Difference in sound between a AC701k and 6072A in a ELA M251?

[Double G]

I've been doing some more research and from what I've found the 251 had both the shallow dish and the deep dish CK12s. Mid-1960 seems to be when the deep dish started to get used. The 251 I compared the 414 EB to, should have the deep dish because it is from 1961.

https://gearspace.com/board/showthread.php?p=14012532

Also, I haven't found any indication that AKG used the shallow dish CK12 in any of their later microphone models after the 251.

So, unless the 251 was made pre mid-1960 and sold in 1961, both it and the 414 EB should have the deep dish version of the capsule.

EDIT: The 251 in those two shootouts are the modern reissue by Telefunken USA. If it is from the early 2000s it might have an original CK12 in it, otherwise it would be a recreation.

 

[Accelerator]

@Double G​

I've been doing some more research and from what I've found the 251 had both the shallow dish and the deep dish CK12s. Mid-1960 seems to be when the deep dish started to get used. The 251 I compared the 414 EB to, should have the deep dish because it is from 1961.

https://gearspace.com/board/showthread.php?p=14012532

Also, I haven't found any indication that AKG used the shallow dish CK12 in any of their later microphone models after the 251.

So, unless the 251 was made pre mid-1960 and sold in 1961, both it and the 414 EB should have the deep dish version of the capsule.

Nope…

All the AKG-Telefunken ELA-M 250 & AKG-Telefunken ELA-M 251 (E and non E) microphones had the CK-12 Deep Dish Capsule and T14/1 Output Transformer…

As you can see by the attached schematic all of these ELA-M’s (E and non E) were “officially” dated at 1961…

The AKG – Siemens SM 204/3 was a Cathode Bias microphone like the AKG-Telefunken ELA-M 250 & AKG-Telefunken ELA-M 251 (E and non E) microphones, but from the other hand it has the CK-12 Flat-Shallow Dish Capsule and the Rohde & Schwarz V-2545 Output Transformer…

Also the AKG – Siemens SM 204/3 had a different circuit than the AKG-Telefunken ELA-M 250 & AKG-Telefunken ELA-M 251 (E and non E) microphones had and it is more “close to” an AKG C-24 Stereo Microphone circuit or to a C-12 Microphone System circuit…

Your AKG 414 EB microphone although it was produced back at 1976, it had by designer’s choice the CK-12 Flat-Shallow Dish Capsule, because back in this time at the AKG AG they tried to re-produced the “vintage vibe” of the 50’s C-12 Microphone System, but this time used FETs…

If you want like it to see it in a synth "analogy", it was something like the Moog Voyager monosynth, as the Moog Co. tried to replicated with the Voyager the sound of the legendary Moog Minimoog with more modern features…

Now as I wrote you before if someone’s like to have a more extended range of the low end in the AKG-Telefunken ELA-M 250E & AKG-Telefunken ELA-M 251E circuits and in the AKG – Siemens SM 204/3 circuit with a 6072A / 12AY7 tube, he can easily use 2 Signal / Rectifier Diodes (0.6 Volts), wired them in Series and use them as Cathode bias element in the place of the 1k8 Cathode Resistor…

He can either use a ECC81 / 12AT7 tube with a 2k7 Cathode Resistor or just a Red LED (1,6 Volt) as Cathode bias element in the place of the 2k7 Cathode Resistor and then he will get again more extended range in the low end with the ECC81 / 12AT7 tube…

In a more “advanced way” he can either wired the ECC81 / 12AT7 tube “en parallèle” and then he can use just a White LED (1 volt) as Cathode bias element…

As you can see as DIY’er there are many more “tricks and tips” that someone’s can do today, than they couldn’t have been done by AKG AG, back in the times of ‘50’s and ‘60’s…

EDIT: The 251 in those two shootouts are the modern reissue by Telefunken USA. If it is from the early 2000s it might have an original CK12 in it, otherwise it would be a recreation.

