A Tale of Two Tubescreamers

Doghouse_Riley

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Let me preface this by saying last December I got back into playing guitar after playing bass for the last 25ish years.

I bought a new TS9 at the beginning of the year. I liked the sound fine but after awhile I decided to try modding it. I did the 2 resistors and a socketed JRC4558D chip. I loved the improvement. I read about some more possible mods but I liked the way this pedal sounds and I didn't want to screw it up. So I bought another used TS9.

Before modding the 2nd TS9 I A/B'd it with the first, now modded TS9. The 2nd un-modded TS9 was very bright compared to the 1st. Too bright and fizzy sounding. 1st TS9 sounded much better.

So I mod the 2nd TS9. I do the 2 808 resistors but it already had the JRC4558D chip so I left that alone. Now on this 2nd TS9 I decided to do another mod that gives less gain at lower knob settings but more gain at higher knob settings.

After I'm done I now A/B the 2 modded TS9's. The 2nd one now sounds much better; better than the first one. The fizziness is gone and now it sounds awesome. Now I think the first one sounds like a blanket was thrown over it. I'm going to do the "less/more" mod to the first one. I don't think that is the difference, though.

Question: is there a way I can brighten up the sound of the 1st to sound more like the 2nd?
 

ICTRock

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without knowing what exactly has been done to the first one, its hard to say.
I'll go through the mods I typically do with a tube screamer

We'll work our way through the circuit from input to output as there's no circuit board labelling on a TS-9.

Increase the 20n input cap to a 47n film cap - better bass response, part of the analogman silver mod
Change the 1uf non-polar electrolytic cap to a 1uf film cap - prefer no electrolytics in the signal path
Change the op amp to the jrc 4558 if it isn't one already.
Optionally, if it is a 4558 and you want an upgrade, consider a higher quality low noise op amp and socket the op amp so it can be swapped more easily. I even like stacking a second op amp on there.
Increase the 51p cap in the feedback loop to 100p - this will help because I'm about to change clipping diodes and gain structure.
Change the clipping diodes to 1S1588(I bought a large amount on ebay for peanuts) - these tend to have a higher Vf than stock and are what the original 808s have. If you want asymmetrical clipping, add a bat41/1n34a to one side. I'm also a fan of the MOSFET clipping of the zendrive. I think LEDs take things too far and the pedal loses character.
Change the drive pot to 1MA - best thing about the Boss SD-1, more gain
Remove and jumper the 51K resistor in the feedback loop - makes the initial gain much lower. If you don't want to jumper, place a 1K resistor in there.
Change the 4K7 resistor in the feedback loop to 1K - increasing the gain
Change the 47n capacitor in the feedback loop to a 470n - increasing the bass
Change the 220n tantalum capacitors in the tone section to 220n film capacitors - better tone
Optionally, change the first 220n (off the 1K resistor) to a lower value like 150n for more treble. I think this is a bit unnecessary with the active tone control. If you want more treble, turn the tone knob up.
Change the 1u nonpolar electrolytic to 1u film - again, I prefer film to electrolytic in the signal path
perform the "808 mod" on the output stage - better output impedance
Optionally, change all remaining electrolytics to at least 25v rating for 18v operation - boutique tube screamers all do.

If I
 

Doghouse_Riley

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"without knowing what exactly has been done to the first one"

The OP had what I did to the first one: "I did the 2 resistors and a socketed JRC4558D chip."

I guess I didn't explain my question well. I've already done the TS808 mod to both. I'm wondering why the tone of these pedals is so different and if there's a specific mod to address the dark, less open tone of the first TS9 to sound brighter and more open like the second TS9?
 

ICTRock

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all the "808 mod" ie the two resistors does is change the output impedance ... changing the op amp may help but still not the drastic change you are describing.
now I misspoke when I said without knowing what exactly was done ... I meant the second pedal and what your less gain /more gain mod was. I have a hunch it was the 4k7 resistor in the feedback loop and depending on what was done in that mod it could have changed multiple things about your pedal.
 

cousinpaul

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The less/more mod sounds like it might involve lowering the value of the minimum-gain resistor and raising the value of the .047 cap that forms the HP filter with the 4k7 resistor. I've never heard of it referred to that way but am familiar with the mods. It would help to know exactly what was done before making suggestions.
 

Doghouse_Riley

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Here's what I did (except for the one crossed out in red):

TS9%20Mods%20Done.jpg


Both now have the exact same mods done. They are ostensibly the same. From the beginning, when both pedals were bone stock, #1 has always sounded darker than #2 and it still does. So, is there something specific that would brighten #1 to sound more like #2?
 
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ICTRock

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ok, so the explanation of what you did ... I'll reiterate that the 808 mod changes the output impedance, lowering the 51k to 20k sets the minimum gain (gain knob fully counterclockwise) lower than it was stock. Changing the 4k7 to 2k4 shifts the notch frequency of the high pass filter from 720.8Hz to 1411.7Hz. This rolls off a lot of mids, low mids, and bass while increasing the gain. basically you've turned the tube screamer from a mid-emphasis pedal to a treble booster.
 

Doghouse_Riley

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That's excellent information and I appreciate it, but that doesn't answer my question. What, if anything can be dome to make these 2 pedals, which are the same for all intents and purposes, sound more like each other? Maybe the answer is- nothing.
 

luckett

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I did the 2 resistors and a socketed JRC4558D chip. I loved the improvement. I read about some more possible mods but I liked the way this pedal sounds and I didn't want to screw it up. So I bought another used TS9.

