proposed dr. boogey layout -- seeking comments

[gaussmarkov]

argh!!! i forgot to change the MID pot around.  one more try coming soon.

done. 

[John Lyons]

Thanks Gauss

I have one built up with the scaled tone stack values... except for the pots and trimmers.
It gets pretty tight even with 63v box caps and some resistors on end.
The soldering isn't too bad though.
Once I get the rest of the parts I'll report back.

John

[gaussmarkov]

Thanks Gauss

I have one built up with the scaled tone stack values... except for the pots and trimmers.
It gets pretty tight even with 63v box caps and some resistors on end.
The soldering isn't too bad though.
Once I get the rest of the parts I'll report back.

John

in the spirit of responding to the comments that i originally sought  what do you all think of this version?  i have re-inserted a column that we removed a while back and spaced out the capacitors some.  does this address the tightness issues enough?  i believe that we want to keep the signal traces as short as we can because that is helpful in high gain circuits.

[audioguy]

Looks good!

[John Lyons]

Comparing my board to the layout gauss just posted, the new layout looks a lot better and has more space.
Looking good. Thanks for doing that.

Also in looking at the way the pots are layed out I think the bass pot is good is best next to the gain pot since the oscilation is more likely at the higher frequencies...so this gives a little buffer zone between the gain control and the mid and treble pots. Nothing need to be changed...just thinking out loud.

John

[Pushtone]

I'm just looking at the outline for C1.
Are there any 1uf film caps that fit that outline? Or the leg spacing?

I had to use electrolytic at C1.
Fitting a 1uF film cap at C1 looks hard, but I'm sure it can be done if it has long legs.

I'm interested in what caps others are using/planning for the 1uf film caps.

[gaussmarkov]

I'm just looking at the outline for C1.
Are there any 1uf film caps that fit that outline? Or the leg spacing?

I had to use electrolytic at C1.
Fitting a 1uF film cap at C1 looks hard, but I'm sure it can be done if it has long legs.

I'm interested in what caps others are using/planning for the 1uf film caps.

WIMA MKS 2  16VDC   3.5mm x 7.2mm  and  5mm lead spacing.  i think that's what i have shown.

all the best, gm

[gaussmarkov]

hi,  my name is gaussmarkov.  i am a layout addict ... this is a little simpler ...  i need help ...

[John Lyons]

Here's my board so far.
The blue 1uf caps aren't Wima brand but they are 5mm spacing I believe...They fit at least.




John

[gaussmarkov]

ah, and it's a beautiful sight, too ... that 22nF for C7 is a healthy sized cap.    you and pushtone do lovely work.

[Nashtir]

is this layout the latest you posted on your website?

[Bucksears]

Not to derail all of the work done on this or hi-jack this thread, but to take it in a slightly different direction.......

I know that we (myself included) have looked at making PCBs as small as possible (to fit in cases as small as possible) due to pedalboard real estate being at a premium.
But why not simply give up a little bit of space and spread things out a bit? I'm definitely taking some of the cues from this new thread (scaling down the values in the tonestack/volume), but my next DB build is going to be in a case larger than the 1590BB that my current DB is in. The gain controls are going to be far from the tonestack, volume and input. The PCB is also going to be at least 50% larger than my current one so things will have room to breathe. I'm pretty sure that my PCB has pads for everything on the ground rail, so that's a universal grounding point.
I'm measuring centering the case now and will be drilling it tonight for a precoat of primer; I'll have more info as soon as it's available - waiting on some more trimmers from Smallbear.

Anyone else have any input on the physical proximity playing a part in the noise generated in high-gain devices?

- Buck

[gaussmarkov]

is this layout the latest you posted on your website?

yes. 

Not to derail all of the work done on this or hi-jack this thread, but to take it in a slightly different direction.......

no worries!  i think you are completely inside the spirit of this thread.

I know that we (myself included) have looked at making PCBs as small as possible (to fit in cases as small as possible) due to pedalboard real estate being at a premium.
But why not simply give up a little bit of space and spread things out a bit? I'm definitely taking some of the cues from this new thread (scaling down the values in the tonestack/volume), but my next DB build is going to be in a case larger than the 1590BB that my current DB is in. The gain controls are going to be far from the tonestack, volume and input. The PCB is also going to be at least 50% larger than my current one so things will have room to breathe. I'm pretty sure that my PCB has pads for everything on the ground rail, so that's a universal grounding point.

i think you are correct that component placement can make a difference.  and trying your experiment seems well worthwhile.  i suppose we would all like to know where the boundary is between too close and unnecessarily far apart.  or principles for keeping components from interacting badly.  what i tried to do was follow some of the principles that i had seen described:  a signal path that does not double back on itself, grounded guard traces, and star grounding.  the first two address the same issues that you are talking about, i think.

some of the noise, and i don't think we know yet how much, is fundamental to the character of the circuit.  the high gain of the dr. boogey is going to come with higher noise than other circuits.  no matter how we arrange the components that noise will be there.

i don't think a "universal grounding point" is the same thing as star grounding--but i also don't know how much that has helped us.  a good test of the layout i posted above would be to build it, your original layout, and your newest layout all with the same components and enclosure and make a side-by-side comparison.  unfortunately, that is unlikely to happen.  we do have pushtone's two builds to go on and they suggest that we have made progress on the oscillation issues but not the noise.  if i were placing a bet, i would go with saying that we cannot reduce the noise appreciably from where it is.  but i certainly do not know this for a fact.

so i (for one) certainly want to encourage the additional discussion and experimentation that you are bringing to the table.  i'm sure everyone else feels the same way.

cheers, gm

[Pushtone]

Other than  fitting the pots in a 1590BB there seems to be spare room for a larger board.

