DIY effect, Need help!!

Tony-bobs · #1 04-17-2009, 03:45 PM

I'm building a bazz fuss based on the schematic found here:
http://www.home-wrecker.com/bazz.html

but I moved the pot back to the front to act as a gain pot, not volume. I have everything together, but when I tried to play through it, there are some problems.

first off, when it's in the "off" position, it cuts all the signal instead of bypassing the effect, is it supposed to do this or am I retarded?

Second, the gain pot seems to have almost no effect, other than killing all the signal if I turn it all the way up. I'm not sure what kind of pot it is, it was from an old squire bass and I had it laying around and grabbed it. do I need a new pot?

Third, when I dig in or play lower than an open A, its like I'm putting too much signal through and it clips and builds back up, like its moving through a tube rectifier, if that makes sense.

I've checked back to the schematic and made sure everything looks right, but i'm still not quite getting it right!

Tony-bobs · #2 04-17-2009, 04:06 PM

Tony-bobs · #3 04-17-2009, 04:27 PM

anyone?

megadan · #4 04-17-2009, 04:42 PM

It sounds like you need to do some more reading. You probably need a specific value of a pot (not to mention specific values and orientations of the other parts).

Start here:
http://www.beavisaudio.com/techpages...aticToReality/

Pbassred · #5 04-17-2009, 05:06 PM

I don't think this is the right forum. You might try at www.diyaudio.com .

I'm not an expert but........
What did you replace the 100K pot with? It needs to be there to bleed off some of the voltage from the hot side of the transistor. you should leave a pot there or wire in a 100K with the output connected to the top end.

It depends how you wired in the pot to the front. You might be choking off the signal. Also Both pots should be logarithmic.

Distortion below A? Well there IS a lot more energy down there.

Tony-bobs · #6 04-17-2009, 05:23 PM

everything is to spec with the home-wrecker schem besides the pot. according to the orriginal schem: http://personal.inet.fi/koti/holmberg/images/bazz.jpg

the pot is at the front of the circuit. The only thing that is different from the schematic is the value of the pot, of which I am uncertian. would that difference in value cause all of these problems?

seanm · #7 04-17-2009, 05:32 PM

Quote:

Originally Posted by Tony-bobs

everything is to spec with the home-wrecker schem besides the pot. according to the orriginal schem: http://personal.inet.fi/koti/holmberg/images/bazz.jpg

the pot is at the front of the circuit. The only thing that is different from the schematic is the value of the pot, of which I am uncertian. would that difference in value cause all of these problems?

Strange, I thought the bazz fuss needed a high impedance input. 50K isn't that high.

Are you using an active bass? And can you measure the pot? It may have a number on it, or just stick an ohmeter across the outer two terminals.

Tony-bobs · #8 04-17-2009, 05:36 PM

passive bass, I would guess that the pot is either 250 or 500, it was the volume pot from my old bronco bass, I don't have it in front of me right now.

All components used are per the home-wrecker schem, I used the other to check for moving the pot back to the front of the circuit to use as a gain instead of volume.

seanm · #9 04-17-2009, 06:07 PM

Which version of the bazz fuss?

And you did leave a 100k resister to ground on the output? Where it shows the pot, you put a 100k resister. The output is then where the cap meets the resistor.

Tony-bobs · #10 04-17-2009, 06:31 PM

V1, I didn't leave a resistor to ground, that might help a little. When I get home a little later on, I'll have to try that and see if it helps, also, I think I may have wired the pot wrong, but I can't remember for sure how I wired it up...

the original schem: http://personal.inet.fi/koti/holmberg/images/bazz.jpg doesn't show the resistor at the end, so that's why I didn't put it in.

Tony-bobs · #11 04-18-2009, 09:47 AM

well, after getting away from it for a while, when I got home last night, I realised that I had wired the pot in backwards. after fixing that, it works much better. putting in the 100K resistor to ground at the end seemed to stabilize the signal as well, so it cuts out less often. I'm going to see if I can get my hands on a 100K pot and a different switch today and she should be ready to go! Thanks for all the help guys, I'll post up some sound clips if I can find a way to get something recorded.

rcubed · #12 04-18-2009, 10:05 AM

Get another pot for the output or you might have an issue with getting unity volume when the effect is engaged. A cool mod for that would be a switch that lets you select between germanium and silicon diodes.

Tony-bobs · #13 04-18-2009, 10:35 AM

what do you mean by unity volume?

rcubed · #14 04-18-2009, 10:41 AM

Maybe you don't care about the volume of the fuzz, but you have a huge volume loss or boost when you engage the pedal (depends how you wired up the 100k resistor). An output pot would get the sound of the pedal to be approximately the same loudness as your bypassed signal. With a volume pot, you could crank the gain on the front end and not have to worry about volume issues.

Wren and Cuff · #15 04-18-2009, 12:36 PM

I'd imagine the bronco has 250K pots. You can "fake" the 100K pot by laying a 220K (or something close) resistor across lugs 1 and 3 on the pot. Lift the 100k resistor you put to ground of course.

