BSIAB2 treble /bass tone stack?

[earachemyeye]

Hello there fellow DIYers. I've been lurking here for years and found a ton of help and knowledge for my builds. Thanks to those who unselfishly share. I talk this place up whenever I can. I have built and use a BSIAB2 pedal. I like the way it sounds with just one exception. It sucks a fair amount of the low end out of my tone when I kick it in. I have done the cap swaps I found (to add bass) after searching here and while it definately improved the pedal I still find I could use a little more. Has anyone added a tone stack to one of these that gives more flexability? A schematic would be great. Any help would be appreciated.

Joe

[brett]

Hi
probably the simplest thing to do is add the tone section and output stage from a Big Muff.  One pot, one transistor, simple.

[Ice-9]

The BSIABII already has the tone stack from the Big Muff (different comp. values) followed by two 10K/2n2 low pass filters.  How about trying a Baxandall 2 pot tone circuit.

[punkin]

I too was looking for a little more tone control. I ended up using a VOX circuit. I really like the results.

[earachemyeye]

I'd be willing to try either of these suggestions. I'm good at assembling things from instructions and schematics but beyond that my understanding is still at the rookie level. I'm thinking there has to be a gain recovery stage following a tone stack with 2 or more knobs. I have Jack Ormans disc that shows the Mini Tubes with a different stack and a buffer but it sounds like it needs more work from what's given there (true?).

[earachemyeye]

Ok, I've revisited the Jack Orman cd and found the info that I need. Hopefully I don't screw anything up. Looks like I'll have to re-box it too. Thanks for the help.

Joe

[waltk]

I've made a half-dozen BSIAB2s with a Baxandall (James) tone stack.  The flexibility (and tone) is great.  Here are some suggestions based on my experience:

If you just lop off everything after Q5 on the GGG BSIAB schematic, and replace it with a Baxandall tone stack, the result is too trebly.  Crazy trebly.  If you search the forum for "infinity", you'll find a DI preamp project based on the BSIAB.  Figure 4 in the PDF for the infinity is the "Distortion section output filters".  I use that piece after Q5 and before the Baxandall.

The BSIAB has a boatload of gain, and you can add the tone stack without a recovery stage, but I usually add one anyway.  I've tried an opamp buffer/booster, and the AMZ MOSFET booster as the recovery stage, and they both sound good.  If you decide to reduce the overall gain of the BSIAB by substituting low-gain FETS, the recovery stage comes in handy.

About the Baxandall - if you increase C3 (from Duncan's Tone Stack calculator), you can get a huge mid-range boost (that extends down to enhance low-range frequencies) .  I always add a cap in parallel with C3, and put it on a switch.

Good luck with your project.  Let us know how it turns out.

[liquids]

Hey earachemy eye...reviewing some of my old posts it looks like we've been here before...waltk too with his love for the BSIAB+baxandall!    Keep trying and you'll get it!

I'm curious what 'cap mods' you actually did to the BSIAB and are still unhappy with...simply because it is interesting to me.  Did you mod the caps in the tone stack?

It seems that few people seem to need as tight a bass than it offers, and the tone pot does cut bass...making a few of those caps bigger keeps the tone pot 'off' the bass, which I find more usable.  

But are you looking for a chug-chug kind of sound in terms of more bass?  I'm learning "more bass" means very different things to different people, and that the ears understand frequency well, but only in context and comparison to another frequency...hence my question.

Well, if you want that deep chug, you probably want some more exaggerated bass, which means a scoop in the midrange, and maybe a more narrow scoop, but the question of where is complicated, and even the AMZ presence control can only offer so much there.  In reality, the only way to get a big bass is relative to a mid dip.  I do agree that if you want a scoop, a baxandall is far more flexible given it's two knobs, especially if you know what you're doing in terms of which frequencies.....even adding the AMZ presence control to the BMP only can do so much to control a scoop.    I've found that it's really important to know where in the mids you want to add or scoop--"more bass" and "more/less mids" often matter less than which mid band and how wide of a bandwith.

Along those lines, WalktK, what values and settings do you use in your baxandall? I'm curious what your ears are liking.   If you reference the Tone Stack Caculator....also, what sounds do you use it for, what amps etc?  

