BSIAB2 - IT'S ALIVE!!

Started by spud, July 28, 2007, 06:01:46 PM

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spud

Well, just finished the last solder and it's up and running... :icon_biggrin:

Only issue is a hum/noise that seems pretty constant, although it gets lower as you turn down the gain/volume.  At max it is pretty awful (the hum/noise). 

I will post pics and if I can manage a clip - I think I can with my USB direct connect thingy.  I biased Q5 by reading + on the drain and with - on GND.   It is pretty close to 4.5, like 4.49.  I used a 100k but it is only at about 10 oclock - should have used a 50k. 

Well, it sure is fun even with the noise/hum.  I have an enclosure (a clone of the 1590BB), so i have lots of room to work with. Oh, the PCB I got from GGG - only comment I would give on that is that some of the leads are kind of close.  I prefer more space between runs but that's just me and my clumsiness.  I'm also in the process of building an HO from AX84 and man those things give you all kinds of space to work in on that eyelet board.  Man size components too - caps the size of a roll of quarters and resistors that you can actually read the color code own without resorting to magnification (1/2 watt jobs)!

Need to get to de-bugging this thing, I suppose it's a bad ground connection or something like that. 


96ecss

Hi,

I've built 3 of them so far and I've had no hum issues. Are you using a battery or a power supply? I have a cheap Strat copy guitar that makes any pedal I play through hum. What guitar are you using?

Dave

snoof

could be a power issue if using a wallwart.  are you testing it out of the enclosure??  If so, my pedals are all noisey until they are housed in a box.  I get all sorts of RF, and hum when testing with alligator clips and such.

shadowmaster

In my case before, I've been using a +9V wallwart with a transformer rating of 200mA. Using this on my BSIAB2 yeilded all kinds of noise. I thought this was inherent since the noise is a common complaint here in this forum. I've since then converted this wallwart to ouput +18V (for my 301 Flanger) and created a new +9V wallwart using a transformer with a 750mA rating. When I tried my BSIAB to it, I was shocked that the noise I was expecting were gone. Even on max settings the noise is tolerable to think that I employed the use of plastic enclosure (no aluminum sheilding) and did not even use shielded wires for my input and output . The same is the case with my Orange Squeezer. Noisy with my old wallwart, quiet with my new wallwart.

Experts, care to comment what happened?

Thanks!

Ed G.

It doesn't like unfiltered, unregulated power supplies.
It works fine with a onespot supply as well as a supply I built some time ago with a regulator chip.

It hates my danelectro "zero hum" adaptor. Apparently, despite the name, it is not regulated and full of hum.

spud

First thanks to all for the great responses!  From a quick read it looks like power supply may be the cause.  Hmmm (no pun intended!)...

Dave:   

Thanks for the input - I wish mine would be as silent!  I'm just running a battery at the moment as I have yet to wire in the PS socket.  I used a cheap Charvel I had laying around (Korean knock off from the late 80's/early 90's) as I've packed away my other guitars, Fender '57 reissue strat & Ibanez AR100 - an early '80s one.  The Charvel has "Charvel" single coils in it - not sure of the qual.  I have overhead florescents, so that might contribute - turned the computer monitor off and my desk lamp while I tested it.  Thanks for the post and I'll try my Ibanez (2 HBs). 

snoof:

Good point - I just wanted to bench test it and see if it would DOA or what - plus I was just impatient!  As above, right now using a battery and as you guessed, it's out of the enclosure, just on my bench/desk.  That could well be the issue - I need to drill my enc and put it in there.   

shadow: 

Thanks for the insights.  I have yet to try a wallwart but the suggestion is sound.  So a regulated PS would be the way to go.  I'll have to see if any of the Radio Wallwarts are regulated as that was what I planning to get for it.  One thing is the 750mA - isn't that kinda high.  Most pedals I own are like 300mA or so, I think.  BTW - I shielded the input but not the output - from your comment it seems like it shouldn't matter.  Or should I do it just as a precaution?  Need to rewire the output anyway so I may do it.


Ed: 

Thanks for your input - I really like the sound from it.  It really has quite a range on all the controls - tone control and the Volume and Drive/gain.  I made one mod I saw mentioned - removal of the last 2 caps near the output (C13/14).  But instead of removing them put in a mini DPDT w/C.off to control the last caps (13 and 14).  I have it wired like this:  Center = bypass, up - .0022 uf, down - .001 uf.  I don't see a lot of difference between the .0022 and .001 but there is a real marked difference when it's bypassed - very open.  I might try other cap values - do you have any recommendations?  Again, I really liked the sound and the build was pretty easy (just wish some of the pads had more spacing between them on the PCB) - I know you don't control it as GGG makes/sells them but just thought I'd mention it.  Again, great circuit.  Are you planning on making any other pedals?  I'm sure everyone would be interested in checking it out.  I know I would be. 

Here's how I wired the DPDT: All GNDs are connected together and then run to GND on the Bd.

GND--.0022uf--|||--.0022uf--GND
C13 Input------|o|---C14 Input
GND--.001uf---|||----.001uf--GND



Oh, one other thing - I'm using a pair of old self powered computer speakers (quite large, really) and with the pedal bypassed, I get 0 hum - very clean sound.

Again, I really appreciate the input and I'll look into and try the various suggestions.

Pics and clip are still in the works.   

spud

Well, I've tried the following:

Put shielded on input (jack to 3pdt), main signal line in (3pdt to pcb), output (3pdt to jack).  I'm still getting the hum pretty bad.  Here are my tranny voltages if that should matter:

Q1:  D=4.71, S=0.76, G=-0.0
Q2:  D=8.54, S=4.71, G=2.83
Q3:  D=4.26, S=0.04, G=0.0
Q4:  D=8.54, S=4.26, G=2.83
Q5:  D=4.08, S=0.92, G=0.0

The GGG build guide says: 

Q1:  D=4.5, S=0.95, G=0.0
Q2:  D=8.0, S=4.5, G=3.8
Q3:  D=4.3, S=0.75, G=.3
Q4:  D=8.0, S=4.3, G=3.8
Q5:  D=3.4, S=0.9, G=0.5

I still have to go and find a regulated PS and wire up the 9v jack (right now I'm running off battery).

I should prob finish putting shielding on some of the other lines.  Esp the output run from the board to the 3pdt  as it's kind of long.   

I was hoping I could get it debugged before I stuck it into the case - a lot easier. 

Well, one thing, this is my first SUCCESFUL (at least partially) build - my first was a ROG DD that just wouldn't sound right (very low level and bad dist sound). I plan to redo it after I get this hum taken care of. 

For what it's worth, I did re-arrange some things (more in how they are in the enclosure) - I moved the 3pdt switch and jacks below the PCB where as they were depicted above it.  I left the pots above the pcb.  I also re-arranged the grounds to correspond to their new location - shorted runs from the parts.  I also put in a dpdt switch for C13/C14 bypass (see above post). 

Appreciate any insights on getting rid of the hum  :icon_mad:  or if you see something odd about my voltages, let me know. 

Thanks -

Spud