Boss - DS-1 Distortion mods (what works, what doesn't?)
My mods gets it a little more modern sounding. Here is the base from what I worked with and I made a few small value changes (sorry I wrote them in my notebook and it is in the garage.)
R16- 1K
R14- 10K
C10- .001uF
C5- 1uF
C9- 1uF
D4- 1N4001
D5- LED (clear blue 5mm still inside the case I didn't want to drill a hold for it.
I made a few small upgrades and the result was amazing. I just need to add more volume and I think but I am not sure that there is another resistor that I can change and add more distortion. I need to look into that.
I cut the highs out well the bad sounding ones (my personal taste that is) with C10 but as your value goes up it rolls off less of the highs. So adjust to taste I suppose.
Like I said I made a few small value changes and it sounds nice to me ... except the volume.
My next mod to her will be locating the resistor to add a little more distortion and change its value. Changing the way my volume only works to the 12:00 (straight up) position ... after that it doesn't change ...
Anyhow these are extremely fun to mod!!! I am just beginning and I am starting to get the hang of some of the stuff!
Thanks to everyone who post good information on the boards I could not have done any of this without these boards. I would still be looking and playing with a stock ds-1 turd!
Thanks
- AFF
R16- 1K
R14- 10K
C10- .001uF
C5- 1uF
C9- 1uF
D4- 1N4001
D5- LED (clear blue 5mm still inside the case I didn't want to drill a hold for it.
I made a few small upgrades and the result was amazing. I just need to add more volume and I think but I am not sure that there is another resistor that I can change and add more distortion. I need to look into that.
I cut the highs out well the bad sounding ones (my personal taste that is) with C10 but as your value goes up it rolls off less of the highs. So adjust to taste I suppose.
Like I said I made a few small value changes and it sounds nice to me ... except the volume.
My next mod to her will be locating the resistor to add a little more distortion and change its value. Changing the way my volume only works to the 12:00 (straight up) position ... after that it doesn't change ...
Anyhow these are extremely fun to mod!!! I am just beginning and I am starting to get the hang of some of the stuff!
Thanks to everyone who post good information on the boards I could not have done any of this without these boards. I would still be looking and playing with a stock ds-1 turd!
Thanks
- AFF
Hello,
I make the Robert Keeley mod. to an older DS1 unit (IC7136P) and when i turn the distorsion up i can hear a plop plop plop sound..
I record that sound, is here: http://www.megaupload.com/?d=PTM4EUJR
Any idea??
thanks in advance!
Lolo
I make the Robert Keeley mod. to an older DS1 unit (IC7136P) and when i turn the distorsion up i can hear a plop plop plop sound..
I record that sound, is here: http://www.megaupload.com/?d=PTM4EUJR
Any idea??
thanks in advance!
Lolo
- 5thumbs
- Solder Soldier
Well, considering you have a Made-In-Japan DS-1, I'd personally recommend removing all the Keeley mods and putting it back to stock configuration. The M.I.J. DS-1 pedals sound as good as most post-1994 DS-1 mods. (1994 was the year Roland/BOSS moved DS-1 production from Japan to Taiwan.)
Even if you don't want to keep your M.I.J. DS-1 stock, I'd still recommend putting it back to stock configuration, even as a starting point for trouble shooting. Put it back to stock, then repeat each step of the Keeley mods one by one, testing the pedal after each part replacement. Eventually, you should find the change that is causing the ticking sound.
Even if you don't want to keep your M.I.J. DS-1 stock, I'd still recommend putting it back to stock configuration, even as a starting point for trouble shooting. Put it back to stock, then repeat each step of the Keeley mods one by one, testing the pedal after each part replacement. Eventually, you should find the change that is causing the ticking sound.
Modding a DS-1? Please read 'Build Your Own DS-1 Distortion'.
"Other than a good first-in-line buffer/booster, using other FX to improve bad clean tone is like gift-wrapping garbage."
"Other than a good first-in-line buffer/booster, using other FX to improve bad clean tone is like gift-wrapping garbage."
- modman
- a d m i n
Information
- Posts: 4890
- Joined: 19 Jun 2007, 16:57
- Has thanked: 4394 times
- Been thanked: 2131 times
Keeley is a boutiquer, and as such he's a bullshitter like so many of them. But he's a funny and in some way smart one: he published "his mods" so everybody would do them and think, well that doesn't sound good, I am a technical moron, let's pay some buck to Keeley. Kaching!lolobomac wrote:Hello,
I make the Robert Keeley mod. to an older DS1 unit (IC7136P) and when i turn the distorsion up i can hear a plop plop plop sound..
I record that sound, is here: http://www.megaupload.com/?d=PTM4EUJR
Any idea??
thanks in advance!
Lolo
The above post is the only good advice. Then check this thread from the beginning to compare what you did to what is suggested by members here.
Use your own ears! It's perfectly feasible to have your boss pedal plugged in while working on it. Check how it sound after every single component change.
good luck
Please, support freestompboxes.org on Patreon for just 1 pcb per year! Or donate directly through PayPal
Hi,
This Ds1 is made in taiwan! But comes with the IC7136P. The inscription in the pcb is ET-28F. I go to try putting back the stock config. But, before the mod the ds1 dont work XDD and the pcb is in a really bad condition, anyway i try go back!.
thanks!
This Ds1 is made in taiwan! But comes with the IC7136P. The inscription in the pcb is ET-28F. I go to try putting back the stock config. But, before the mod the ds1 dont work XDD and the pcb is in a really bad condition, anyway i try go back!.
thanks!
- MoonWatcher
- Diode Debunker
I just did this mod today, and I have to say that it is one of the best DS-1 mods out there, IMO. As long as the Dist knob doesn't go much higher than 4:15, it's got just the right blend of EQ, harmonics, and body. And that's with the stock NJM chip, to boot!5thumbs wrote:Funny you should ask...my newest mod, the Huevos Grandes mod, pumps up the bass and darkens the tone.
Check out Page 27 of the doc linked in my signature below to listen to sound clips of the Huevos Grandes mod and see if it's to your liking.
The only thing that didn't really work for me was .056uF for C10, but that can be compensated for at the tone control. And the tone sweep is such a subjective preference, I've found. I tend to like my high gainers on the brighter side, so the .0039uF piggybacked to D4 (I kept it separate from the bridge rectifier in D5's slot) is sufficient for me.
I had a couple of DOD pedals in the 80's that had crossover distortion circuits that I really liked, and I like this one, too.
Great work!
I can't get the sound clips to work for me, though. Did you move them from the mybloop server?
- 5thumbs
- Solder Soldier
I wanted the HG Mod to be noticeably darker than the stock and Keeley/Analogman/Monte Allums/etc modded DS-1 pedals. On small practice combos with single 8" - 12" speakers, all that trebly fizz helps boost the presence somewhat on those amps. However, to me it sounds like a$$ on some larger speaker cab combinations. I wanted to cut the fizz and bump up the bass, so after trying 0.068μF (too dark) and 0.047μF (good, but wanted a shade darker for the HG Mod), I ended up compromising on 0.056μF for C10.MoonWatcher wrote:I just did this mod today, and I have to say that it is one of the best DS-1 mods out there, IMO. As long as the Dist knob doesn't go much higher than 4:15, it's got just the right blend of EQ, harmonics, and body. And that's with the stock NJM chip, to boot!5thumbs wrote:Funny you should ask...my newest mod, the Huevos Grandes mod, pumps up the bass and darkens the tone.
Check out Page 27 of the doc linked in my signature below to listen to sound clips of the Huevos Grandes mod and see if it's to your liking.
The only thing that didn't really work for me was .056uF for C10, but that can be compensated for at the tone control. And the tone sweep is such a subjective preference, I've found. I tend to like my high gainers on the brighter side, so the .0039uF piggybacked to D4 (I kept it separate from the bridge rectifier in D5's slot) is sufficient for me.
FWIW, my next DS-1 related project uses 0.047μF in C10 to get that "best of both worlds" compromise. That cap value brings more treble than 0.056μF, but is not as bright as stock.
Thanks. Crossover distortion is usually ugly to my ears when used alone or without moderation. However, it is good to give a little top-end sizzle to a dark sound, which is why I used it in the HG Mod. The hard part about Xover dist was figuring out the balance point for dry versus xover and the in-line resistor values to use in that resistor/diode network.MoonWatcher wrote: I had a couple of DOD pedals in the 80's that had crossover distortion circuits that I really liked, and I like this one, too.
Thanks. As for the sound clips, Mybloop.com crashed in June 2009 and hasn't been up since. I wasn't previously aware of this issue, so I'll have to move the sound files to another host and update the doc with fresh links. I'll try to get that done ASAP, but I can't promise as to when I'll get it done. (Very busy with work right now.)MoonWatcher wrote: Great work!
I can't get the sound clips to work for me, though. Did you move them from the mybloop server?
Modding a DS-1? Please read 'Build Your Own DS-1 Distortion'.
"Other than a good first-in-line buffer/booster, using other FX to improve bad clean tone is like gift-wrapping garbage."
"Other than a good first-in-line buffer/booster, using other FX to improve bad clean tone is like gift-wrapping garbage."
- 5thumbs
- Solder Soldier
OK, the sound clips links should once again work in the 'Build Your Own DS-1 Distortion' doc. Modman graciously hooked me up with some space to host these sound files, so thanks to him for helping me get this fixed quickly.
Just click on the link in my signature and you'll download the latest version of the doc. Thanks!
Just click on the link in my signature and you'll download the latest version of the doc. Thanks!
Modding a DS-1? Please read 'Build Your Own DS-1 Distortion'.
"Other than a good first-in-line buffer/booster, using other FX to improve bad clean tone is like gift-wrapping garbage."
"Other than a good first-in-line buffer/booster, using other FX to improve bad clean tone is like gift-wrapping garbage."
- sinner
- Old Solderhand
Information
- Posts: 4709
- Joined: 06 Nov 2008, 17:16
- Location: ...no more
- Has thanked: 1031 times
- Been thanked: 909 times
I was thinking to modify my MIJ DS1 to use regular power supply, any of you know how to make ACA/PSA conversion?
I did the 'JCM' mod listed on the Premier Guitar website and it turned out great.
http://www.premierguitar.com/Magazine/I ... _Mods.aspx
I use it as a one-trick pony in full gain distortion for bedroom play - not sure it will cut through the mix in a live setting, but pretty impressive nonetheless. I run the tone knob at 9 o'clock and it sounds smooth and creamy.
I picked up another (cheap) to futz around with the circuit and dated it to 1981 - so I guess I have the Japanese version. At any rate, it sounds okay stock and smooths out nicely when I lower the tone knob, but I would still like to try a few variations. I have read through this entire thread and was drawn in particular to the AMZ 'Phat mod' - changing R6 and R9 to make it less of a fuzz. Will this make the pedal cleaner or perhaps more transparent?
I also noticed that I have enough Silver Micas in my stock to replace C16 thru C19. Will this give me a bit more transparency or a cleaner signal to dirty up later?
Are there different mods for the Japanese versions or some things I shouldn't ever touch?
Also, has anyone tried a 50k pot on the distortion control for a bit more push?
This could become addicting.. thanks!
http://www.premierguitar.com/Magazine/I ... _Mods.aspx
I use it as a one-trick pony in full gain distortion for bedroom play - not sure it will cut through the mix in a live setting, but pretty impressive nonetheless. I run the tone knob at 9 o'clock and it sounds smooth and creamy.
I picked up another (cheap) to futz around with the circuit and dated it to 1981 - so I guess I have the Japanese version. At any rate, it sounds okay stock and smooths out nicely when I lower the tone knob, but I would still like to try a few variations. I have read through this entire thread and was drawn in particular to the AMZ 'Phat mod' - changing R6 and R9 to make it less of a fuzz. Will this make the pedal cleaner or perhaps more transparent?
I also noticed that I have enough Silver Micas in my stock to replace C16 thru C19. Will this give me a bit more transparency or a cleaner signal to dirty up later?
Are there different mods for the Japanese versions or some things I shouldn't ever touch?
Also, has anyone tried a 50k pot on the distortion control for a bit more push?
This could become addicting.. thanks!
I tried the AMZ "Phat Mod" and it does indeed work. The fuzzy fizziness that annoyed me about this pedal before is gone. The overall gain of the pedal is lowered, but the useful range of the Gain knob is much wider, pretty much over the entire knob's range know. I've been toying with changing C4 to 100pf instead of the stock 250, and maybe dropping C3 a notch to get some of that tightness and high end sting back.
- 5thumbs
- Solder Soldier
You can use either the old ACA or the new PSA adapters on the MIJ DS-1 pedals. You can't use the old ACA adapters on the post-1994 DS-1 pedals, as those pedals are missing the D3 and R38 components required to use the ACA adapters.sinner wrote:I was thinking to modify my MIJ DS1 to use regular power supply, any of you know how to make ACA/PSA conversion?
I've used the PSA adapters on my MIJ DS-1 with no issues.
Modding a DS-1? Please read 'Build Your Own DS-1 Distortion'.
"Other than a good first-in-line buffer/booster, using other FX to improve bad clean tone is like gift-wrapping garbage."
"Other than a good first-in-line buffer/booster, using other FX to improve bad clean tone is like gift-wrapping garbage."
- sinner
- Old Solderhand
Information
- Posts: 4709
- Joined: 06 Nov 2008, 17:16
- Location: ...no more
- Has thanked: 1031 times
- Been thanked: 909 times
Funny thing, but I just come in to this topic to post that I got this by myself and ask to veryficate it I should remove em and place the jumpers, right?
Thank you 5thumbs
Thank you 5thumbs
- 5thumbs
- Solder Soldier
Usually, to get more clean headroom or a "more open/less compressed" distortion, you'll either need to reduce the gain of the pre-clipping gain stages and/or increase the proximity-to-clip of the D4/D5 diodes. (Increasing proximity-to-clip means replace low-clipping-voltage diodes like 1N4148 with ones that clip at higher voltages, like two 1N4148 diodes in series or an LED/etc.)humfree wrote:I did the 'JCM' mod listed on the Premier Guitar website and it turned out great.
...
I picked up another (cheap) to futz around with the circuit and dated it to 1981 - so I guess I have the Japanese version. At any rate, it sounds okay stock and smooths out nicely when I lower the tone knob, but I would still like to try a few variations. I have read through this entire thread and was drawn in particular to the AMZ 'Phat mod' - changing R6 and R9 to make it less of a fuzz. Will this make the pedal cleaner or perhaps more transparent?
To me, Jack Orman's Phat Mod increases the "fuzz" qualities of the pedal. What the deuce do I mean by that? Well, when the bass frequencies are not properly handled in a distortion circuit, you get too many low frequencies in the distortion, producing a "flabby" or "fuzzy" quality to the distortion. This is why the DS-1 (and most other pedals producing "modern" distortion) limit the bass in the signal prior to clipping...to keep the resulting distortion nice and "tight" sounding (like the JCM800 and, consequently, most glam-metal from the 80s.)
What the Phat Mod does exceptionally well is rebias the Q2 transistor to reduce the frequency-dependent gain characteristics. (Translation: It properly biases that transistor so you don't get a big friggin' treble boost like in the stock configuration.) I personally prefer my "rebias of Jack's rebiasing" in the Huevos Grandes mod. Even if you don't try everything in that mod, I'd encourage you to at least try my HG mod values for R6 and R9. It's just a different flavor of Jack's great mod concept.
I've never been a big fan of mods to the flip-flop switching circuit that supposedly produce an audible difference in the final output. I've tried a few and didn't see any appreciable difference. You can do it if you want, but don't be surprised when all you've accomplished is change the color and shape of the installed capacitors, but not the final tone. (Of course, if you try it and find out I'm utterly and completely full of excrement, please report back with your findings. I'm skeptical, but can be convinced with independently-reproducible results.)humfree wrote: I also noticed that I have enough Silver Micas in my stock to replace C16 thru C19. Will this give me a bit more transparency or a cleaner signal to dirty up later?
I wouldn't mess with a MIJ DS-1. If you don't like the way it sounds, sell it for $160 on eBay and go buy four post-1994 DS-1 pedals to practice your mods on. The MIJ DS-1 pedals aren't perfect (meaning, you CAN beat them with some mods for the post-1994 pedals), but they are quite good on certain amp types. Given the high price you can get for the MIJ DS-1 pedals, I'm a big fan of keeping them stock and then experimenting on the post-1994 pedals.humfree wrote: Are there different mods for the Japanese versions or some things I shouldn't ever touch?
Nope. Once you've hot-rodded the DS-1 opamp stage to resemble the opamp gain level of the RAT (which some of my mods approach), you really don't need to boost the top-level gain any further. It's largely unusable past 4 o'clock with any guitar with reasonably-powerful pickups in it. (And no, the RAT isn't necessarily "higher gain" than the DS-1...they just boost the living hell out of the signal with only an opamp before clipping, whereas the DS-1 uses the Q2 transistor in conjunction with the opamp before clipping to get all of its gain.)humfree wrote: Also, has anyone tried a 50k pot on the distortion control for a bit more push?
Besides, replacing pots on the DS-1 is more work than replacing C8 and R13, so I think most folks just change those values and don't mess with the B20K DIST pot.
It is. Remember to leave the workbench and pursue other "finer things in life" after each pedal-based triumph.humfree wrote:This could become addicting.. thanks!
"Give me women, wine, and snuff
Untill I cry out "hold, enough!"
You may do so sans objection
Till the day of resurrection:
For, bless my beard, they aye shall be
My beloved Trinity."
- John Keats
Or, if you prefer...
"Give me resistors, diodes, and capacitors
Untill I cry out "That's enough, sirs!"
You may do so sans objection
Till the day of resurrection:
For, bless my beard, they aye shall be
My beloved Trinity."
I'll take the former, but I would have a hard time faulting the latter as well. I mean, one has to have something to do on the morning after the former, right?
Last edited by 5thumbs on 03 Sep 2009, 19:02, edited 2 times in total.
Modding a DS-1? Please read 'Build Your Own DS-1 Distortion'.
"Other than a good first-in-line buffer/booster, using other FX to improve bad clean tone is like gift-wrapping garbage."
"Other than a good first-in-line buffer/booster, using other FX to improve bad clean tone is like gift-wrapping garbage."
- 5thumbs
- Solder Soldier
Sorry about making you do your own work on this one, mate. I saw this post the other day, but due to a crazy-busy business travel schedule this week, this is the first chance I've had to reply.sinner wrote:Funny thing, but I just come in to this topic to post that I got this by myself and ask to veryficate it
Good job on figuring it out on your own.
I wouldn't. Just use a PSA-style adapter (or equivalent, like OneSpot, etc.) and you're golden. And for future reference, I talk about the D3/R38 stuff on Page 31 of 'Build Your Own DS-1 Distortion' doc.sinner wrote:I should remove em and place the jumpers, right?
You're welcome.sinner wrote: Thank you 5thumbs
Modding a DS-1? Please read 'Build Your Own DS-1 Distortion'.
"Other than a good first-in-line buffer/booster, using other FX to improve bad clean tone is like gift-wrapping garbage."
"Other than a good first-in-line buffer/booster, using other FX to improve bad clean tone is like gift-wrapping garbage."
- sinner
- Old Solderhand
Information
- Posts: 4709
- Joined: 06 Nov 2008, 17:16
- Location: ...no more
- Has thanked: 1031 times
- Been thanked: 909 times
5thumbs wrote:Sorry about making you do your own work on this one, mate. I saw this post the other day, but due to a crazy-busy business travel schedule this week, this is the first chance I've had to reply.sinner wrote:Funny thing, but I just come in to this topic to post that I got this by myself and ask to veryficate it
Good job on figuring it out on your own.
I wouldn't. Just use a PSA-style adapter (or equivalent, like OneSpot, etc.) and you're golden. And for future reference, I talk about the D3/R38 stuff on Page 31 of 'Build Your Own DS-1 Distortion' doc.sinner wrote:I should remove em and place the jumpers, right?
You're welcome.sinner wrote: Thank you 5thumbs
No need to be sorry mate I should use my brain more often than ask questions I'm a paramedic, not a skilled electrical technician, so I'm not fully convinced what I'm doing
About the jumpers in D3/R38, if I desolder those two components, and replace them with jumper, nothing's gonna happen to my unit?
- sinner
- Old Solderhand
Information
- Posts: 4709
- Joined: 06 Nov 2008, 17:16
- Location: ...no more
- Has thanked: 1031 times
- Been thanked: 909 times
One more thing... I was thinking about midrange control, similar to AnalogMan's How do you feel, If I replace R16 with 10K pot + 1k (or 2,2K) resistor in series will I be there? When I read about AMZ BMP presence control I come up with this idea, is there any logic in there?
BTW great job with your .pdf you did mate
BTW great job with your .pdf you did mate
I gotta say that I am really impressed with the responses I have gotten on the few posts I have put forth.
Thank You 5thumbs for the taking the time to break it down for me. I thought long and hard about whether to turn this pedal over for profit, but I think I will use it when it is done. The few changes I made have already produced a monster.. a little tweak here and there and I will be a happy camper. I snatched that 'BuildYourOwn DS-1' PDF from one of these threads and have been relying on that for much of my information - what a great file!
I like to have at least four dirt boxes on my board and if they all like each other, even better. I haven't had a true distortion box for a long time, so sifting through all of these possibilities will be fun.. and now with a proper soldering iron, EASY and CHEAP. There's just something about breathing tone into a scoffed at 'POS'.. hehehe - Oh, and I made some knobs out of wine corks for those who would sniff around my board at a gig..
I would still like to find a 'Timmy' style mod for an SD-1, but I have a feeling I'll be modding these little orange stepchildren for a long time to come!
Thanks again!
Thank You 5thumbs for the taking the time to break it down for me. I thought long and hard about whether to turn this pedal over for profit, but I think I will use it when it is done. The few changes I made have already produced a monster.. a little tweak here and there and I will be a happy camper. I snatched that 'BuildYourOwn DS-1' PDF from one of these threads and have been relying on that for much of my information - what a great file!
I like to have at least four dirt boxes on my board and if they all like each other, even better. I haven't had a true distortion box for a long time, so sifting through all of these possibilities will be fun.. and now with a proper soldering iron, EASY and CHEAP. There's just something about breathing tone into a scoffed at 'POS'.. hehehe - Oh, and I made some knobs out of wine corks for those who would sniff around my board at a gig..
I would still like to find a 'Timmy' style mod for an SD-1, but I have a feeling I'll be modding these little orange stepchildren for a long time to come!
Thanks again!
It looks like two things are going on with the Phat mod.
The first is the change in input impedance from the R6 change. R6 (100K stock) and C3 (.047µF stock) form a high-pass filter with a corner frequency of 33.9hz. That's below the lowest string of a guitar in standard tuning (E2=82.41Hz), Drop C (C2=65.41Hz), a seven string (B1=61.74Hz) or even a detuned seven string (A1=55Hz, you crazy bass lover you). Since all but the seven string tuning tunings are at least an octave above the corner frequency, I cannot see how this filter could have anything but a minor effect on the bass response of the guitar tone passing through the pedal at this stage, but since the guitar's lowest notes are not so high as to be above that -3dB curve I won't argue that the high-pass filter made by R6 and C3 have no effect. If you were trying to use a stock DS-1 with a bass guitar, then this high-pass filter would have much more effect. Either way, when R6 is changed to 150K, the corner frequency of this high-pass filter changes from 33.9Hz to 22.6Hz, placing the lowest notes on the guitar further away from the corner frequency, and that filter's effectiveness at filtering out the lowest bass of the guitar. However, we can get the filter almost back to it's original response by dropping C3 from .047µF to .033µF (33.2Hz, close enough).
The second thing that seems to be going on is rebasing of Q2. When I look at the schematic for Q2, it looks similar to one for a cathode-biased class A gain stage that one sees in the preamp of a guitar amplifier. When one changes the value of the cathode resistor on such a gain stage, one changes the voltage drop across the resistor, and thus the voltage at the cathode, changing the bias of that stage. It seems to me that the same thing would be happening here with Q2, change the emitter (cathode) resistor, you change the bias. I realize I could be making an error here, since transistors are not vacuum tubes and may not behave the same thus. I've tried to read the datatsheet for the transistor at Q2 (Toshiba 2SC2240 is what I found with some Google searching) but I'm not sure how to make sense of the graphs provided (though a couple do look a lot like the curves from a vacuum tube pentode). Either way, I don't think the change in R6 effects the bias of Q2, just R9.
Either way, the combination of both a) changing the corner of the low-pass filter and b) changing the bias Q2 definately has an audible effect.
The first is the change in input impedance from the R6 change. R6 (100K stock) and C3 (.047µF stock) form a high-pass filter with a corner frequency of 33.9hz. That's below the lowest string of a guitar in standard tuning (E2=82.41Hz), Drop C (C2=65.41Hz), a seven string (B1=61.74Hz) or even a detuned seven string (A1=55Hz, you crazy bass lover you). Since all but the seven string tuning tunings are at least an octave above the corner frequency, I cannot see how this filter could have anything but a minor effect on the bass response of the guitar tone passing through the pedal at this stage, but since the guitar's lowest notes are not so high as to be above that -3dB curve I won't argue that the high-pass filter made by R6 and C3 have no effect. If you were trying to use a stock DS-1 with a bass guitar, then this high-pass filter would have much more effect. Either way, when R6 is changed to 150K, the corner frequency of this high-pass filter changes from 33.9Hz to 22.6Hz, placing the lowest notes on the guitar further away from the corner frequency, and that filter's effectiveness at filtering out the lowest bass of the guitar. However, we can get the filter almost back to it's original response by dropping C3 from .047µF to .033µF (33.2Hz, close enough).
The second thing that seems to be going on is rebasing of Q2. When I look at the schematic for Q2, it looks similar to one for a cathode-biased class A gain stage that one sees in the preamp of a guitar amplifier. When one changes the value of the cathode resistor on such a gain stage, one changes the voltage drop across the resistor, and thus the voltage at the cathode, changing the bias of that stage. It seems to me that the same thing would be happening here with Q2, change the emitter (cathode) resistor, you change the bias. I realize I could be making an error here, since transistors are not vacuum tubes and may not behave the same thus. I've tried to read the datatsheet for the transistor at Q2 (Toshiba 2SC2240 is what I found with some Google searching) but I'm not sure how to make sense of the graphs provided (though a couple do look a lot like the curves from a vacuum tube pentode). Either way, I don't think the change in R6 effects the bias of Q2, just R9.
Either way, the combination of both a) changing the corner of the low-pass filter and b) changing the bias Q2 definately has an audible effect.