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Changing a tube in a mic pre

Member for

14 years 8 months
I'm curious - is it common to replace tubes in mic pres (before they burn out)? And does it actually make a lick of a difference?


Member for

16 years 3 months

CoyoteTrax Tue, 01/23/2007 - 14:39
Rolling in different tubes always makes a difference. It's like swapping in higher grade opamps or upgrading your capacitors.

But with low budget gear especially you'll notice quite a bit of difference between tubes of the same gain category. When you start lowering the gain factor you'll notice even broader differences.

For instance, the behringer t1953 thingy really kinda sucks right out of the box. The signal's distorted with spitty high end, gritty low end and grainy mids. But roll in a pair of JJ ECC83S's and everything changes; all of a sudden the high's are smooth, mids are a lot more acurate and the lows are so much tighter. All of a sudden you have a tool that's actually useful providing much more of a dimentional quality and a nice clean wide-open pre. Roll a pair of RCA 12AY7's into the unit and you have a very quiet, more focused quality. The list goes on.

Swap out the 12AT7's that come with your presonus box for a nice NOS Philips 12AT7 and you'll find new life, color and excitement with a much smoother response from a cheap little pre that usually just sounds like a cheap, slow, gritty mess. You'll actually be able to hear smooth transients that let you hear the qualities of your live room in the background but the midrange presence will be dense and solid.

Tubes are cheap, take a chance. Have some fun.

Member for

15 years 11 months

RemyRAD Tue, 01/23/2007 - 22:39
Not all tube preamps are created equal.

For instance, a real tube preamp will generally require a minimum +250 volt DC plate supply, for proper operation.

Whereas some imitation tube preamp's run with low or suppressed/starved plate supplies. These tube preamp's are not really using the tubes for any amplification purposes. The real preamp is still an integrated circuit chip. Feeding the signal through a starved plate tube. Doing that will give you plenty of added harmonic distortion, gritty stuff and other peculiar artifacts, in an attempt to mimic a good tube preamp.

And of course, tubes, even if they have the same model numbers, all sound different from one another and so consistency was achieved by semiconductors, a.k.a. transistors and chips.

My world for a VF14. Now if only I had a U47??? OK, I have a 67.
Ms. Remy Ann David

Member for

15 years 5 months

BobRogers Wed, 01/24/2007 - 13:12
I've read on a keyboard discussion board somewhere that the bluetube works as Remy describes: basically a solid state preamp with a tube "stomp box" hard wired in. I don't know for sure that that's true, but it sounds about right. I bought one for my Nord Electro keyboard to act as a DI/Preamp (the Nord has a notoriously low output) and to add some distortion to the Leslie sim. (Wish I had the room around here and the money for a real Leslie.) Works fine for that with the original tube. But I expect you are looking for something a little more subtle than "Steve Winwood with all the stops out and the pedal to the floor" sound, so a better tube may be the ticket. At any rate it's not that expensive a mod - worth a shot.

Member for

20 years 6 months

AudioGaff Mon, 01/22/2007 - 21:05
It is normal/comon to replace a tube when it needs to be replaced. It is also normal/common to change a working tube for another tube to obtain a different tone. Like most things in audio production, it depends on several variables with the tube being one of them. Depending on the gear design and how it performs with a specific tube combo, determines how much, if any, real difference in tone there is. I would think in most cases for a high quality tube mic pre using a good high quality tube meant for that mic pre, you would not notice much, if any real difference.

Member for

17 years 8 months

jonyoung Tue, 01/23/2007 - 07:02
I own three ART Pro MPA's, which use 12AX7 tubes. I have swapped the original tubes (which are mediocre quality) with high end NOS tubes. One unit has 12DF7's, another has 12AT7's and the third has high quality 12AX7's. The latter displays the least noticeable tonal difference, but there's more air and smoother upper mids and highs. The first two units showed dramatic tonal differences. The 12DF7's are very dark and smooth, the 12AT7's hype the mids, and each are low gain models and almost impossible to clip. I'm sure that the overall component quality in the build of the gear, as well as the circuit design contribute to more noticeable results. I've read that swapping tubes in a low end piece of gear isn't worth the trouble, ie: ART Tube MP and the like.