# Sherwood Drive - How to add more low end?



## ThinAir (Oct 1, 2019)

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.


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## Nostradoomus (Oct 1, 2019)

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  ?‍♂️


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## Chuck D. Bones (Oct 1, 2019)

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 (Oct 1, 2019)

ThinAir said:


> 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.


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## Chuck D. Bones (Oct 1, 2019)

Well put.  It's really not about adding more low end because the low end is already there.  It's about taming the high end so it's all in balance.  At the end of the day it's JATS.


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## jubal81 (Oct 2, 2019)

Try checking to make sure C8 is 220n and not 22n.


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## ThinAir (Oct 3, 2019)

Chuck D. Bones said:


> 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.
> ...



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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## sticky1138 (Jun 26, 2021)

Chuck D. Bones said:


> 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.
> ...


I just finished this build and it sounds great but shrill when the treble isn't at zero, so I'm going to try #1 as well.

By GND you mean the hole on the bottom of the PCB labeled "GND" or somewhere else? And is "Vref" one of the IC holes? Never heard that term before, and I'm not yet familiar with reading schematics. JATS = __ __ Tube Screamer? Pretty new to this and trying to figure things out.


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## Chuck D. Bones (Jun 26, 2021)

Welcome.  The discussions in the Mod forum can get pretty technical, so being able to read a schematic and decipher the jargon is key. 

GND is any hole on the PCB labeled GND.  It's also the sleeve on the In & Out jacks and the minus on the power jack.  Once the jacks are installed in the box, the entire box is GND.

Vref is wherever the schematic says it is.  It varies from one circuit to another.  Sometimes one of the IC leads connects directly to Vref, but not always.  On the Sherwood, Vref can be found at the end of R15 closest to Q1.

JATS = Just Another Tube Screamer


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## sticky1138 (Jun 26, 2021)

Thanks for your help.

I did the 1nF mod, but ended up liking it stock better. The extra cap does makes the EQ more versatile, but it also makes the pedal sound more like a generic Tube Screamer (JATS) with subdued highs and a bit of a mid boost. For some that's an improvement, but it takes away the character of the Sherwood and I'm thinking the treble boost option might even be useful with dark humbuckers.


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## Feral Feline (Jun 27, 2021)

I'm thinking of upgrading my JATS to a YATS.


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## Feral Feline (Jun 28, 2021)

😸 I got my first yawn!


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