That being said, This may not work for you, but the more I mess with tone stacks, them more I like tweaking the fender blackface tone stack.  Stock, it's scoop is just too wide and deep for most applications, but small easy tweaks can really do a lot! Following, recently I've found there are definite ways around the high gain loss, the mid dip, and the control of frequencies if you can handle adding three pots, and especially if you drive it with an emitter follower...try 470p/100n/10n, and make the mid pot 50k.  It's amazing, and the one way it beats the BMP or Baxandall is that the the frequency of the scoop is extremely stable no matter the settings, by comparison, when you mess with the bass or treble controls.  Also, if you want the change where the scoop is or how wide it is, you can just tweak the balance between the 470p and the 10n caps.  

[waltk]

I don't want to take the thread too far astray, but this might useful for anyone looking for tone stack alternatives...

Along those lines, WalktK, what values and settings do you use in your baxandall? I'm curious what your ears are liking.   If you reference the Tone Stack Caculator....also, what sounds do you use it for, what amps etc? 

So, Matthew, you've finally been lured to the dark side - trying real tone stacks instead of capacitor tweaks. 

Using Duncan's tone stack calculator, on the James tab, I like to increase C3 from 330pF to 890pF.  I usually do this by leaving in the 330pF and adding a 560pF in parallel on a switch.  I saw this suggested on another forum, where it was described as a "mid boost".  It sounds to my ear like a good bass/mid boost, and you can see on DTSC that the peak of the boost is actually at 115Hz.

I also like to substitute linear pots for the "logb" pots specified on DTSC.  Depending on the amp I'm playing through, I like to set the bass knob high (like 100%), and the treble knob backed off to 75% (if you were using logb pots, this would be equivalent to about 100% and 85%).  The net effect of the pot settings is a relative boosted bass, a mid-scoop, and the treble leveled halfway between the bass and the scoop.  When you switch in the extra cap, the mid-scoop gets shallower, and also shifts the mid-scoop lower to center around 450Hz.  I love the tone I get from this, but sometimes play through radically different amp gear - including self-made chipamps, home stereo, small SS practice amps, large homemade amps based on car stereo, and old tube amps (a Harmony 303A, a Silvertone 1484, and a Peavey Mace w/6 6L6 tubes).  That's why I like the flexibility of a real tone stack.

I've just about exhausted everything I wanted to try with the Baxandall, so maybe it's time to move on to Fender or Vox tone stacks - thanks for the suggestions...

[liquids]

Waltk - interesting.  I'm assuming that on the BSIAB, this configuration replaces instead of the BMP tone stack AND the two RC filters (10k/2.2n) at the end?

Seeing the EQ curve now, I see why you like the Baxandall, given your tone desires uses.

People often tout the baxandall as being so great because you can do a true mid bump and extreme scoop.  To my eyes, the problem is 1) huge gain loss 2) the frequency being scooped is way to interactive with the bass control setting 3) the width of the scoop is so widge in the range...   

Likewise, The BMP is touted as having the luxury of "being able to control bass and treble simultaneously."  But in reality, my eyes see that while I like that the BMP is highly and easily tunable for a specific sound if you carefully choose values, 1) if set to scoop mids as most are, the frequency of the mid scoop is continuously changing along the pot 2) the configuration with 'equal values' for R1/R2 and C1/C2, while able to be flat, the bass and treble boost/cut corner frequencies invariably takes the treble or bass with it in the cutting and boosting rather than leaving the mid range alone...so both are not ideal across the board.

For you, your configuration overcomes the above compromises of the baxandall.  Your leaving the bass knob up keeps the mid dip from being too extreme, keep the gain loss low, and keeps the mid dip in the same frequency range and somewaht narrow along the range of your turning the treble pot. It also affords an unusually high frequency for mid-dip-- somewherearound 950hz-1k, with a switch on the treble cap controls a "mid boost"  to even out the mid dip, and likewise your treble control allows for massive shaving of highs -- something that is really useful with the BSIAB, especially stock with the harsh and fizzy J201s.    Hopefully this helps you see why your ears like it....

For me, keep in mind that the BSIAB was my first major builds and two BSIAB PCBs, from first and lengthy breadboard experiments within those parameters. With the stock BMP style on the BSIAB, with limited experience I was able to swap parts until I got it the way my ears wanted, which was to have the tone control leave the bass, low mids and high mids mostly untouched, to effectively turn the tone pot it into a treble control for all intensive purposes, and likewise to sculpt the high end further with switching of caps.... 

