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12AX7 for a mic preamp - confused by tubes

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Hi all,


I have a Behringer MIC100 that uses a 12AX7. It's supposedly for warmth, but realistically it doesn't seem overly tubey at all. It's standard starved-plate, low-voltage, there-for-marketing-purposes kind of job. Anyway, said tube has now started to fail. It goes all quiet at times and is very distorted. So I need a new tube! Now, I'd never bother tube rolling with this thing, it's not like it's a vintage SVT, but at the same time it would be silly to waste my time putting the 'wrong' tube in. I know that they sound different, have different distortion and outputs, some have more or less bass, etc etc.


What's a good tube for this DI box, being used only on bass guitar, for less than £20?


I can get a new preamp for £25 and they're much less than that second hand so there's no point putting a £250 tube in it. Having said that, I appreciate that there may be some sonic gains to a nicer tube. I have to get this thing back working again and I'd prefer to spend the £20 on a new tube rather than a new di box. It just seems less wasteful!

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Any 12AX7 would work in there, Watford Valves has an extensive range with very thorough descriptions of the sound of the different tubes. It’s certainly worth a browse of their website if nothing else. 

Also bear in mind that Behringer kit is built to budget, so by putting an upgraded tube in there will probably improve the sound noticeably.

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Not forgetting that the 12AX7 is the American designation, the ECC83 is exactly the same valve.

I'd agree with bert's recommendation of the JJ ECC83.

From what I've learned, it would seem that the 12AX7/ECC83 valves that were placed in pre-amp's were there solely for their qualities when overdriven, rather than for "warming" the sound. Overdriven pre-amp valves tend to sound too "spikey" when driven, rather than the smoother distortion achieved from driving a valve power-amp stage.

A non-valve pre-amp should be able to be made a bit warmer, just don't "push it into the red".

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