Topic: SP-CMC-4U and other SP mics with new "low-sensitivity-mod" for very high SPL

[Arni99]

Does any of you guys know if the 4.7K mod is now available from soundprofessionals?
Check the dropdown-menues of the mics.....this is new.

http://www.soundprofessionals.com/cgi-bin/gold/category.cgi?item=SP-CMC-4U&type=store&template=specifications

[Arni99]

chris from soundprof. just confirmed that the 4.7k mod is now available for this mic.
he mailed me:
> Hi,
> the SP-CMC-4U cardioids are offered with a low-sensitivity modification
> for 25$ regarding to the dropdown menues. Does this imply the 4.7K MOD?
> Please let me know.

Yes, it is.

If you have any questions, please let me know.

Best Regards,

Chris Carfagno
The Sound Professionals, Inc.
3444 Sylon Blvd.
Hainesport, NJ 08036
USA
www.soundprofessionals.com
Toll Free: 800-213-3021
Phone: 609-267-4400
FAX: 609-267-0054

[boojum]

Just so you have it straight: $25 if you order it in a new set of mics.  It is $35 plus postage to have it retrofitted.   

[Arni99]

I just ordered the SP-CMC-4U(AT853U) cardioids with the 4.7k mod from soundprofessionals.
hope they arrive before June 29th.... some shows need to be taped soon!

[kozakz]

i got the new SP-CMC4U and if i running on a 2 wire battery box even at a moderate loud concert my recording has too much distorsion. if i am running the same mic with a preamp in 3 wires cable mode there is no problem even at really loud shows.

My mics are terminated in mini xlrs and i have cable which convert to stereo jack, this is the way i can use it on 48v preamp or a 2 wire battery box unit.

in my openion sound pro should offer this mod free of charge because without this their product is not working properly on 2 wire setup with battery box.

The old version of CMC4 with AT853A capsules do not suffer from this problem.

[Arni99]

I just ordered the SP-CMC-4U(AT853U) cardioids with the 4.7k mod from soundprofessionals.
hope they arrive before June 29th.... some shows need to be taped soon!

my low-sens SP-modded SP-CMC-4U arrived today.
will test them in 2 weeks at a big openair show.
www.lovelydays.at will be their 2nd run 1 week later.

[Church-Audio]

Its nice to know someone is making some money off my 4.7k mod but just to let you know I do the mod MY MOD for $10 + return shipping.

[Arni99]

Its nice to know someone is making some money off my 4.7k mod but just to let you know I do the mod MY MOD for $10 + return shipping.

I know Chris, but shipping from Europe to Canada and back is not cheap .
I bought them new so it made sense SP did the mod BEFORE shipping them to me.

[illconditioned]

Its nice to know someone is making some money off my 4.7k mod but just to let you know I do the mod MY MOD for $10 + return shipping.

Do you know if SP is doing the 4.7k mod, or are they just putting mini XLRs on there and using a three wire battery box?

Overall, I feel that the original SP models, whether AT or their "house" brand, were never suitable for concert recording.  I just bought my mics (AT853) there because it was the cheapest place to find them at the time.  I immediately rewired them...

  Richard

[Arni99]

Its nice to know someone is making some money off my 4.7k mod but just to let you know I do the mod MY MOD for $10 + return shipping.

Do you know if SP is doing the 4.7k mod, or are they just putting mini XLRs on there and using a three wire battery box?

Overall, I feel that the original SP models, whether AT or their "house" brand, were never suitable for concert recording.  I just bought my mics (AT853) there because it was the cheapest place to find them at the time.  I immediately rewired them...

  Richard

I asked Chris Carfagno from SP and he told me it would be the 4.7k mod.
"Separation" of left + right channel is great.

Had some old AT853s for testing last week where separation was almost gone after the mod.
When I touched the left mic the right mic´s levelmeter bounced up 80% of the left mic.

With my SP-modded SP-CMC-4U all is fine .

Richard, check the 2nd post in this thread .

[Kindguy]

Its nice to know someone is making some money off my 4.7k mod but just to let you know I do the mod MY MOD for $10 + return shipping.

I think Chris's cards sound just as good. If not better & are cheaper. Funny you posted how to do this mod about a month ago. Now they offer it. In all you should be proud how well it works.