Bucksears's layout







Gaussmarkov's layout






Why a bigger box? Both these builds work fine.

The biggest difference is how the two builds handle the grounding.
For Buck's layout, the shield on the I/O wires go to the nearest ground point
and the LED, I/O jacks and DC jack connect to the PCB ground trace.
I did  something strange I didn't remember.
I used the two conductors of shielded mic cable to connect the MID pot lugs 1 & 3. Why? I don't know.
I really need to get back to the Buck build and replace that weirdness.
It needs a few thing to bring it into line with some of the Gauss build improvements.

For Gauss's layout all grounds go to the out jack.

[Pushtone]

About the noises.... hum and hiss.

Hum:
I'm biasing at 7.78V at Q1 to reduce the hum and buzz.

What do you all think of that?


Hiss:
I'm hoping that the MPF102 at Q1 and Q2 will reduce the hiss. Just ordered some.
Maybe then I can get closer to 4.5V on the bias with it.

[John Lyons]

The BB size layout is a good standard standard to use. Most people use those size boxes.

Personally I use larger than that but...
It would be nice to have a larger sized layout but I'm not sure how the noise will change. The "noise" from my Buck Sears layouts (when they were working well) was just a bit of "snow" / rushing noise, that's per usual with all high gain builds as well as the actual amp!

Making the board larger is fine with me because I make large pedals in general, but I'm not sure is making it larger would cut down on any "audio boogers" It would make sense that a larger layout would help...I'm just not sure in our case here.

Pushtone
Near 8v is pretty high on the biasing. I usalluy go something like 4.5-6v across the board with all the trimmers depending.
Turning down the gain pot takes Q1 out of the mix pretty well. I don't have a DB here that is operational to try it out now, but you might want to experiment with the trimmer voltages other than Q1. Set Q1 about 5v... Q1 sets the gain level of the first stage which is the most critical signal, so setting this too far off may throw of the initial gain to the whole circuit. Whereas adjusting the voltages here and there may give you a better all in all tone/noise floor.

Also, individual FETs can ne noisey and have higher or lower gain. Making that FET matcher is looking better and better!
Try a few Fets (J201s) in the first position and see what you come up with.

John


John

[Bucksears]

Overall, I guess are we moving away from biasing to 1/2 the supply voltage and simply biasing each transistor to a 'sweet spot'? Mojotron mentioned this when he first introduced his Plexizer, he said that he would turn the gain up and then adjust each trimmer to the 'loudest' point. I've always been biasing to 1/2 voltage, but I'm open to suggestions.
Thanks guys,
- Buck

[Pushtone]

The "noise" from my Buck Sears layouts (when they were working well) was just a bit of "snow" / rushing noise, that's per usual with all high gain builds as well as the actual amp!

Thats exactly what I meant by "hiss".  I also call it "waterfall noise".
Both my build have it in equal amounts.

There is little difference in sound between my two builds and what difference there is I guessing is caused by the 100k VOL pot and lack of the 68k input resistor. I need to normalize these differences to make the builds more comparable.



About the bias. Adjusting Q1 bias does the most for reducing hum and buzz and does not seem to effect the amount of gain, just the smoothness of the distortion. Adjusting the other trimmers seems to do little to reduce hum or effect the tone. I set Q3-5 at 5.5v

[John Lyons]

Pushtone
Q1 is the most sensitive FET I would think. It sets the level for the whole circuit and is the most sensitive to hum, noise pickup and external noise getting in the circuit.

Hum is a grounding issue, or at least a layout/wiring issue.  I don't think the biasing will affect it. Q1 biasing will affect the input level and any hum there but otherwise I think hiss will be affected by FET choise (gain and noise inherent to the particular FET and FET number (MPF102, J201, 2N5457 etc)

The general hiss/waterfall/snow is just the circuits noise, I would think will be in any build using these parts values.

John

[Victor]

Pushtone
Q1 is the most sensitive FET I would think. It sets the level for the whole circuit and is the most sensitive to hum, noise pickup and external noise getting in the circuit.

Hum is a grounding issue, or at least a layout/wiring issue.  I don't think the biasing will affect it. Q1 biasing will affect the input level and any hum there but otherwise I think hiss will be affected by FET choise (gain and noise inherent to the particular FET and FET number (MPF102, J201, 2N5457 etc)

The general hiss/waterfall/snow is just the circuits noise, I would think will be in any build using these parts values.

John

Is there any chart/value/graphic/indication that shows those noise characteristics on each FETs datasheets?