I just got done building the GTC Bloody finger ( chrome dome) and the noise floor is just insane. I built the board just as it called for but used MSPA18 in Q2-3...I read about some people having issues with the tone control, everything works fine......its just sooo loud. Is there anything I can do to possible bring down the noise floor?
CD4049UBE noise
- Thread starter knappster
- Start date
Feral Feline
Well-known member
You might have a bad CD4049UBE chip. Try swapping chips, and if possible get an NOS chip. I recall Chuck D Bones had trouble with a circuit that worked well once he got rid of the newer 4049UBE (TI?) and put in an original-manufacturer IC (UTC? Intersil? I forget..).
Oh, and ...
POST PICS!
Oh, and ...
POST PICS!
I'll post picks later today. I ordered some other chips from stompboxparts. I also read about grounding 3 pins on the IC that aren't being used... As a noob does that mean running wire to those points and hooking it up to ground?You might have a bad CD4049UBE chip. Try swapping chips, and if possible get an NOS chip. I recall Chuck D Bones had trouble with a circuit that worked well once he got rid of the newer 4049UBE (TI?) and put in an original-manufacturer IC (UTC? Intersil? I forget..).
Oh, and ...
POST PICS!
I forget right now which pins. Maybe 9-11-14 something like that
Feral Feline
Well-known member
The Chrome Dome PCB should already have grounded any pins needing grounding... 
Otherwise, yes: ground pins 9, 11, and 14. Use a DMM to check if they're grounded or not.
Dang, I've got some notes I made in my build doc, but forgot to attribute them — I don't know who/where they're from, but one of them suggests adding a 10k resistor at C7.
Just lift one lead of C7, the side connecting to TONE's lug-1 and tack in the resistor so it's in series with C7.
Another mod suggests upping C9's 22p to 100p+.
There's also ...
a Q mod at R9 and
boost mod at R20 ...
I don't see those last two helping any with the noise issue, though.
Otherwise, yes: ground pins 9, 11, and 14. Use a DMM to check if they're grounded or not.
Dang, I've got some notes I made in my build doc, but forgot to attribute them — I don't know who/where they're from, but one of them suggests adding a 10k resistor at C7.
Just lift one lead of C7, the side connecting to TONE's lug-1 and tack in the resistor so it's in series with C7.
Another mod suggests upping C9's 22p to 100p+.
There's also ...
a Q mod at R9 and
boost mod at R20 ...
I don't see those last two helping any with the noise issue, though.
Chuck D. Bones
Circuit Wizard
The current production CD4049s from TI are crap for audio use because they are noisy. These are CMOS digital parts which are designed for digital use, not audio. The fact that some of them work for audio is a happy accident. Unfortunately, with all of the consolidation in the semiconductor industry, Texas Instruments is the only company currently manufacturing CD4000-series parts and their process is optimized for performance & yield, not for low noise in an audio application.
If you want to build a CMOS OD using a CD4049 or 4069, you have to get your hands on some vintage parts made by National Semiconductor, RCA, Intersil or Hitachi. These are the ones I know are good. There may be other brands. Good luck finding some. There are some advertised on eBay but they are pricey and you really don't know what you are getting until they arrive and you test them. I found some on EG and bought them out (they only had a couple dozen). I also found some at a local Electronics store and bought them out too (again, only obtained a couple dozen). I paid around $1 each at both vendors. Buying parts from an unauthorized supplier is risky because you don't know how they were handled or stored. CMOS parts are very susceptible to ESD and the damage may or may not be obvious. A weakened part might be noisy, it might be unreliable. I have returned CMOS on eBay because they were not properly packaged in and ESD safe manner.
I don't like the Bloody Finger circuit because is has a serious design problem. The Crybaby circuit was designed to drive a high-impedance amplifier input, not a CMOS distortion stage. Pedal PCB faithfully replicates production pedals circuits, warts & all. If the original design has problems, the clones will too. There are better ways of making CMOS ODs. You can read about them in Chucks Boneyard.
If you want to build a CMOS OD using a CD4049 or 4069, you have to get your hands on some vintage parts made by National Semiconductor, RCA, Intersil or Hitachi. These are the ones I know are good. There may be other brands. Good luck finding some. There are some advertised on eBay but they are pricey and you really don't know what you are getting until they arrive and you test them. I found some on EG and bought them out (they only had a couple dozen). I also found some at a local Electronics store and bought them out too (again, only obtained a couple dozen). I paid around $1 each at both vendors. Buying parts from an unauthorized supplier is risky because you don't know how they were handled or stored. CMOS parts are very susceptible to ESD and the damage may or may not be obvious. A weakened part might be noisy, it might be unreliable. I have returned CMOS on eBay because they were not properly packaged in and ESD safe manner.
I don't like the Bloody Finger circuit because is has a serious design problem. The Crybaby circuit was designed to drive a high-impedance amplifier input, not a CMOS distortion stage. Pedal PCB faithfully replicates production pedals circuits, warts & all. If the original design has problems, the clones will too. There are better ways of making CMOS ODs. You can read about them in Chucks Boneyard.
Chuck D. Bones
Circuit Wizard
Sorry I had to be the bearer of bad news.
Interestingly, TI's CD4007 triple inverter is quiet. Not a drop-in replacement for CD4049 or CD4069, but worth considering for new designs.
Interestingly, TI's CD4007 triple inverter is quiet. Not a drop-in replacement for CD4049 or CD4069, but worth considering for new designs.
