# Modding your tube screamer



## Guest (Jul 18, 2008)

check out this link

http://www.geofex.com/Article_Folders/TStech/tsxtech.htm

Just tweaked my TS-9 and it was a whole lot of fun. Great starter project.


----------



## Ripper (Jul 1, 2006)

Tons of great articles on the web about tubescreamer mods, easy and fun to do. Glad you had fun with it.


----------



## PaulS (Feb 27, 2006)

If you have put a socket in for the chip you can try out all types of chips. Try a JRC4559D or DD


----------



## greco (Jul 15, 2007)

Ripper has provided some info to me about modding my BD-2 and also informed that it can be addictive.

Glad you enjoyed modding your TS-9. Did you like the tonal results? 

Dave


----------



## Teleplucker (Feb 5, 2006)

I did the same thing with mine and like the results. I didn't stray too far from the TS formula though since I wanted that sound. Getting the socket in was a be-atch after adding some boxed caps (short leads, so didn't think I could do it the other way around). I went with the Keeley approved, stacked RC4558 chips in mine.


----------



## mhammer (Nov 30, 2007)

You'd be shocked by the percentage of boutique pedals out there that are essentially TS-9s with a component value change here and there.


----------



## PaulS (Feb 27, 2006)

A few of the high end builders use the 4559 instead of the 4558. My fav is the RC4558P.


----------



## mhammer (Nov 30, 2007)

After Dave Barber posted some excited threads over at the DIY Stompbox forum about stacking chips a few years back (hell, probably more like 6 or 7 years back), I tried some stacked chip experiments. I had a whack of NE5534 chips someone had given me so I sweated the pins of several together and tried them out. I have to say that stacking does not necessarily provide improvement. The principle underlying chip-stacking is that the paralleled op-amps will produce more output current. First off, whatever output current is produced will depend on the remainder of the circuit and how/whether the pins of more than one op-amp are tied together or not. Second, greater output current does not provide any universal benefit independent of the actual context.

In my case, I found that it produced a much less ragged sound from my MXR Distortion+ clone, compared to a single NE5534 or an LM741.

Though there is much to-ing and fro-ing about op-amps in tube screamers, my sense is that the desirability of this one or that one often arises from a "mystical" and happenstance combination of the diodes used, the pickups used, and normally-occurring component tolerances. A little more of this, and a little less of that, and all of a sudden you hit a sweet spot. The properties of op-amps are not that robust that switching from a 4558 to a 5532 or TL072 or 4560 will always and forever yield a particular target tone, _*irrespective of the actual values of all the other components in the circuit*_. Sometimes you will get lucky, and sometimes you won't. Certainly chip changes will often net you differences in battery consumption or noise, but chip changes do not, and will not, by themselves, produce "instant Stevie".


----------



## Teleplucker (Feb 5, 2006)

mhammer said:


> After Dave Barber posted some excited threads over at the DIY Stompbox forum about stacking chips a few years back (hell, probably more like 6 or 7 years back), I tried some stacked chip experiments. I had a whack of NE5534 chips someone had given me so I sweated the pins of several together and tried them out. I have to say that stacking does not necessarily provide improvement. The principle underlying chip-stacking is that the paralleled op-amps will produce more output current. First off, whatever output current is produced will depend on the remainder of the circuit and how/whether the pins of more than one op-amp are tied together or not. Second, greater output current does not provide any universal benefit independent of the actual context.
> 
> In my case, I found that it produced a much less ragged sound from my MXR Distortion+ clone, compared to a single NE5534 or an LM741.
> 
> Though there is much to-ing and fro-ing about op-amps in tube screamers, my sense is that the desirability of this one or that one often arises from a "mystical" and happenstance combination of the diodes used, the pickups used, and normally-occurring component tolerances. A little more of this, and a little less of that, and all of a sudden you hit a sweet spot. The properties of op-amps are not that robust that switching from a 4558 to a 5532 or TL072 or 4560 will always and forever yield a particular target tone, _*irrespective of the actual values of all the other components in the circuit*_. Sometimes you will get lucky, and sometimes you won't. Certainly chip changes will often net you differences in battery consumption or noise, but chip changes do not, and will not, by themselves, produce "instant Stevie".


Though I know a miniscule amount about circuits and properties of op-amps, certainly not enough to obtain any predictable or targeted responses, I know what my ears tell me. And, they usually tell me that any particular change yields relatively small and subtle changes (same with swapping similar tubes, pickups, etc....maybe I just don't have sensitive enough ears, or maybe I don't have the patience to care :smile.

In the case of the mods I did with my TS pedal, I just swapped in a few chips and kept the one I liked. It happened to be a stacked RC4558P combo that I soldered together when I was attempting to mimic some Keeley mods on my SD-1. So, it was sitting there and I gave it a whirl. I liked it the best, but, honestly, I have no idea if stacking the chips did anything. It's quite likely that I just like RC4558P's in *this* TS pedal regardless of whether they are stacked.

I've done a lot of work on my SD-1 to see how far it can be pushed. I always come back to a TL072 in that pedal. It always sounds better. I can't even explain why, it just does.


----------



## mhammer (Nov 30, 2007)

Let me emphasize, lest it seem otherwise, I am not saying the chip changes have NO IMPACT WHATSOEVER (and I don't think that was what YOU were saying about me, either, just so that we're clear on that too). Rather, the issue is that in the vast majority of cases, when people employ chip changes, they tend to do so on THEIR pedal, and their pedal alone, without taking or posting any notes about the actual component values in the circuit. Moreover, they do so without engaging in any blind A/B comparison, and often with a sizeable enough gap between when they last listened to the other chip and when they audition the new chip that their auditory memory can be called into question.

The fact that they think they heard discriminable changes in tone is good news, of a sort, since it suggests some fertile ground for experimenting. But thinking you heard something, and having that be treated as virtually equivalent to a design change, are two separate things. Its not that the chip change has NO effect. It is that there is seldom any basis for assuming a *consistent* effect, such that *any* TS-5/7/9/10/808 will sound a particular predictable way when any old JRC4559 or OP-275 or RC4558P is stuck into the socket. I wholeheartedly *encourage* people to experiment with chips where there is some _a priori_ basis for anticipating audible changes. I also encourage them to be realistic in their expectations, and not be puzzled when they read a post somewhere about how a Burr-Brown chip has simply revolutionized the way a pedal sounds to the poster and find nothing even *audible*, let alone "improved", when they go through the trouble, effort, and expense to do the same change.

Some folks have suggested that actually a great many of the chip-to-chip differences heard can be effectively simulated/accomplished simply by having a variable resistance (e.g., a 1k trimpot) in series with the diodes in the feedback loop. Series resistance in that context can serve to "soften" the clipping produced. Indeed, a slightly larger value (4k7) in series with a clipping pair used the same way forms the basis of the "soft limiter" that Boss uses in the BF-2 flanger to keep the feedback signal in check. Also used in a great many other commercial pedals for similar purposes.

I also hasten to remind people that neither Ibanez nor Boss make any special effort to select diodes in the clipping path for equivalent forward voltage. Your basic 1N914, 1N4148 or 1S5888 or any equivalent silicon diode varies over a range. It is quite easy to end up with a pedal that uses a simple back to back pair yet clips asymmetrically over much of its range. Depending on where you like to set your Drive knob, the degree of asymmetry may totally override whatever a chip change might introduce.


----------



## NB-SK (Jul 28, 2007)

I've done the whole 'brown sound' + bass capacitor thing. Even changed how how the 'drive' tapers off (very weak on 'low' for clean boost, then regular in the middle and a bit more humph on 'high' than stock). I also changed some diodes. It sounded better, but the most marked difference is by changing the op-amp chip. I don't like the stock chip, too smooth. I've got a dozen or so chips that I play with (installed a slot). I prefer the ones with a bit more gain.


----------



## mhammer (Nov 30, 2007)

You DO realize the chips themselves have no gain, right? The gain is set by the components around the chip. What the chips *have* is "open-loop gain" or what is also called a "gain-bandwidth product".

Quick lesson. Think of op-amps as if they were cars with the accelerator pedal permanently epoxied to the floor. The only thing you can do is apply brake pressure and steering to determine how fast it goes. The amount of *negative feedback* one provides (determined by what sits in the feedback path and what gets bled off to ground) determines how far from the absolute maximum "speed"/gain the chip will end up. That absolute maximum is not perfectly equivalent for all frequencies, though. For example, if you look at the datasheet for the venerable LM4558 ( http://pdf1.alldatasheet.net/datasheet-pdf/view/168905/HTC/LM4558.html ), at the bottom centre of page 3, you will see a graph with the title "Open loop frequency response". This plots what the absolute maximum open-loop (i.e., NO negative feedback whatsoever is applied) gain can be across the frequency spectrum. You can see that if one applies the amount of negative feedback required to provide 41db of gain (which is the maximum gain of a Tube Screamer), the response is flat well out to 20khz. If one aimed for a gain of, say, 50db (hotter than a Dist+ but much cooler than a Rat), you'd start to see a natural tapering off of frequency response above 6khz or so. Of course, since the lowpass filtering built into the TS trumps that particular constraint, it doesn't really matter. I will also ntoe that this is all "gain in theory" - there ARE limits to how much gain you can create with a 9v battery and a 100mv input signal.

The upshot is that even if you look at some truly "garden variety" op-amps, there are still no practical limitations in terms of what specific gain settings will mean for the frequency response of the chip. Some folks will turn to slew rate as a possible explanation, but even the 0.5v/us slew rate of bargain basement chips is more than enough for the requirements of a guitar with 40db gain applied.