Nope again…

The Telefunken Elektroakoustic USA ELA-M 251E microphone(s) HAVE NOT any original AKG AG “Brass” CK-12 capsule in them, as they nether they had or have…

Since they haven’t (as Telefunken Elektroakoustic USA) reviled who is the original manufacturer of the capsule, it may be a Chinese one…

 

[tomas.borgstrom]

I just have to “correct” you that the AKG-Telefunken ELA-M 250 and the AKG-Telefunken ELA-M 251 microphones were with the AC701(k) tube…

The AKG-Telefunken ELA-M 251E microphone, in which the E means Export, was with the 6072A / 12AY7 tube…

I already know this. I'm trying to keep my posts short.

 

[ricardo]

You don't need the AC701 to have a better tube than the 12AY7. For a new build or a diy mic, try a EF86 or similar pentode. I prefer the C12 or U67 bias instead of cathode bias of the 251

Are you using the EF86 triode connected? Pls show us your pentode circuit for LN

If pentode connected common cathode (like 251 & C12 etc), sensitivity would be VERY high ... but also rather distorted and noisier.

 

[Accelerator]

@ricardo​

Probable LevinGuitar «typically» means by his point the extra ordinary “pentode wired as triode” mod. as he points out that he’s like the Neumann U-67 grid-leak bias, but it is good here to be said that the EF86 tube in “pentode wired as triode” mod. can be biased ever as fixed-adjustable bias (Cathedral Pipes Notre Dame Tube Condenser Microphone) or as grid-leak bias (Neumann U-67 Tube Condenser Microphone) or even as cathode bias (Microtech Gefell M-92.1-S, Microtech Gefell UM-92.1-S, Microtech Gefell UM-75 Multi-pattern Tube Condenser Microphone).

 

[rock soderstrom]

The Neumann U67 is not "grid leak biased", the negative bias voltage is obtained from the (also negative) heater voltage. For me, this is a classic "fixed bias" of the EF86.

 

[rock soderstrom]

Are you using the EF86 triode connected? Pls show us your pentode circuit for LN

If pentode connected common cathode (like 251 & C12 etc), sensitivity would be VERY high ... but also rather distorted and noisier.

Absolutely correct, true pentodes are not well suited for this position due to their characteristics.

But I am pretty sure that member @LevinGuitar knows this too, as he has already built several Mics. He will mean pentodes wired as triodes...

 

[LevinGuitar]

Right! Pentode wired as a triode in U67 or G7 mics, nothing new.

I have compared AC701, 6072, EF86 and more tubes in the same mic (SP T3) and the EF86 did sound a little "bigger", more in your face, but also a bit brighter. The 701 seemed more flatter, a really nice even for the 797 k67. The GE 6072 did not sound as good as the previous ones (to my ears). Maybe with a good ck12 things would be different.

 

[tomas.borgstrom]

Right! Pentode wired as a triode in U67 or G7 mics, nothing new.

I have compared AC701, 6072, EF86 and more tubes in the same mic (SP T3) and the EF86 did sound a little "bigger", more in your face, but also a bit brighter. The 701 seemed more flatter, a really nice even for the 797 k67. The GE 6072 did not sound as good as the previous ones (to my ears). Maybe with a good ck12 things would be different.

It's important to mention when swapping tubes in the same microphone that you can get different results in another circuit. Besides optimizing the bias of every tube, the match with the capsule and transformer is a determining factor.

If you wan't a reliable pretty cheap tube EF86 is a great choice. A NOS Valvo, Telefunken or another Western Europe tube is well worth the extra cost. You don't need to aim for an EF806S.

I think many high quality NOS 12AT7 sound just as good or better than GE6072. All the RCA 6072 I've tried (at least 15) have been way too noisy.

 

[LevinGuitar]

Besides B and H voltage differences, both EF86 and AC701 have been succesfully used in a same mic, matching capsule, transformer, and rest of the circuit in M269/U67. The bias voltage (and type) was a bit different in 269 vs 269C, right.

