Dr. Boogie (my first post)

[Talentless_Hack]

So, I've been lurking here for a while.
Just recently a friend of mine and myself have gotten interested in building amps and guitar effects.
The Dr. Boogie is the first project we think we'll attack.
Here (http://www.contradyk.com/Dr.Boogie.htm) are the parts with their respective quantities and prices.
We're not sure we have selected the best/cheapest components, so we're looking for some verification.

Neither of us has experience building projects like this.  I took an Into to Electrical Engineering class while
studying mechanical engineering, but it's about the extent of my knowledge (basic analog circuitry).

Anywho, if anyone has a suggestion as to what I should change, please let me know in this thread, and I will continue
to update the BOM as it progresses, and keep it available for all who are interested.

I would really like to source all parts from one supplier to keep shipping down.  All things are sourced from either
Mouser or Smallbear.  I have prices for all parts on Smallbear, but some components are not exactly what is asked for.  This is why some of it is sourced from Mouser.

-the hack-

[ubersam]

Welcome!

Just a few things:

• the 2.2M resistor you have listed is a SMD, not leaded.
• the 1uf Xicon polyfilm cap is about an inch wide (23mm). If you want something with narrower lead spacing, the AVX BF/BQ box caps have 5mm lead spacing. Their drawback is that their leads are substantially shorter than non-box type film caps. Actually, think of them more as pins rather than leads.
• the 20pF cap you have is also SMD, not leaded
• the fluted knob is very cool. Might be the same as the ones a got from mouser. If so, they are about 1" in diameter- something to consider when planning out the knob's layout on the box.

I would also suggest that you get some 150pF/180pF caps to use from gate to ground of the JFETs (do a search for "miller cap") to help control the high-frequency content.

[John Lyons]

I built mine with 220 pf caps from gate to source on FETs 1,2 and 4 (soldered on the back of the board for space reasons)
The 20pf I changed to 150PF (helps kill the squeal)
Gain pot to 500K from 1M (lowers gain...trust me it's got too much)
.0068 cap instead of  .001 (1n) on Gain pot, better balance of high end at lower gain settings)
220K to ground 220K in line before 4th FET instead of 330k/220k( lowers gain a little)
470K to ground instead of 1M before 3rd FET ( lowers gain a bit...again!)

I am going to fool a bit with the Tone stack to get the values closer to marshall spec.
470pf treble cap

John

[ubersam]

...Gain pot to 500K from 1M (lowers gain...trust me it's got too much)

I am thinking of doing something similar. But, instead of just a 500k pot, I will tie a 500k resistor on the ground side of the pot, to ground. It would be like limiting a 1M pot's travel to 500k.

....0068 cap instead of  .001 (1n) on Gain pot, better balance of high end at lower gain settings)

I want to try that one too. Right now I have no cap there.

...220K to ground 220K in line before 4th FET instead of 330k/220k( lowers gain a little)
470K to ground instead of 1M before 3rd FET ( lowers gain a bit...again!)

Great ideas John. I might try these too.

[John Lyons]

Won't putting a 500K resistor on the ground side of a 1M pot make the pot 1.5M total resistance and then only being on able to turn the pot down to 500K resistance?
I tried a 500K gain pot with a 470K across the ouside lugs and a 47K from wiper to ground (to retain the audio taper...) It lowered the gain too much that way, not enough gain there, still a lot but not quite over the top.  Good for a general distorter if you don't need the gain and still sounds huge but...

I put in the .0068uf in place of the .001uf as the gain pot treble bypass and it seems to have the right amount of treble at low gain. The .001 had to much high end at lower gains, mybe just my personal taste.

john

[ubersam]

Won't putting a 500K resistor on the ground side of a 1M pot make the pot 1.5M total resistance and then only being on able to turn the pot down to 500K resistance?

I was planning on a 500K pot and a 500K fixed for a total of 1M. You made me think it over and I think I should put the fixed resistor on the hot side of the pot. So, on full CCW rotation of the pot, the signal is going through 1M. On full CW rotation, the signal goes through 500K.

[Talentless_Hack]

Alright, for version 2 there is a change to the 2.2M resistor.
The 1uF cap is changed, but i don't know if i chose a better one.
I picked a different 20pF cap, but the only thing i seem to find is the ceramic disk ones.  Anyone have a better one?

The knobs i have linked are fluted, but the shafts on the pots are not.  I don't seem to see fluted shafts on pots available at Mouser OR Smallbear.  Any thoughts on this?

I didn't change the other things (although i like the ideas), because i'm trying to keep this bill stock to the original schematic
(although i might follow your advice for myself).

Any other suggestions?

