BSIAB2: What will j201's do for me?

[Thomeeque]

 Hi!

I've built BSIAB2 few months ago, but since I had no j201s at the time, I've used 2N5457s for all Q's, including Q3 and Q4.

Because my supplier probably sleeps all the winter and I still don't have j201's and I quite like effect produced now, I just wonder what exactly will change when I use j201's for Q3 and Q4? Can somebody tell me?

Thanks, Tomas

BTW. I've designed my own PCB layout, almost twice smaller than GGG's, so if somebody is interested, I can provide it (the layout, not the PCB ).

[cpm]

j201s will put loads of distortion, when i built it the gain pot started at quite high gain. too much for my taste.

I preferred the sound of lower gain fets, like BF245, or MPF102 and the like. It started from nearly clean, to crunch, up to heavy. I dont remember if i changed all transistors or leave some stage with j201s

[Thomeeque]

j201s will put loads of distortion..

..but compared to what, even to 2N5457s?

[liquids]

It's been a little while since I used anything but my current configuration in there that I've stuck with, which is two MPF102 at the input, with the called for two J201 at the second stage and the 2N5457 for the third stage, but I remember a lot of the tweaks I've tried.  In the end I tweaked about 25 of the 40 or so values on that schematic, though, in the end--a few of which reduced gain to more 'usable' levels, for me, while still allowing for rather high gain settings.  I think this thing is a gain beast, really, so it's not even low gain after my mods, it just limited gain along what I found is the usable range.  In previous and early posts I read most guys felt that with the stock schematic, anything beyond 2/3 on the gain knob was unusable mush anyhow.

When I tried it stock, I instantly had what I would say is a satisfying, heavy Marshall tone. A great starting point, but I knew it needed work for what I wanted--it had what sounded like too much fizz on the input, too much gain all around , and 'too tight' and bass shy for my tastes.

As is usual with multi-stage circuits, the first stage and those JFETs make the biggest difference, as is my opinion.  I use this pedal exclusively with bridge position humbuckers which are hot -- around the range of a Duncan JB. There was a "overloading the input" sounding fizz with anything but MPF102 in the first stage for me because of that.  Lowing the gain of the first stage just by changing the JFETs kept it from sounding like my pickups were over driving the first stage in a nasty way, and to boot gave me BoR and Vintagey marshall-like cleanup using my guitars volume knob, which I was looking for, and which was lacking with the stock 2N5457's.  For my tastes, the difference between the 2N5457 and the J201's  was there, but not that huge to my ears given that I wanted less gain.  Granted, I eventually reduced the gain of stage two by increasing the value of the source resistor significantly, too...So while I have the J201's in that stage, unless you need MORE gain, I don't think going to J201 there will do much for you overall any more than messing with that resistor will.  So, in short, I don't think you need to up the gain with J201s unless you're maxing out your gain pot.  Some people claim J201s are more consistent, but if you're happy with yours and like the gain, your probably not missing much than can't be changed with the knobs.

I've got two heavily tweaked out BSIAB 2's with additional toggles etc, on my board, because I love the capabilities and WIDE range of tones this circuit, at it's core, offers.  If you or anyone for that matter, are interesting in talking mods (I've  breadboarded this out multiple times and tweaked values for weeks at a time), feel free to PM me, as it would be a lot to list here. Contacting Ed directly is useful too -- his suggestions are/were a great starting point for me.  I really love toying and talking about this circuit!

[Thomeeque]

Wow, thanks for this huge answer! Since I'm rather looking for lowering the gain, I'll probably stay with actual Q's than, thanks!

What are your actual R3/C3* values (did you tweak R4/R5/C2 somehow?)?