As I've experimented I've learned there are far better ways to do all that the tone stack does from scratch, but given the PCB limitations, even through tons of mods, it functions wonderfully for me, still and that's what I use in mine even still, very happy with my vintage gain, mid-happy, bright-to-smooth tones...of which I get compliments on regularly, might I add.     

That's not what tone you are going for now, and also less versatile since you use a variety of amps, seeing your EQ curve...and it is difficult to get as consistent a mid scoop with only the BMP tone circuit. 

Ironically, both of us are in essence mostly utilizing an EQ curve we like, with a treble control and some switching in/out caps for variety.   

Each passive tone stack has it's oddities that can't be reproduced...which is why it's good to learn them all as well as possible!

Thanks for the tips on the Baxandall and tweaks...very interesting in that regard from someone to whom that stack is mysterious.   

[flo]

The following link explains that the Baxandall tone-stack with bass and treble boost resembles the Fender/Marshall tone-stack.
I tend to agree: When you do not need the bass & treble cut but only the boost, use a Fender or Marshall tone-stack variant.
Also, the "brown sound" is supposed to come from a Marshall top with its tone-stack set at max. 

From:
http://www.duncanamps.com/technical/baxandall.html

BASS and TREBLE BOOST (MID CUT)
Consider what the circuit looks like with bass and treble at max.
...
This circuit can be related directly to the Fender tone circuit
...
Why don't guitar amps use the Baxandall circuit? Some do, but again,
most guitarists prefer bass and treble boost. Also higher component
count. And it's best to minimize the number of components in the
signal path. The Fender-type circuit is simple, and if it does what
you need, then stick with it.

[earachemyeye]

Man..I was ready to just plow into it but I've got more to absorb now Great posts guys! OK, here's what I've done to my BSIAB2:
1. Replaced C5 with a toggle switching between 561pf - 681pf. Not much difference I know but with the other changes made the 681 scoops it a tiny bit.
2. Swapped out C12,C2, to .1 uf
3.Changed C10 to 4.7uf
4.Changed C8 to .33uf
5.Removed C13
6.Used 2N5457 for all Jfets
Thanks to Liquids and others for suggesting the swaps. I too found that as you increase the size of the caps to get more bass, mids become scooped and things can get fuzzy. Not something I'm looking for. What I AM looking for (and it's pretty close) is a fuller, richer sound from around 800hz and down. Those are the sliders on my eq that I want to push when I kick the pedal in to compensate for whats lost. Like others have said before, a little less JCM, a little more JMP Marshall. I LOVE the sound of the Infinity but from what I've read so far it's a preamp, not a stompbox, so I'm not sure it'll work in front of my amp. Thanks WaltK for working that stuff out and sharing the info. You've saved me a bunch of time for sure. I'm a gigging musician with a family so the less time I have to spend soldering the better. But I'm also hooked on DIYing pedals.  

[liquids]

I don't follow increasing the size of what cap gets you more bass and scooped mids?  C10 is the only one I can think of that fits that description...hmm.

I hope it was a typo when you said C10 is 4.7n, and not 4.7uf!

Anyhow, where are you setting the tone pot given this?

Every try pulling out R6, and or making C5 1n?  Pulling R6 would eliminate the treble peaking, which is a mod (on a switch) I like a bit as mentioned, since the resistor and cap combo effectively preserves high frequencies and some high mids, meaning it attenuating bass and most mids, early on in the circuit..exactly the opposite of what you want it seems. 

I don't see how 680pf scoops it...if anything, 560pf should sound a tad more scooped, compared to 680pf due to 560pf passing less low mids than 680pf...making it even bigger than 680pf, like 1n (experiment) would give you even more mids there, while keeping the bass attenuated, with the ability to shave treble later with the tone controls etc...


Hopefully you are auditioning things on the TSC with the tone stack.  From what I see, nothing in the tone stack is is creating any mid scoop if C8 is .33uF R8 is ~82k or greater and C10 is 4.7n instead of 22n.  Keep in mind that the high gain with JFETs running near full tilt is still very bright, so the ears hear the treble as exaggerated compared to the mids and lows, and maybe hence it still sounding scooped to you?   

With a passive tone control, the only effective way to 'boost everything below 800hz' is, well, to cut everything above 800hz like a shelving control...doable but not easy--roll offs are much easier.  But that's part of why there is so much low pass filtering in the stock circuit.  But you are pretty much attenuating a lot of treble if C10 is now 4.7n and you  turn the pot down, and compensate with some added volume for what is lost...now you've got a 'bass and mid boost. 

It will be pretty difficult to duplicate boosting frequencies with an active graphic EQ does, with just a passive tone control.   But you may find a 'mid point' you like.  As a side note, when I've found graphic EQs most useful compared to passives, it's often a speaker issue, I.E. an amp speakers (by size or number of speakers) inability to reproduce fat low frequencies and mids, rather than a pedals ability to produce them... but YMMV.  Baxandall is going to be a passive way to get closer to active filter-type shelving and mid boost, definitely

Anyhow, sticking with the stock circuit, if you find it has too much treble/not enough mids, removing C13 was probably not good plan...put it back, make it 1n if you found 2.2n too dark... or something....this should affect stuff more so in the 2k and higher ranges...the fizzy frequencies.

To get the tone control to affect treble more and further away from anything ~800 hz and belo, you could change R7 to something like 82k (try not to make it bigger than your value for R8) and make C10 even smaller, like 2.2n. 

I apologize if I'm losing you, I really amp trying to help.    the BMP may just not be the thing for you here, and the baxandall is the only passive tone stack you can get a true and relative mid boost from, especially with waltk's mod to make C3 around 1n and C4 more like 2.2n...ideally add the gain recovery stage and or buffer...so all that said, waltk's mods may be just what you are looking for! 

AS a comparison, if you can breadboard it up and elminate the tone stack completely to start...tape a volume control off the output of C9, to hear the 'tone' of the gain stages...It might be enlightening!  Then you can put different tone stacks on different breadboards and compare the sound of one to another till you get what you like.  It's work and time, but its a blast and satisfying when you get what you want!   

[earachemyeye]

 Remember I said I was a rookie at this. I apologize for the confusion. I'm sure you're right about C5 I've got it backwards And yes another mistake, it's 4.7n Maybe "scoop" isn't the right term either , "less cut" could be what I'm trying to say. I suppose I've also chosen the wrong amp and speaker for this pedal and I should probably get rid of them too along with my eq. I have the TSC but I like my ears to make the final decision. But it looks like I can't trust them. BUT I wouldn't say that I'm unsatisfied, it's a great pedal. I just feel a more flexible tone stack could get me more of the tone I want. I agree that I should try as many as I can and it will be fun . Thanks again WaltK. Out.

Joe

[liquids]

Another way to increase bass is completely eliminate R8 - that 82k resistor off the tone stack to ground.   I was just experimenting with a BSIAB, again...seems I come back to it seasonally as I learn more and more.  Anyhow, I was getting more bass out of the one on my breadboard, which should have been identical to the boxed one I had next to it....I realized, I hadn't put that resistor in there, since I was mostly breadboarding it off the top of my head and checking back when I wasn't certain.  Wouldn't you know, putting it back in tightened up that bass even with C9 as 2.2uF and C8 at 1uF.

If the tone stack was buffered, it wouldn't make an audible difference according to the R-C calc, but it isn't buffered, and my ears do hear a difference.

For the sake of curiosity I experimented with making C2, C3, and C7 all  very large, 10uF or 22uf.   Each swap added a subtle amount of bass, but changing them all just made it muddy distortion...if I had to only do one It would be C7, but I find the aforementioned resistor snip more useful for a fuller bass, though making C2 and C7 also 1uF might be a good in-between, or a starting point.

[liquids]

Since we were talking about bass improvements, I thought this expirimenting might prove useful to someone...

Recently I've been experimenting with active filters, and an ACTIVE baxandall tone stack following mu amps is awesome.  I was feeding 2 cascaded mu-amps of various kinds at high voltages into a passive filter stage or two (10k/22n, etc)-->a non-inverting op amp buffer--->a modified version of the baxandall schematic linked below....wow!

I think this is ideal for a fet or Mosfet-based OD, but even op amp diode clippers, to some degree.  Even at high voltages (I'm prototyping with 24v), bass get unnatural sounding and nasty if you don't trim and control it within and between gain stages.  On the other hand, 'real cranked tube amps' often get a lot of  fat lows when cranked. Passive filtering can't really simulate that 'bass boost' yielded by cranking an amp....I think this is part of the ticket to getting closer!

