Madbean Pasty Face (Soul Bender) - Increase Output Level

[chromesphere]

Gday everyone!
Hope you are all doing well.

I have a small question about the Madbean Pasty Face.  I recently built 2 (soul bender layout) of these and notice the output level is very low.  Infact, if i crank the volume to 100% i can 'nearly' get unity, but still not quite there.  Just wondering, is there a resistor value or mod that i can do, to increase the output level (and hopefully not change the sound of the pedal too much)?

Thanks for any help you can give, here is a link to the project file:

http://www.madbeanpedals.com/projects/Pastyface/docs/PastyFace.pdf

paul

[bean]

You can reduce R11 to 1k. That will give you a little extra. You can also use 500kB for Volume to push unity back a little bit. You definitely should be able to achieve unity with the effect...are your transistors behaving (getting good sounding fuzz)?

[chromesphere]

Thanks Brian!  (Probably should have posted this on MB forum first )

Hmm, i'll have to check my transistors.  I think i just pulled 2 randoms out of the 60-80hfe bags and 1 out of the 90-110 hfe bag, so they could be sitting anywhere in that range.  Also they are modern russians and have very low leakage (less then 100ua on q3), i've heard q3 should be leaky.  Dont know if thats going to effect the output level, though i will try the swap for curiosities sake.  Not sure if it sounds as it should, but it sounds great to my ear! Not full on fat fuzz, sort of like the buzzaround but less 'messy'.

If messing around with the transistors doesn't work i'll try to lower R11 as well.

Thanks again mate, ill start with your suggestions!

Paul

[LucifersTrip]

the buzzaround, which this a rip of, easily hits unity...and yes, I have found that it sounds far better with leakage in Q3 (note the voltage change on the collector when you try different leakages). The darlington pair Q1/2 is best with low leak, so you're good there...

[sgmezei]

I know mine have been quite loud with the newer Russian germs in them. I would double check the orientation for the transistors because I found I have to twist the legs on all my russian transistors.

[chromesphere]

Lucifer that was your advise i was referring to (q3 leaky ), thanks again.

I'm pretty sure my buzz around can go over unity.   Also pretty sure the orientation of the transistors is correct, i have used these before i know they have a weird pinout.  Something like Base Collector Emiter, with the base being the one connected to the transistor casing.  Many transistors died to bring you this information.  I will double check though cause i may still have put one of them in the wrong way.  I also have some leaker specimens showing up soon so i will wack one of those in q3 when they arrive as well to see what happens. Thanks again!

Paul

[chromesphere]

Checked Q3, it was about 90 hfe, which is a bit low from what ive read so upped it to approx 110.  It sounds abit fuzzier when you crank up the sustain which is good but still low volume output.  Both Soul Benders i've built do this (barely break unity).

Also changed R11 to 1k.  I think it's added some extra output, but yeah, still pushing to break unity...

Any other ideas?  Is this just the way its suppose to be?  Seems old though, if you kick on the fuzz pedal you lose volume...

Thanks again for your help!
Paul

[chromesphere]

Jacob seems to have had the same problem with another variant of the Pasty Face.  I'm starting to think its just the nature of the beast.  Bugger...

http://www.madbeanpedals.com/forum/index.php?topic=1321.0

Paul

[ode2no1]

if you remove r11 and replace it with a jumper cable you'll get more output.

[chromesphere]

Hey ode2no1,

I was thinking of this yesterday actually, but thought, maybe its there to limit current or something...Might have to try it though, because im pretty much at the point now of building 2 alembic stratoblaster and putting them after the soul benders, although the effect sounds great, the volume drop has got to go.  I'll try the jumper cheers!
Paul

[chromesphere]

An update incase anyone is following this.  I have found an error on the BOM for the soul bender.  R10 is listed as 'jumper' but on the schematic it should actually be a 10k resistor.  I forgot to mention, but the tone was acting more like a 2nd volume knob.  Putting that 10k in there fixed this.  However the orginal issue (volume on max = less then unity) is still there.  I tried removing r11 (swapping it for a jumper).  I think it helped a little, but yeah, im still pushing for unity....im used to volume controls that have unity in the middle somewhere.  This pedal is definitely less then unity on full volume.

Anyway other suggestions welcomed.

I will also post this on the madbean forum for Brian in case he wants to update the project file.
Paul

[chromesphere]

Just an update on whats happened so far.  The layout is actually correct.  If your building the soul bender form the pasty face project file and using the diy etch board, you have to following the schematic on the last page and not the BOM.  There are a couple of differences between them.

I have managed to get very close to unity...What i have done so far is increase R10 from 10k to 33k (the resistor that goes from the tone pot to ground).  I suspect its just increasing bass in the output as you turn up the tone and not the whole signal but thats ok because it sounds good anyway. I have also swapped the 10k and 18k voltage divider resistors near Q3.  It was suggested this would increase the voltage to q3 and increase the output.  I also removed the 47k on the output and used a jumper.  Of these modifications increasing r10 to 33k made the most difference, removing the 47k made a slight difference, and im not sure swapping the 10k and 18k made any difference...may have but it was subtle.