*GGG schematics (ggg_bsiab2_sc.pdf)

[tackleberry]

I used all j201s in mine. I have a book with an older maybe original version of BSIAB it calls for 201s. I used the 1m for R4/R5 and R11/R12. R3/C3a/C3b I socketed and is a good place to adjust gain to taste, But I just used R3/C3 not a second cap. The book design I have also gives the option of caps at R10 and R15 to further affect the gain also has much different values for these resisters. A big difference I found is the GGG BSIAB only has the 1 trim pot at Q5 but the original design has a trim pot for each gain stage. It made a huge difference in mine to go back and put these trim pots in. C2 and C7 you could use sockets to be able to tweak these values to taste.

[Thomeeque]

I used all j201s in mine. I have a book with an older maybe original version of BSIAB it calls for 201s. I used the 1m for R4/R5 and R11/R12. R3/C3a/C3b I socketed and is a good place to adjust gain to taste, But I just used R3/C3 not a second cap. The book design I have also gives the option of caps at R10 and R15 to further affect the gain also has much different values for these resisters. A big difference I found is the GGG BSIAB only has the 1 trim pot at Q5 but the original design has a trim pot for each gain stage. It made a huge difference in mine to go back and put these trim pots in. C2 and C7 you could use sockets to be able to tweak these values to taste.

Hmm, interesting! Thanks!

[liquids]

Wow--more gain, with caps to ground off the emitters of stages two and three?  I can't even imagine how much gain that would create all else being equal, and if it would be usable or just oscillate and howl...  And what book has the BSIAB in it?...

I don't have the values I use in front of me or exact numbers off the top of my head, but I have them all documented at home for reference. If you PM me I can give them to you. That being said, if I recall I have MPF102s in the first stage, and C3 as just a 1uF, R3 as 1K.  But keep in mind that the MPF102s are much lower gain, so the same values with the 2N5457s you have will produce higher gain than mine, all else being equal.

If you want to lower gain overall, and the sound of better volume-knob clean up interests you, but keep the 2N5457, the easiest thing to do on stage one is just remove the C3 cap(s) altogether, and/or tweak the R3 Resistor. That being said, the cap(s) in there also shape the way the gain is produced by that stage (EQ), not just the amount of gain. You can also toy with leaving the cap in there, but raising the value of R3, and that may subtly effect the gain and other things.  Try 1K, 1.5K, 2.2K, 3.3K up to 4.7K and beyond...try it, and see what your ears find.  But that will certainly have less effect on gain than removing the caps does, if any--it  will not offer the same gain range as if there was no cap there.  Also, consider that as you lower gain drastically, you will need to compensate on the volume knob AND the gain knob for all else to be equal.

You can see stage two and three have no such caps on the source to ground.  Putting caps on the source on those stages will, for one, significantly INCREASE gain of that particular stage and the circuit overall.   Since these stages as stock have no caps, if you want to lower the gain of that stage, again, raise the resistor values going to ground, from no resistor (just a wire) up to 5K for near-unity gain, and beyond.  The gain will be effected fairly linearly; gain reduced as you increase the value of the resistor. 

I can't recall, but I have R10 somewhere around 3.3K rather than stock 120R (120 ohms)!  To each their own. As per above, 120R is nearly as low as you could get to being simply a wire to ground and approaching max gain for the stage, compared to 2K or 3K being somewhere the middle. 

In mine, R4/R5 R10/R11 are 1M as per spec, though I've heard that some guys 'half' them to around 470K for the tonal change, rather than a gain change, I believe...I forget if I've tried that, actually.  Another reason to re-breadboard it! 

The beautiful thing about this circuit is it is multi stage, and everything fairly straightforward if you understand JFETs/tubes and filtering.  It was the first circuit I messed with and I researched it a ton on here, and hence learned a lot about shaping gain stages right away.  Very educational circuit to experiment with.  It sounds rather good from the go, and it can be amended, customized, tweaked, etc to product nearly any kind of distortion tone you are after, with the beautiful sound of overdriven JFETs. It need not be a "like it or leave it" kind of build, it can be very accommodating to your tonal needs.  I'm getting the best smooth dynamic Robben Ford overdrive I've heard yet from it, with chimey arpeggio tones, and classic Marshall, to Joe Satriani tones just three knob turns (and a toggle switch or two if I'm feeling quirky) away at any given moment! 

