CHURCH-AUDIO
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How to build a Stereo Microphone and Battery Box
CHURCH-AUDIO replied to greenmachine's topic in Live Recording
Um that's not the way to match a capsule.. Actually doing it that way will introduce phase issues that will fool you into thinking a capsule is matched.. The best way for a person who does not have a lot of knowledge to match capsules is with a 1k tone.. You make up some kind of jig that allows the capsule to be held in the exact same spot. Then you measure the output voltage in AC from the capsule after a coupling cap. Then with out turning the 1k tone off you place the second capsule in the same exact spot and do the test again you want to match the ac voltage at the capsule output. This method is used for matching sensitivity of the microphones and is very accurate. This test is the industry standard test for sensitivity. I use an acoustic coupler that has been custom designed for my capsules and a very expensive software and hardware. BUT the DIY guys can do it the way I mentioned above and get very good results. Chris Church Church Audio -
Unlike headphone attenuators my preamp is a real active circuit that has a real gain control so your not losing any battery voltage and we provide the full voltage your battery is at so if your battery is 9.5 thats what the mics will see. Our preamp also draws only 8ma so it will run for up to 50 hours on a signal 9 volt.
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How to build a Stereo Microphone and Battery Box
CHURCH-AUDIO replied to greenmachine's topic in Live Recording
And now you’re qualified to say that my preamps distort at concert levels??? WOW..... Now you’re qualified to say that a preamp is not necessary for concert recording??? Man I don't get people that have been doing it for 2 months, can come along and bash people that have been doing it for 10 years, And pretend to know more about mics and concert recording then a sound engineer with over 20 years in the business. Can you Please explain this to me? I would love to hear it. -
Well sadly if that was the case, then this user would not comment on every single opportunity about my products. Read his posts over the last few months, I see a very obvious pattern of his comments. He uses his "power" here to sell his product and steer people away from mine, by misleading them about my product, when in fact he has never used it. I do not go out of my way to steer anyone away from anything, but when someone is totally misleading people, and talking about me behind my back, I will and do have the right to defend my self. That’s all I wanted to say about this subject. Sorry for hijacking this thread. I think you can sell things with out having to resort to slander in the process. I guess I feel my product is good enough, that I have never said anything negative about anyone else’s product. Funny I don't hear any comments from Greenmachine now? aint it. Chris Church
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Are you kidding me?? JB3 devices record great audio I have measured them in my lab and compaired them with MD. You dont want me to tell you who won. I guess you think your handing out good advice. But I have read most of your posts and to be honest I think you do not know what your talking about. When you say things like that about the JB3.
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00- is a term used for a signal that is totally attenuated, 0- db refers to unity gain, not boosted or cut. So my preamp will do from all the way off, to +20 this includes the 0-db range or unity gain like a battery box. In situations where you do not want to boost or cut. The gain control on my preamp covers the whole range to +20 db. As do most of the other preamps out there.
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That is a false and misleading statement my preamps work great and they do not cost "enormous amounts of cash" I guess you just want to sell more battery boxes so you put preamps down. Well maybe its because you don't know how to build a good preamp? Your misleading people in saying all anyone needs is a battery box. That is not true.
