VO-BB - 20 YEARS OLD!

[Bill Roberts]

Who has $ 8,000.00 dollars for a microphone? I have decided to add a Tube Mic to keep my lonley Sennheiser 416 company, a brand new Apex 460 ($ 249.00 Retail) into something that "Pimped Out" gets rave reviews all over the internet. Dozens of professional Microphone Modders/Builders use several different versions of the Apex 460, and change out the parts (additional $ 200.00 – 600.00 Retail) to more resemble the classic C12. Keep in mind that this is a TUBE Microphone, and the power supply voltages can KILL you if you do not know what you are doing when making internal changes to the power supply in addition to the Microphone.

While looking to find a large diaphragm microphone, I was looking at the TeleFunken R-T-F m16 that retails for $ 1700.00 dollars and it is said to sound close to a C12. While researching this mic, I found out that Telefunken did nothing more than re-label the Apex 460 and put the high price tag on it. As the http://recordinghacks.com/microphones/Apex-Electronics/460 Artical about Apex 460 article indicates TeleFunken decided to change it's “Bad” to the TeleFunken R-T-F m16 MKii by doing a few factory Pimp Mods!. The microphone was basicly replace by the "Copperhead" to remove the bad taste from the entire issue!

http://recordinghacks.com/microphones/Apex-Electronics/460

Armed with an awesome Hako Soldering Iron, and the willingness to risk destroying a brand new microphone, I decided to proceed. Ordering parts is about the most frustrating part of the project due to the fact that you buy a $ 1.69 capacitor and pay $ 4.95 shipping, it seems that you can go broke on all the parts, because the vendors don't have all the parts needed.

The following is the design that I will follow, I have changes about 50 percent as I test-and-go, this is the safe way to make the changes. After each couple changes, I re-assemble the microphone to make sure it's working, as well as listen to the little changes that happen with each new part.
I expect that it will take 3-5 hours for the project.

Changed Capsule to RK-12 (C12 Type Clone)
Changed C3 to 4700pf Mica capacitors
Change C5 to 4700pf Mica capacitors
Change C4 to 1000p Polystyrene capacitor
Change C6 to 47uf Nichion electrolytic audio cap
Change R7 to 1.8K ohm
Change C8 to 1uf 250V Metal Film capacitor of Audio Quality
Changed Transformer to Cinemag CM-2480
Removed R1 - Installed Jumper in it's place
Removed 2 layers of wire Mesh inside basket
Installed a GE 6072a Military Tube.
Black Crinkle Painted the body
Cinemag - Old (Switch wire diagram)
Red - Red
Brown - White
Orange - Black
Yellow - Green



You can see the power supply in the back on top of the mBox!
Notice the capsual throught the mesh screen, this is after removing the 2 layers of wire mesh. You must have a good pop screen, I use a double mesh Blue pop screen.

This is an adventure in progress, as I will get the Capsule tomorrow. At this point the microphone would match up with the Telefunken R-T-F m16 MKii without the Capsule, and will sound even better with the RK-12 Capsule.

Total cost for Microphone and all parts: $ 476.70

I have enjoyed building this project so much, even thinking about building and selling on eBay.
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VO-BB Member # 764 (Dec 2009)

[Frank F]

Good move.

I did the mod on an Avantone CV-12 and two APEX 460's (taking time and a little extra work to make a stereo pair). The results sound delicious.

Here is what I have done to the microphones:

1. Removed C9 and C10 to remove the 25Khz peak resonance in the high end.

2. Changed the caps in the signal path: Polystyrene input and 1uF polypropylene output (C

3. Changed the tube to a 6072.

4. Added a tiny EQ cap like that found in the ELA m251 design, between the Anode pin of the 1st stage tube and ground. (I like 200 pF capacitor, but it depends on your capsule, sometimes 330pF is a better sound)

5. Changed the cathode bypass cap from 100uF to 22uF to reduce low frequency rumble and distortion.

6. Changed the cathode bias resistor to 1.8K to increase plate current.

7. Removed the two inner layers of mesh from the head basket

8. I also added a 220K damping resistor to the output circuit across the transformer primary coil (after the capacitor).

I did not need to change the transformers, but have done so on the Avantone CV-12. With the Avantone I also changed the capsule to an Peluso Microphone Lab CEK-12. The Apex 460's capsules are not great, but not bad.

