How To Mod TS9 Tubescreamer pedal

basic modding SuppliesEach of the modifications discussed here require the following :

Solderingiron 60/40rosin-coresolder(dontbuylead-free) Soldersucker(notmandatory,butveryhelpful) Desolderingbraid Smallsidecuts/wirecutters Felt-tipmarker

If youve ever owned an Ibanez TS9 Tube Screamer or a Boss SD-1 Super Overdrive, youve probably noticed two things: You like the way they sound, but they could also really use a little some-thing more. Weve come up with some custom modifications that we feel give these pedals that something moreand the best part is that you can do the mods on your own! All you need to be able to do is follow instructions and know how to solder and desolder. (If you havent soldered beforeor if you are a bit rusty and need a refreshergo to YouTube and watch CuriousInventor.coms video How and WHY to Solder Correctly, and ExpertVillage.coms How to Solder: Removing Solder.)

Modifying pedals can be an intensely rewarding experienceits like creating an entirely new pedal that feels and breathes differently

than before. Sometimes its a battle, a game of wits, with you pit-ted against a mechanism that you so bravely took apart with the intentions of creating something more wonderful and awe inspiring. Sometimes it can be an emotional rollercoaster, especially if you are somewhat attached to the pedals that you are modifying. Its very frustrating to be pumped up to play through your newly modded pedal and have it not work. Thats why its so crucial to follow all of the instructions outlined in this article. No one wants to break a perfectly good pedal while trying to improve it. Fortunately, if you follow the instructions outlined here, youll have an awesome-sounding pedal for you and the rest of the world to enjoy for the rest of your musical daysand that is where the fun lies.

Okay, lets get started!

premierguitar.com PREMIER GUITAR OCTOBER 2012 77

FEATURE > 5 DiY moDS

Story and photoS By Brian WaMpler

Pedal maestro Brian Wampler of Wampler Pedals shows us how to make two of the most popular overdrive pedals on the planet rule even more.

Pedal maestro Brian Wampler of Wampler Pedals

than before. Sometimes its a battle, a game of wits, with you pit-ted against a mechanism that you so bravely took apart with the intentions of creating something more wonderful and awe inspiring.

CLICK HERE to head online and

view the visuals

for this story.

StAGe 1: Assess mod DifficultyThis first stage is important because its when you decide whether to attempt a specific modification. The steps include:

1. Read all of the instructions.2. Make a supply list (if one is not provided).3. Determine the overall difficulty of the modification.4. Decide whether or not you can pull off the mod without

adversely affecting your pedal.

This last step is very important. If you dont feel comfortable with the mod, dont do it! Start with something easier and work your way up to build confidence and skill. Some of the modifications were talk-ing about here are pretty tricky, and they will be much more difficult (though not impossible) for beginners. Note: Neither I nor anyone at my company, Wampler Pedals, can provide technical support for these modifications or assume responsibility for pedals damaged while perform-ing these mods. If these modifications are too difficult for you, we may be able to perform them on your pedal, depending on our workload at the time. Visit wamplerpedals.com and click the Contact link for more details.

StAGe 2: prep for the modIf, in stage 1, you decided the mod isnt a good idea at the moment, this stage includes boxing up your pedal and sending it in to us. If you are doing the mod, the steps include:

1. Turn on your soldering iron. I do this first so that it will be up to temperature by the time I am done with the rest of the steps.

2. Gather parts, wire, and tools as described in your supply list.3. If you use a sponge to clean your irons tip, wet it now.4. Take a deep breath.

StAGe 3: mod time!This is the stage where it all happens. The steps include:

1. Remove the pedals back panel and take pictures of how the circuit board and other internal parts are oriented before mak-ing any changes.

2. Take the circuit board out of the pedals enclosure. Note: Some circuit boardsincluding those in Boss and Ibanez unitscannot be removed all the way due to the way they are wired. In those cases, you can make it easier to move the circuit board around while its still attached to the case by loosening the potentiom-eters and/or the 1/4" jacksbut be careful not to break the wires.

3. Use a felt-tip marker to mark the leads of the components that need to be removed from the circuit on the solder side of the cir-cuit board. Note: If you accidentally mark the wrong component, you can either just leave the mark on there as it will not affect the sound, or you can lightly heat the joint with your iron to remove the mark.

