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AKG SolidTube problem - solved!

Several months ago, I had a conversation with Bos about a mic I own - the AKG Solidtube, and how it was making some noise after it heated up.

The noise was similar to what you would hear if you took a tissue or a paper towel in your hand and scrunched it.

Yesterday, I dug the mic out again, thinking I'd pop the top on the power supply to see if there were any obvious indicators - like blown caps, etc...

I didn't see any issues, so, I decided to take the mic apart. After doing so, I decided that I would replace the tube - I really didn't think it would solve the problem, but I figured that while I had the mic apart I might as well...

So, I took out the stock tube, which was a National 12AX7/ECC83 - and because I didn't have an exact match to replace it with, I ended up using a Mesa 12AT7/ECC81, from a box of spare tubes that I keep around.

I fired the mic up again, let it warm up for about 15 minutes (long past the time the mic would have taken to start making the noise I'd been hearing ) and. silence!
The noise was gone. ;)

I recorded some vocals through it, and found the tonal coloration to be very pleasing.
It was very warm, yet with a very nice upper end edge ( not the bad kind of edge) ... it was a very pleasing "presence" yet still maintaining the warmth... I actually found it to be more appealing than what I'd heard when using the stock 12AX7.

Replacing the tube wasn't at all difficult. Once I found the owner's manual online and read about out how to take the mic apart (just 3 small Phillips screws on the bottom of the mic where the power supply jack is) it took less than 5 minutes to open the mic, replace the tube and then put the mic back together.

I am now wondering what different tubes might sound like; perhaps a Telefunken 12AX7? :)

Yeah, I know... putting a Telefunken tube into my mic won't turn it into a Telefunken mic. ;)

Anyway, just thought I'd share.

:)

Comments

pcrecord Sat, 10/04/2014 - 06:11

Good for you Donny ! Reviving failling gears is always rewarding and good on the budget !

I'm fairly newb on tubes and find it more and more interesting to investigate.
Since I got my used LA610, I'm wandering if I should get a set of new tubes to make sure I start to use it to its maximum potential.
On the other hand, it sound very good like it is !! On UA website, they say a tube will sound the same up to the day it fails. But many people say they loose quality over time. Sorry, I should start a new thread on that instead of hi-jacking yours ;)

I wonder where I got the sickness of wanting to make everything better !!! :)

Eric Apoe Wed, 09/26/2018 - 21:16

DonnyThompson, post: 419940, member: 46114 wrote: Several months ago, I had a conversation with Bos about a mic I own - the AKG Solidtube, and how it was making some noise after it heated up.

The noise was similar to what you would hear if you took a tissue or a paper towel in your hand and scrunched it.

Yesterday, I dug the mic out again, thinking I'd pop the top on the power supply to see if there were any obvious indicators - like blown caps, etc...

I didn't see any issues, so, I decided to take the mic apart. After doing so, I decided that I would replace the tube - I really didn't think it would solve the problem, but I figured that while I had the mic apart I might as well...

So, I took out the stock tube, which was a National 12AX7/ECC83 - and because I didn't have an exact match to replace it with, I ended up using a Mesa 12AT7/ECC81, from a box of spare tubes that I keep around.

I fired the mic up again, let it warm up for about 15 minutes (long past the time the mic would have taken to start making the noise I'd been hearing ) and.... silence!!
The noise was gone. ;)

I recorded some vocals through it, and found the tonal coloration to be very pleasing.
It was very warm, yet with a very nice upper end edge ( not the bad kind of edge) ... it was a very pleasing "presence" yet still maintaining the warmth... I actually found it to be more appealing than what I'd heard when using the stock 12AX7.

Replacing the tube wasn't at all difficult. Once I found the owner's manual online and read about out how to take the mic apart (just 3 small Phillips screws on the bottom of the mic where the power supply jack is) it took less than 5 minutes to open the mic, replace the tube and then put the mic back together.

I am now wondering what different tubes might sound like; perhaps a Telefunken 12AX7? :)

Yeah, I know... putting a Telefunken tube into my mic won't turn it into a Telefunken mic. ;)

Anyway, just thought I'd share.

:)

How do you get the Mic open? Is there a foam that covers the diaphragm?

Eric Apoe Wed, 09/26/2018 - 21:19

DonnyThompson, post: 419940, member: 46114 wrote: Several months ago, I had a conversation with Bos about a mic I own - the AKG Solidtube, and how it was making some noise after it heated up.

The noise was similar to what you would hear if you took a tissue or a paper towel in your hand and scrunched it.

Yesterday, I dug the mic out again, thinking I'd pop the top on the power supply to see if there were any obvious indicators - like blown caps, etc...

I didn't see any issues, so, I decided to take the mic apart. After doing so, I decided that I would replace the tube - I really didn't think it would solve the problem, but I figured that while I had the mic apart I might as well...

So, I took out the stock tube, which was a National 12AX7/ECC83 - and because I didn't have an exact match to replace it with, I ended up using a Mesa 12AT7/ECC81, from a box of spare tubes that I keep around.

I fired the mic up again, let it warm up for about 15 minutes (long past the time the mic would have taken to start making the noise I'd been hearing ) and.... silence!!
The noise was gone. ;)

I recorded some vocals through it, and found the tonal coloration to be very pleasing.
It was very warm, yet with a very nice upper end edge ( not the bad kind of edge) ... it was a very pleasing "presence" yet still maintaining the warmth... I actually found it to be more appealing than what I'd heard when using the stock 12AX7.

Replacing the tube wasn't at all difficult. Once I found the owner's manual online and read about out how to take the mic apart (just 3 small Phillips screws on the bottom of the mic where the power supply jack is) it took less than 5 minutes to open the mic, replace the tube and then put the mic back together.

I am now wondering what different tubes might sound like; perhaps a Telefunken 12AX7? :)

Yeah, I know... putting a Telefunken tube into my mic won't turn it into a Telefunken mic. ;)

Anyway, just thought I'd share.

:)

How do you get the Mic open? Is there a foam covering the diaphragm?

DonnyThompson Thu, 09/27/2018 - 04:48

Eric Apoe, post: 459143, member: 51422 wrote: How do you get the Mic open? Is there a foam covering the diaphragm?

Hi Eric :)
That repair was quite awhile ago... like maybe three years. I ended up selling it around two years ago; so honestly I don’t recall if there was foam over the diaphragm or not... but I don’t think there was; though there was a foam filter that covered the grill of the mic; a big ugly yellow foam condom that slipped over the grill on the outside.
As I recall, the mic had several screws...
Man, I really wish I could help you and remember, I’m not trying to be evasive with you.
I THINK that I stumbled upon a post or a video that helped me to get inside the mic? - I don’t recall that it was difficult, though.
Sorry I can’t be of more help to you... just that there has been a lot of water under the bridge since then; I’ve repaired probably a half dozen other mics since, and they all sorta run together in my memory.
:)
-d.

x

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