You may also have a biasing problem, especially if it's farting out. that circuit has been around a long time, and sounds solid when you get it right. Very synthy IIRC. You should socket the tranny (you can get crappy sockets at rat-shack, but they'll work). Just get the 8 pin IC socket and cut it in half and ignore the 4th socket. try the 5088 as recommended, 2n3904 would sound nice in there too, and easy to find.

But... That is such a simple circuit (and a great one to start with) I'd get the right pot (they put it at 100k for a reason) Get 100k "A" or "logarithmic" $3 at rat shack IIRC, and start over. You'll spend more time trouble shooting the other board and only save a couple bucks.

Quote:

I don't think this is the right forum. You might try at www.diyaudio.com .

true pbassred.

But don't just post that you want someone to instruct you on fixing it, those guys will eat you alive and tell you to search, and read the FAQ's. Great guys once you know your way around. Years ago it wasn't so crowded, so you'd get a ton of help as long as they saw that you were also trying to "help yourself" learn. Bit different now....

If you want to keep it really simple, bail the switch. The Dan Armstrong method...

good luck. PS, make sure your diode is facing the right way.

matt

Tony-bobs · #16 04-18-2009, 02:06 PM

success!! I went to the shack to get a 100K pot but the closest they had was a 10K, I think we have the all time worst rat shack in the world. I bought it tho, cuz it also had a switch on it that I though I could us as the switch for my clean signal. I wired it it and made sure everything was grounded well and when I plugged her in, Beautiful fuzz. the clipping has come way down and only shows up if I play really hard. I think that it's putting out more boost than I had thought, so I might end up putting a volume pot at the end. So far I'm very pleased with it, and its sounds fantastic through the valve jr. cranked. I wish I had a way to record a clip, I had never heard one on bass so I was kinda jumping into this blind, sound-wise.

rcubed, as far as the 100k resistor, I kinda jumpered it in between where the .1 cap connects to the ouput and the ground from the tranny. Is that what you were talking about? It did seem to stabilize the signal pretty well.

seanm · #17 04-18-2009, 03:49 PM

And if it sounds good, it is good! Congrats on getting it going

rcubed · #18 04-18-2009, 04:23 PM

Quote:

Originally Posted by Tony-bobs

rcubed, as far as the 100k resistor, I kinda jumpered it in between where the .1 cap connects to the ouput and the ground from the tranny. Is that what you were talking about? It did seem to stabilize the signal pretty well.

Yep. The way you did it will let the most signal pass. If you had soldered the output after the resistor then you're going to get a really quiet pedal. In other words you did it right.

vin*tone · #19 04-18-2009, 04:26 PM

Quote:

Originally Posted by Tony-bobs

...first off, when it's in the "off" position, it cuts all the signal instead of bypassing the effect...

In general - effect schems ignore the off board wiring ie: all your in/out jacks, battery, DC in switch etc... so the bypass is not included on the schematic.

For different offboard wiring schems check this....
http://www.tonepad.com/project.asp?id=35
... and download the pdf.

If you want to build it into a pedal with true bypass switching you'll want a good quality 3PDT foot switch and follow the schem on page 5.

Congrats on the successful build. Now go here for the next adventure.

Wren and Cuff · #20 04-19-2009, 12:17 AM

hmmm...

My above comments were assuming you were following this schem:

With the output pot (100K) only and no pot on the front. Tony-bobs you have referenced 2 different schems (maybe you knew that). Just tossing in my .02 cents, if you pick a shem., stick to it, get the right pots, you'll hear what it's really supposed to sound like. Then if you tweak it, you know what you're tweaking it from. If you still haven't put the right pot in, and have sort of patched it together, it may work, but you won't hear what the original designer intended it to sound like. As I said before, there is a reason he chose those values. I will say though, that I'm not sure which schem. came first, but I would stick with the one above, put the 100k on the end, bail the pot at the beginning, then go from there.

If you can't find a 100k at rat-shack, get any HIGHER value LINEAR POT, NOT VOLUME (when you tweak vol. pots, the taper gets real funky, in a bad way), you can always swap a LINEAR for a volume, but the other way around can get weird. With linear, the taper will still be workable, and useable, it just won't sound quite as smooth as the proper VOL pot. The "tone" of the pedal is unaffected either way, as long as the value is right.

If you "fake" the pot, follow this:

Buy a:

1M put a 100k resistor across lugs 1 & 3= pot will then be close to 100k (close enough for rock n' roll as they say).

500K pot + 120K resistor across 1&3 = around 100k

I think thats the only other values rat shack has (aside from the 100k and 10k).

Just take your 10k back. You don't even have to lie. Just tell them you bought the wrong pot, doesn't matter if it's been soldered, as long as you're just exchanging for another.

LOTS OF COFFEE = LONG POST FOR ME.

Cheers!

matt