T+

[Church-Audio]

Its nice to know someone is making some money off my 4.7k mod but just to let you know I do the mod MY MOD for $10 + return shipping.

I think Chris's cards sound just as good. If not better & are cheaper. Funny you posted how to do this mod about a month ago. Now they offer it. In all you should be proud how well it works.

T+

The whole reason that mod was invented was because I had some cardiod mics I wanted to sell to the taping community but, before I did that I wanted to make sure they did not distort at loud levels. So I invested a lot of money in test equipment to be able to measure the distortion of these microphones BEFOR I sold them. I found out that my capsules when they were stock from the factory had a distortion of more then 8% when wired in a two wire configuration. I then measured the 853 mics and found that they had almost 10% distortion. I then discovered over 4 years ago that if I put a 4.7k resistor in my microphones the distortion decreased from 8% to 0.5% and with the 853 from 10% to 0.5% decrease. The only draw back was a reduced output level. Since we know that using 3 wire for these mics reduces the level by 10db. I thought that an additional 2db was a small price to pay for being able to use the 853 or my Cardioid mics with ANY recorder providing a plug in power input. Thus eliminating the need for a 3 wire battery box.. And all the extra things required to run these mics.

I feel that I should have received some credit for coming up with this mod and for making my discovery public. Some people have decided to charge people for this mod and make money from my hard work. In the end I cant stop them from reselling this. But I want everyone to know it was me who came up with it and it was my hard work and hours of experimentation to come to this 4.7k mod. I just wish all people wanting to do this mod for others just charge for the cost of parts. Its not magic my ideas came from experimentation. I am not some electronics genius, just someone that wanted to make sure the products I sell work and do what I say they will. Not distort when your using them at a loud concert.

Chris

[nameloc01]

is this discussion re: the 853 clipping issue mostly?

i just used my newest setup for the 2nd & 3rd time this past week. the first run was the Black Sabbath show in cleveland,it was quite loud,but there was absolutely no clipping whatsoever and the recording came out a-1.

and the second run was the TOOl show in SC. and i'll tell ya' what,i was 14th row from the stage,and you can imagine how loud it was, and those mics with the nadys and dececke pulled a beautiful recording. and again ,there was no clipping or brickwalling at all.none.the low end is very solid,the mids are full and rich and the highs are crisp.

i'm not trying to toot my own horn, i am just curious as to the exact reason for this mod? is it to avoid having the phantom power mod done, and avoid the power supply purchase?
i am just curious.
as the AT techs will tell you (fyi) while they do technically work with the SP joint 1/8" mini termination, the were designed to use their AT power modules. they do not hide that fact, the second best way is the nadycbm40s>phantom power (denecke) 
i dont see how with either of those two setups these mics can possibly be overpowered.

[Church-Audio]

is this discussion re: the 853 clipping issue mostly?

i just used my newest setup for the 2nd & 3rd time this past week. the first run was the Black Sabbath show in cleveland,it was quite loud,but there was absolutely no clipping whatsoever and the recording came out a-1.

and the second run was the TOOl show in SC. and i'll tell ya' what,i was 14th row from the stage,and you can imagine how loud it was, and those mics with the nadys and dececke pulled a beautiful recording. and again ,there was no clipping or brickwalling at all.none.the low end is very solid,the mids are full and rich and the highs are crisp.

i'm not trying to toot my own horn, i am just curious as to the exact reason for this mod? is it to avoid having the phantom power mod done, and avoid the power supply purchase?
i am just curious.
as the AT techs will tell you (fyi) while they do technically work with the SP joint 1/8" mini termination, the were designed to use their AT power modules. they do not hide that fact, the second best way is the nadycbm40s>phantom power (denecke) 
i dont see how with either of those two setups these mics can possibly be overpowered.

Some guys dont want to run three wire because they dont want to use a full size phantom preamp and want to use it with a recorder like a r-09. With out any other preamp or battery box, my 4.7k mod allows you to use the 853 mics and my mics with out any battery box or external preamp and get the same or better distortion handling as you do with your three wire setup for loud shows. When the shows are not so loud and signal to noise is an issue you can then use a 2 wire preamp like my st-9100 with the 853 or my cardioids, and get the same quality as a full size phantom power supply/preamp. But in a much smaller package. Thats why people want the 4.7k mod and reduced distortion that my mod gives you. Your setup is 3 wire so your getting the advantage of reduced distortion but with a little bit bigger size setup but if you compare my setup to yours the performance is the same my rig is just smaller.