-The Hack-

[John Lyons]

Keep in mind that the original schematic will squeall like a pig and will be at least partially unusable.
The mods made by adding the 150-220 pf caps to the Gate and source pins were made to get the circuit usable over most of its gain range. The other mods I (at least) made make the pedal a little more versitle with lower gain and no squeal at full bore.
I'm not sure anyone has built this stock without the squeal.

Look for film "box" caps with a 5mm lead spacing.
You want smooth shaft pots not the fluted. Most are .25/ 1/4" smooth shaft which is what you want as most pots work with these.
The 20pf cap ceramic or silver Mica will work fine. It's a treble cut cap and there isn't much difference you (or anyone) will hear.

John

[ubersam]

The 1uF cap you picked, AVX boxed film, is good. I have been using them in my projects. Re: the 20pF cap, I actually replaced that with a 180pF (Xicon Polystyrene).

When I breadboarded this project, I added 180pF caps from gate to ground, everything else was the same as in the schematic. There were no squeals whatsoever in the breadboard version, even with everything on full. So, I designed my pcb, included the 180pF caps and replaced the trimmers with fixed value resistors. The PCB version of my project is a squealer. This brings me to the conclusion that the layout makes a huge difference in this circuit. On the breadboard, components were farther apart and the input was farther away from the tone controls and output. On my pcb, the input was on the same edge of the card as the tone controls and the output, with the treble control solder pads right next to the input solder pad. Removing the 1nF cap from the gain pot helps bring the squealing down, so does replacing the 680pF cap with a higher value. Moving the treble control board connections farther away from the input made a big improvement on the squealing. It is still not perfect but I can now turn the gain up higher before I get squealing. So, now I am going to re-do my layout.

[John Lyons]

Ubersam

I should have said the original layout is sketchy instead of the schematic...Obvously the schematic works in the actual amps....
I think the layout is the problem as well. There can't be so much differernce in the soldano/mesa/5150 parts and the Jfet versions.
The 680pf "treble" Cap is a higher value than in the marshall and other similar amps. Fender uses 250pf and gets much more mid scoop. (or more treble and bass)
Raising the 680pf value is going to give more mids and raise the overall level I think. Play with it in Duncan's Tone Stack Calculator.
Odd how that would stop the squeal a bit more...

John

[ubersam]

It may have been coincidental because I changed the value at the same time that I moved the treble pot board connections. In the Duncan calc., raising the treble cap from 680p to 1n just seems to raise the lowest setting for the mids, i.e. mids cannot be scooped as much. It was also interesting to notice how the bass, treble & mid controls interacted with each other. I wonder if a three band (non-interacting) eq would work better. Something like what STM had designed, for example.

[John Lyons]

I've been waiting to try a baxandall/ james EQ set up for some time now. Basically a separate (ono interactive)  treb,mid, bass arangement where you can actually boost the mids if you want.

With the 250pf fender value treble cap you get the most mid scoop but the mids aren't as strong in any possition, depends on what you want...

john

[Talentless_Hack]

version 3 is available here http://www.contradyk.com/Dr.Boogie.htm

it is now all sourced from www.smallbear.com

there are a couple of notes, and some mod stuff suggested by Basicaudio.

[calculating_infinity]

I love you talentless_hack.  You just made my parts hunting  a WHOLE LOT EASIER!!!  Thanks a lot buddy.  Also thanks to Basicaudio for the mod suggestions.  If you have any other bill of materials excel file for any other projects lemme know I might find it useful too! 

[Ardric]

Perhaps the input jack should be a stereo jack, to switch power.  You could also add to the BOM an isolated switching power jack, battery snap connector, board mounting standoffs and LED stuff.

[Talentless_Hack]

alright, for version 3b gets the stereo input jack (wire it as a on/off switch and learn how in the FAQ).
i added a battery snap, and some plastic self adhesive standoffs.
the file is at www.contradyk.com/Dr.Boogie3b.htm
all parts sourced at www.smallbearelec.com/StoreFront.bok (not smallbear.com).

more to come, keep the ideas rolling.

and if anyone has a good BOM of their own, i will be happy to spreadsheet it in similar fashion and host it on my site
(unless there is such a place here).

[Grocha]

there  is an official  Dr. Boggie v2.0 layout/schematic/parts ??

[Grocha]

up !!

[ubersam]

Nah... the versions he is talking about are of his BOM sourcing spreadsheet

[Talentless_Hack]

yes, these versions are referring to the bill of materials i am trying to compile.
it is pretty much ready to go for the stock dr.boogie build, with some changes in a few values.

basic audio has a few extra caps you can use, and i believe he has a layout and everything utilizing his changes.

i'm going to be building this for a friend this month (if i get the time) and i'm going to actually change a few things from
the BOM i've written, but for the sake of 'stockness', this is pretty close.