All of which means that the presumed properties of the chips are all too often the properties a given chip will have *with those components around it*. Conceivably a real effect, just not a reliably replicable one.

There ARE some cases where change of a chip can reliably alter the sound of a pedal. The venerable Proco Rat uses an LM308 op-amp and tons of gain specifically to tax the chip in a certain way.

Gotta run. Hope this is clear and useful.


----------



## NB-SK (Jul 28, 2007)

mhammer said:


> You DO realize the chips themselves have no gain, right? The gain is set by the components around the chip. What the chips *have* is "open-loop gain" or what is also called a "gain-bandwidth product".
> 
> Quick lesson. Think of op-amps as if they were cars with the accelerator pedal permanently epoxied to the floor. The only thing you can do is apply brake pressure and steering to determine how fast it goes. The amount of *negative feedback* one provides (determined by what sits in the feedback path and what gets bled off to ground) determines how far from the absolute maximum "speed"/gain the chip will end up. That absolute maximum is not perfectly equivalent for all frequencies, though. For example, if you look at the datasheet for the venerable LM4558 ( http://pdf1.alldatasheet.net/datasheet-pdf/view/168905/HTC/LM4558.html ), at the bottom centre of page 3, you will see a graph with the title "Open loop frequency response". This plots what the absolute maximum open-loop (i.e., NO negative feedback whatsoever is applied) gain can be across the frequency spectrum. You can see that if one applies the amount of negative feedback required to provide 41db of gain (which is the maximum gain of a Tube Screamer), the response is flat well out to 20khz. If one aimed for a gain of, say, 50db (hotter than a Dist+ but much cooler than a Rat), you'd start to see a natural tapering off of frequency response above 6khz or so. Of course, since the lowpass filtering built into the TS trumps that particular constraint, it doesn't really matter. I will also ntoe that this is all "gain in theory" - there ARE limits to how much gain you can create with a 9v battery and a 100mv input signal.
> 
> ...


Yes, I did know that, but I was not fully aware of the details.


----------



## keefsdad (Feb 7, 2006)

Wow, a lot of good knowledge and info here.
It's a bit above me, I'm afraid, but does anyone know of mods for the lowly TS-5? That's my only screamer:rockon2:


----------



## Ripper (Jul 1, 2006)

keefsdad said:


> Wow, a lot of good knowledge and info here.
> It's a bit above me, I'm afraid, but does anyone know of mods for the lowly TS-5? That's my only screamer:rockon2:


Find c10 and replace it with either a .1uf or .22uf that helps to add more bottom end.

Change r19 to 10k as this will make is cleaner when the gain is turned down.

Change r18 to something around 3.3k or 1K, this gives you more distortion on tap.

change one of the diodes to a LED or a LED/germanium diode (1N34 is good) in series, this changes the dynamics of the distortion, or you could put a 1n4001 in, any of the normal tubescreamer diode mods will work.

If you want, you can play around with c11, bigger value means less highs, lower value means more highs.

hope that helps:smile:


----------



## mhammer (Nov 30, 2007)

I sold a pedal to Ottawa's respected Tony D to replace his vanished/busted TS-9. I was honoured that he felt so strongly about it given how central to his tone the Screamer is.

What I sold him was a TS-808 spec pedal with a single added "warp" control.

The control is actually quite simple. There is a "back-to-back" pair of diodes that do the clipping in a stock TS5/7/9/10/808. How much each diode clips on its side of the waveform can be varied by inserting a resistance in series with that diode. What I did was simply install a pot (somewhere between 10k and 50k, I honestly forgot) in series with one of the diodes so as to vary the degree of asymmetry in clipping. As one decreases the pot resistance to zero, it sounds like a normal compressed TS. Increase the resistance on one diode and the clipping starts to get more asymmetrical. You also notice more dynamics and volume since one side of the waveform is no longer limited to the threshold of the diode. Note that you won't really hear the difference between warp settings unless you dig in with your pick.


----------



## Guest (Jul 31, 2008)

I suspect the op-amp alone does very little to change the sound but tweaking the closed-loop gain, the diodes and the output impedance might in fact "smooth" things out. I did change the op-amp to a JRC for shits and giggles, I changed the output resistors and the cap and resistor combination next to the diodes. I didn't do a frequency response of before/after but I'm satisfied with what I hear which is a crunchy but slight boost without the high-gain hiss I would get with an SD-1 for say. It sounds very,very nice straight into a Classic 50. If your looking for low-noise you'd probably do better with a NE5532 op-amp assuming the pin-out is compatible (I'd have to check). Remember much of what you hear about mods is subjective similar to the on-going debate about blonds, brunettes and redheads.lofu


----------