Chris

[Javier Cinakowski]

[edit: post deleted to protect the innocent]

[nameloc01]

thanks for the info, and kudos for your brainstorm/creation.thats about the only downfall with mine, its not quite as stealthy as i'd like it to be.

[Alchemy]

Interesting, considering when I was in the market for microphones a month or two ago, Chris C claimed they had no interest in offering this famous 4.7k mod. Now this all of a sudden.

I've still yet to have clipping issues with the 831s.  An upgrade is imminent though...

[Church-Audio]

Interesting, considering when I was in the market for microphones a month or two ago, Chris C claimed they had no interest in offering this famous 4.7k mod. Now this all of a sudden.

I've still yet to have clipping issues with the 831s.  An upgrade is imminent though...

You sent me an email on March 03, 2007 You said Hey Chris I think I can do the mod my self can you supply me with the resistors lol.. You never asked me if I could do the mod for you. I would have said yes. I get at least 10 customers a month that pay me $10 each to do MY 4.7k MOD.

 

Chris

[Alchemy]

Interesting, considering when I was in the market for microphones a month or two ago, Chris C claimed they had no interest in offering this famous 4.7k mod. Now this all of a sudden.

I've still yet to have clipping issues with the 831s.  An upgrade is imminent though...

You sent me an email on March 03, 2007 You said Hey Chris I think I can do the mod my self can you supply me with the resistors lol.. You never asked me if I could do the mod for you. I would have said yes. I get at least 10 customers a month that pay me $10 each to do MY 4.7k MOD.

 

Chris

No, I was talking abou Sound Pro Chris in my last post. I forgot you guys both have the same initials (CC).

[illconditioned]

Its nice to know someone is making some money off my 4.7k mod but just to let you know I do the mod MY MOD for $10 + return shipping.

Hey Chris,

It sucks to see noone crediting your mod, but I'm sure you'll continue to do a good business here.
Unlike random websites and Ebay, here is where the rubber hits the road and people get to hear real feedback about all kinds of products.
Your (modded) cardioids are a solid product and great value as far as I'm concerned.
Just keep adding new stuff, like omni caps, "ultrastealth" preamps, etc, and we'll keep buying them...

  Richard

[Church-Audio]

Interesting, considering when I was in the market for microphones a month or two ago, Chris C claimed they had no interest in offering this famous 4.7k mod. Now this all of a sudden.

I've still yet to have clipping issues with the 831s.  An upgrade is imminent though...

You sent me an email on March 03, 2007 You said Hey Chris I think I can do the mod my self can you supply me with the resistors lol.. You never asked me if I could do the mod for you. I would have said yes. I get at least 10 customers a month that pay me $10 each to do MY 4.7k MOD.

 

Chris

No, I was talking abou Sound Pro Chris in my last post. I forgot you guys both have the same initials (CC).

Sorry

[Church-Audio]

Its nice to know someone is making some money off my 4.7k mod but just to let you know I do the mod MY MOD for $10 + return shipping.

Hey Chris,

It sucks to see noone crediting your mod, but I'm sure you'll continue to do a good business here.
Unlike random websites and Ebay, here is where the rubber hits the road and people get to hear real feedback about all kinds of products.
Your (modded) cardioids are a solid product and great value as far as I'm concerned.
Just keep adding new stuff, like omni caps, "ultrastealth" preamps, etc, and we'll keep buying them...

  Richard

Well you have done a lot more for the community then I have. Your words mean a lot to me thanks..

Chris

[Roving Sign]

Not sure if this is fair to call this "your mod" - I think this info was bandied about USENET back in the day...

Originally published: http://sound.westhost.com/project58.htm
Siegfried Linkwitz, Shaped Tone-Burst Testing, JAES, Vol. 28,  No. 4, April 1980

http://sound.westhost.com/project93.htm

[Church-Audio]

Not sure if this is fair to call this "your mod" - I think this info was bandied about USENET back in the day...