Compared to my original AKG C12's which were stolen last year, they are really close in sound and not a quarter as expensive. The projects took approximately one and a half hours for each donor microphone.

This mod is not for the faint of heart or beginner modder. You do have to have the right equipment and know how to solder well.

Frank F
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Be thankful for the bad things in life. They opened your eyes to the good things you weren't paying attention to before. email: thevoice@usa.com

[Bill Roberts]

Frank,

Thank you, I forgot to add that GE 6072a Military that I had installed as well. Wish I would have known about these Mic's and Mods long ago. I am going to save up for a real m251 and purchase one someday.

Bill
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VO-BB Member # 764 (Dec 2009)

[georgethetech]

This stuff sounds like a lot of fun...
Now I know what I'll be working on when my kid moves out of the house in 15 years. The only time I get to pull out a soldering iron is to fix a broken toy,
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[heyguido]

Once again, Frank...... Wow.... You, too, Bill.

We are not worthy.
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Don Brookshire
"Wait.... They wanna PAY me for this?"

[todd ellis]

i am to mic mods as lego is to commercial construction.

you two are killin' it. still want to dig deeper and try more one day.
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"i know philip banks": todd ellis
who's/on/1st?

[Ed Gambill]

It appears that you modification is spot on. When it comes to a “real 251” they would be 25 years plus old and about $15,000

There are many compaines selling their version of 251.

I live a little over an hours drive from the Peluso Labs and have visited with John on several occasions. I don’t think profit is his primary motivation for building quality microphones. He is passionate about sound recording. I have seen part of his capsule construction methods, his quality process is solid and his commitment to service is strong. I had one cable on one 22-251 to go bad and he quickly arranged for a warranty replacement.

Years ago John worked in Chicago as a recording engineer doing VO sessions. I have three (3) matched 22-251 that John matched for me. I personally believe for the price point that his 251, C-12 and 47 type microphones are a solid investment.

As for me, with experience in designing transmitters, receivers and amplifiers and then building them, I am at the point of not doing much electronic DIY any more.
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[Frank F]

Bill,

I would have been surprised if you had not changed the tube with all you had done.

I have also pimped out an Rode NT-1A, I am not as impressed with the changes as I thought I would be.

With that in mind I found a set of classic PCB's for a Neumman U87, a donor mic for $75.00, am having SAMAR Audio do the transformer, putting in an M7 capsule, and have created a little better classic EQ circuit. When completed I should have a really classic purple badge U87-ish microphone to replace my old one. Should be fun!

In addition I have designed a Voice Over Line Array Short Shotgun microphone with a wider sweet-spot and less compression through the microphone body tube. Just painted the tube to be a metalized blue... it looks sharp and the prototype sounds incredible.

Frank F
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Be thankful for the bad things in life. They opened your eyes to the good things you weren't paying attention to before. email: thevoice@usa.com

[Monk]

Man this is like porn to me. I have a couple of mic projects in the works presently, some small 6mm electro capsules for recording that I'm trying to find the right circuit for.

but this sounds awesome! Might make a great winter project! Sell kits!

did you record a before so we can hear the after?
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Company, villainous company, hath been the spoil of me...

www.monksvoice.com

[Frank F]

Yes Monk, I have some before and after stuff and will see if I can find them to post.

Gimmee a call and we can chat about your small capsules and the right circuit for them. I can think of some pencil mics you can easily create with those capsules and a piece of 1" aluminum tubing.

Frank F
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Be thankful for the bad things in life. They opened your eyes to the good things you weren't paying attention to before. email: thevoice@usa.com