AKG

[ln76d]

C2000 B Service Manual

 

[ln76d]

C3000 Service Manual

 

[ln76d]

C3000 B Service Manual

 

[ln76d]

C4000 B Service Manual

 

[MS Vienna]

Early C12 brochure showing 1st generation CK12 and different tube.

EDIT: 
During the cold war there were export restrictions of American goods against the Sowjets and it´s allies that became more rigid due to the Korean war. That was at the time the C12 was introduced. So a small number of C12 that were exported to embargoed countries - means no GE 6072 available - were equipped with a 12AU6 tube. It was deemed the second best suitable tube to the GE6072.

The 6072 was found during the development of the C12. It was the BBC who requested an internationally available tube. They received already samples of the AKG C2 and wanted this kind of maintainence improvement for the new model. 
The main customer at the time was the ORF (Austian broadcast) who ordered a microphone that had to be smaller/slimmer than the existing Neumanns and remote controllable with constistent output/frequency response at all patterns (that´s why the CK12 had to be developed). 

 

[Matt Nolan]

Essentially the same tube

 

[panman]

Essentially the same tube

There was a thread about this tube in the pic on another forum some time ago, but I cannot remember if it ever became clear what it is. The pic was the same, but there was no mentioning of what the tube was. Here it is supposed to be 12ay7, but it looks like a rimlock-type tube to me. So I wonder if it really is so? Maybe the mic in the pic is a prototype and the tube something that happened to be tried out at the moment.

 

[Matt Nolan]

Essentially the same tube

There was a thread about this tube in the pic on another forum some time ago, but I cannot remember if it ever became clear what it is. The pic was the same, but there was no mentioning of what the tube was. Here it is supposed to be 12ay7, but it looks like a rimlock-type tube to me. So I wonder if it really is so? Maybe the mic in the pic is a prototype and the tube something that happened to be tried out at the moment.

The picture is pretty pixelated. I didn't spot the funny looking tube base - may be part of the tube or may just be a more elaborate socket. I tried to search for the old thread. It would be interesting to read. No joy. Can anyone else find it?

 

[ln76d]

Prospekt clearly say "eine Röhre 12ay7". Base looks like part of external screen tube socket. Tube internal looks weird but it could be used different tube only for picture.  I would stick to the written word more than the picture.

 

[MS Vienna]

For info on tube please see edit of my earlier post.

 

[mjrippe]

"12AU6 tube. It was deemed the second best suitable tube to the GE6072"

12AU6 is a sharp cutoff pentode with a 7 pin base, 6072 is a dual triode with 9 pins.  They would require a completely different circuit.  Perhaps you meant 12AU7?

 

[panman]

"12AU6 tube. It was deemed the second best suitable tube to the GE6072"

12AU6 is a sharp cutoff pentode with a 7 pin base, 6072 is a dual triode with 9 pins.  They would require a completely different circuit.  Perhaps you meant 12AU7?

Yes, Iremember now, that it turned out to be 12au6 in the earlier thread. I see no problem using this tube. heating 12.6V current 0.15A same as 12ay7. Works as triode too. These are the main things anyway.

 

[ln76d]

Values taken from the real circuit and collected informations.

 

[chefducuisine]

C 3000
Original 1993 version OM including schematic.

 

[Kryss]

Here the schematics of the AKG Perception 800/Project 800/P820 tube mic. It appears the exact same tech is used in the Takstar CM-450 tubemic, most likely a result of the deal AKG made to design and build the mic using chinese manufacturers.
The transformers used in this design aren't standard. I found a factory who made these, but they claimed it was a special ordered batch for a specific customer.

 

[mrclunk]

AKG S42E Remote

 

[mrclunk]

AKG 422

 

[erik_DK]

AKG BX5 reverb

User and service manual with schematics.

/Erik

 

[cyrano]

AKG C3000 service manual:

 

[cyrano]

AKG C3000B service manual: