<[Lonely Star]> Project: A versatile OD / Distortion stompbox

[Auke Haarsma]

After a couple of weeks of finetuning I feel the Lonely Star is ready to be posted. I hope you enjoy building it!

This circuit wouldn't sound the way it does without the great help I received from several forumites in this thread. Thanks guys!

Origin
The Lonely Star is 'inspired' by the Mesa Boogie Lonestar Amp. Following the RunOffGroove amp emulation I modified the preamp circuit for use with J201 transistors. I have changed quite some values, added some options, removed some parts... so I don't think I should call it an Amp emulation. That is were it started, but it turned out to be a very versatile stompbox.

Description
This is a versatile stompbox, that responds well to the player. The Volume control on your guitar can be used to go from Clean to Dirt. Too my ears it has a warm sound, even a bit bassy. It has a broad range of gain settings. It can be a 'clean with an edge' sounding pedal, but by flipping some switches you go to full on warm thick lead tones. It doesn't have the high gain of a Dr Boogey (it is not voiced like that), but it does have a lot of gain. I have played it with both my guitars. One is a PRS-clone with humbuckers, the other a Taylor T5 acoustisc/electric hybrid. The Taylor has a lot less output, however by flipping the Input switch to Hot I still get a decent amount of gain at my command! And, the other way around. If I for example play the PRS with the Normal Input setting, I get a warm bluesy sound out of it. With the available switches you can completely change the character of the pedal. (and yeah, you can drive it over the top...).

The tonestack is very interactive. Especially the Bass and Mid controls are very much related. It took my some getting used to. However, it is a 'common' Fender style tonestack.

Controls
The full version has a lot of controls. Seven knobs, two footswitches and two toggle switches.

A picture of my Lonely Star in an old (test) enclosure (BB Hammond):

And out of the enclosure (I was still finetuning, those wires are way too long ):

A description of the controls:

• Knobs
  
  
  • Bass, Mid, Treble. This is a fender tonestack, in front of Q3.
  • Presence. Some EQ at end of the signalpath. It can go from dark, mellow, muddy to hash earpiercing high. Funny control, works well.
  • Gain.This controls the Gain.
  • Drive.This controls the gain of the Lead channel. You can kick this extra gain stage in with the Lead-switch
  • Volume.This pedal has a lot of output, so use this wisely
• Toggle Switches
  
  
  • Hot / Normal input. This sets the input signal level. With Hot you have a lot more gain. Normal lowers the total gain and character of the pedal.
  • Thick / Normal / Thicker.This toggle switch allows you to let some signal bypass the tonestack. Normal sends all through the tonestack. Thick lets some signal pass and thus increase the gain and also change the tone of the signal. Thicker lets even more signal pass and gives max gain.

• Foot Switches
  
  
  • Normal / Lead Channel. This kicks in an extra gain stage. The gain for this stage is set with the Drive-knob.
  • Bypass.This would be your normal bypass footswitch

___
Schematic
The schematic can be found here:

PCB
The 600 dpi PCB image can be found here. (Right click, save as...)
The size of the image is 1709 x 1253 dots. So, that equals 2.85 x 2.09 inch and 7,23 x 5,3 cm.

As can be seen above, the PCB fits an BB sized enclosure easily. But it can even fit a Hamond B-sized enclosure for a Zvex-style layout:

The wonderfully etched PCB was made for me by Andre.

Parts Layout
And here is an parts layout. As you see, all pots have three pads on the PCB. However, you do not need three wires all the time. The dotted wires can easily (and better!) be connected on the pot as shown.

Partslist

Capacitors C1      0.1uF C2      15uF C3      15uF C4      15uF C5      15uF C6      4n7 C7      6n8 C8      68n C9      2n2 C10      1uF C11      0.47uF C12      120pF C13      220pF C14      220pF C15      220pF C16      220pF C17      47nF C19      47nF C20      10n C21      1n C22      100uF C23      5n

Resistors R1      470k R2      2M2 R3      82k R4      2M2 R5      1K5 R6      68K R7      1M R8      220K R9      100K R10      220K R11      1K5 R12      27K R13      10M R14      10M R15      100K R16      82k R17      100k R18      1K5 R19      1M R20      1K5 R21      220k R22      100R R_LED      4K7

Pots TRIM1      100k trimpot TRIM2      100k trimpot TRIM3      100k trimpot TRIM4      100k trimpot POT1      1M LIN drive POT2      25k LIN treb POT3      25k LIN bass POT4      1k LIN mid POT5      1M LIN gain POT6      500k LOG Level POT7      100k LOG Presence Transistors Q1      J201 Q2      J201 Q3      J201 Q4      J201 Diode D1      1N4001

Switches Thick / Normal / Thicker is an On/Off/On switch Normal / Hot Input is an DPDT switch Normal / Lead Channel is an DPDT or 3PDT if you prefer Jumper There is one jumper near C21, don't forget it!

Mods
There is plenty to mod to this pedal if you want to. It sounds good on my setup, but you may need to finetune it to your setup. Here are some components to mod:

• Thick/Thicker switch
  
  
  • C7 and C8 are part of the switch. Increase these values for more gain, lower them to get a more subtle effect
• Q1-Q4
  
  
  • I used J201's here, but 2n5457's work just as well. They have a little less gain. Also remember transistors can vary a lot from one to the other. I did not measure them (if you want to, check the ROG site), but used swapped a couple in from my stash.
• Drain Voltage
  
  
  • The trimpots set the the voltage on the Drain of the transistors. I bias them to ~5V. You can bias by ear. By changing the bias you can change the sounds of each stage.
  • If you want you can replace the trimpots with fixed resistors. Just measure which value the trimpots have and swap in a resistor.
• Volume pot
  
  
  • I use a 500k Log pot. Originally I used a 100k pot. A different value has a different character. If you want to experiment try 10k vs 500k. You will hear the difference!
• Change the gain of a stage
  
  
  • If you lower the source Caps (C2, C3, C4, C5) you will lower the gain. Increasing the caps will increase the gain.
  • If you increase the value of the source resistors (R5, R11, R18, R20) you will lower the gain. Lowering the value will increase the gain.
• Fixed Drive or Fixed Gain
  
  
  • I have added an additional pad at both the Gain and Drive pot. This allows for easy replacing on or both of the pots with a fixed setting. I really like both controls separately a lot. However, if I had to pick one, I would make the drive-pot fixed. This way you can still control the overall gain of the pedal with the Gain-pot, but also still have the Lead-channel function.

Three Knob Version

Soundclips

Vero

I hope you all like it. It would be great to read some of the build reports here!

Rock on!

Auke Haarsma
June 2009
[/list]

[trixdropd]

Looks very cool.  Rock on!!

[Ripthorn]

If I can find the time, I will build this shortly.

[Auke Haarsma]

Looks very cool.  Rock on!!

Thanks!

If I can find the time, I will build this shortly.

I am really curious to hear your findings!


I hope to add the 3-knob version end of today. And, if I manage to get my m-audia soundcard running under Linux I may have time to do some clips. The problem is that when I use the effect I just enjoy playing with it a little too much. I forget about all the things I sitll have to do!

[Auke Haarsma]

Added the three-knob-version layout in post #1.

[DWBH]

How does it sound?

[Auke Haarsma]

To my ears: good! 

Now that the 3knob version is uploaded I will try to get my pc to record some clips.

[Auke Haarsma]

I recorded a quick clip and put it on youtube (after struggling with file-conversions etc..)

http://www.youtube.com/watch?v=VIDKarOeMFo

It shows in an unorganized way the sounds of this pedal. Remeber, recorded with a small amp (Epi Valve Jr 5 watt at low volume).

I hope to be able to get some more clips up when I can find the time.

[Ripthorn]

That clip is sounding pretty great.  I have one project to get out of the way (hopefully tonight) then I can give this a shot.

[mnordbye]

Nice clip!

Where do you get that ribbon wire you use? It looks really neat and nice!

[slacker]

That sounds really good, nice work.

[Auke Haarsma]

That clip is sounding pretty great.  I have one project to get out of the way (hopefully tonight) then I can give this a shot.

Good stuff! Hope you like it.

Nice clip!

Where do you get that ribbon wire you use? It looks really neat and nice!

Thanks! I got that wire from a local (Netherlands) supplier. It is for PC stuff I think. I just tear the number of wires I need from the bunch:
http://www.dickbest.nl/webshop/index.php?act=viewProd&productId=1843

That sounds really good, nice work.

Thanks Ian! Hope to get some more clips with different settings and different guitars up soon!

[Auke Haarsma]

I just had this cool idea for the three-knob version: instead of using fixed resistors for the pots we don't use... why not replace them with trimpots on a little daughter board inside the enclosure? The pots I am thinking of are Drive and Presence. This gives you the best of both worlds:
-reduced number of knobs
-full control of the tone/gain-shaping like the full-knob-version.

It's pretty obvious, but sometimes the obvious can appear pretty amazing

[Auke Haarsma]

I just updated the 3-knob version.

After trying my initially posted version with the big muff style tonestack I noticed that it didn't work as expected. The drain of Q3 started to react on the tone-pot. Reducing the value of the tonepot did solve that. However, the control over the tone was not good. Next I tried some of the tonecontrols as you can find them at muzique.com, but I wasn't satisfied. The option that gets the closest to the 'real-thing' (the tonestack with bass,mid,treble) is ... the real-thing with some pots replaced by fixed resistors.

[Auke Haarsma]

Startpost updated with seven soundclips.

I think you can hear that the Lonely Star allows from a little break-up to warm OD, to harsh OD to thick lead and fuzzy piercing tones.

If you want to listen to a clip multiple times, please do a Right click, "Save as...". Thanks.

Hope you like it!

[Paul Fehr]

I'm really liking how this pedal sounds

Hopefully I might be able to make this pedal in the near future

[~arph]

Sounds really nice, I like the low gain settings with the low input signal the best. Hot input and max gain sounds buzzy and misbiased to me.

[valdiorn]

I really like the sound of this, until it gets gain-y ... wayyy too much fuzz. It should only be a bias problem, have you tried changing the bias??
If that won't fix it, you might want to try changing either the first or two first JFETs to a lower gain unit, like a 2n5484 or MPF102, the problem might be that the first two stages are saturating too much, giving a harsh cutting saturation.

Other than that, good job and thank you for documenting the project so well

[Auke Haarsma]

I'm really liking how this pedal sounds

Hopefully I might be able to make this pedal in the near future

Thanks Paul, hope you gonna build it. I'll be curious to hear your experiences! And if you run into trouble feel free to post here!

Sounds really nice, I like the low gain settings with the low input signal the best. Hot input and max gain sounds buzzy and misbiased to me.

I really like the sound of this, until it gets gain-y ... wayyy too much fuzz. It should only be a bias problem, have you tried changing the bias??
If that won't fix it, you might want to try changing either the first or two first JFETs to a lower gain unit, like a 2n5484 or MPF102, the problem might be that the first two stages are saturating too much, giving a harsh cutting saturation.

Other than that, good job and thank you for documenting the project so well

@Arnoud and Validorn: Thanks guys, I appreciate your feedback.

The buzzy/fuzzy not-so-nice-sounding high gain is not caused by mis-biasing. All Q's are biased around (and a bit upwards of) 1/2Vcc. So with a 9V supply that is somewhere between 4,5V and 5V.

Q4 simply runs out of headroom in a pretty nasty way. But this happens only when driving the signal a lot. High Gain and Drive, Hot input and humbuckers.

When I first posted the schematic I got some good advice from Transmogrifox (see link in 1st post to that thread) about the gain ratio of the amp this pedal is 'inspired' on. The Mushroom-story Bottom line: Because of less headroom with 9V compared to the ~300ish volt in the amp, we have to reduce the input signal accordingly. This is exactly what the 'Normal'-input does. The Hot input does not reduce the input signal significantly and thus you will run out of headroom way quicker.
My findings however where that with low-output pickups (like single coils, or my taylor guitar) the available gain was on the lowish side. That is why I kept the Hot/Normal input switch.

Bottomline: The circuit is not designed with a hot signal through the hot-input at max gain/drive in mind. However, since in a 'demo' I wanted to show all the sounds with different drive/gain settings. I guess I succeeded

That said: trying lower-gain trannies is a good thing. My oscilloscope showed that the most gain happens at Q4 and a bit less at Q3. Q3 still has nice round clipping at high gain. Q4 turns it into almost a square wave (as you heard).
I swapped in 2n5457's for Q3 and Q4 and it did 'soften up' the sound some. I think I like it better that way. At max gain/drive it still gets fuzzy with humbuckers, but not as soon as with J201's.

I will stick with 2n5457's in Q3 & Q4. Thanks for the suggestion!

A made a new clip (clip 8 ) to demo the sound with Q3 and Q4. The clip is posted in the start post of this thread.

I am not a reincarnatio of Jimi, however I hope you can enjoy the sounds of this pedal 

[Brymus]

First off Great Work!
There seem to be alot of skilled DIY in the Netherlands area.
I imagine it took as long to document and share in such a professional presentation as it did to build and debug.
Would you have any clips of the amp its modeled after?
I am gonna breadboard your pedal when I get a chance.
ALso be honest-an AC30? with an amp emulator in front of it
Which sounds better the pedal with the amp on clean or the amp cranked up with no pedal?
Again thanx for sharing excellent work!
PS do you have any O-scope pics of the clipping at the different stages that would be of intrest to me.