA forum seems to be dead so I thought I'd post this here. I just got a used KSM32 and the first pre I tried to test it with is an N72, and it didnt work. I thought the mic was dead but I tried a few other preamps and it works fine on the others. Every other mics I have works fine on the N72. The KSM32 is an electret condenser is the only difference. I cant find a schematic for the KSM32, so I was hoping someone had some insight. Thanks.
 
Don't think that's an electret condenser, just a condenser, meaning you need to supply phantom power, which I assume you were?
 
Ya I definitely was supplying phantom. Voltage checked out on pin 2 & 3, other microphones worked also. It worked on a T15 preamp in the same chassis too. Also, it is an electret condenser. It's just a big one :)
 
It may be that the N72 has a 10 k phantom series resistor before the 6.8k resistors, hence the Shure won't get enough power to work.

 
I had the impedance jumper set completely wrong. I dont even know how it was working. But I switched it to the correct way, and it still doesnt work :\ I checked the voltage on the phantom. Its like 47.5, same as the T15 that it works correctly on. The KSM32 can run on something like 17v.
 
Measure p2 & 3 wrt p1 with the mike connected and powered up.

The KSM32 might be one of the nasty mikes that take power only on one leg.  This is REALLY icky.

Ask Shure about this combination.
 
Yah both legs were 47v. I think theres a problem with this mic. It was used and shows some wear. I plugged it into another preamp I made that has a transformer input and it doesn't work either. It works on IC based preamps though. I think it must have something to do with the impedance being wrong. Guess I will return it.
 
ksm32 specs
Type
Permanently-biased Condenser
Frequency Response
20 to 20,000 Hz
Polar Pattern
Cardioid
Output Impedance
150 ohms (actual)
Phantom power required?
48 Vdc +/- 4 Vdc (IEC-268-15/DIN 45 596), positive pins 2 and 3

So you should be o.k.  I'm sure you tried a different mic cable. I had a cable once that was fine but for whatever reason didn't pass phantom. Never found out why as I just gutted it for the ends and made a new one.
 
ricardo said:
Measure p2 & 3 wrt p1 with the mike connected and powered up.

The KSM32 might be one of the nasty mikes that take power only on one leg.  This is REALLY icky.

Ask Shure about this combination.
If it takes power on only one leg, it won't like transformers connected like this.
 
pucho812 said:
ksm32 specs
Type
Permanently-biased Condenser
Frequency Response
20 to 20,000 Hz
Polar Pattern
Cardioid
Output Impedance
150 ohms (actual)
Phantom power required?
48 Vdc +/- 4 Vdc (IEC-268-15/DIN 45 596), positive pins 2 and 3

The specs say power on pins 2 & 3
 
i had major grief with a N72 kit i bought years ago, ill never buy anything from sca again. there was basically no help from the vendor insisting i send the kit in for a very pricey rebuild, eventually i found that one of the "via's" were open circuit on the pcb. I had to solder in a short piece of wire to complete circuit, not impressed!!
 
Back
Top