Topic: Is a preamp increasing maximum SPL of a mic like a battery-box would do ?

[fandelive]

Hi,

I own a pair of SP-BMC-12. Specifications over at the SP website claims :

Maximum Input Sound Level: 110 dB SPL, 1 kHz at 1% T.H.D. (125dB when powered by our battery module)

But what about powering the mics with my preamp (Church Audio CA-9100) ??

Thanks

[runonce]

Check out what their battery module does...

I think some of these put the 4.7ohm high SPL mod on the preamp side.

[fmaderjr]

Hi,

I own a pair of SP-BMC-12. Specifications over at the SP website claims :

Maximum Input Sound Level: 110 dB SPL, 1 kHz at 1% T.H.D. (125dB when powered by our battery module)

But what about powering the mics with my preamp (Church Audio CA-9100) ??

Thanks

It definitely will increase the SP level handling as much as their battery box. I'm sure their battery box does not have a 4.7 mod built into it. I've not heard of any battery boxes that have the mod built in, although you can get a CA preamp with mini-xlr connections & a switchable mod built in.

[fandelive]

I'm sure their battery box does not have a 4.7 mod built into it. I've not heard of any battery boxes that have the mod built in, although you can get a CA preamp with mini-xlr connections & a switchable mod built in.

Does that mean the CA-9100 has a built-in 4.7k mod ? How can I check this ?
I have a CA-9100 v4.4. I can only see a HPF switch (which I assume is kind of a bass roll-off filter) and the volume knob.

Because when I asked Chris Church to mod my MM-HLSC-1's, he told me I'd need a preamp to run my modded mics. That's why I bought one.

He didn't told me about a possible switchable mod inside the preamp. That would have been a way better option !

[fmaderjr]

I'm sure their battery box does not have a 4.7 mod built into it. I've not heard of any battery boxes that have the mod built in, although you can get a CA preamp with mini-xlr connections & a switchable mod built in.

Does that mean the CA-9100 has a built-in 4.7k mod ? How can I check this ?
I have a CA-9100 v4.4. I can only see a HPF switch (which I assume is kind of a bass roll-off filter) and the volume knob.

Because when I asked Chris Church to mod my MM-HLSC-1's, he told me I'd need a preamp to run my modded mics. That's why I bought one.

He didn't told me about a possible switchable mod inside the preamp. That would have been a way better option !

The standard CA-9100 does not have a 4.7 k mod built in. He probably modded the mics instead of making mod inside the CA-9100. If your CA-9100 has the normal 1/8 input, its definitely the mics that are modded. The mod reduces the sensitivity of the mics, so he told you that you should use a pre to run them.

If your CA-9100 has mini-xlr inputs, it may have the mod built in, but it would then have an internal switch to turn it off & on.

[Cheesecadet]

When Chris did my miniXLR 9100 with the 4.7 mod there was a tiny square button on top near the gain knob to turn on and off.  The switch inside was just the HPF. 

[SmokinJoe]

The battery box sends 9 or 12v (depending on the battery) to the mics.  The higher voltage allows the mics greater headroom, therefore they can take a hotter signal without brickwalling compared to using plug-in-power from your recorder, which is something like 3v.  If a preamp sends that same voltage, you would get the same results.  if it doesn't you won't.  Making a blanket statement "a preamp will definitely increase SPL handling as much as a battery box" isn't always true for all mics.  I had a set of AT853's where the difference between 12v from the battery box and 8V from the preamp was just enough to avoid clipping at a Trey show.  I deliberately ran battery box for 1 set, preamp for the other.  no brickwalling with the battbox, slight brickwalling from the preamp.  If you are living on that edge, then it matters.

The 4.7k mod is something completely different.  To make a long story short, if you 2 mics are already terminated to a single miniplug, it's not something that can be switched on/off inside a preamp. That was originally intended for AT853's, I'm not sure if it even applies to BMC-12.

There were some early ST9100's that put out something like 3volts, then Chris made a change that makes it about 8volts, that was probably 3 or 4 years ago.  I think it might have been when he came out with version 3, but I'm not positive.  to check your preamp, find a typical cable with male mini-plug on both ends.  Plug one end into "mic in" on the preamp.  Turn on the preamp, check the voltage between tip and sleeve with a voltmeter.  What you see is what you got.

