pre-amp tubes-

dadt · Post by **dadt** » 15 Feb 2011, 05:02

I recently picked up a used Behringer VT999 vintage tube monster pedal. I replaced the stock tube with a old low stress Baldwin 12au7 which makes it sound worlds better. Im looking for a great just- barely starting to break up clean tone

. At this point I have the gain set to just under 1 on the pedal. Is there another tube that would fit this thing with even less gain/fuzz/distortion than the 12au7?? Id like a tube that has the .75 to 1 sound

that I am getting now when the gain knob is actually set to about 7 on this pedal. So a tube with a wider range of hardly any fuzz???

matt239 · Post by **matt239** » 28 Feb 2011, 03:53

I don't remember enough about tubes to know which tube would give you that. I think there are some guides online?
If you can't get a tube that will do it for you, might not be too hard to just lower the pre-gain a bit?
Since you are getting pretty close, just changing the pot might give you some more adjustment range?
Is the Behringer a "clone" of something? Is the schematic available?
Alternatively, you could put a compressor or booster before the unit, but set for less than unity gain...
Sounds like a cool tone you're chasing! I'd love to hear a clip once you find your solution.

Mattdive · Post by **Mattdive** » 05 Mar 2011, 00:26

If you think of a normal 12aX7 as having 100% gain, the 12aU7 has about 19% gain. A 12aT7 has about 60% and a 12aY7 about 45%.
If you're using a 12aU7 already, you have pretty much the lowest gain noval pre-amp tube you can get. You may be able to lower the gain in the pre-amp stage by switching out some of the caps, but you'd need to look at the schematic first to figure out what swaps to make.

You can also attenuate the signal going into the tube stage.

hope that helps.

bancika · Post by **bancika** » 18 Apr 2011, 19:52

if this is similar to butler tube drive and other starved plate designs, tube gain won't change much at all as far as drive level goes, unlike with tube amps. I played with tubes in dean markley overlord I got yesterday and also found that I loved 12au7 the best, and it doesn't lack drive compared to 12ax7, just sounds maybe fuller.

dadt · Post by **dadt** » 03 Sep 2011, 22:29

anyone out there have any ideas on changing caps or pots on this thing to lover the gain and range- so far with the 12AU7 --0 to 2.25 is the only range of gain I need and i wouldnt mind if the 0 setting was even a little cleaner.

kleuck · Post by **kleuck** » 03 Sep 2011, 22:43

I suppose it's close to the IBZ tubeking, so just replace the 500K pot for a 100K one.

bajaman · Post by **bajaman** » 03 Sep 2011, 22:43

12AU7 or ECC82 has very low plate resistance = higher current capability into low impedance load - this is probably why it sounds "fuller".

DrNomis · Post by **DrNomis** » 04 Sep 2011, 04:04

The easiest way would probably be to replace the stock Drive pot with one that's say half the value, if the Behringer Vintage Overdrive pedal has the same circuit as the BK Butler 3-Knob Tube Driver (see schematic below), then the stock Drive pot is a 500k Log, therefore you could try replacing it with a 250k Log...