Originally published: http://sound.westhost.com/project58.htm
Siegfried Linkwitz, Shaped Tone-Burst Testing, JAES, Vol. 28,  No. 4, April 1980

http://sound.westhost.com/project93.htm

That's actually not my mod... This shows a two wire capsule that is converted to three wire. My mod converts a three wire capsule to two wire and gives you the same performance as this mod except my mod is backwards to this one. And for the record I have never seen this mod but like most things in electronics. I am sure its been done before, I was the first one to figure out why some AT capsules were distorting. I found a way that is similar to this mod except that my resistor goes from the negative side of the capsule to ground and you only connect the ground side of the resistor + the output of the capsule. So I guess I can say that the 4.7k mod I do is in fact still my mod..


I am not someone that takes other peoples ideas and says they are my own. To my knowledge no one has done a mod exactly like the one I have done.. Linkwitz actually ended up with a better mod then the original one shown here. But its much more complicated then my mod.



If you take a three wire capsule and take the Negative side of the capsule connect it to ground then take the ground side and connect it to audio ground and the positive side for output you have done my mod. The problem has always been that 2 wire mics always distort, when I started building mics I needed a way to use the cheaper cable lol because I could not afford mogami. I needed a mod that would work on two wires so that's why I came up with it.. I wanted to not have to use three wire mics with three wire battery boxes but still get three wire performance.. No big mystery.

What Linkwitz did was convert a two wire capsule into three wires. I wanted to go the other way round. But I did not copy his design I came up with this all by my self. Using a low distortion source @1k @114db and changing resistors until I found the right value that allowed for maximum output and minimum distortion 4.7k happened to be the right choice. I dont understand why I only know that I tried every other value I could and nothing worked better then 4.7k I did not read about linkwitz and copy his idea..




PS.. The mod below is the only 2 wire Linkwitz mod I have ever seen.. And its nothing like my mod.. Even the mod you posted is not exactly like my mod.

Chris

[sjoe]

And for the record I have never seen this mod but like most things in electronics. I am sure its been done before

It has been done before if you consider it in the context of FET amplifier design, which is what this is really about.   (The fact that there's a microphone capsule involved is mostly irrelevant; the important bit is the proper biasing of the FET circuit.)

The "4.7k mod" is a form of common-drain or source-follower circuit.   These things have been around since the 1960's, and the design methodology is very well known and extensively documented.    Here's a couple of links:

http://www.rason.org/Projects/jfetamp/jfetamp.htm

http://www2.eng.cam.ac.uk/~dmh/ptialcd/spice/simulation.htm#SelfBiasJFET

http://ist-socrates.berkeley.edu/~phylabs/bsc/PDFFiles/bsc5.pdf

There's several very interesting bits of information in there, including the explanation for the decrease in distortion, and a possible work-around for the loss of gain.

Joe

[Roving Sign]

And for the record I have never seen this mod but like most things in electronics. I am sure its been done before

It has been done before if you consider it in the context of FET amplifier design, which is what this is really about.   (The fact that there's a microphone capsule involved is mostly irrelevant; the important bit is the proper biasing of the FET circuit.)

The "4.7k mod" is a form of common-drain or source-follower circuit.   These things have been around since the 1960's, and the design methodology is very well known and extensively documented.    Here's a couple of links:

http://www.rason.org/Projects/jfetamp/jfetamp.htm

http://www2.eng.cam.ac.uk/~dmh/ptialcd/spice/simulation.htm#SelfBiasJFET

http://ist-socrates.berkeley.edu/~phylabs/bsc/PDFFiles/bsc5.pdf

There's several very interesting bits of information in there, including the explanation for the decrease in distortion, and a possible work-around for the loss of gain.

Joe

Ahhh - thats a good explanation. I suspected the theory in play wasn't a secret. (although I leave it to the experts to determine if your info here is relevant)

I'll disagree somewhat here:

The fact that there's a microphone capsule involved is mostly irrelevant

Well it's relevant as to who first applied this theory to a electret microphone. (which is what is being debated) Chris seems to have a solid claim on that aspect.

[kfrinkle]

I had such a pain in the ass time recording high SPL shows (heavy metal stealth taping of course) that I ended up getting a three wire mod with my CMC-8s... Definitely improves the sound.  Seems like many of the mics that SP.com offers really do have this issue (at least going into JB3s and MT 24/96s etc...).  I wish I had known about a fix earlier, so I think it is awesome that a few people on the board do the mods.  It beats sending them back to SP.com where I already explicitly asked them what to get to ensure all worked fine at heavy metal shows.