All those mods lead to an output approx unity, but i still think it needs more output.  The volume control currently is redundant as you'd just leave it on 100% permanently.

If anyone has any suggestions to further increase the output on the soul bender i would appreciate the info!
Paul

[JRC4558D]

hi mate, try R9 and R10 33K, remove R7 (no jumper at all) and BIAS trimpot completely (no jumpers at all there), also remove R11 (put a jumper there) and R12, if volume goes too high you could put a 10K or 12K resistor from Q3's collector to -9v, also try 1uf for C4 to get more volume and bass. Please let me know if that helped to increase your volume.

cheers.

[chromesphere]

Hey thanks for the suggestions jrc4558d.  I gave these mods a try and removing R11 did increase the output noticably.  Not a huge amount though, and i still need to have bass and vol on 100% to get unity (or a bit over unity now).  It could be my imagination but i thought i also noticed the sound of the effect change with this mod.  I think it made it sound wilder and less smooth? (more crunch)

I think at this stage im going to wait for my leakier transistors to show up and try those.  I've read that a leaky q3 may increase the output as well?  (not sure if thats true though).

This ones been much harder to get to my liking.  The buzzaround was a piece together and enjoy sort of affair.

Paul

[JRC4558D]

ok mate. I guess that a Q3 with more Hfe will do it better, I mean that one will give you more output volume.

yes, it make sense that replacing R11 for a jump makes the pedal crunch sounding (more highs), probably it's because you are driving less signal to earth trough C7, wich is a filter to remove the very top end .

cheers.

[ode2no1]

i built the general guitar gadgets "boutique bender" and owned a soul bender about 7 years ago. i will say that i always keep the bias trimmer turned all the way up. it gives you more volume, but also gives a ballsier tone. even then though, it isn't the loudest pedal. i definitely get more than unity, but nothing compared to most modern distortion/overdrive pedals.

[LucifersTrip]

  I've read that a leaky q3 may increase the output as well?  (not sure if thats true though).

i don't remember much output volume difference, just a big difference in tone

[chromesphere]

i built the general guitar gadgets "boutique bender" and owned a soul bender about 7 years ago. i will say that i always keep the bias trimmer turned all the way up. it gives you more volume, but also gives a ballsier tone. even then though, it isn't the loudest pedal. i definitely get more than unity, but nothing compared to most modern distortion/overdrive pedals.

Yep, I agree, the output volume for the soul bender must be 'normally' low.  

The volume stays the same, no matter which pick up im using when the effect is engaged, which is normal of course.  But, obviously when the circuit is off, the clean signal is louder with the neck pick up on my guitar.  The soul bender is louder then the bridge pick up, but struggles to be louder then the clean signal neck pick up.  I'd say it's definitely less.  It's also less then unity for my ibanez PF150 which has high output pick ups. I was hoping to mod it so that i would have enough volume that it wouldnt matter which pick up or guitar i'm using.  But the volume now is just going to stay on 100% and 'sometimes' be lower.  That kind of sucks imo.

I think im done with this pedal.   Im going to put that 10k res back in at the cost of losing some output, cause i think it sounded better before, less harsh, although that could be a good mod to have on a switch (a "bright" switch or something).

I'll try some leakier q3's for tone sake, but i'm giving up trying to get this thing any louder, it just doesnt want to co-operate.  It sounds great.  But the volume drop is a huge draw back imo.

Thanks for everyones help and tips etc, i appreciate it.  I'll post a demo / build report when i'm finished boxing it up.

Paul

[Skreddy]

The output volume from the last transistor (Q3) is set by means of a voltage divider between its power rail and its collector.  R13 is the resistor going to power, and R8 is the resistor going to the collector.  The output is taken from the junction of these.  The maximum voltage swing would be found at the collector, and zero voltage swing will be found at the power rail.

The Soul Bender schematic calls for 10k for R13 and 18k for R8.  This divides the output such that you'll be getting only 36% of the available voltage swing.  Swap these two resistors around, and you'll be getting 64% instead, and without changing the transistor's bias one whit.

If you wanted the maximum available output, make R13 28k and R8 a 0 ohm jumper; but that's probably overkill and would likely create oscillation problems.  Highly recommend just swapping R13 and R8.  You've already reduced some of the series resistance at output, and that would be the 2nd place to go after this.

[chromesphere]

All makes sense thanks for the explanation Skreddy, i appreciate it.  

This is pretty much where i have left it at: I have replaced R8 with a 33k and left r13 as 10k which increased the output (as you explained).  The other improvement was increasing the tone 10k to ground with 33k, adding more bass makes it sound louder, but it helped. oh yeah, and removing that output r11.  All these things contributed to increasing the output slightly with each mod. Its pretty much at unity now.  Like i was saying before, depends on the pick up im using, but its all very close.  Could be my imagination too, but my leaky germs should up, stuck one in q3, leakage of 300ua, despite sounding different, i could swear its also a bit louder.  

Yeah so now im at around unity & the volume control is still pretty much totally redundant and stays on 100%.

Paul