BSIAB2 finished! yusssss! ..but..

[philbinator1]

I need more tone.  Literally!  It has stacks of volume, gobs of gain, but I have the tone knob cranked up to full and feel like
i need more.  I am using 100K-B's for the tone and volume instead of 100K-A's like the layout says, would that make a difference?  
or would a mod be the answer?

Also, what is the deal with the trimmer?  Is it the bias for one of the resistors?  It doesn't seem to much of a scope to it
between min and max or whatever.

One other thing...my wiring's getting better, but I still don't know why the effect won't turn off when I unplug the input jack.
I don't use batteries in any of my pedals, so it's not a huge deal, but i still want to know this for the future.  I have a suspicion
it's something to do with the input ring...does anyone know this?


thanks guys you rock  

the guts:

[therecordingart]

This is one of the best sounding distortion boxes I've heard, but I agree that it needs more shaping. I'm planning on building an EQ to use with it. My trimpot was pretty responsive, and it is used to adjust the drain voltage of Q5 to 4v. I just adjusted it by ear.

[Ed G.]

Too dark? bypass one or both of the LPF's (10k resistor followed by .002 cap) at the end of the circuit.
That'll do it.

[John Lyons]

Yep, just pull one of the .002 caps. Still too dark? Pull the other.
You may just need to lower them. .001 or one use .001 etc etc etc.

[liquids]

Just a plug - part of the joy of the breadboarding is that you'd know this (and much more) before you ever set it in solder  

Pulling C14 will have more of an effect than pulling C13 in terms of brightening.  I'd pull C13 first.  Also, don't be afraid to make C10 smaller - like 4.7n.  It will make it seems less dark, but will also make the tone control have less affect on the low and high mids along it's range.

While you are there, if you are like most people and you want more bass, just jumper C8 and clip R8....will keep the bass bigger along the tone pot travel...

[philbinator1]

That's great advice guys thanks!  will go do that now.  A couple more q's...will using linear pots as opposed to log have
any effect on the tone?  Also how do i measure the voltage of Q5 so i can make it 4V?  And about the input ring as mentioned above...?

It is a great pedal, sounds amazing...just like a cranked Marshall.  Sounds quite Firebird-ish (if you haven't heard of them,
check them out for great blues-hard rock).  Would be great to see it with the same controls as the Dr. Boogie.

[Zapp Brannigan]

Hello guys, I like BSIAB very much too, it sounds really cool, but I built this version:

As you can see, it contains no trimmers, bias is set automatically, no need to adjust it. Tone knob works fine, it changes sound from dark to extremely bright. Trannies are j201.

[waltk]

Also how do i measure the voltage of Q5 so i can make it 4V?

Normal biasing for Q5 is 1/2 the power supply voltage, so you may want to start by setting it to 4.5 volts if your battery/PS is at 9 volts.  You can tweak it by ear if you think it's better a little higher or lower.

Take your meter (you have one right?), set to DC Voltage.  Hook the black (-, com) lead on your meter to any ground point on your board or the negative battery lead.  Hook the red (+) lead on your meter to the drain lead on Q5.  If you are looking at the flat side of Q5, the drain lead would be the one on the left (consult the datasheet for a nice picture of this).

[philbinator1]

Normal biasing for Q5 is 1/2 the power supply voltage, so you may want to start by setting it to 4.5 volts if your battery/PS is at 9 volts.  You can tweak it by ear if you think it's better a little higher or lower.

Take your meter (you have one right?), set to DC Voltage.  Hook the black (-, com) lead on your meter to any ground point on your board or the negative battery lead.  Hook the red (+) lead on your meter to the drain lead on Q5.  If you are looking at the flat side of Q5, the drain lead would be the one on the left (consult the datasheet for a nice picture of this).

Cool thanks for that!  I have heaps of things to do with this build (replace 2 pots, jacks and bias...maybe bass mod too.  and dim the led it's destoying my retinas   )
It's funny though i tested it through my big rig, and the tone went from full to only having to be on 3/4.  so i might leave it.

cheers again 

[differo]

Hi Phil, how do you wire dc jack & input jack? if you wire it in 'usual' way then it switches off effect only if you use battery - but you could use the same principal but instead wire dc and input so that external dc is switched off.

[TamuT]

And while you're at it, ground the input as well (drawn red on the pic).

[philbinator1]

thanks guys!  muchos gracias!  man i love this place   

[KrazyKarl]

1 suggestion, you may want to socket your transistors so you can try swapping them out for other ones. I liked the sound of the j201s, but they didn't have enough dynamics for me. I swapped 2N5457s into the first stage right now and I find it's a good balance of gain and dynamics. MPF102s in the first stage have even more dynamics, but have less gain. I was glad I gave it a shot to tweak it a bit more, you may want to take a look at it.

[philbinator1]

1 suggestion, you may want to socket your transistors so you can try swapping them out for other ones. I liked the sound of the j201s, but they didn't have enough dynamics for me. I swapped 2N5457s into the first stage right now and I find it's a good balance of gain and dynamics. MPF102s in the first stage have even more dynamics, but have less gain. I was glad I gave it a shot to tweak it a bit more, you may want to take a look at it.

Hi KrazyKarl, I have found that anything above 3 oclock and it gets a little 'fizzy'...i might try de-soldering and socketing, thanks!  what do you mean the first stage?  how do you define a stage?  I don't yet understand this talk of stages.   

I wonder if someday someone will create the BSIAB3...a little more bass, a little less gain, and a complete eq section, like the Dr. Boogey. 
I think people would love it, and it's such a great pedal it deserves it       

[KrazyKarl]

The first two transistors are the first stage, the next two are the second stage, and the last one is the third. I wasn't sure when I first read about it either. Yeah, the 2N5457s and MPF102s are warmer I found than the J201s, so you might like them better.

[philbinator1]

This is one of the best sounding distortion boxes I've heard, but I agree that it needs more shaping. I'm planning on building an EQ to use with it. My trimpot was pretty responsive, and it is used to adjust the drain voltage of Q5 to 4v. I just adjusted it by ear.

I'm trying to bias it, but should I have the pedal switched on?  When I don't, it's stable at 4 volts.  If it's on the readings jump up and down a bit, and drops down to around 3.5 V...?
I'm using a regulated 9V power supply.

[philbinator1]

Sorry for the double post, but I had a thought that I might like to increase the bass as well, but make it switchable...how
would I do this and what kind of switch would I use?

Thanks mates!   

[philbinator1]

Bumparooney.

[Scruffie]

I Suggest downloading Duncans Tone Stack Calculator and rolling your own big muff tone stack for this... as someone who clearly likes metal (from your avatar   ) this doesn't offer much of a mid scoop which is probably what you're after... infact, the tone stack doesn't play too nicely for me in Duncans at all... but that's my opinion.

For more bass though... try increasing the 100n in the tone stack (C8 on the GGG schematic) to 470n... it'll give a little more bass across the knob.

As for voltage readings... i'd do it while the pedal was off.

[philbinator1]

yeah i installed a dpdt to switch between 100nF and 1uF...just tried it before.  Didn't really make a huge difference at all,
but i tried it on my little line 6 so will try the big guns tomorrow, when the flatmates are awake 

I hear what you're saying about the scooped thing.  but this is actually gonna be my 'rock' pedal, my next build will
probably be a Dr. Boogie for the metal...then we'll see how close I can get to that Skwigelf tone!    \m/