*sigh*...

[Church-Audio]

And for the record I have never seen this mod but like most things in electronics. I am sure its been done before

It has been done before if you consider it in the context of FET amplifier design, which is what this is really about.   (The fact that there's a microphone capsule involved is mostly irrelevant; the important bit is the proper biasing of the FET circuit.)

The "4.7k mod" is a form of common-drain or source-follower circuit.   These things have been around since the 1960's, and the design methodology is very well known and extensively documented.    Here's a couple of links:

http://www.rason.org/Projects/jfetamp/jfetamp.htm

http://www2.eng.cam.ac.uk/~dmh/ptialcd/spice/simulation.htm#SelfBiasJFET

http://ist-socrates.berkeley.edu/~phylabs/bsc/PDFFiles/bsc5.pdf

There's several very interesting bits of information in there, including the explanation for the decrease in distortion, and a possible work-around for the loss of gain.

Joe

What you say is true, but again I was the first one to use it in a mic capsule... I came up with the value by using a distortion meter and a 1k test tone. And I am the one that figured a workaround for existing microphones. I know that everything in electronics has been done before. But no one to my knowledge has ever applied this to a electret fet on a capsule with a resistor that is 4.7k and I would have to strongly disagree that the context of the applied method has no relevance.. This mod had come about not because of my knowledge of the technique you describe but purely because of experimentation. And there for its still valid that I came up with a method to reduce distortion in electret mics that has not been done before. And one last thing none of the schematics you show actually show my method although there are similarities none of the methods exactly describes my modification. Not that I have come up with some revolutionary electronics theory. But I did come up with a method to reduce distortion in a microphone capsule. I guess there will always be theory's that are close to describing someone else's work that's the part of science that makes things interesting, please show me the circuit on the Internet or anywhere that describes using my method on a mic capsule. You cant because I am the inventor of it. None of your methods are exactly like the mod that I do...

Chris

[GDfan]

patent that mod and get paid for it 

[Church-Audio]

patent that mod and get paid for it 

No that was never my intention.. I only got pissed when another company was doing the mod and charging for it and not giving me proper credit... I also got pissed when a few people were saying I was lying and did not come up with this.. So I defended my self. I never had any intention of making money from this..

[sjoe]

I would have to strongly disagree that the context of the applied method has no relevance..

I'm talking about the FET circuit itself. It doesn't matter that the FET happens to be inside a microphone.  The FET circuit design works the same way regardless of what it's attached to.

This mod had come about not because of my knowledge of the technique you describe but purely because of experimentation.

OK, but it's not magic or voodoo. The links I provided show exactly what is happening with the 4.7k mod.   The addition of that resistor configures the FET into a textbook example of a source-follower circuit, and the standard math and engineering principles that apply to that circuit also apply when the FET is inside a microphone.

There's lots of information out there about what the source-follower circuit does and how it works.  If you're not interested, that's fine but I've seen several technical people discussing this here and maybe one of them can make good use of it.  Consider it my contribution to the research.

none of the schematics you show actually show my method

Look at the very first diagram on the rason.org site. That's exactly what the 4.7k mod does, it would be R2 in that schematic.

If it helps you to visualize things, pretend that .1uf cap on the input is the microphone's diaphragm.  R1 and the 4.7uf output cap are the standard battery box components.

Joe

[Church-Audio]

I would have to strongly disagree that the context of the applied method has no relevance..

I'm talking about the FET circuit itself. It doesn't matter that the FET happens to be inside a microphone.  The FET circuit design works the same way regardless of what it's attached to.

This mod had come about not because of my knowledge of the technique you describe but purely because of experimentation.

OK, but it's not magic or voodoo. The links I provided show exactly what is happening with the 4.7k mod.   The addition of that resistor configures the FET into a textbook example of a source-follower circuit, and the standard math and engineering principles that apply to that circuit also apply when the FET is inside a microphone.

There's lots of information out there about what the source-follower circuit does and how it works.  If you're not interested, that's fine but I've seen several technical people discussing this here and maybe one of them can make good use of it.  Consider it my contribution to the research.

none of the schematics you show actually show my method

Look at the very first diagram on the rason.org site. That's exactly what the 4.7k mod does, it would be R2 in that schematic.

