proposed dr. boogey layout -- seeking comments

[John Lyons]

The Source bypass cap and resistor will make a difference is gain and tone. No cap will have less gain (which can be a good thing) as well as less treble. 1uf is a treble boosting cap as used here. Boosting the treble/cutting bass is how these high gain amps get a nice crinch sound without getting "farty" or "flubby" in the low end. Changing the resistance will change the bias a little depending on how far you change from the original value. More drain voltage will yeild a cleaner sound which can sound nice with the DB.
You can solder a couple wires to the source resistance points on the board and experiment with different resistance and capacitance.
I would think you could get some nice lower gain sounds without the some of the 1uf bypass caps.

John

[Pushtone]

Troubleshooting the backwards MID pot wasn't so hard.
I noticed Buck's MID and BASS pot wiring was a little different.

I reversed the MID pot so that lug-3 on MID went to lug-1 on BASS.
Works better now.



Gussmarkov, I used your March 14 2007 project file.  Backwards MID pot wiring.
Simple to fix, just reverse lugs-1 and 3 on MID pot. Most folks will figure it out on their own.
I did and I'm no electronics wiz.






Sounds good on almost every amp I tried so far EXCEPT for a new 2005 Fender Twin. I think it's a reissue version??
Could not get a good tone out. I wonder if the Twin didn't like the high output impedance?
But the sound was all high-end, hissy and brittle, not darker.

This same amp didn't like my other "Buck" Dr Boogey either.
Same result - ultra sonic high end, brittle, unpleasant.

The Twin sounds great clean. I was disappointed.

Here's a kicker, I had several of my new distortion builds "on demo" and
several players agreed the Thunderchief sounded best (with the same Fender Twin) !

Go figure.

I also remembering someone asking if these "amp" pedals can be used as a regular preamp and patched into the amp's effects return.
I tried it and I get MORE THAN ENOUGH gain to drive the power amp section of my combo. The sound through the return was warmer, and less noisy.
The tone controls worked well to shape the sound, better in fact that thru the amp's preamp.
Bass response was the same as thru the preamp. In combination with the TREBLE control and the Presence on the amp I am able to control the high end from dark to sparkly.

I find I set the TREBLE control low around 9 o'clock when plugging into the amps input preamp.
But when connected to the effects return the TREBLE control is much warmer when turned past 12 o'clock.
The sound is more open, less harsh and generally better than  when passed thru the amp's input preamp.

Tried it with the ROG English Channel too. Same deal. It sounds better.
I only have one solid state amp with an effects loop to test with but I'm going to say yes, they can be used as preamps to drive power amps.

[MetalGuy]

Instead of messing with the tone stack why not just add to the layout a simple buffer /switchable?/ after the TS like the one found in Randall's preamp?

[John Lyons]

Adding a buffer after the TS sounds practical. Maybe just another source follower?

John

[Victor]

I've made some improvements over the gm's layout. Added output buffer, mid pot wiring corrected and made connections "board-pots" as simple as possible. My board looks a little diferent. Here it is:

http://rapidshare.com/files/23212138/gm_layoutDr._Boogey_mid_pot_corrected_added_output_buffer.rar.html

I'm not sure about the output cap position (before or after Q6)...... 

[dschwartz]

My express pcb throws an error trying to open the files...
can you make a pdf or image file please?

[John Lyons]

I could not get to the file either. I can host it for you if you want. just email me.
A schematic would be good as well as the layout. I know Gauss will amend his layout as well when he gets back here.

John

[Victor]

My express pcb throws an error trying to open the files...
can you make a pdf or image file please?

I used Eagle for layout prototyping, as usual.

Here are the imgs:

[Victor]

I could not get to the file either. I can host it for you if you want. just email me.
A schematic would be good as well as the layout. I know Gauss will amend his layout as well when he gets back here.

John

John, check your email please. 

[audioguy]

As much as we all appreciate the image files... PLEASE WARN BEFORE SENDING US TO A WEBSITE WITH PORN ON IT!