[scott1568]

Anyone experience a great amount of hiss/buzz with this circuit?  Mine is a little more noisy than my BMP, and a bit difficult with single coils.

[tackleberry]

The book is "Advanced DIY effects pedals, how to design customize and build effect pedals" by Brian Wampler. There is a section discussing mu-amps. Its not labeled as BSIAB but as mu-amp OD/Dist, the schematic is identical up to the tone controls after C12 things are optional like tone controls low/high pass filters depending on your tastes. Only differences is the trim pots and some values. In the notes section it says "C9 and the optional caps for Q3/Q5 will boost the gain alot, smaller caps = less gain in conjunction with the resisters". "If you want alot of distortion make R1 1k or so, if more of an overdrive R1 4.7k - 22k". "Alternatively removing C9 and the other caps will make it more a smooth overdrive, especially if R1 is 10k or larger". Also says the trim pots are pretty important. The BSIAB2 when I built it didnt sound very good it was splatty and not very smooth, also the stock values for the tone control didnt work very well(if the tone controls was less then 12:00 the volume went down fast to no volume at 8:00). I never could get the voltages they listed at each transister. Even the Q5 with a trim pot was hard to dial in. I made some little boards with trim pots and sockets to mount Q2 and Q4 they hovered above the original board on short wires. After that when I set the voltages according to the book it works really good and sounds really good. Smooth and sustains very well. I only have 1 cap on Q1 and can dial the gain back to next to nothing if needed. I went back and redrew the PCB to include the extra trim pots and the extra caps with sockets. Havent reetched it yet as it does work really well now with the mods I made. Just not pretty with the 2 little extra boards hovering over the main board. Got some other boards Im working on Ill etch em all at once and rebuild my BSIAB.

[brett]

Hi

[Mine is a little more noisy than my BMP, and a bit difficult with single coils/quote]

Internal noise is an issue because it's a JFET circuit and the gain is high.
It'll also amplify any noise in the input signal because the gain is so high.

(You can see the recurring theme here....)
cheers

[scott1568]

Thanks Brett. I will probably have to shield my guitar. The problem goes away with H/B's.

[wampcat1]

The book is "Advanced DIY effects pedals, how to design customize and build effect pedals" by Brian Wampler. There is a section discussing mu-amps. Its not labeled as BSIAB but as mu-amp OD/Dist, the schematic is identical up to the tone controls after C12 things are optional like tone controls low/high pass filters depending on your tastes. Only differences is the trim pots and some values. In the notes section it says "C9 and the optional caps for Q3/Q5 will boost the gain alot, smaller caps = less gain in conjunction with the resisters". "If you want alot of distortion make R1 1k or so, if more of an overdrive R1 4.7k - 22k". "Alternatively removing C9 and the other caps will make it more a smooth overdrive, especially if R1 is 10k or larger". Also says the trim pots are pretty important. The BSIAB2 when I built it didnt sound very good it was splatty and not very smooth, also the stock values for the tone control didnt work very well(if the tone controls was less then 12:00 the volume went down fast to no volume at 8:00). I never could get the voltages they listed at each transister. Even the Q5 with a trim pot was hard to dial in. I made some little boards with trim pots and sockets to mount Q2 and Q4 they hovered above the original board on short wires. After that when I set the voltages according to the book it works really good and sounds really good. Smooth and sustains very well. I only have 1 cap on Q1 and can dial the gain back to next to nothing if needed. I went back and redrew the PCB to include the extra trim pots and the extra caps with sockets. Havent reetched it yet as it does work really well now with the mods I made. Just not pretty with the 2 little extra boards hovering over the main board. Got some other boards Im working on Ill etch em all at once and rebuild my BSIAB.

So *YOU* were the one that bought my book, huh? 
Actually, that schem will be one of the many updated in the new version of the book. Please delete the trim pots on the mu-amp circuits and go straight to DC+ but keep the trim on the last jfet stage.

If you can find it, do a search for "booster 2.5" IIRC - it's a great sounding similar circuit from Aron I believe

bw

[tackleberry]

Im pretty happy with the way it works with the extra trim pots. It didnt seem to work so well by the GGG plans. I notice the orman booster 2.5 doesnt have Q5 or any of the filters at the end. Didnt know if it would work better at 18v. I building a preamp with 12v tubes and will be adding some power jacks for pedals so will have easy access to several voltages. I know my DoubleD works pretty good on 18v.

[Thomeeque]

 Cool discussion so far!

My idea was to implement either "BOOST" on-off-on switch switching between C3a, no C3 and C3b or "GAIN1" pot instead of the switch ("treble boost" to the left, no /minimal/ boost in center, "full boost" to the right) plus maybe increasing R3 value a bit to have smaller base gain. It seems, after reading your answers, like it should be worthy

T.

[liquids]

Great ideas with the toggle switch for choosing caps in/out and differing values from source to ground!  So many options here!

But if you can, definitely breadboard it out to hear the difference between the settings.  Sometimes ideas and values for mods that sound great on paper gain 'new light' when implemented in a circuit.   

[jimma]

So *YOU* were the one that bought my book, huh?
[/quote]

Make that two- I bought it also and it's been a great help for me, thanks a bunch!

This thread has been a great help also, thanks to all involved. I've built 3 BSIAB's, but it looks like I need to breadboard a BSIAB and try some of these ideas. To answer the question in the title of the thread, my 2 cents is that J201's may drive you crazy in a way, at least they have to me in regards to tonal consistency from batch to batch. I haven't found any that sound "bad", just some are less woofy than others in my experience. I do really like the circuit stock (with j201's in the proper places) at gig volume (Strat or Tele through a loud, clean Twin Reverb, a similar rig to what it was designed around).

[liquids]

I do really like the circuit stock (with j201's in the proper places) at gig volume (Strat or Tele through a loud, clean Twin Reverb, a similar rig to what it was designed around).

I think you're right about that.  Vintagey single coils are going to cause major differences in perceived gain here, and they are what Ed used as a starting point I believe.  I'm using pretty hot humbuckers, while wanting the circuit to clean up when backing the volume off at that.  I've not gotten around to trying my Strat with my tweaked out BSIABs, but I already imagine they will not sound as sweet with my mods tweaked around my hot, midrange-heavy humbuckers.  The amazing thing to me about cascading mu-amps is that so many people are able to tweak a little here and there and get the circuit to sound right to them, along the full range of input signals as testified here.

It's also not necessarily a nasty or 'metal' sounding circuit, it's pretty classy sounding, professional, from low to med-high gains, even stock. 

This is yet another way that we can see cascading JFET gain stages are "tube-like."  Among tube amps, you talk about which of the vastly different sounding tube preamp/circuit you prefer with your rig and for your desired tones, but they all have multipl;e tube gain stages at their core. 

Likewise with the possibilities for this and many other cascading JFET stage circuits -- if there is intelligent design behind them (I.E. tweaking reasonable, usable levels of gain rather than starting with maximum available gain at every stage), you can tweak it until you find the 'right sounding preamp' for you, whatever sound that is.   I'm hooked and I haven't had so many, so good sounding, so versatile, convincing dirty tones--both at home and on stage--as I now have with the pair of BSIABs.  No more avoiding playing low notes because they're too bassy, or high notes that are too shrill, having to keep the gain a litle too low because it gets too nasty, having to keep the gain a little too high because it too shrill.   My other dirt pedals have, by default, been sold for cash to build more projects or are collecting dust waiting to be EBAYed from lack of use...they were plenty good, until I customized the BSIAB circuit!  Now they are old news.      And anything I want a change, it's plug and play...er, solder and go.