Ever modded a BK Butler Real Tube rack mount unit ?

[JFX09]

Hello,

I was given a Real Tube rack mount unit and was wondering if it was possible to mod it and bring it into distortion territory (it's more of an overdrive with a 12AX7) ?

As of now, it starts to sound like what I want when I max out everything.

I search a bit on the net but could'nt find anything yet.

thanks in advance for any pointers (schematics would be awesome too )

jf

[JFX09]

So, if I understand any of this, say if i increase load  resistance, i get more gain ?

[aron]

I would just add a booster in front and be done with it. I broke my friends BK butler tube driver pretty easily. WHat a bummer!!!!!

[merlinb]

Is it anything like this schem?
http://i197.photobucket.com/albums/aa211/bajaman002/TubeDriverschematic.png

You could reduce the 10k resistor right before the first valve grid, since that is currently dropping half the signal. Also increase the 22k grid leak on the second valve, since that is loading the first valve pretty heavily.

[JFX09]

I haven't opened it yet, just played a bit with , will check that. Thanks

Will aslo try your suggestion Aron. I have a mosfet booster, i could have thought about it, duh!

[nitraus]

I have an old Butler RealTube rack with a 12AX7. It sounds pretty good, almost fuzzy with the gain cranked up.

[sault]

When I'm playing, my signal chain is  :

guitar -> distortion pedal -> chorus pedal (sometimes) -> Real Tube -> Crate Power Block, line out (w/cab simulation) -> mixing board -> overheads

If I have a lower-gain 12ax7 it has a greater range of chime and warmth, if I have a higher gain tube like an ECC83S it crunches sooner, but has less noise (spiral wound filament?). After some experimenting, I find that I prefer the lower gain tubes - I like my clean sound (thank you Seymour Duncan) and as long as I get a decent distortion tone from the pedal I figure I'm good to go. I prefer getting some tube in the preamp rather than the power amp... I like to avoid an amp on stage (fewer mics = less feedback), and that way I can scale my volume without changing my tone.

Anyways, what I don't like about it is that the "boost" cranks the volume along with the gain, so there's no real way to use it as a 2nd channel.

I've been wanting to raise the input capacitance and cut out a little more bass to tighten it up a bit, and figure out how to tame that boost function to something that's actually useful.

I've really been wanting to find a schematic, because I opened it up to take a look and my eyes kind of glazed over. I mean, it's no Boss pedal, but it was a little more involved than I thought it would be...

[iccaros]

Is it anything like this schem?
http://i197.photobucket.com/albums/aa211/bajaman002/TubeDriverschematic.png

You could reduce the 10k resistor right before the first valve grid, since that is currently dropping half the signal. Also increase the 22k grid leak on the second valve, since that is loading the first valve pretty heavily.

I would follow Merlin's lead on this.
if you made the 10K a 1 - 5K (pot?) you would get more signal from the OPAMP.

adjustments on the grid would change your sensitivity on the second triode.
I would put a 100K pot and adjust for taste, then measure what you have and replace with the closest value.

[steveneddy]

Actually that unit should be either first or last in your line up.

It is a great pre-amp or line booster before going into your amp.

I used to use on in an old rack I used when playing live and it was first in line to warm up the tone a little before going through all of the processing.

If you want fuzz just build a fuzz pedal - or go find an old Chandler Tube Driver - same concept but made for lots of distortion.

The Real Tube is a great tool as it is stock - giving you instrument ins and outs - as well as line ins and outs. Using foot switches on these will give you a slight boot in gain like for leads or something.

IMHO - increasing the gain on this rack unit would defeat the purpose of this unit.

[pinkjimiphoton]

if you want more distortion, try a 100-220k resistor going to the plate of the first half of the 12ax7...you MAY have to adjust the cathode resistor as well to get it to bias right.
it looks to me like it's already pretty juiced, for what it is...you can't really get much more gain out of it when starving a 12ax7 like it already is...100 k should give you more distortion, at the expense of some output. you may wanna try replacing that plate load resistor with a 100k or so pot, and dial it in til you find the "sweet spot" for you, then measure the pot and use a resistor that's close.

i'm not really familiar with hybrid circuits like this too much, but you can absolutely juice it some by starving it a little bit more.

you could also try a bigger coupling cap feeding the first half of the 12ax7, more bass will make more breakup, but could cause motorboating issues.

last thought would be maybe a diode clipper just after the last coupling cap(s ) before the volume control. that will also cost some output, but should increase the distortion some.

i used to use these things live, they can sound really good, so good luck!