Craig Anderton's Stack in a box Build Report and Questions...

[gaddargaddar]

Hi at last I've finished it...First of all that's really a great circuit  to use with bass guitar and a Crate 15W bass amp ... With minor tweaking it really sounds great:D SIM1 and SIM2 sounds nearlet the same but I know how they would react to a electric guitar. They're useless for bass ...Anyway I've got some questions for the ones who has the original PCB from PAIA ...

1) Does BRIGHT and FAT switches really make a difference??? Becouse they're useless with bass. BRIGHT switch hasn't got an effect on the sound while playing with a bass,     
    also FAT switch has got a very very weak effect on the sound Why

2) According to the schematic in "Craig Anderton's Do it yourself projects for guitar" power section need to supply +42V for the tube but at mine gives out only 37-38V DC ... IS it correct??? According to the schematic we have to use CD4049, I used CD4049UBE...

3) Any other suggestions to mod it for bass


I could send the PCB pattern for it but it's really hard to get a neat PCB pattern transfered to copper without PNP paper(I've used transparency for laser printer and a marker:D) It took 3 days to complete the pattern:D (Drawing the PCB took 1 week)...

Thanks for all of the members Also Thank you Aron for this great forum

oooh here are the pics:D:D:D


     

[Mark Hammer]

Generally, what works for guitar as a "bright" switch won't work as noticeably for bass.  This is because what counts as not-quite-so-bright is already high end for bass, so adding treble above that is not all that audible.  I guess think of it like the impact of a 12khz cut/restore switch on a guitar amp whose speakers roll off around 5khz.

More concerning/puzzling is the lack of audible effect of a fat switch.  You can see from the schematic ( http://www.paia.com/prodimages/siabsch.pdf ) that all the fat switch does is stick a bass-cutting cap in the signal path or bypss it.  Since what counts as merely audible bass cut for a guitar is drastic bass cut for a bass, something is amiss.  Either you misread the value of C4 (which should be 2200pf/.0022uf) and stuck in something large enough to provide only barely audible difference compared to bypass, or else the switch or its wiring is incorrect/malfunctioning.

The 4049 you used is likely fine, since it is being used for a clock here, not as a linear amp.  That the supply provides only 38v instead of 42 is not all that troubling.  Remember that it achieves that 42V by taking the output of the 4049 clock and tripling it, minus some voltage loss for each step in the tripling.  Easy to imagine that you lose a bit on each step and end up with 38 instead of 42, especially if you start out with a bit less than 15V.

[gaddargaddar]

Thank you for your kind answer ... Anyway if you put a 0.33 microfarad capacitor across Crunch pot it sounds amazing Still I couldn't find the error related with the FAT switch...still working on it

[jimbeaux]

Jack Orman has a SIAB build report with mod's

http://members.aol.com/jorman3/siab.html

And thanks Mark for explaining the 4049 - I have been curious about that part of the schematic.

I have the SIAB kit - but haven't had the time to build it > maybe next time I get into a "building frenzy".

-JDW