tube distortion pedal

[coreybox]

in a tube amp, what does the distortion....the preamp or output tubes? this was my idea. an effect thats basically a tube preamp, but with a rangemaster or something in front of it, with some sort of tone circuit. so a tone, drive, and volume knob. would this work? also could i just use some preamp out of an amp (say a champ or something), or is there some other tube preamp that would be better suited. i also dont know how to power it. would i still need a power transformer like in tube amps, or could i use a smaller cheaper one. just i need some overall help, bvut i like my idea..do yal think it would work well? thanks

corey

[runmikeyrun]

Distortion is made in both sections of a tube amp.  Preamp distortion is mainly determined by how hard the input is driven while power tube distortion is based on a number of factors:  How hard the power tubes are driven, what they are biased at, and especially the kind of tubes they are.  for example, a 6L6 has more headroom than 5881s, so 5881s clip sooner and distort more, all other things considered equal.  

There is some debate about where the best distortion is made, in the preamp or power amp tubes.  There are numerous tube circuits based on creating preamp type distortion (using 12ax7 tubes, such as the Real Tube and several others) and there are a few based on very small output tubes for output tube type distortion (pentode driver, correct me if i'm wrong guys).

If you have a hybrid amp (tube preamp, solid state power amp) you are hearing preamp distortion, or if you really crank it up, SS power amp distortion which you will know by its horrible sound.  

If you have an all tube amp, try listening to the different types of distortion.  Slam your input stages with a booster (NOT a distortion pedal) and turn the preamp up to 10 but keep the master volume below 2-3.  This is going to be primarily preamp distortion you're hearing.  Now plug straight into your amp but turn it up to 6 (or higher if you dare) and you'll start hearing power amp distortion.  Disclaimer: do not turn your amp up this high if you don't want to risk killing your amp.  I told you so.  

You can also check out preamp distortion by slamming the input as above, but send the signal from your direct out (if your amp has one) into a solid state power amp and then back into your cabinet.  Keep your amp hooked up to another speaker, but muffle it so it doesn't color your regular speaker.  Do NOT leave your tube amp unplugged from a speaker!!  Bad things will happen.  This will basically give you your preamp distortion sound but you can crank it up loud to hear the difference at a reasonable volume.  The rangemaster/tube preamp sound you spoke of would sound similar to this.


As far as using a champ (per your example) as a preamp, you can do it if you have a qualified tech install a line out jack, which you would run to another amp or power amp.  Remember you will still need a speaker load or the amp will blow.  There are companies that make dummy loads for amps but their use is questionable as to if they damage your amp.  

I have also seen plans on making an inductive load out of an old speaker, and then having a line out off of that to get a line level signal of power amp distortion.  This is also questionable as to whether it can damage your amp.  In either case with line outs remember that the speaker has a LOT to do with the sound of the amp.  Sending a champ's line out signal into a solid state combo might sound horrible.  

You've got a lot of thinking to do.  Just my two cents.  Please correct me if i'm wrong, i'm in the midst of a sickness and the fever may be clouding my brain...

[coreybox]

ya, this seems like it is gonna be dificult. i want it in a stompbox design. i tried searching for some tube distortion pedal schematics to look upon and get some ideas...but i didnt have much luck. thanks for the input though

corey

[mlabbee]

Try this:

http://www.dogstar.dantimax.dk/tubestuf/mctube.htm

It's my next project, so I can't tell you how it sounds, but if I recall correctly, it has gotten some good comments.

[petemoore]

A good place I started on Tubes Is the Shaka Tube.
 I cheated tho, building only the 12ax7 stages, both sides of the one tube, and using a power supply.
 Once I got the pins straight, wiring the circuits signal path and setting up the tube bias is about the same as transistors.
 For the PS, I used an old printer adapter 30VDC. Running the tubes less than 12v for the circuit [starved plate] is possible, they can operate up to 330v IIRC, but that is potentiall lethal voltage.
 For the Heaters, I used a 9VDC power supply, measures 11.6v when the heater is loading it...I got lucky, but a voltage regulator and a 12v supply would do the trick Ez enough if you couldn't find one that gets close enough to the tube rating..+/- 10% of 12v for the heater. There is also a low voltage tap you could use to run the heater. Basically not hard to get the heater going right.
 The only drawback to this method is it needs 2 power supplies.

[vdm]

you could also try the hotbox.

i havent built it, but from what i hear of matchless stuff, it should be pretty good.

it's basically a tube preamp that switches from 1 stage to 3 stages and a cathode follower tone control.

it doesnt have true-bypass, but my bet is if you have a SS amp you'll prefer to leave that first tube stage in the path anyway.

you could always but a rangemaster in the same box and maybe run it off the tube heaters power supply if you use 12V and use a 9V regulator.

good luck!

trent

[coreybox]

would something liek this work?

[petemoore]

would something liek this work?

>>>I can't see the link

[coreybox]

well i dont knwo why that doesnt work, but this is what it was.

a jack into the rangemaster circut, then the output from that going straight into the input of the hotbox....but only the first stage of the hotbox. everything below the switch of the hotbox was omitted. i was exactly sure on how to emit the rest of it though.

corey