If it helps you to visualize things, pretend that .1uf cap on the input is the microphone's diaphragm.  R1 and the 4.7uf output cap are the standard battery box components.

Joe

I dont think I ever used the word "voodoo" to describe my mod actually just the opposite. Like I said before there is no such thing as a simple electronic circuit that has not been done before in one way or another. I simply was the first one to use it to convert 3 wire mics into high performance 2 wire mics. Many companies were selling these 3 wire mics with out doing very basic distortion measurements to see if the mics there were selling were actually in spec. I was one of the first to measure some of the more popular stealth mics and determined that they did overload when used in 2 wire and I was the first to find a solution to that problem. I did not want to put a product out that distorted. So I experimented and came up with my 4.7k mod.

[SparkE!]

What the 4.7k mod Chris does is electrically identical to the 2-wire Linkwitz mod, except that the drain and source connections are reversed.  The type of JFETs that are used in these mics are sufficiently symmetrical to allow to swap the source and drain connections (which is what the 2-wire Linkwitz mod does) and still get substantially the same performance.  So yes, Chris's mod produces substantially the same results as making the 2-wire Linkwitz mod.  It's just an easier way of accomplishing nearly the same thing.  Personally, I prefer the 3-wire Linkwitz mod because it uses the JFET in the polarity that its manufacturer specified, it attenuates the signal less than Chris's mod and I sometimes use the mics going straight to a NJB3 where I can't afford the additional loss in signal amplitude.

The thing that people aren't talking about here is that most battery boxes have their own pull-up resistor.  If you want to be compatible with a conventional battery box, then you can't use a 2 wire Linkwitz modded capsule because the battery would be in the wrong polarity.  And of course you can't use the 3 wire Linkwitz mod with a conventional battery box because a conventional battery box is wired for 2 wire connections, not 3.  That's where Chris's mod shines.  It uses a conventional battery box, it maintains the correct polarity of current flow through the transistor, but it incurs an additional 6 dB of signal attenuation with respect to the 3 wire Linkwitz mod.  To me, that's a small price to pay for compatibility with your conventional battery box.  Not only that, but if your conventional battery box uses a 4.7k pullup (and most do), then Chris's mod minimizes the harmonic distortion.  In fact, it should have harmonic distortion that is a little bit better than the 3 wire Linkwitz mod.  The price for the lower distortion is a very slight increase in noise floor.  (It's pretty common in electronic circuits to be able to trade noise performance for harmonic distortion or vice versa.)  In the case of loud source material like you have at most live music venues, the increase in noise floor is imperceptible and therefore, of no consequence.  For reference, here are the 2 and 3 wire Linkwitz mods as shown on the page referenced by Roving Sign previously in this thread:

[sjoe]

if your conventional battery box uses a 4.7k pullup (and most do), then Chris's mod minimizes the harmonic distortion.

I'm fairly certain the boxes sold by SP use 10K resistors.   (The one I bought many years ago did, at least.)  If that's the case, is 4.7k still the optimum value for the source resistor?

How about running the mics straight into an R-09 without a battery box?   I've done this so I know it works, but the same question applies.    Can we measure the open circuit voltage and short circuit current at the R-09 mic jack to determine the effective value of the internal pullup?   Or does the R-09 use some kind of current source circuit?   I don't have an R-09 service manual yet, so I can't tell.   If it turns out that the R-09 uses a 2.2k pullup (for example), what happens to the source resistor value?   Do we still want 4.7k there?

Last but not least, does anyone know the types or part numbers of the FETs used in these microphones?  It seems to me that the circuit design would be a lot better/easier if we knew the actual characteristics of the devices.

Joe

[SparkE!]

if your conventional battery box uses a 4.7k pullup (and most do), then Chris's mod minimizes the harmonic distortion.

Last but not least, does anyone know the types or part numbers of the FETs used in these microphones?  It seems to me that the circuit design would be a lot better/easier if we knew the actual characteristics of the devices.

Joe

For Panasonic WM 61 capsules, it's reputed to be 2SK3372 (a Panasonic part number - surprise, surprise)

As far as what is the best resistor, it varies by mic element, by bias voltage and by battery box resistor, but in most cases it's going to be 4.7k. Of the common values, Chris really did pick the right one.