I've been doing some experimentation with two starved plate designs that I own. One is a VT999 'Tube Overdrive' pedal and the other is Behringer's Mic200 preamp. Both are part of the current popular trend of so called 'toob' designs. Personally I think the circuit is more important than whether there is a valve - however these two are nicer examples than you might think.

Selecting/Choosing/Picking valves/tubes for a Starved Plate design..
A lot of people like boxes with valve/tubes in and intend on changing the 'crappy stock Chinese no name'. Personally I think that modern equipment is designed around modern valves - people don't always seem to realise this..

Anyway - I have an old all tube Laney and a pile of valves - so I thought I'd test out the theory.. Bet you'd like to know what happens?

Although you CAN hear the character of different valves trademark responses - their outputs and noise levels are not as expected in this circuit.

I tried a range of NOS RFT, Z&I and Philips ecc82, ecc81
I also tried a NOS Mullard ecc83, an East German NOS ecc83, Philips 12AX7WA JAN
And finally two good modern valves I like, the JJ ecc83s and the Sovtek 12AX7 LPS

Basically I found that an ecc81 or 82 gave more distortion - not less - lowering headroom.
Shorter plate designs seemed to give lower, weaker outputs and the JJ ecc83s was very quiet and also rather noisy.
The NOS valves didn't magically light it up as they couldn't seem to get going - so don't waste money there - just for research I tried a Mullard ecc83, an RFT 83 (both short/mid length ladder plate) and a 12AX7WA Philips JAN (which was pretty good actually with the longer plates).
Chinese highgain (which the Behringer tube is) came in strong with a smoother, bright and less crumbly 'overdrive' sound - however this then faded after a few seconds (as the valve self biased presumably) - then they were weak and quiet which was a surprise.

The best by a mile was the Sovtek 12AX7 LPS - with the big long plates - this gave 10db more than all the other valves I tried and seemed to be a much stronger signal to noise, smoother sound.

To me it would appear that there are only certain valves that will actually work in these low voltage circuits - I'm happy to report that the Sovtek LPS is one of them and it is a great valve. In this circuit I think it keeps the character I've heard it have in amps. You do need to boost the treble a bit though for a biting chuggy overdrive/distortion - but that's what the EQ is for.

Lastly - the differences between the sound of different valves/tubes is very very subtle - in this case it's finding valves that WORK properly that is important!

In the end I have used a Philips JAN 12AX7WA in the MIC200 preamp - it's warm and quiet - a characature of the sound of the valve really - but in fact that is what I use the box for.
The VT999 got the Sovtek - and it's great for jamming - valve amps are too heavy to cart about all day


Of the Behringer VT999 - Is it any good?

Both are strong and quite well made boxes. The components and layout inside also feel of a higher quality than Behringer's cheaper plastic pedal range. The switch stomp switch is excellent.

The equaliser is responsive, allowing a good scoop for metal, or roll offs of the top and bottom. The master volume effects the output level of the 'overdrive' effect - in relation to the bypass. This is good if you want to use it through a near clean channel on your amp (to give a two channel feel) - but is perhaps a missed oppurtunity. I would have rather there was a gain boost giving a cleaner/ dirtier switch instead. A boost/drop pedal before the VT999 can facilitate this very easily however, and I built a passive gain dropper switch to put in front myself.

The sound is quite good. You get a decent higain preamp - suitable for grungy or chuggy metal. However this could have been achieved easily without a valve, it is also not the sound advertised to be found with the pedal.

Fortunately there's more in the preamp though - most of the finesse is lost because the Gain control itself has too sharp an onset and is in fuzz distortion before you ever hear an overdrive breakup. Using a gain dropper/ volume pedal etc - you can lower the input to get a decent overdrive feel. The pedal in it's off the shelf state seems to like a fairly higain setting on the dial, and a low input signal - this give an edgier, hotter feel that is more like a valve amp. The noise gate is good - which is just as well as a higain on the pedal and a low input from the guitar does make for a noisier operation.

I highly recommend the use of Bitmo modifications that increase the useable range of the Gain knob - it is VERY easy to perform if you have basic soldering skills. I performed this mod and while the sound didn't really change - the control over it was vastly improved and the focus was brought onto the character of the edgy breakup area.

Overall - This is a good preamp in a box - doesn't have the power tube business going on - but it sounds good on a clean -ish channel on a solid state amp. It's the opposite of a tube driver pedal if you like. It's like a nice alternate to a big muff really - but I quite like it all the same.