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

[Double G]

I recently had the opportunity to compare my C414 EB with an original (untouched, except for some light dusting) brass CK12 to a real AKG made 251.

The studio I've been working out of has the 251. They told me it was maintained by Toby Foster and that he said it is one of the best sounding real 251s he's ever heard.

So of course the 414 was gonna lose. How could anyone expect this little solid state microphone to even compare to a $40000+, holy grail, Big Five legend of the industry? I was certainly not expecting the 414 to measure up.

Well, it did. At worst, they sounded nearly identical. At best, the 414 was subtly but noticeably bigger sounding with a richer low end. I was shocked.

They both went through the same mic cable and through the same exact preamp. I had to adjust the preamp because the 251 was much hotter. I used an iPhone playing a 1khz tone measured 4 inches from the mics to set the levels. It wasn't the most scientific but I at least took some measures.

The 251's capsule is 100% original. Never reskinned. Never disassembled. And it was the first time I can remember ever seeing a CK12 with black paint around the edge. I've seen the white/clear paint and the red.

It also has the 6072A tube in it. I've read that they don't sound as good as the AC701k.

If the 251 had a AC701k would it have beaten the 414? Or did I just happen to get really lucky with the capsule in this mic?

What are the general differences in sound between a AC701k and a 6072A?

 

[thomasdf]

Interesting ! What was the preamp ? And what do you mean by AKG made 251 ? AKG C12 or Telefunken 251 ?

 

[Double G]

Interesting ! What was the preamp ? And what do you mean by AKG made 251 ? AKG C12 or Telefunken 251 ?

The preamp was from one of the channels of an SSL AWS900 console.
It's an original Telefunken 251 which was made by AKG because Telefunken never made microphones. They just sold them and had their logo put on them. The current Telefunken actually makes their 251s.

As a side note, I just discovered that you can find Telefunken branded U67s. I always thought it was just the U47 that got the Telefunken branding.

 

[Accelerator]

@Double G​

I recently had the opportunity to compare my C414 EB with an original (untouched, except for some light dusting) brass CK12 to a real AKG made 251.

The studio I've been working out of has the 251. They told me it was maintained by Toby Foster and that he said it is one of the best sounding real 251s he's ever heard.

So of course the 414 was gonna lose. How could anyone expect this little solid state microphone to even compare to a $40000+, holy grail, Big Five legend of the industry? I was certainly not expecting the 414 to measure up.

Well, it did. At worst, they sounded nearly identical. At best, the 414 was subtly but noticeably bigger sounding with a richer low end. I was shocked.

They both went through the same mic cable and through the same exact preamp. I had to adjust the preamp because the 251 was much hotter. I used an iPhone playing a 1khz tone measured 4 inches from the mics to set the levels. It wasn't the most scientific but I at least took some measures.

Totally un-correctly comparison between apples with oranges…

If you need an correct comparison between your AKG C-414 EB microphone with something “identical” to it in the AKG tube microphone analogy, then you have to compare it with an 50’s AKG C-12 microphone system with the same -all original- 1950’s AKG CK-12 flat-shallow dish capsule and fixed-adjustable bias…

In this case I believe that there is no need to tell you how much $$$$$$$+ you need to pay to get the Holy Grail, Big Two legend of the industry…

The 251's capsule is 100% original. Never reskinned. Never disassembled. And it was the first time I can remember ever seeing a CK12 with black paint around the edge. I've seen the white/clear paint and the red.

Both the AKG-Telefunken ELA-M 251 (non E) microphone (with the AC791k tube) and the AKG-Telefunken ELA-M 251E microphone (with the 6072A - 12AY7 tube) they had the 1960’s AKG CK-12 Deep Dish capsule and they both were Cathode Bias…

It also has the 6072A tube in it. I've read that they don't sound as good as the AC701k.

2 deferent tubes in 2 deferent circuits, with 2 deferent Grid-leak Resistors, 2 deferent Cathode Bias Resistors, 2 deferent Coupling Output Capacitors, so we are speaking about 2 deferent AKG-Telefunken ELA-M 251 tube microphones with deferent “taste”…

So don’t believe any B.S. that you read in the Gearslutz’s High End …

If the 251 had a AC701k would it have beaten the 414?

Before someone is starting to “playing” the “Russian Rullete” with his wallet just to find & get any good and workable AC701k tube out there, he can more easily spend only his 20 cents for buying 2 Signal / Rectifier Diodes (0.6 Volts), wired them in Series and use them as Cathode element in the place of the 1k8 Cathode Resistor…

In this case your C-414 EB would have been beaten by the AKG ELA-M 251E with the 6072A – 12AY7 tube…

Or did I just happen to get really lucky with the capsule in this mic?

You have be really lucky with the capsule in this mic, because the 1950’s AKG CK-12 flat-shallow dish capsule is a favorite capsule…

What are the general differences in sound between a AC701k and a 6072A?

The AC701k tube was a very dedicated (low Ra) tube especially manufactured & crafted for the German – Austrian microphones with low (120 DC Volts) voltage…

The 6072A – 12AY7 tube from the other hand was the general (high Ra) tube for everything –all around- American back in time…

It was the “American king” tube back in time of late '50's - early '60's, from the Fender Tube Guitar Amplifiers to any RCA / General Electric / Tung-Sol / Universal Audio Tube pre-amps…

If you don’t want to be a newbie in all of your life, it will be good to understand that the tubes doesn’t have any “specific” sound on them by their own and it is the whole electronic circuit that makes the general differences in sound between tube A with the tube B…

 

[LevinGuitar]

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