Sherwood Drive - How to add more low end?

ThinAir

Member
I built a Sherwood Drive a few months back and found the overall tone to be kind of shrill and treble-heavy. No matter how I adjust the bass and treble knobs, I can't dial the treble-heavy tone out of the pedal. I tried a couple different OpAmps but that really only changed the granularity or feel of the gain, not the overall tone. When comparing my IC voltages to those graciously shared by DevouredDeth, they were pretty reasonably in-line with his.

What mods could I make to maybe let more bass get through the signal? Any idea which caps or resistors I'd look at swapping out and which values I'd use? As I recall, I built this one according to the build docs and didn't make any substitutions.
 

Nostradoomus

Well-known member
Try bumping your input cap up to 220n (C9) and see how you like it. If it’s still no good we can work on the EQ!

Edit: A good idea may be to socket that cap and play around with higher values, 220 should be good though but I haven’t built this one so 🤷‍♂️
 

Chuck D. Bones

Well-known member
C9 & R14 have a 47ms time constant. Translates to 3.3Hz corner freq, so changing C9 won't get you there. Messing with C8 can add a little more bottom-end. C8 & R13 have a 1ms time constant = 154Hz corner freq, not high enough to explain the treble-heavy tone. A treble booster has a corner freq up in the KHz range. I think in this case it's EQ controls causing the bright tone. The TREBLE control is boost only. The flat tone setting is TREBLE at zero and BASS at noon. So if you are 100% sure that the board is built exactly to the drawing, we can go for mods in the EQ section. First, make sure that there is continuity from pin 1 on the TREBLE control to Vref. If pin 1 is floating, there would always be treble boost.

I can think of two mods right off the bat:
1) Add a cap from BASS pin 1 to Vref or GND (doesn't matter which). 1nF should be more than enough. The TS and its derivatives usually have a cap there to roll-off the high end.
2) Disconnect TREBLE pin 1 from the board and connect it to BASS pin 1. This will make TREBLE boost and cut, like the BASS control. Flat setting will then be BASS & TREBLE both at 50%.

I'd experiment with door #1 first using clip leads because it's easy. Try 330pF, 1nF & 3.3nF to see if any of those do what you want. You can apply both mods, but I'd try them one at a time first.
 
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Devoureddeth

Active member
I built a Sherwood Drive a few months back and found the overall tone to be kind of shrill and treble-heavy. No matter how I adjust the bass and treble knobs, I can't dial the treble-heavy tone out of the pedal. I tried a couple different OpAmps but that really only changed the granularity or feel of the gain, not the overall tone. When comparing my IC voltages to those graciously shared by DevouredDeth, they were pretty reasonably in-line with his.

What mods could I make to maybe let more bass get through the signal? Any idea which caps or resistors I'd look at swapping out and which values I'd use? As I recall, I built this one according to the build docs and didn't make any substitutions.
Yeah it is fairly trebly sounds like it functions as normal. I use it primarily for clean downtuned bass sections and never as an always on thing with the bass almost max and treb turned down. If you can tame the treble a bit it would be a great always on pedal.
 

ThinAir

Member
C9 & R14 have a 47ms time constant. Translates to 3.3Hz corner freq, so changing C9 won't get you there. Messing with C8 can add a little more bottom-end. C8 & R13 have a 1ms time constant = 154Hz corner freq, not high enough to explain the treble-heave tone. A treble booster has a corner freq up in the KHz range. I think in this case it's EQ controls causing the bright tone. The TREBLE control is boost only. The flat tone setting is TREBLE at zero and BASS at noon. So if you are 100% sure that the board is built exactly to the drawing, we can go for mods in the EQ section. First, make sure that there is continuity from pin 1 on the TREBLE control to Vref. If pin 1 is floating, there would always be treble boost.

I can think of two mods right off the bat:
1) Add a cap from BASS pin 1 to Vref or GND (doesn't matter which). 1nF should be more than enough. The TS and its derivatives usually have a cap there to roll-off the high end.
2) Disconnect TREBLE pin 1 from the board and connect it to BASS pin 1. This will make TREBLE boost and cut, like the BASS control. Flat setting will then be BASS & TREBLE both at 50%.

I'd experiment with door #1 first using clip leads because it's easy. Try 330pF, 1nF & 3.3nF to see if any of those do what you want. You can apply both mods, but I'd try them one at a time first.
I tried option No. 1 with a 1nF cap and I think it really did the trick at taking a good amount of bite out of the treble. Many thanks!!
 
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