 

[ricardo]

anyone got views about the MG method for 'triode connection' with G2 & G3 together ... vs the more usual method used by Neumann with G3 connected to cathode.

see Accelerator's
https://groupdiy.com/threads/differ...1k-and-6072a-in-a-ela-m251.88876/post-1172311

IIRC, EF86 triode connected, usual method, has characteristics very similar to ECC83 or maybe 82

 

[Accelerator]

@ricardo​

anyone got views about the MG method for 'triode connection' with G2 & G3 together ... vs the more usual method used by Neumann with G3 connected to cathode.

Just to set something clear and straight about the “pentodes wired as triodes”, I have to tell you that Georg Neumann had used both of these topologies…

In the Neumann U-47 & U-48 microphones as you can see he wired G2 & G3 together with the anode of the VF14 tube…

In the Neumann U-67 microphone more typically he wired G2 with the Anode & G3 with the Cathode of the EF86 tube……

Don’t forget that the Microtech Gefell AG were and are the original Georg Neumann’s colleagues in the original Georg Neumann’s factory at Gefell, they had a physical bond with him ‘till 1958 and they always honorable referred to him as their ex-leader.

The Neumann - Gefell CMV563 and the Neumann - Gefell UM57 microphones were co-operation between Georg Neumann with his ex-colleagues at Gefell…

And as you can see for the Neumann - Gefell CMV563 and the Neumann - Gefell UM57 microphones, they had choose the EC92 tube, which is the “little – half brother” of the “double brother” ECC81 – 12AT7 tube…

IIRC, EF86 triode connected, usual method, has characteristics very similar to ECC83 or maybe 82

When you connect the EF86 – EF806 tube in the typical “pentodes wired as triodes” topology (G2 with the Anode & G3 with the Cathode of the EF86 – EF806 tube) it has Ra = 16K and μ factor = 34, but the EF86 – EF806 tube characteristics as "triode" has nothing to do with the other typically triodes characteristics, as the grid lines are very “isometric”…

 

[Accelerator]

@tomas.borgstrom​

Besides optimizing the bias of every tube, the match with the capsule and transformer is a determining factor.

I Diddo with you to this point!...

For me the “optimal” output transformer that “match” pretty close the 6072A – 12AY7 tube (if you wired it “en parallèle”…) or the EF86 tube in a “pentodes wired as triodes” topology (G2 with the Anode & G3 with the Cathode of the EF86 – EF806 tube) is a Moby Transformers ~ V2545 (C12, SM204) Ratio: 12,3-1 or the CineMag CM-9766 Microphone Output Transformer Ratio 12-1

The Moby Transformers ~ T14/1 (C12, ELA M 251) Ratio: 11,5:1 or the CineMag CM-2480 Microphone Output Transformer Ratio 10.5-1 makes “match” better with the ECC81 – 12AT7 tube or any other tube which have lower Ra…

 

[Accelerator]

Just for fun but also quite interested as all of these deferent companies and factories use deferent capsules, deferent tube wired topologies, deferent components, deferent output transformers etc, etc, etc. for their microphones

VK Shootout: ELA M 251-Style Microphones

 

[tomas.borgstrom]

Besides B and H voltage differences, both EF86 and AC701 have been succesfully used in a same mic, matching capsule, transformer, and rest of the circuit in M269/U67. The bias voltage (and type) was a bit different in 269 vs 269C, right.

The bias type is different but the voltage is the same. It's the difference between the grid and the cathode that counts. In m269 you have 2,4V on the grid and 4V on the cathode, 2,4 - 4 = -1,6V. In m269c you have 0V on the grid and 1,6V on the cathode 0 - 1,6 = -1,6V. Both result in a current of 0,55mA on the anode.

In the schematics of m49b, m50b, they have placed the arrow between the grid and cathode and hence 1,6V instead of 2,4. This makes more sense.