[fmaderjr]

There were some early ST9100's that put out something like 3volts, then Chris made a change that makes it about 8volts, that was probably 3 or 4 years ago.  I think it might have been when he came out with version 3, but I'm not positive.  to check your preamp, find a typical cable with male mini-plug on both ends.  Plug one end into "mic in" on the preamp.  Turn on the preamp, check the voltage between tip and sleeve with a voltmeter.  What you see is what you got.

I may be wrong but I was pretty sure the Church boxes have been putting out 9 v. or a little more the last 3-4 years. I just tested out a 3 year old CA-9100 using your system (thank you-I never knew how to test under load) and got 9.17 volts with an Imedian rechargeable that hadn't been charged in months.

That's why I thought it would be as good as a battery box because I forgot that some use a 12 volt box. I never liked the idea of the 12 volt boxes because of the batteries they take. I'd rather use a rechargeable 9 volt battery. Obviously if the mics need more voltage that the 9 volt preamp delivers, then it's worth dealing with a 12 volt box, but I've never had a problem with my mics running on what the Church pre provides (and have even done fine running CA-14's & DPA-4060's straight into a Marantz PMD-620, which provides about 4.6 v. PIP, I think).

[Roger Gustavsson]

9 V rechargeable? Does they really excist? NiMh use to be 7.2 or 8.4 V. Lithium use to be 7.4 V. That is when they are fresh...

Electret microphones use to have the supply in series with a resistor. The voltage that reach the JFET of the impedance converter inside the microphone will be lower as it passes the resistor. An exemple: If 9 V reaches a series resistor of 3.3 kohm and the current drawn by the JFET is 0.5 mA, the voltage will drop from 9 V to 7.35 V. You need to meassure the supply voltage at the JFET under load! The lower the voltage, the lower the SPL limit but there are limits to how far this can be pushed! Even very high quality microphones use to have rather low supply voltages. I think the Schoeps uses 6.2 V and it can still take 130 dB.

[fmaderjr]

9 V rechargeable? Does they really excist? NiMh use to be 7.2 or 8.4 V. Lithium use to be 7.4 V. That is when they are fresh...

There are few of them available now. Here's one of them and it is low self discharge as well.
http://www.amazon.com/PowerEx-IMEDION-Low-Self-Discharge-Rechargeable-Battery/dp/B004NVVPJC

[adrianf74]

And those PowerEx batteries are the only rechargeable 9V you should even think about.   I have access to Energizer Industrial 9V batteries otherwise I would be going that route.

[Church-Audio]

Hi,

I own a pair of SP-BMC-12. Specifications over at the SP website claims :

Maximum Input Sound Level: 110 dB SPL, 1 kHz at 1% T.H.D. (125dB when powered by our battery module)

But what about powering the mics with my preamp (Church Audio CA-9100) ??

Thanks

Funny thing is for 2 wire mics throwing more voltage at the mics does not really increase max spl. There is very little difference between 9 volts and 12. Its more to do with the way the fet is biased in the mic. That being said my mics are designed to work well at 9 volts. As far as the 9100 goes your preamp does not have the 4.7k mod on it. The 9200 or 9100 is available with the 4.7k mod but your mics need to be re terminated to three pin mini xlr. The AT 350 Mics I am not sure if they would work I would need to look at them to determine if they can be modified and what value resistor is optimal for it. Or it might be possible that the 4.7k resistor would work well in that case you can get a 9100 or 9200 with the 4.7k switch mod and send your other mics back to me to be unmodified and made to be 3 wire.

All Church Audio 9100 made in the last 4 years are 9v dc at the input for mic power. All Ugly preamps ever made were 9 volts all 9000 preamps  were 9 volts all 9200 are 9v.

A preamp or battery box does not increase max spl proper design of a mic is where you always want to start to get the least amount of distortion.

[eman]

I run my CA9100 off of a Wally World 9V DVD battery with a 9V battery clip spliced into the cable, that is when I run openly. I stuff the 9100 and the battery into a pouch and hang it off of the mic stand, run the mini cable down to my recorder. I got tired of dealing with all of the dead 9Vs that I was creating, so now only when  ing.