4. Remove the first component and replace it with the new one using the desoldering and soldering techniques learned in the videos mentioned at the beginning of this article.

5. Test the pedal to make sure it still works after the new com-ponent is in the circuit. Testing after each component change can save you a lot of time and frustration in the troubleshoot-ing process, because you will know the exact point at which the circuit failed. You dont have to put the circuit board back in the casejust make sure the 1/4" jacks are still connected to the case to ensure proper grounding.

6. Continue replacing or adding parts, one at a timeand test-ing the pedal after each addition or replacementuntil the mod is complete.

StAGe 4: troubleshootingIf stage 3 went well and your stompbox works properly, skip this step. If not:

1. Relax! Its fairly common for a pedal not to work right after modding due to some easy-to-make mistakes.

2. Check to see if everything that is supposed to be grounded is grounded, and that everything that shouldnt be grounded isnt. Look for places where the input or output jack may be touching the case where it shouldnt be. Also, check that the solder side of the circuit board is not in direct contact with the case. In the case of the true-bypass mod, check to make sure the lugs of the foot-switch are not touching the case. Double-check all the solder joints. Note: It often helps to use a multimeter here. For a great video on how to use them, go to YouTube and search for AfroTechMods THE BEST Multimeter Tutorial (HD).

3. If youre still having problems, watch Chromesphere.coms YouTube video called DIY Guitar Pedal Tutorial 9: Fault Diagnosing to see several things you can check first-hand.

StAGe 5: Final testing This is the most exciting stageits where all your hard work pays off with an awesome, unique, and fresh-sounding pedal. The steps include:

1. After testing the pedal with the modification completed, carefully put the pedal back together, making sure to tighten everything down snugbut leave the back plate off.

2. Test the pedal one last time.3. If it still works properly, install the back plate.

Now that you know all the stages, lets get on to the fun stuff! All of the following mods are separate projects. You can do one of them, all of them, or maybe pick and choose two or three. No matter what mods you choose to do, your pedal will sound great when youre done. However, if you decide to do the true-bypass mod, I suggest doing it first because youre going to remove a couple of FETs, diodes, resistors, and capacitors, which will change the tone of your pedal a bitand you dont want to get the tone you want dialed in with these other mods only to have it changed by making it true-bypass. Just keep in mind that in the pictures shown here, I did my true-bypass mod last so there wasnt a big hole in the unit for all of the pictures.

78 PREMIER GUITAR OCTOBER 2012 premierguitar.com


There are generally five stages to pedal modding, depending on how suc-cessful you are with replacing and/or adding parts the first time around. Read them carefully and remember to flip back and reference them at any point during the mod process to make sure youre on the right track.

One very important warning before moving on to the stages: Avoid the temptation to try to work on two mods simultaneously. For example, dont try to do the true-bypass mod while doing the variable mid-control mod. Working on different mods simultaneously usually makes the troubleshooting process a nightmare. Complete one modifi-cation starting at stage 1 and going through stage 5. Once that mod is finished, start over at stage 1 with the next mod.

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10. Solder one end of a 3" wire (or you could reuse the red-and-white-striped wire) in

1. Desolder the red-and-white-striped wire from the circuit board (upper-left corner in Photo 1) and cut the black wire that connects the input jack to the original foot-switch. This allows you to remove the circuit board from the case.

2. With the circuit board removed, drill a 1/2"-diameter hole in the middle of the case where it says TS9 (under the Ibanez logo). You may want to prop your pedal up on blocks so that the top is level and you can get a straight shot at the surface (otherwise, the hole will end up being elliptical instead of round).

3. The TS9 uses whats called a flip-flop circuit to turn on and off, but with the new true-bypass switch, the parts in this circuit arent necessary. Remove the following:

TwoFETs Two510kresistors Twodiodes Thejumperwire Thecapacitorlabeled

104 (its the blue cap at lower-right on this board, but it may be a different color on yours)

4. Desolder the end of the pink wire on the main circuit board that connects to the LEDs cir-cuit board.

5. Remove the short jumper wire (bottom middle of the circuit board in Photo 2) and replace it with a longer jumper that begins at the same right-side hole as the previous jumper but extends to the hole in between where the two FETs removed in step 3 used to be. The correct hole previously contained the bottomlegofoneofthe510kresistors also removed in step 3. (Note: Disregard the two clear LEDs that appear in place of clipping diodes at middle right in Photo 2they were from a previ-ous mod.)

6. Now that most of the board work is done, lets move on to the footswitch. To make wir-ing more convenient, place it upside-down in the case, with the holes in the lugs facing you (see Photo 3). Referencing the schematic in Fig. 1:

Connectpins2and9witha jumper wire



Tools and Parts for This Mod Powerdrill 1/2"drillbit Wirestrippers 3PDTfootswitch 2.2k4.7kresistor Threejumpers(thesecouldbeclippingsfrom

the leg of a resistor or capacitor) Twoorthree3"piecesofwire Needle-nosepliers(handy,butoptional)

Mod 1: Make Your TS9 True-Bypass

photo 1. Components and wire leads to be removed from the main TS9 circuit board.

photo 2. Replace the original short jumper wire with a longer one extend-ing to the hole where the bottom leg of a 510k resistor used to be.

photo 3. Prop the new 3PDT foot-switch in the newly drilled hole for convenience while soldering jumper wires and other leads.

This mod requires drilling a big ol hole in the middle of your Tube Screamers case. Here goes nothing, right? I know it sounds crazy, but it has to be done so you can install the shiny new 3PDT (three-pole, double-throw) footswitch thats necessary to make your pedal true-bypass.

Connectpins7and8witha jumper wire

Note: Make sure the jumper wires dont touch any other lugs.

7. Desolder the yellow wire at the upper right in Photo 1 (its in the hole labeled 11) from the main circuit board and solder it to footswitch pin 2. See Photo 4.

8. Solder one end of a 3" wire in the now-empty hole 11. Solder the other end to foot-switch pin 5.

9. Desolder the white wire from the upper-left corner of the main circuit board (the hole labeled 1).


the now-vacant hole 1. Solder the other end to footswitch pin 3.

11. Solder the white wire from the output jack to footswitch pin 6.

12. Strip a little insulation off of the pink wire.

13. Solder one leg of your new 2.2k4.7kresistor(resistorsarent polarized, so it doesnt matter which leg) to the pink

wire. Connect the resistors other leg to footswitch pin 1.

14. Solder one end of a 3" wire to the sleeve lug of the input jack, and the other end to foot-switch pin 4. If youre having trouble finding the sleeve lug, heres how: See how the jack has three lugs, one with a yel-low wire, one with a black wire going to the battery terminal, and one with a black wire going to the output jack? That last

lugthe one with the black wire going to the output jackis the one you want to solder to.

15. Connect the new foot-switch to the pedal housing.

Congratsyour TS9 is now true-bypass! Your footswitch should look something like Photo 5 when its done and installed.


Fig. 1. Schematic for wiring a 3PDT true-bypass footswitch.photo 4. The true-bypass switch with steps 714 completed.

photo 5. A completed TS9 true-bypass mod.


You can get different shades of distortion by swapping clipping diodes in your Tube Screamer or Super Overdrive. For example, replacing the existing diodes with germanium diodes will yield a compressed, smooth fuzz sound. In contrast, sili-con diodes (1n4148, 1n4001, 1n914, etc.) tend to provide a crisper, tighter, more focused sound. LEDs sound warmer, offer a great crunch, and usually make the pedal sound louder.

You can also experiment with different diode configura-tions. Two types of clipping can be achieved through different configurations: symmetrical and asymmetrical. Asymmetrical clippingthe type of clipping achieved in a stock Boss SD-1 circuit (see Fig. 2)tends to yield a more dynamic and responsive overdrive resembling the feel and response of an amp overdrive. You can get asym-metrical clipping by putting two

series-wired diodes in parallel with one diode oriented in the opposite direc-tion (as shown in the mod instructions). You can also achieve asymmetrical clip-ping by removing an original diode and replacing it with an LED, which tends to yield more head-room and volume.

To get more headroom out of a symmetrical clipping circuitthe type of clipping achieved in an Ibanez TS9 circuit (see Fig. 3)you can add an extra set of diodes in series with the original diodes, or you can change both diodes out for LEDs (as shown in the diagrams). However, keep in mind that this will change how much clipping you hear.

When replacing diodes, make sure you orient them cor-rectly. The stripe on the diode always goes on the same side as the bar at the tip of the triangle on the diode symbol thats stenciled on the circuit board. For LEDs, the short leg goes towards the bar.

Now that you know more than you probably ever wanted to know


Mod 2: alter TS9 and SD-1 Distortion by Swapping DiodesTools and Parts for This Mod

Variousnumbersandtypesofdiodesand/orLEDs,dependingon which symmetrical or asymmetrical mod you decide to do

Fig. 2: Asymmetrical clipping. A stock Boss SD-1 schematic (left), and an SD-1 schematic with an LED swapped out in place of the original clipping diode to yield a louder, warmer, more responsive feel (right).


about diode configurations, well show you how to do some diode mods on a TS9 and an SD-1.

tS9 Asymmetrical clipping modLets start by changing a Tube Screamers clipping from stock symmetrical to asymmetrical by adding a diode pair in series.

1. Locate the diodes on your TS9s circuit board. See Photo 6.

2. Desolder diode 1 (D1) or diode 2 (D2)it doesnt matter which comes first. Note: I rec-ommend using a felt-tip marker to mark which components you need to desolder on the underside of the circuit board.

3. Wire two diodes in serieseither pair one stock diode with a new one or pair two brand-new diodesby twisting

their legs together as shown in Photo 7. Note: See how the black stripes are both on the left hand side of each diode? This is very important to get rightyour pedal wont work unless they are oriented correctly.

4. Solder the twisted-together legs as shown in Photo 8, and then place heat-shrink wrap or electrical tape on the exposed solder joint (not shown), and bend the legs as shown.

5. Place the series-wired diodes legs back through the D1 or D2 holes (depending on which you removed in step 2) and solder them in place. See Photo 9. Note: Make sure the diodes black stripes are on the same side as the bar on the tip of the triangle marked on the board.

Now that you know how to place diodes in series, you can read the schematics in Figures 2 and 3 and execute any of them that use series wiring.

SD-1 Symmetrical clipping modThe SD-1 circuit is different from the TS9 in that it comes standard with an asymmetrical clipping arrangement. Take a look at the circuit layout in Photo 10. D4, D5, and D6 are the clipping diodes. D5 and D6 are already in series with each other and in parallel with D4. If you want to make this a sym-metrical arrangement, you can remove D5 or D6it doesnt matter whichand place a jumper wire where it used to be.

If you want a symmetri-cal arrangement with more

headroom, I suggest leaving D5 and D6 alone and adding a diode in series with D4, just as we did in steps 3 and 4 in the previous TS9 Asymmetrical Clipping Mod. If you want more clipping with an asym-metrical setup, you could also place a diode in series with D4 and D6. You can try many variations of series and parallel pairings of different types of diodes, and its a bit easier with the SD-1 as compared to the TS9 because of the SD-1s setup and its roomier circuit board. So dont be afraid to experi-mentjust make sure you dont put your diodes in backward. If you do, it wont hurt anything, but your pedal wont work right. All you have to do is turn them around and you should be good to go.


to view the photos and other visual elements for this mod, visit premierguitar.com/oct2012


You can adjust the tonality of an SD-1 or a TS9 in many ways simply by using different resis-tor-and-capacitor combinations for the components in the large oval in Fig. 4 and Fig. 5.

This component combination (aka the feedback to ground, or 4.5V in this case) helps set the gain, as well as what frequencies get amplified and clipped by the op-amp (the triangle thingy in the schematic). A stock TS9 is set to clip around 720 Hz. Lowering the value of the resis-tor will provide more gain, but it will also change what frequency is getting clipped. If you dont want to change the pedals tone, you have to change the capacitor value with the resistor value. You can also squeeze some bass out of

the pedal by adjusting the value of the capacitor in this combo. Table 1 shows some values that I suggest you try. If you want to play around with the values and frequencies a bit more, I suggest visiting muzique.com/schem/fil-ter.htm. This website has a great frequency calculator for resistor/capacitor pairs. Note: The TS9 and SD-1 are very similar in this part of the schematic, so all of the same mods apply. Just be careful with the SD-1: If you increase the gain too much without adding the proper circuitry, the dis-torted signal will start to bleed into the bypassed signal. If you run into this problem, you can find mods to rectify the situation online.

Before we jump into the actual mod, lets look at Figures 4 and 5

again. See the lone circled resis-tor in each schematic (R5 in the SD-1 circuit, and R7 in the TS9 diagram)? This resistor sets the minimum gain when the drive

knob is turned all the way down. Isuggestchangingittoa10kin both pedalsitll enable them to clean up a lot better.

Okay, lets replace the SD-1s R5 resistor, the TS9s R7 resis-tor, and the C3 capacitor and R6 resistor in both the Boss and Ibanez pedals.

1. Locate the minimum-gain resistor in your SD-1 (R5 in Photo 11) or TS9 (R7 in Photo 12), desolder it, and sol-derina10kreplacement.

2. Then test your pedal.

3. Locate C3 and R6 on your SD-1 or TS9, desolder them, and replace them with different values based on the chart above or per-haps a recipe you come up with using the widget at muzique.com. Note: If youre modding your SD-1, dont be afraid to remove the gunk thats globbed all over C3.


Mod 3: Tweak Feedback in Your SD-1 or TS9


Tools and Parts for This Mod .1F,.22F,and.47Ffilmcapacitors 1k1/4-wattresistor 10k1/4-wattresistor

Fig. 4: SD-1 Gain Stage. (LeFt) You can achieve myriad tones with a Boss SD-1 by varying the values of the resistor and capacitor shown inside the large oval. Fig. 5: tS9 Gain Stage. (riGht) Altering the values of the resistor and capacitor shown here inside the large oval can yield a wide variety of tones with a Tube Screamer.

photo 11. Replacing your Super Overdrives R5 resistor with a 10k part will enable you to clean up the signal more. Also, swapping the C3 and R6 components with different values will vary the available gain and which frequencies get amplified and clipped by the op-amp.

table 1. Suggested capacitor-and-resistor combinations to try in your SD-1s or TS9s feedback to ground. (Numbers in parentheses represent what will be written on your capacitors. Resistor color codes vary, depending on whether they use 3- or 4-color coding bands. Visit Wikipedias Electronic color code page for details.)


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The steps for installing a passive tone control are pretty much the same for a Tube Screamer and a Super Overdrive (see Fig. 6 for a reference schematic), so well cover both together here and note any divergences within the appropriate step.

1. For a TS9: Remove wires 6, 7, and 8, as well as components R11 and C9 (see Photo 13). For an SD-1: Remove wires 5,

8, and 11, as well as components C5 and R8 (see Photo 14).

2.Removetheold20k tone pot.

3. TS9: Attach a 3" wire from lug2ofyournewA1kpotto the hole where wire 7 used to connect to the circuit board.SD-1: Remove R7 and replace itwitha1kresistor.Thensolder one end of a 3" wire to

lug2ofyournewA1kpot,and solder the other end where wire 5 used to connect to the circuit board.

4. TS9: Remove C5. SD-1: Remove C4.

5. Stick one leg of your new .22Fcapacitorthroughlug1of your new pot and solder it in place. Attach another 3" wire to the open leg of the cap (see Photo 16). Note: When making a connection like this, I suggest stripping a little extra off of the wire and wrapping it around the caps leg before soldering it. Its also a good idea to put electrical tape or heat-shrink wrap around bare spots such as this one.

6. TS9: Solder the other end of the 3" wire into the negative hole where C5 used to be (the nega-tive hole is the one thats not next to the plus sign). See Photo 17. SD-1: Solder the other end of the 3" wire to the sleeve lug of the output jack. See Photo 18


Mod 4: Make Your TS9 or SD-1 More Transparent


Tools and Parts for This Mod 1k1/4-wattresistor(oneforaTS9,twoforanSD-1) A1kaudiopotentiometer .22Fcapacitor 2.2Felectrolyticcapacitor 1"pieceofjumperwire Two3"piecesofwire Potknobforthenewpot

Have you ever noticed how, when you turn your TS9s or SD-1s tone knob up, it sounds like the pedal is boosting frequencies? Thats because it is. Both pedals have an active tone control. Some players like that, but others prefer a passive tone control. This mod shows you how to install a passive tone control to make your Tube Screamer or Super Overdrive sound much more transparent.

Fig. 6. Schematic for the TS9 and SD-1 transparency mod.

photo 13. Remove the indicated wires and components in your TS9.

photo 14. Remove the indicated wires and components in your SD-1.



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7. TS9: Attach the 1" piece of wire from where wire 6 used to be to the hole where wire 8 used to be. SD-1: Attach the 1" piece of wire from where wire 8 used to be to the hole where wire 11 used to be. See Photo 19.

8. TS9: Solder your new 1k resistor where C9 used to be andplaceyour2.2felectro-lytic capacitor where R11 used to be (see Photo 20). Note: Make sure the negative side of your electrolytic capacitor is clos-est to your Tube Screamers IC chip, and that the positive side is closest to the 1k resistor you just installed. The negative side is usually signified by a stripe on the cap, and the positive side is almost always the long leg. SD-1:Solderyour1kresistorwhere C5 used to be and your 2.2Felectrolyticcapacitor

where R8 used to be. Note: Make sure the capacitors negative side (the short leg or the

short leg near the stripe on the cap) is in the hole closest to the edge of the circuit board, and the

positive side (the long leg) is closest to the newly placed 1k resistor.


photo 15. Connect a 3" wire from the new tone pot to hole 7 on your TS9s circuit board.


1. TS9: Remove resistor R8. SD-1: Remove resistor R7.

2. Twist one leg from each of thetwo10kresistorstogetherso that their bodies are almost touching.

3. Wrap one end of a 3" piece of wire around the connected resistor legs, solder the joint (see Photo 24), and put electri-cal tape or a heat-shrink tube around the joint (not shown).

4. Twist the legs of your .0068 Fcapontothelonglegsofthejoined10kresistorsandsolder the joint, then twist the end of another 3" wire onto the longlegofonethe10kresis-tors and solder that connection. See Photo 25.

5. TS9: Place the long leg of the resistor that has the 3" jumper in the hole from R8 closest to the dot (pin 1) on the IC chip. Place the other resistors leg in the hole vacated by R8. Solder the legs in

place. See Photo 26 and Photo 22, if necessary. SD-1: Place the long leg of the resistor that has the 3" jumper in the vacated R7 hole that is closest to the IC chip. Place the other resistors leg in the other vacant R7 hole. Solder the legs in place. See Photo 27.

6. Solder your .033 F cap tolug1ofyourB100kpot,then solder the last piece of 3" wire to lug 2 of your pot, and thensolderthe.0047Fcapto lug 3 of the pot. See Photo 28.

7. Solder the wire attached betweenthetwo10kresistorsto the remaining leg of the .033 Fcapthatssolderedtolug1of the pot.

8. Solder the remaining wire attached to the long leg of the 10kresistortotheremaining

legofthe.0047Fcapthatssoldered to lug 3 of the pot.

9. TS9: Solder the 3" wire con-nected to lug 2 of your pot to the leg opposite the stripe of the diode located right next to the power jack (see Photo 29). Test the pedal and be sure that your modifications worked.10. TS9: Measure 5-6 mm (about 1/4") from the upwardly angled part of the case and draw a horizontal line from the right side of the case to about where the tone knob is. SD-1: Measure 1 cm to the right or left of the edge of the 9V adapter jack on the front of the case. Draw a vertical line there.

11. TS9: Draw a vertical line starting smack dab in the middle of the volume pots hole

until it intersects with the line you just drew. This will be the center of the hole for your new pot (see Photo 31). SD-1: Draw a horizontal line 1 cm above the bottom of the case until it intersects with the vertical line. This will be the center of the hole for your new pot (see Photo 32).

12. Drill a 1/4"-diameter hole in the marked spots.

13. Wipe the lines off of the enclosure, secure the new pot, reassemble the pedal, and enjoy your new variable-mid control! Note: On the SD-1, be sure to install your pot so that the lugs face the top of the case so they dont get grounded to the back plate (see Photo 33).

Mod 5: Install a Variable Mid Control in Your TS9 or SD-1



Tools and Parts for This Mod Two10k1/4-wattresistors .0068Fcapacitor .0047Fcapacitor .033Fcapacitor B100kalphasingle-gang9mmright-anglePCmountlin-

ear potentiometer from SmallBearElec.com Potknob Three3"piecesofwire 1/4"drillbit Markingutensil Ruler

Our final mod gives you control over the nasally mids that have long plagued the Tube Screamer and Super Overdrive. Be aware, though, that youll lose quite a bit of volume with this mod due to insertion loss. To make up for this volume loss, I recommend you also either replace the original diodes with LEDs or wire the original diodes in series (neither of which is covered here).

Fig. 7. Reference schematic for the TS9 and SD-1 variable-mid-control mod.

photo 22. Remove R8 in your Tube Screamer.

Documents

How To Mod TS9 Tubescreamer pedal