[John Lyons]

Yikes!
Yeah, maybe that isn't the best place to host stuff...or at least to send links to people here ...
Nothing wrong with sex but there are way too many issues with porn to get into here.
Ah the internet!

Heres the schematic at any rate.



With the Layout you should probably take out the registration marks so you can read the values. Also, the pots won't fit unless you are using long PCB lugs (do they even make those anymore?) The pots overlap...

John

[Victor]

Sorry,

I had some trouble using imageshack.us here........ 

Let me try again to see if works.....

[dschwartz]

If we were "Bender" from Futurama, all the stuff we work on would be porn..

Thanks god my 4 year old nephew is not into bouilding a DB!!! fuiuuu

now These one could be called a "dual rectal" as mine does!!! hahahaha

[Pushtone]

Heres the schematic at any rate.

Great evolution in this thread as you've stated.

I was about to ask what's different on this schematic.
Now I see the file name for the image, "Boogey with Buffer".

So is the buffer the only difference from Guss's last schem?
Good idea to keep Guss's component reference numbers. Just seeing C17 thru 22 tells me a lot.

[Victor]

With the Layout you should probably take out the registration marks so you can read the values. Also, the pots won't fit unless you are using long PCB lugs (do they even make those anymore?) The pots overlap...

John

I considered the idea of using pots directly soldered to the PCB, but it was not going to be very practical, at least for me..... then I re-organized the pots' holes so I can solder wires to them and minimize those crossing lines between floating components (oscillation madness).

[John Lyons]

Is C22 Necessary? The Tone stack decouples the output of the buffer already.
Don't forget 1M pulldown at the end of the circuit right before the output jack.

Pushtone
Q6 and it's components (Source 10K and C22 and C23) are the only additions to the schem as gauss had it.
I'm sure you could add in the buffer as a small satallite board. Shame to waste all your work on the one you have now.

Gauss should chime in soon as he's "back" tomorrow.

Anyone see anything we can improve on with the output buffer? I don't know my buffer theory.
Will it do for our  purpose as Q5 does fore the tone stack?

John

[Victor]

1M pulldown resistor at the end? If we add it to the circuit, I believe that the output impedance would be its value in parallel to Q6's source resistor....... resulting in about 9.9K ohms, aprox........ is that correct? And why would the circuit need a pulldown resistor just at the end of it?

I also believe the output buffer is OK, gain is around unity, a little less. Source follower has high input impedance and low output impedance.

[John Lyons]

The puldown resistor at the end is for pop protection and discarging the output cap...with the bypass switch.
I didn't think about it enough though...
The Impedance is 10k at the output of the buffer correct?
So maybe adding a pulldown resistor to equal 10K overall resistance to ground would be fine...

Maybe making the buffer have s light bit of gain would be good as well. The tone stack eats up a lot of signal gain.


John

[Victor]

The puldown resistor at the end is for pop protection and discarging the output cap...with the bypass switch.
I didn't think about it enough though...
The Impedance is 10k at the output of the buffer correct?
So maybe adding a pulldown resistor to equal 10K overall resistance to ground would be fine...

Maybe making the buffer have s light bit of gain would be good as well. The tone stack eats up a lot of signal gain.


John

We should proceed with caution about that. Dr. Boogey has a lot of gain, I believe it wouldn't be necessary to add another "gainy" stage (even with JFET topology in common drain config - gain around -10). Our main goal at this moment is just to lower the output impedance, I think. A buffer w/ gain can cause some frequency boosts (or not). And almost all the pedal schems seen around have a source follower buffer after tone-stack and/or vol. pot.

I'll try to add an external buffer to my Dr. Boogey (Buck layout), and see what happens with it on and off my signal chain...... maybe is worth the shot.... 

[Victor]

There you go, finally Imageshack.us worked here......

Layout with just components names:



Layout with just components values:



Schematic: