AKG experts

[soundguy]

does anyone know if the pin and power requirements are similar for an AKG c28 and a C60? I have a power supply that was built for a C28, wondering if I can use it with a C60 without causing the puff of smoke...

thanks

dave

 

[edanderson]

well, the c28 uses a 7586 nuvistor which gets 120v on the plate supply, and the c60 uses an ac701k which wants 100v. so it probably isn't a good idea. i don't know what the maximum rating on the ac701k is, but going 20% over seems unsafe. also, i think the filament supplies are different too.

ed

ps- the akg site has most of the datasheets for their old mics archived. it used to be a seperate site, but i know i saw the listing in there somewhere.

 

[Marik]

There were 3 versions of C28--A, B, and C. While A and B used 6072 tubes, the C had 7586 Nuvistor. The 6072 tube is a 6.3 filament, and 7586 is a 5V filament. The AC701 needs 4V. You would be able modify your filament supply to get those 4V. Also, you can drop B+ to 100V with a single resistor.

 

[soundguy]

thanks guys! Im pretty sure my c28 has a 6072, doesnt sound like these supplies are interchangable at all.

thanks again

dave

 

[dukasound]

[quote author="soundguy"]thanks guys! Im pretty sure my c28 has a 6072, doesnt sound like these supplies are interchangable at all.

thanks again

dave[/quote]

Dave C28 with 6072 use same PSU like C12 - N12 -120VDC and 6,3VDC

 

[Rob Flinn]

It is easy to build a PSU for the C60, which is what I did for mine. If you speak to Brian Sowter he even does replacement mains transformer for the supply (not on the website), though it isn`t cheap.
I made the HT circuit the same as the original but used an LM317 for the heater so I could dial up 4v.


I must say I love the sound of this mic more than my C451`s

 

[Gus]

Maybe the Royer supply with a LM317 for the heater.

 

[Marik]

[quote author="soundguy"]thanks guys! Im pretty sure my c28 has a 6072, doesnt sound like these supplies are interchangable at all.

thanks again

dave[/quote]

In fact, AKG made a N6128 supply, which could feed C12, C12A, C28 and C60 mics. It had a switch for different filament voltages. The B+ remained the same. The biggest problem with DIY is that it has a very expensive weird connector, which is different from the mic one. Of course, you could accomodate 5 pin XLR there, and change cable end.
Whatever you do remember that AC701 is very sensitive to filament voltages. It should be dead 4V.

 

[zebra50]

An idea: for safety, you could use a 6 pin XLR with the two filament voltages on separate pins. Leave the inappropriate connector unconnected at the cable side. This should prevent accidentally leaving the switch on the wrong setting and frying something.

 

[Guest]

[quote author="soundguy"] AKG experts[/quote]

AKG experts ? now ?

Rudolf Goerike is dead for a long time.

xvlk

 

[Marik]

[quote author="xvlk"][quote author="soundguy"] AKG experts[/quote]

AKG experts ? now ?

Rudolf Goerike is dead for a long time.

xvlk[/quote]

??????

Sure thing, only him would know if C28 PSU good for C60...

 

[soundguy]

I havent been able to get a good sound out of my strat since jimi hendrix died, who knew...

dave

 

[lictme]

In fact, AKG made a N6128 supply, which could feed C12, C12A, C28 and C60 mics. It had a switch for different filament voltages. The B+ remained the same. The biggest problem with DIY is that it has a very expensive weird connector, which is different from the mic one. Of course, you could accomodate 5 pin XLR there, and change cable end.
Whatever you do remember that AC701 is very sensitive to filament voltages. It should be dead 4V.

Marik just worked on two 6128s for me (and, did a damn fine job!). I thought the connectors we're "after-market" because they looked so alien...staring at the back right now, you should be able to replace one of the conns with an xlr without an issue.

-james

 

[volki]

anyone have the schematic for the c28 versions?

btw, if anyone's still interested, abs. max voltage for ac701 is 120v.

 

[JLM Audio]

The C28A is exactly the same circuit as the C12 but with only a two plate mic element so the electronics for all the pattern switching is left off. C451 elements screw straight on so pattern changing is possible this way. Most AKG valve mics have a single transistor constant current circuit so only one resistor R1 on the C60 needs to be trimmed to bring the 105mA to 150mA for the C28A. Constant current is used so different cable lengths not affect the voltage at the tube filament in the microphone.
BUT as much as the C60 power supply could run the C28 easily a custom cable would have to be made to get the power pins to line up and also the balanced output would have to be split from the cable before the power supply as the C60 has its output transformer remote in the power supply unit. My C28A runs on a modified Neumann U67 power supply so anything is possible with a few changes.

C60 circuit can be found here

http://www.geocities.com/SiliconValley/Peaks/5212/c60_1.pdf

C28A circuit can be found here

http://www.jlmaudio.com/C28A circuit.gif

Joe

Expert pronounced x-spurt can be broken down into
X which is an unknown quantity
and Spurt which is a drip under pressure

 

[Kev]

:green:

thanks Joe
love ya work

 

[Rob Flinn]

btw, if anyone's still interested, abs. max voltage for ac701 is 120v.

I read this on the data sheet for the AC701 as maximum Ua =120v, but above that it says max Uao = 250v. So the question is what is Uao ?

 

[soundguy]

The power supplies I have for my c60's have jensens in them and as a result, I might have the best sounding c60's on earth. I dont use them too much though, and I was trying to figure out a way to bypass the ouptut transformer in the c28 to use the jensens in the c60 supply. Perhaps it would be easier to just swap the c28 transformer and keeep things simple... Is there anything available that would fit in place of the c28 transformer? Figured Id ask, but seems like a small transformer to be a commonly available thing.

Joe, have you ever tried a blue lollipop capsule with your C28? I havent used my c28 capsule since I got the BLUE add on, its pretty amazing. Id reccomend anyone with a c28 to try one out, they arent prohibitively expensive, $450 from blue, its one of my favorite mics with that capsule. I think with a different output transformer on the mic though, it could be absolutely huge.

dave

 

[Gus]

Dave

I would ask Oliver at Tab-funkenwerk

 

[Marik]

[quote author="soundguy"]The power supplies I have for my c60's have jensens in them and as a result, I might have the best sounding c60's on earth. I dont use them too much though, and I was trying to figure out a way to bypass the ouptut transformer in the c28 to use the jensens in the c60 supply. [/quote]

The C60 is a cathode follower, and C28 anode follower, and have very different impedances, so your Jensen (which model?) most likely has a different ratio, which would not be suitable for C28. Also, if you bypass your trafo in C28, you will be running pretty long cable from anode. The impedance of the 6072 is about 25K, IIRC, and it can screw up frequency response, putting the trafo in PSU.
Interesting thing, to make the CF sound its best, Radiotron insists that the ratio should be as high, as for anode follower. I never tried it with mics, but could definitely hear an improvement in my CF output power amplifier.

Perhaps it would be easier to just swap the c28 transformer and keeep things simple... Is there anything available that would fit in place of the c28 transformer? Figured Id ask, but seems like a small transformer to be a commonly available thing.

You could look at LL1636 Lundahl, wired as 1:10 (check if it fits), or, as Gus's suggested, contact Oliver.