why does my brownsource sound like s**t > with audio example

[Doug_H]

I hate to just give you the standard kissoff answer but you really need to check the debugging info located in the stickies in this forum. I would check the bias voltages of the buffer and op amp, make sure you have around 4.5v on inputs and outputs, etc. Maybe it's a cold solder joint. Easiest way to fix that is to heat and reflow all the joints. What kind of op amp are you using? Some op amps don't recover from distortion gracefully and it could be the second stg is not playing nice when you roll the tone control down (which drives that stg harder). I kind of doubt that's it but I'm using a TL072 with no problems. You might try subbing that just in case. Etc, etc...

[John Lyons]

If you still have it out of the box you should just wire it up stardard DPDT without the LED and see what you get. In bypass you should get a clean sound, or at least no sound from the pedal. I'd imagine you do have a problem but I have a similar sound from my BS and I'm pretty sure mine is 100% on with the Nelson PDF.

John

[Doug_H]

What model # op amps are you guys using?

[ulysses]

hey doug/john

thanks for still looking at this thread i appreciate it

im using an ST (brand) TL072CN(knm538) ive swapped it out for a brand new one i know is working. same result.

i swapped out the bc549c for a new one also .double checked the polarity, same result.

i multi'd the opamp. here are the results.

pin1 3.65v
pin2 3.65v
pin3 3.60v
pin4 0v
pin5 2.23v
pin6 3.64v
pin7 3.62v
pin8 7.31v

so either i have made a big mistake or the vero i built it from is wrong. im usually pretty good with an iron and dont usually stuff these simplish circuits up. i got the meatball right first time..

pin5 is a conscern. it should be around 3.6v right, not 2.23?

john/doug, would you mind multi'ing your opamp to check the voltages to see if any of us are close to each other?

cheers
ulysses

[Doug_H]

Pin5 is a little low and should be around 1/2 your supply voltage like the rest. I don't know if that's your problem but it's worth checking. Also, if you're battery's at 7.31v, put in a fresh one.

[ulysses]

hi doug,

the battery is showing 8.03v

should the input of the opamp show 8.03 also?

how would you suggest i debug the 2.23v problem?

thanks again
ulysses

[Doug_H]

Your battery should be around 9v and the op amp supply pin (pin 8 ) might be a little under that, depending on how much current is being drawn.

To sort out bias problems (2.23v) read the stickies.

[ulysses]

hey doug

i read the wiki debugging and tried to diagnose the tranny. would you be able to let me know your multi results? please?

here are my results:
e: 0.4 b: 0.88 c: 7.32
The base is (0.88 - 0.4 =) 0.48V more positive than the emitter, the collector to emitter is 7.32-0.88V = 6.44V

is this a good result right?? base almost double the emmiter and becasue the collector is tied directly into the source voltage its showing around about the correct voltage (-voltage use of the pedal).

cheers
ulysses

[John Lyons]

Here is what I get:

Regulated Boss 9.6v DC supply

2n5089 C = 8.97, B = 3.66, E = 3.16

Texas Instruments NE5532AP
1. 4.28v
2. 4.0v
3. 3.84v
4. 0v
5. 4.32
6. 4.32
7. 4.32
8. 8.97

john

[slacker]

I haven't built the brown source but I think the transistor is just a buffer so your base and collector voltages look too low. They should both be closer to 3 or 4 volts. I'd check the resistor values round the transistor and check that you've got the correct pinout.

[user]

SOunds pretty good to me!! Bassy and Crunchy tone! hehe

[ulysses]

hey guys its me again!

hehe

for starters, i hooked in my boss 9.6v supply to get as close as i could to johns readings. and a dead battery is never helpfull

i also went around the board and resoldered every joint.. just to be sure.

ok.. i found another datasheet for a different brand bc549c which has the orientation around the other way. even though it contradicts the one supplied by jaycar for the one they supposedly sell, i thought id give it a go anyway..

the results are different. the sound is not.
c 8.35v
b 2.31v
e 2.80v

i presume these results mean that i now have the bc549c correctly orientated.

