cdwillis
Well-known member
- Build Rating
I've had this blues breaker pcb sitting around for a while and forgot about it. Found it in my stash last night and decided to finish building it out. I made a couple minor mods to the circuit when I built it. When I was done I realized I was missing the nut for the outie DC jack. I have some more on order. The innie jack uses a similar size nut, but it's just a little too small to thread onto the jack.
I went off the schematic using the 33k and 27k resistors on the first gain stage. The one I built before I used the 4.7k and 3.3k resistors. I'm not sure how much of a difference it made in the tone, but it seems warmer over all. The tone knob really needs to be at least around noon or higher to really deliver a decent amount of presence. I'm using humbuckers here so maybe it would be a little brighter with single coils.
The output volume was just miserable on the first one I built. On that one I used the stock a100k volume pot. On this one I used a linear pot instead. The overall volume isn't really louder, but most of the volume was bunched up at the end of the sweep with the logarithmic pot. If anyone builds one of these I would definitely use a b100k pot for the volume. If I put all the pots at noon it's just under unity gain where on the old one I'd have to have the volume pot up to 3 o'clock or so if I remember right with the gain at noon just to achieve unity volume.
I also put a 100k resistor in parallel with lugs 2 and 3 of the drive pot like the King of Tone. This seems to give it a smidge higher gain at minimum drive setting. With the 100k resistor in parallel with the 100k on the pot at that setting you're getting 50k. If I understand it right, gain should be 220k divided by (50k+10k) so 3.6~ vs the stock 2 gain. The idea here was I was trying to get more output volume with the drive knob turned down. I tried the pedal without the 100k resistor soldered in then with it. It wasn't a drastic change. I do think the overall drive sweep might be a little better. It's hard to tell without putting it on a switch to compare on and off.
Oh and I used a 100pf cap in the first gain stage rather than 47pf. There shouldn't be that much of a difference. At max the low pass filter hits about 16khz, way above a guitar speakers output capability and most people's ability to hear.
I have an NE5532 in there because I had one handy. I'm going to find a TL072 and LM833 to audition to see if they change the sound much. I have one built on a breadboard to try some more mods on. I might try swapping the 25k tone pot and 10nf tone cap to a 10k pot and 22nf cap to see if the lower resistance increases the output volume some more. I replaced the stock tone control with a Stupidly Wonderful Tone Control then eliminated the 6.8k/10nf low pass filter afterward and got a noticeably higher output volume. I think there are some ways to improve upon the circuit without adding more op amps or gain stages.
I went off the schematic using the 33k and 27k resistors on the first gain stage. The one I built before I used the 4.7k and 3.3k resistors. I'm not sure how much of a difference it made in the tone, but it seems warmer over all. The tone knob really needs to be at least around noon or higher to really deliver a decent amount of presence. I'm using humbuckers here so maybe it would be a little brighter with single coils.
The output volume was just miserable on the first one I built. On that one I used the stock a100k volume pot. On this one I used a linear pot instead. The overall volume isn't really louder, but most of the volume was bunched up at the end of the sweep with the logarithmic pot. If anyone builds one of these I would definitely use a b100k pot for the volume. If I put all the pots at noon it's just under unity gain where on the old one I'd have to have the volume pot up to 3 o'clock or so if I remember right with the gain at noon just to achieve unity volume.
I also put a 100k resistor in parallel with lugs 2 and 3 of the drive pot like the King of Tone. This seems to give it a smidge higher gain at minimum drive setting. With the 100k resistor in parallel with the 100k on the pot at that setting you're getting 50k. If I understand it right, gain should be 220k divided by (50k+10k) so 3.6~ vs the stock 2 gain. The idea here was I was trying to get more output volume with the drive knob turned down. I tried the pedal without the 100k resistor soldered in then with it. It wasn't a drastic change. I do think the overall drive sweep might be a little better. It's hard to tell without putting it on a switch to compare on and off.
Oh and I used a 100pf cap in the first gain stage rather than 47pf. There shouldn't be that much of a difference. At max the low pass filter hits about 16khz, way above a guitar speakers output capability and most people's ability to hear.
I have an NE5532 in there because I had one handy. I'm going to find a TL072 and LM833 to audition to see if they change the sound much. I have one built on a breadboard to try some more mods on. I might try swapping the 25k tone pot and 10nf tone cap to a 10k pot and 22nf cap to see if the lower resistance increases the output volume some more. I replaced the stock tone control with a Stupidly Wonderful Tone Control then eliminated the 6.8k/10nf low pass filter afterward and got a noticeably higher output volume. I think there are some ways to improve upon the circuit without adding more op amps or gain stages.