So I mod the 2nd TS9. I do the 2 808 resistors but it already had the JRC4558D chip so I left that alone. Now on this 2nd TS9 I decided to do another mod that gives less gain at lower knob settings but more gain at higher knob settings.

Both now have the exact same mods done. They are ostensibly the same.

You said that the first TS had only the IC and 808 resistors changed and the second had the 808 resistors and another mod done.

Now you are saying that they have had the same mods done and they are "ostensibly the same". Are they actually the same or "ostensibly" the same? Can you clarify what exactly has been done to each of the pedals so there is no confusion what we are looking at here?
 

ICTRock

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from your explanation we have:
pedal A) with only the 808 mods done
pedal B) that also has gain and tone mods done

do the mods to pedal a that you did to pedal b and they're the same. this was the implied answer of my last post where I explained the differences between the two
 

Doghouse_Riley

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I guess I wasn't clear but yes, both now have the same mods done. Both have the mods in the picture above done. This is an ongoing chain of events. You indicated that the difference may be due to the "less/more" mod done to #2 so I did the same mod to #1 so both now have the same mods done. But #1 still sounds noticeably darker.

I am starting to get used to it. If I turn the tone to 3 o'clock on #1 and 9 o'clock on #2 they are pretty close. Close enough for a bar band.

I wanted to know if there was a mod to adjust the treble frequency. I've seen one to boost the bass (the one crossed out in the picture above).
 

Doghouse_Riley

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Ostensibly the same meaning that AFAIK they have the same components in them but they don't sound the same. From the beginning #1 was darker sounding. It's not like they started out sounding the same then I did the mods and then one was brighter than the other. #2 always sounded brighter.
 

ICTRock

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that is where you would need to verify their components being the same which will end up not being the case because we're talking about a rather large difference in sound between the two
 

luckett

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If I turn the tone to 3 o'clock on #1 and 9 o'clock on #2 they are pretty close. Close enough for a bar band.

That sounds to me like your mods shifted the frequency peak differently on the two pedals. I'd go back and confirm all part values that you changed around the opamp feedback loop.
 

songtalk

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Maybe compare all the resistors and caps between the two, find the differences that have eluded you via process of elimination and change the one to match the oNE you like!
 

Doghouse_Riley

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Maybe compare all the resistors and caps between the two, find the differences that have eluded you via process of elimination and change the one to match the oNE you like!

Ugh! I thought the same thing. I also thought about the fact that I have enough projects going on. I think I'll live with it. I have them stacked with a Soul Food following and it's getting a nice raunchy tone I'm looking for. The Soul Food brightens up #1. (Now I need nicknames for them :) Night and Day?, Demon and Angel?...)
 

Alex83Tele

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Although it's been said, repeatedly, I'll mention that, without the pedal in front of me, I cannot make any definitive assessment (might not be able to if it was in my hand). I am not an expert on TS-9's, but where are the diodes, and are they the same? You've probably heard about matched pairs of diodes for symmetrical clipping, which seems like the kind of gimmick made to over charge for a pair of diodes, but I really don't know. I do know that different diodes can drastically change the sound of a distortion pedal. A lot of schems out there have 1N914 diodes for both the TS-9 and for the 808, which is surprising to me (using the same diodes over years of production), but maybe that's a Tube Screamer thing.

Also, I know that electrolytic caps not only eventually fail, but can changed their behavior over time, as the electrolyte compound, which is liquid in most cases, changes. For instance, one scheme I'm seeing online has an electrolytic as the draw-down to ground on the tone knob. Just one example. I'd be surprised if it was one thing, though. Whenever I'm examining an entire Circuit closely, I always find many anomalistic factors effecting the sound, and sometimes they're compounding. When isolated, individual sections of the same pedal (high pass filter, gain stage, clipping section) can be predictably altered, but if I gave you a random bag of parts with the right values to make two TS9s, I wouldn't expect them to sound exactly the same. Personally, I would make the appropriate changes to the filter sections to make the pedal sound how you want, and not worry about why it sounds different. From one schem I'm looking at, it appears the signal is split and Tone Knob is sending more of the signal through the low pass filter as well as being tied in with one of the gain stages. You could try lowering the pot from 500k to 250k and the associated resistor from 51k (so it reads, maybe a typo, maybe a strange resistor) to 18k adding a little gain and sending less through the low pass. But, the likelihood that what I'm looking at is exactly the same as what you have is slim. And I'm assuming 4558 is a normal differential op amp. I still have to look these things up. Why not try playing a bass through it. Maybe it makes a killer bass distortion pedal [emoji53] I have greatly exceeded my pay grade on this one. Someone is gonna take me to task, I know it. But any errors I made aside, play around with those things. Read up on it. You'll get there. http://www.generalguitargadgets.com/ I've found some useful info on the aforementioned website, but there are others. If you can, find a schematic that matches your pedal online and post it here.
 

Doghouse_Riley

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Yeah the next step may be to change all the caps. But I have a guitar build I'm starting so changing out caps is back burner for sure.
 

Doghouse_Riley

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Well, I solved the problem. Sort of. I gave the dark sounding one away to my brother. He likes humbuckers so it should work out for him. Unfortunately the other screamer is off my board too. It lost it's place to my homemade ZenDrive.
 




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