with the boss power supply plugged in, the results on the opamp are slightly different. they are:
1 4.2v
2 4.22v
3 4.16v
4 0v
5 2.5v
6 4.2v
7 4.25v
8 8.36v

so i took dougs advise on biasing the opamp and played around with resistors on leg 5 of the opamp.

changing the 330k resistor to 330r resistor increases the voltage on the 5th leg to 4.2v
changing the 330k resistor to 22k (didnt have a 33k resistor) increases the voltage to 3.82v

none of which seems to make the crackly opamp sound go away.

while i was testing i decided to test the sound on my fender sidekick 25 solidstate amp. the crackle is not nearly as noticable. in fact, you can barely hear any crackle. anyone else would have preumed the pedal was built correctly.

when i plug the pedal into my marshall bluesbreaker 1962 (1998) reissue the crackle is still there. is it possible that my bluesbreaker can't handle this pedal? its a shame becasue i love this amp and was really hoping to crank out some cracking tunes with this pedal.

cheers
ulysses

[ulysses]

i should also mention that i subbed the tl072 for a 4558 with similar multi readings / crackly sound

will post back with what i sounds like on a solidstate amp.

cheers
ulysses

EDIT: here is the fender sidekick 25 sample. recorded exactly the same way as the first example in this thread. sm57 on th front, sm58 on the back. its a prime example of why you should buy a decent amp before you spend money on pedals http://www.mixset.com/fender_sidekick_25_dodgy_brownsource.mp3

[Doug_H]

c 8.35v
b 2.31v
e 2.80v

i presume these results mean that i now have the bc549c correctly orientated.

with the boss power supply plugged in, the results on the opamp are slightly different. they are:
1 4.2v
2 4.22v
3 4.16v
4 0v
5 2.5v
6 4.2v
7 4.25v
8 8.36v

Again, you have the same problem you did before. Pin5, b, and e voltage should be around 4.5 v.

The 330k resistor will not change that voltage and is not the source of your problem. You tell me: Look at the schematic and tell me what resistors affect Vr in the op amp? What resistors affect the bias of the buffer?

[John Lyons]

Doug, by the way I dig your signature...keep forgetting to tell you that.

Ulysses
Take a look at the components connected to pin 5.
Make sure you have correct values for both 22Ks, both 1.2Ms and  the 3.9k on the emitter of the BC549.

john

[ulysses]

thanks again for the replies guys.

above is a modded version of the vero i built from. i added my voltages and red=source voltage, green=ground

the resistors r1 and r2 in conjunction with c1 split the 8.37 voltage to around 4.2v. unfortunatly when it jumps across r11 it drops to 2.5v.

resistors r3 and r4 are supposed to deliver half the input voltage to the base. unfortunatly they deliver 2.3v

i really dont know what is going on here.. is there a problem with the vero? anyone built this vero successfully?

cheers
ulysses

[Doug_H]

the resistors r1 and r2 in conjunction with c1 split the 8.37 voltage to around 4.2v. unfortunatly when it jumps across r11 it drops to 2.5v.

Pull r11 and verify it is really 330k. Check with a dvm if necessary.

resistors r3 and r4 are supposed to deliver half the input voltage to the base. unfortunatly they deliver 2.3v

Pull them and verify that they are actually 1.2M ea.

[ulysses]

hey doug

thanks for your reply.

i previously pulled r11 (330k) and replaced with lower values.

changing the 330k resistor to 330r resistor increases the voltage on the 5th leg to 4.2v
changing the 330k resistor to 22k (didnt have a 33k resistor) increases the voltage to 3.82v

neither the 330r or the 22k resistor made the harsh clipping stop.

i put a new 330k in there and the 5 leg is measuring 2.5v again.

i will pull the 1.2m resistors and see if they are the problem.

thanks again for your assistance.

cheers
ulysses

[Doug_H]

No! You definitely do not want a 330ohm in place of the 330k! Change that back.

[ulysses]

hehe yeah i was just testing to see if it would raise the v on the 5th leg, which it did, but didnt make any difference to the sound i have put it back to 330k.

assuming the resistors are correct. what do you think the problem might be?

im thinking there may be a problem with the caps. in particular c10 and c11. its a tiny little blue one. should this be ok or is there another type of cap i should be using?

cheers
ulysses