BBE Green Screamer Overdrive Schematic

[wampcat1]

Thought someone might get some use out of this:
http://www.indyguitarist.com/schematics/z-unsorted/bbe_green_screamer_schem.gif



bw

[ulysses]

the sound quality of the demos on their website is so appauling it hard to tell what it really sounds like..

cheers
ulysses

[wampcat1]

I haven't heard the soundclip, but it is just a bufferless tubescreamer type circuit with less gain.

nothing new. 

[bioroids]

I think a resistor may be missing from the non-inverting input of the first opamp to Vref, or does it use a bipolar supply?

Regards

Miguel

[Paul Marossy]

it is just a bufferless tubescreamer type circuit with less gain.

So is it more like a dirty booster pedal then?

[Paul Marossy]

it is just a bufferless tubescreamer type circuit with less gain.

So is it more like a dirty booster pedal then?

[RGW]

I think R6 should be

a) on the other side of the input cap
and
b) connected to +4.5VDC versus ground

take care,
Robbie Wallace

[wampcat1]

I think a resistor may be missing from the non-inverting input of the first opamp to Vref, or does it use a bipolar supply?

Regards

Miguel

yes, the bias resistor isn't there, but I figured most people would know that one was needed. Throw a 10k in there and you'll be fine.
bw

[wampcat1]

I think R6 should be

a) on the other side of the input cap
and
------------------same thing basically
b) connected to +4.5VDC versus ground
--------------nope, it's ground

take care,
Robbie Wallace

[RGW]

yes, the bias resistor isn't there, but I figured most people would know that one was needed. Throw a 10k in there and you'll be fine.
bw

If you do that with no input buffer, the input impedance will be around 10K, which is way too low.

take care,
Robbie

[RGW]

I think R6 should be

a) on the other side of the input cap
and
------------------same thing basically

Which side of the input cap it is on makes a big difference. If it is on the input side and going to ground, it is probably a pulldown resistor. If it is on the output side of the cap and connected to the +4.5VDC bias it is setting the input impedance of the circuit and supplying DC bias to the opamp.

take care,
Robbie

[wampcat1]

I think R6 should be

a) on the other side of the input cap
and
------------------same thing basically

Which side of the input cap it is on makes a big difference. If it is on the input side and going to ground, it is probably a pulldown resistor. If it is on the output side of the cap and connected to the +4.5VDC bias it is setting the input impedance of the circuit and supplying DC bias to the opamp.

take care,
Robbie

sorry, I misunderstood you... I thought you meant r6 should've been before c3.
r6 is just for the bypass pop.

bw

[wampcat1]

yes, the bias resistor isn't there, but I figured most people would know that one was needed. Throw a 10k in there and you'll be fine.
bw

If you do that with no input buffer, the input impedance will be around 10K, which is way too low.

take care,
Robbie

yep, sorry I was just thinking of the tubescreamer circuit.... throw a 470k to 1meg in and you'll be fine then...pretty common value there.

[RGW]

yep, sorry I was just thinking of the tubescreamer circuit.... throw a 470k to 1meg in and you'll be fine then...pretty common value there.

Thanks for sharing the schematic, it is time consuming tracing circuits, drawing it out, etc. That is cool of you to take the time and share it.

take care,
Robbie

[Paul Marossy]

I drew up my own schematic for this circuit today as I'm going to be modding one.

Just to make some clarifications/additions/corrections to the schematic above:

1. The 1K input resistor is R5, not R6
2. R6 is a 10M resistor to ground, not a 1M (it is indeed a pulldown resistor)
3. There is a 1M resistor, R4, connected between the Pin 3 of the opamp and Vref
4. There is a 10K voltage divider, R2 & R3, for the Vref supply
5. There is a Vref cap, C2, which is a 10uF polarized type
6. There is a 100pF cap, C5, in parallel with diodes D3 & D4
7. There is a 1K resistor, R12, between C9 and the 10K level control
8. Gain control is VR1, Tone control is VR2 and Level control is VR3
9. The main power filter cap is C1, and is 1000uF (!)
10. The output cap, C9, is a 1uf non-polarized electrolytic type