Hey, I am a Hi-Fi guy, but my friend has recently been bugging me about making a tube distortoin pedal. I don't even know really how a distortion pedal works beyond the fact that it just overdrives the prestage before the power amp (every Hi-fi-er crys a little when they hear how it works). Is there anything more to the functioning of a distortion pedal? Does anyone have a good shcematic for one?
How about The Real McTube?
Haven't heard it, but it looks like it would fit the bill. Cheap too.
Kofi
Haven't heard it, but it looks like it would fit the bill. Cheap too.
Kofi
Unfortunatly the real McTube sounds like nothing more than a cheap fuzz box, UNLESS you tweak those anode resistors down, and get the bias just right, then it's ok. There are alot of other valve based pedalsout there, the Tube Driver, Stack in a box, Radio-Head, shaka tube,...
But at the end of the day, you can't get decent distortion form a pedal (valve or otherwise). There's a lot to be said for the mini 1Watt valve amps such as the Firefly at www.ax84.com, Moonlight at http://www.amptone.com/delftmoonlightamp.htm and another whose name i have forgotten- higherwatt or something. These can be cranked right up, but easily casced via a line out into a regular guitar amp.
But at the end of the day, you can't get decent distortion form a pedal (valve or otherwise). There's a lot to be said for the mini 1Watt valve amps such as the Firefly at www.ax84.com, Moonlight at http://www.amptone.com/delftmoonlightamp.htm and another whose name i have forgotten- higherwatt or something. These can be cranked right up, but easily casced via a line out into a regular guitar amp.
Oh yeah, the other one I was thinking of is the Heaveywatter at http://www.sonicdeli.com/ThunderTweakWeb/links.htm#
So much for tube tone. I could write a whole book about this topic but in short the type of active device used for gain has little or nothing to do with the tone of distortion. The idea is to always pre filter the signal before overdriving a gain stage to clip. After overdriving the signal should be post filtered. Both are done to voice the distortion so it will not be only bass dominated fuzz or treble dominated tablesaw tone. Instead of overdriving the signal to clip, the signal could be clipped with other ways as well. The idea, however, is always to clip the signal somehow. An educating experience is to put a graphical EQ in front and after a distorting amplifier stage and play with the sliders.
If you overdrive a tube stage loaded by constant resistance there will not be much difference in distortion compared to distortion acquired by overdriving transistors or fets. Tubes will clip with less harder "knee" but that´s about it. If you want a harsher tone you will eventually find yourself just overdriving the tube more. The same round knee can be acquired with solid state devices as well. With tubes the idea is to acquire so called "power amp distortion". To get this you have to overdrive a gain stage loaded by impedance that mimicks the one of speaker load's. In comparison to loading the stage with a constant resistance this will give a notable boost on both higher frequencies and at the frequency that corresponds the speaker's resonance. The same thing can be done with solid state devices, however, the rounder knee of clipping would have to be simulated by other means.
As you said, you lack experience about distortion pedals - or distortion circuits in general. I'm not too keen on repeating myself everytime a similar topic becomes under discussion - and i doubt no one is - so your best bet is to search. The internet is full of information about this, even this forum is. About few weeks ago there was a thread about a similar thing in "Musical instruments" section and it raised few interesting topics. Here´s the link:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=79046
If you overdrive a tube stage loaded by constant resistance there will not be much difference in distortion compared to distortion acquired by overdriving transistors or fets. Tubes will clip with less harder "knee" but that´s about it. If you want a harsher tone you will eventually find yourself just overdriving the tube more. The same round knee can be acquired with solid state devices as well. With tubes the idea is to acquire so called "power amp distortion". To get this you have to overdrive a gain stage loaded by impedance that mimicks the one of speaker load's. In comparison to loading the stage with a constant resistance this will give a notable boost on both higher frequencies and at the frequency that corresponds the speaker's resonance. The same thing can be done with solid state devices, however, the rounder knee of clipping would have to be simulated by other means.
As you said, you lack experience about distortion pedals - or distortion circuits in general. I'm not too keen on repeating myself everytime a similar topic becomes under discussion - and i doubt no one is - so your best bet is to search. The internet is full of information about this, even this forum is. About few weeks ago there was a thread about a similar thing in "Musical instruments" section and it raised few interesting topics. Here´s the link:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=79046
You can use the wall-wart power supply for a 1 watt valve amp as well as pedals, since the current demands aren't very high.
Obviously an amp made using your EL84 bits will work great, but it's entering the realms of an actual amp, not just a small distortion modelling tool. I guess it depends what your friend really wants.
I have to disagree with teemuk, the nature of distortion generated by valves is not attainable with solid state (well, maybe if you designed a circuit the size of a suitcase that would simulate just one triode stage!). The reason being, a significant portion of the classic valve drive sound is due to the nature of forward grid current. There is no analogous solid state device that has this characteristic, so it you want the real thing, you have to use the real thing!
Obviously an amp made using your EL84 bits will work great, but it's entering the realms of an actual amp, not just a small distortion modelling tool. I guess it depends what your friend really wants.
I have to disagree with teemuk, the nature of distortion generated by valves is not attainable with solid state (well, maybe if you designed a circuit the size of a suitcase that would simulate just one triode stage!). The reason being, a significant portion of the classic valve drive sound is due to the nature of forward grid current. There is no analogous solid state device that has this characteristic, so it you want the real thing, you have to use the real thing!
Since my name is Tubelab, I really hate to admit this. My favorite simple fuzz box runs on transistors. I first got to play a Vox Tone Bender back in 1970. It makes a sound that is hard to duplicate. I actually took that unit apart and traced the schematic. I built a copy for the guy who let me take his apart, and I made one for myself. I still have it. I have seen the circuit on the web. The same circuit was used in the Dallas Arbiter Fuzz Face (Jimi Hendrix). It is a very simple two transistor circuit.
The secret to making this work is to find two germanium PNP transistors. It will work with silicon transistors, but it doesn't make the same sound. I put sockets in the pc board, and tried several until it sounded sweet. The ones that I used came from an old Sony transistor radio.
I have fance DSP distortion boxes, and an ADA MP-1 vacuum tube guitar preamp which has some very good sounds, but is way too complicated to copy, and is HIGHLY MICROPHONIC! Too much gain in front of your guitar amp will be microphonic (you can't use it loud on stage kind of microphonic).
The Tone bender has the best sound of the bunch.
The secret to making this work is to find two germanium PNP transistors. It will work with silicon transistors, but it doesn't make the same sound. I put sockets in the pc board, and tried several until it sounded sweet. The ones that I used came from an old Sony transistor radio.
I have fance DSP distortion boxes, and an ADA MP-1 vacuum tube guitar preamp which has some very good sounds, but is way too complicated to copy, and is HIGHLY MICROPHONIC! Too much gain in front of your guitar amp will be microphonic (you can't use it loud on stage kind of microphonic).
The Tone bender has the best sound of the bunch.
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