 

[tomas.borgstrom]

Just for fun but also quite interested as all of these deferent companies and factories use deferent capsules, deferent tube wired topologies, deferent components, deferent output transformers etc, etc, etc. for their microphones

I find this really disturbing. Some of these make enormous amounts of money.

The local music shop in my town told me that WA47 is one of their best sellers. I wish the buyers knew what they are paying for.

This is from the WA site: "The WA-47 is an authentic reproduction of the most coveted tube condenser microphone, hailed for its timeless studio sound."

I don't find a double triode cathode follower circuit (Apex 460) to be an authentic reproduction of the U47 design.

Would anyone accept a "truthful recreation/authentic reproduction" of a 1073 with a blue faceplate, Marconi knobs and a bunch of ICs inside?

 

[Accelerator]

@tomas.borgstrom​

I find this really disturbing. Some of these make enormous amounts of money.

The local music shop in my town told me that WA47 is one of their best sellers. I wish the buyers knew what they are paying for.

This is from the WA site: "The WA-47 is an authentic reproduction of the most coveted tube condenser microphone, hailed for its timeless studio sound."

I don't find a double triode cathode follower circuit (Apex 460) to be an authentic reproduction of the U47 design.

Unfortunally, this is the all American Liberal Capitalism, comrade…

“The poor stay poor, the rich get rich” as Leonard Cohen sang in his “Everybody knows” song back in time…

I agree with you that the hilarious B.S. from the WA site:

"The WA-47 is an authentic reproduction of the most coveted tube condenser microphone, hailed for its timeless studio sound."

It is just a laughing joke for me and for you and for everybody out there who knows that the WA47 is a double triode cathode follower circuit (Apex 460) and it is “presented” to be an authentic reproduction of the U47 design.

But from the other hand the hilariously fake “Telefunken Electroakoustic USA” VF14(k) "Made in USA" tube in their hilarious overpriced and overrated “Telefunken Electroakoustic USA” U-47 it is also a hilariously overpriced and overrated B.S., a laughing joke for me and for you and for everybody out there who knows that there aren’t any real VF-14 or EF-14 tubes in our new days current production…

Would anyone accept a "truthful recreation/authentic reproduction" of a 1073 with a blue faceplate, Marconi knobs and a bunch of ICs inside?

If someone’s “on the budget” for a "truthful recreation/authentic reproduction" of a 1073 with a blue faceplate, Marconi knobs in reasonable prices now he/she better looks at the Chilean Stam Audio for their 1073MP- 2-Channel Microphone Preamplifier or for the 1073EQ+ – Microphone Preamplifier & Equalizer …

 

[terry setter]

Does anybody know what tube Telefunken Electroakoustic put inside its VF-14K?

Many years ago I put a real VF-14 up for sale on Ebay and Telefunken Electroakousic bought it within minutes. Somebody got a mic from them with a real one in it!

 

[rock soderstrom]

Does anybody know what tube Telefunken Electroakoustic put inside its VF-14K?

Many years ago I put a real VF-14 up for sale on Ebay and Telefunken Electroakousic bought it within minutes. Somebody got a mic from them with a real one in it!

I don't know it but according to this measurements it could be 407a or similar, a 40V heater version of the 5670/2C51 family.

https://gearspace.com/board/high-end/1327253-vf14k-voltages.html

http://recordinghacks.com/microphones/tag/vf14k?m=0

Just a guess into the blue, but this tube and their 6.3V heater siblings a really interesting valves for mics. I am testing one at the moment in a non U47 project. Member @Thor gave me that advice for a 6.3V CF mic. During my testing I found this version and had the idea to use it as "drop in" replacement in a U47. What do you think?

Edit: attached the data sheet and photo.

 

[tomas.borgstrom]

408a with some resistors can be used as a drop in for VF14. I’ve done that in some original U47 with a bad VF14. It’s a good sounding tube but often noisy. I find that lowering the plate resistor makes it sound fuller.