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Hi Guys. All I wanted to say is a battery box will not work for everything, where as a preamp will the st-9100 preamp I make has a true gain control that goes from -00 db or totally off to +20 db of gain. That way you can attenuate or boost as needed, a battery box is just a power supply. You will notice noise when you try and use a battery box for a concert that is not that loud, and you have to boost it with your recorder or with normalization. Thats the whole point, I was trying to make. This "other" person just wants to put my products down and sell his. Even though he has never used my product. It would be just as unfair for me to say his product was bad. Preamps do have there place in loud concert recording. But I must say we do not use cheap headphone cables for our mics we only use MOGAMI and Nutrik connectors yes you pay a bit more but you also get alot more. I dont waste my time putting other products down I have sold over 2,400 preamps in the last 2.4 years I have been operating. Thats alot of preamps I guess they must be good for something or I would have never sold that many. Chris Church
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I disagree 100% a preamp is very usfull and my preamp is perfect for recording loud concerts. I recommend my cardioid mics and st-9000 preamp package that will give you state of the are reproduction of concerts with no noise and much better signal to noise ratio then just using a cheap headphone attenuator. You have always had it in for me. try and be unbiased in your remarks about me if you can..... I can see you sell mics and battery boxes I guess you dont know how to build a good preamp or you would be saying that preamps are importaint. I sell both battery boxes and preamps. I have no bias I know a preamp is better. I think its sad you have to shoot some else down because you need to make "sales" that badly.... Saying that all you need is a battery box is rediculous. Go to Tapperssection.com and say that. They will laugh at you. A battery box will work great under some situations, But my preamp the st-9000 and ST-9100 will work in all situations. PS... we don't USE cheap headphone cable for our mics we use MOGAMI and Neutrik connectors. I dont think using CHEAP dollar store headphone cable is a very good method for connecting mics and reducing noise. DO YOU? I would rather have a solution that will do everything then a cheesy battery box that will MAYBE work in some situations. You have to admit the less normalization you do the better your recording will turn out. When you plug into a line input your already at -20 db the mics them selves can swing anywhere from -10 to -30 ( depending on mic sensitivity) on the output with very loud music. So that means your putting into the line input a signal of -20 to -40! on average that means you need atleast +25 db of gain from your MD and +15 thru normalization. Why not start out with a nice -10 signal and get +5 from your MD and +5 from normalization? insted of getting all that noise? Lets stop handing out bad advice my preamps are not the only good preamps out there, I am not piping in because I want to sell something. I have all the sales I could ever want. But I am tired of your one sided remarks, and the fact that you always do your best to stear people away from my products. When you have never used them. Chris Church
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Just ordered the MZ-RH910 and a ECM-M907
CHURCH-AUDIO replied to geestring's topic in Live Recording
My cardioid mics are smaller then the AT 853 mics they measure 12 mm x 14 mm We have a new preamp that has a real gain control and works well with the AT 853 mics that provides up to 20 db of gain and is so quiet it can be used with a mic input or a line input with ZERO noise. That way you can get the boost you need and nomalize Less. It comes in two versions 3 wire mini XLR or 2 wire mini stereo 3.5 mm in and out the distortion with a -9 db signal is 0.02%. The self noise is -98 db with the gain full no input connected. Fre Chris Church Church Audio You should try our new ST-9000 preamp it has less then 0.02% distortion with a -9 db input. This is about 10 db to 20 db more then your AT 853 mics will put out. This preamp works with AT 853 mics I have two versions one with three wire mini xlr and 2 wire stereo mini jacks it provides 20 db of gain via a real gain control and has a high pass filter at 80hz that can be bypassed all this for $150 for the 2 wire and $175 for the three wire. This preamp has a self noise of -98 db full spectrum freq resp of 20hz to 90khz FLAT. Chris Church Church Audio -
No one makes them as far as I know check this company out they sell the jack if your good with soldering you can do it your self or hire someone to do it for you here is the link. http://www.btx.com/ItemForm.aspx?item=CA-B...b3-5cee8464acbf they are expensive for plastic shell connectors but they are one of the only sources for this item. Chris Church
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I am not sure what you mean about thermal noise? the definition is the thermal agitation of electrons in a conductor also called Johnson noise. You might be confusing this with static dischage easly fixed by using good cable This also refurs to noise generated by a semiconductor when it gets heated. I do not see the connection there. The other type of noise is Inducted noise from badly sheilded capsules when placed close to the body. But that can be eliminated by good sheilding. The other noise of the clothes and being close to the head is a simple fix make sure the source is louder then you are . Then the noise you make will be several db down from the source being recorded. Even though you have the " inverse square law " working agenst you, this law states that, in very simplistic terms. Relaying to the field of sound the closer we get to a source the louder it is. So when you are wearing mics if you have your gain control cranked you are going to pickup more of you and less of your recording. How ever if you are say putting out 60db and what your trying to record is putting out 90db from where you are seated you will pick up the source and be 30db down from the 90 db. Thus less likly to pick it up move ten feet closer to the source your trying to record and you will be at 93db aprox, depending on directionality of the source. You might be 95 db its simple and most people know about it but few understand why. Look at sound waves from a band OR any sound source as a giant sphere. The closer you get the the sphere the closer you are to the core, the closer you are to the core the orginator of the signal the louder it is. This is a law of phyiscs and can not be changed. Some speaker companies use extreme directionality to minimize this effect and create a loud sound field further away from the core. But all sound is subject to the friction of air particules. These particules slow down the sound wave and reduce its power thus the further you are away the lower in volume or amplitude the sound wave becomes. Also temperature and humidity and sea level effect the distance of a sound wave will travel and its speed. Chris Church Church Audio Chris Church
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To understand why some mics with different polar patterns pick up low end better then others you have to understand wave forms. Low frequency is a long wave form 50 Hz takes 23 feet approx before it is a fully developed wave form so. What we know from this is frequency’s below aprox 200hz are Omni directional in nature ( non directional ). So omni mics tend to pick up low frequency much better then Cardioid mics do. One of the other problems with cardioid mics is they operate on phase cancellation to derive directionality. The ports on the back of a cardioid mic are in fact 180 degrees out of phase from the front of the cardioid capsule thus giving the cardioid mic directionality. There for some wave forms get canceled some get reinforced. Thus cardioid mics tend to not be Flat in frequency response they tend to have a rise in high frequency and a gradual rolling of at low frequency’s. Good cardioid mics use various methods to reduce the nasty effects of phase cancellation and try to improve low frequency by tuning the front and back of the capsule also re-tensioning the capsule helps. Increasing the output of the mic is one way around this problem because of the Fletcher Munson curve the louder a sound gets the more high end it seems to have, the lower a sound gets the softer the high frequency is. So if we increase the sensitivity of the mic we can in fact capture more low frequency’s even with a cardioid mic. The only problem is that there is a limit to how much you can increase sensitivity and still how low distortion. So if you want to capture sounds exactly as they happen an omni is good, but it will pickup reflections from all surfaces. Some will reinforce the sound nicely some with cause phase cancellation. Cardioid mics do not have this problem as much because they are directional and can be pointed at the source in order to understand the benefits we have to understand phase cancellation. Phase cancellation is simple its two frequency’s that arrive at the microphone at the same time, with the same amplitude and the same wave length and in phase with one another. This last bit is complicated. In phase with one another means that both signals are positive or negative going with respect to one another when they enter the sound ports of the microphone or ear in question. So with omni mics phase cancellation is much more likely to happen. That’s why we have the jecklin disk its a boundary between two omni mics that prevents phase cancellation. It creates a boundary or separation between two omni mics and causes them to be less interactive with one another. Thus less likely to have phasing problems between each other and more likely to produce a good stereo image. I would like to write more about complex subjects of audio if anyone is interested in my knowledge that I have gained being a sound engineer for the last 20 years I would love to share it Chris Church Church Audio
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GM you bring up some good points. One of the reasons why we Church Audio do not use a potentiometer in the input stage of the mic, before an active preamp is simple, while you are infact reducing the input level, you are reducing the BIAS voltage at the same time Thus increasing the distortion by starving the FET of its needed supply voltage. LESS bias voltage = more distortion = bad sound. In some cases you can use this and " get away with it". Here is another problem the headphone attenuator. It is designed for HI level signals, not low level signals of a electret capsule. So it is unsheilded because RF and EMI induction is not a problem with a hi level signal. It becomes a big problem with low level signals like the ones comming from a microphone. Thus it will increase the noise floor of your mics in some situations like a concert this might not be a problem. But if you have attenuated too much and have to normalize the crap out of a signal via a computer You will hear that noise. Chris Church
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Send me one of your recordings, I would very much like to hear it. Thanks for the comments about our product. It was designed for voice pickup, its very sensitive and I am glad its working well for you. Chris Church