Note that when I play live, my BSIAB pedals don't sound thin or bass shy in the mix.  I get a lot of compliments. But I agree that getting a fatter bass could be a nice feature, if done properly and with realtime control to compensate for volume, gain, etc.  When I'm cranked up high or turned down really low, I wish I had more bass control.   I've tried passive mods to add bass here, there, and every where, and came up with my mods which in part offer that.  But the bass never gets fat, just less tight.   It's hard to keep the bass fat because at high gain levels need things mush out, which is worse.  I think the stock BSIAB is too tight for one, and passive mods can improve that, but only to a point, I agree. 

Anyhow, an active baxandall offers two things I think this pedal can utilize, active bass boost, and sharper curved treble filtering - mostly cut is useful, but even treble boost is cool.   I like that because I feel like I want a lot of filtering of the highest highs for a smooth sound, but to get it, you are always encroaching on a dull sound, or affecting to wide a frequency band into the high mids with just the passive roll off stages.  I got frustrated and put my prototype down a week ago, because all the midding and passive filtering I was expirimenting doing felt like a compromise, or yielded a final tone only moderately better than the BSIAB mods on my board.

So I starting with a baxandall, much like what is pictured here:  http://sound.westhost.com/dwopa2.htm#baxandall I'm sure this has been done before, but it's new for me and one one mentioned it in tis thread.   

To start, I still got the BSIAB about where you want it for bass--out of mush territory, tight and controlled.  Likewise, the BSIAB and the million related circuits need a fair amount of filtering of the highs, so while I removed the BMP, some of the 'standard passive filtering' out of the last stage (feeding a buffer) just to tame those ultra highs, and to keep it from sounding 'buzzy.'  I liked that better than reelying solely on the active treble cut for filtering.  You want a good sounding starting point with the active EQ set 'flat,' to some degree, and I want control over the highs in a certain frequency range, without it also accenting the 'buzzy' frequencies, if you know what I mean.

From there, you can add in the sub bass boost.  But It doesn't get mushy like increasing the caps in the mu-amp stages does after a while.  it's just 'feels' more like turning your amp (or amp bass knob) up.  If you want a tighter sound, you can leave the bass EQ 'flat' or cut it.  If you want to boost or cut to affect low mids and bass, you make the cap more like 33n, 22n, 10n, but at the sacrifice of approaching 'muddy.'  IF you want to control just those sub lows, 47n, 68n (my current favorite), or 100n, etc.

Likewise, an active treble filter has more range available, with a sharper knee than any passive stage.  Increased resistance adds more cut/boost with a stable corner frequency, rather than continually lowering varying the corner frequency like a passive cut.  To boot, boosting the highs after having smoothed the nasties out with the stock passive filter yields a sweeter sound to my ears than does not doing any 'passive' filtering and leaving it set 'flat'.  Likewise, you can cut the highs and sculpt the frequency you cut/boost by making that cap bigger or smaller - 1n, 1.5n, or 2.2n seemed useful to my ears.  It also has less interaction with the high mids...unless you want that, in which case, you can make the cap bigger (3.3n, 4.7n, etc).

Also, you can do research...it's not hard to give each filter more or less range, or favor cut/boost.

I instantly thought of this thread...the james and active baxandall are of course related, but I think this active option is great due to less interaction between controls and more stable corners, and it really leaves the mids alone.

Likewise, there is definitely a way to tweak an active filter for active mid boost/cut, getting into graphic EQ territory but with a similar configuration as the above 2 band here: http://freecircuitdiagram.com/wp-content/uploads/2008/11/3-band-graphic-equalizer-circuit.jpg

Enjoy!   

[philbinator1]

Oh my gosh.  I was after a simple mod for more bass, but there are a million things here...I did put...what was it...
C8 think, on a switch with a 1uF cap.  It adds a tiny bit more bass but not much.  I have read the thread, but there's
too much complexity for me...can anyone suggest anything a bit more basic?  It would be nice if it was switchable,
since I've already drilled the hole   

thanks   

[alfafalfa]

If it sucks too much of the original tone why not use it with a blender ?

Alf

[philbinator1]

I'm trying to cut down on my use of pedalboard kitchen appliances.   

Seriously though, I have no idea what you're talking about.     Explain please?

[alfafalfa]

It's a way to blend your original signal with the effect(ed) signal : you mix in the amount of effect you want just as with a mixing desk.

Try the search button on "blender"