Stumped- TS808 for bass

[jlullo]

Hey everyone,
here's the deal.  I'm making a TS808 using the tonepad layout for my roommate.  he's a bass player.  I've made one of these before for the bass player in my old band, and it sounded amazing.  I've done the same thing this time-

all stock components, except changed the input cap from .027uf to .1uf
asymmetrical clipping

my voltages seem ok to me, but here they are anyways:
Q1
E = 3.15
B = 3.67
C = 8.98

Q2
E = 3.26
B = 3.69
C = 8.98

IC1
P1 4.40
P2 4.46
P3 4.42
P4 .01
P5 4.40
P6 4.40
P7 4.40
P8 8.98

D1
A = 4.46
K = 4.40

D2
A = 4.40
K = 4.20

D3
A = 4.20
K = 4.46

The problem is is that he's not getting any gain on his bass and amp.  It's working fine on my amp with my guitar, and sounds exactly as it should.  It just sounds like a boost with his setup.  I've tried a number of transistors (mpsa18, bc109, 2n3904, 2n5088, 2n2222 and others), and nothing is drastically changing the amount of gain.  He has a fender mexican jazz bass and an ampeg b15hp.  Is it just his rig?  He said that he has used a Frantone Peach Fuzz before, and it worked fine with his setup..

This is driving me nuts!!!

thanks,
Jonathan

[John Lyons]

So the problem is that it's not distorting/clipping and it just boosting clean?
If so that's odd. Is he rolling off the treble off on his bass?
Maybe is a matter of the TS 's rolling off bass and the clipping diodes are not clipping the low end so it just sounds boosted.
Although you said the last one you made was fine for bass.

john

[jlullo]

his settings on his amp seem completely normal... it's boosting, and adding the *tiniest* bit of grit.  Nothing close to sounding the way the bass player in my band's did.  I used MPS18 with his, and granted he had an SVT head through an 8x10, but i just can't see how this should be this clean...

all his controls are up on his bass as well... nothing rolled off...

do you think i should be experiment with the clipping diodes?

[jlullo]

i can't seem to find the correct voltages for the clipping diodes anywhere... these seem correct though, no?

[John Lyons]

The diodes are passing small AC voltage. When you play they conduct, when idle they should not have any/much voltage at all I don't think.
Since the tubescreamer has a good bit of bass roll off with the standard 1K/.047 combo off the clipping section there might not be much action in the clipping there with a bass. Although this is only theoretically since I've never built/played one with bass 

The most clipping and distortion will be with silicon diodes. LEDs less. Germanium more than silicon. etc etc

Maybe the clipping section has a soldering bridge. Or possibly on of the diodes isn't working.
Try replacing the diode to make sure that you are actually clipping the signal.
Wait...it works well with your setup on guitar right? Hmmm that's odd....

john

[jlullo]

yes it sounds correct with my setup, but i'll try out some new ones when i get home.  I have a bunch of Germ diodes, so i'll give them a shot...

would you suggest raising the values of the 1k/.047 combo? 

Thanks for your help!

[soulsonic]

Try swapping the .047 to .22 or maybe .47uF - this will juice up the gain, especially on the low-end. This would probably be a good general improvement for bass anyway. Leave the 1K resistor as is for now.
If it's still not enough gain, you could really juice it and change the 1K resistor to 420 ohm and change the cap to 10uF. But then I guess it wouldn't count as a TS-808 anymore...

[John Lyons]

There are two sides to this.
One being that the 1K/.047 cuts bass to the clipping section.
This can bve good and bad. Good because it keep the clipping on the mids and highs which helps keep the articulation and note definition.
For bass it's really going to thin out the sound, but that can be good, just depends on what you are going for.
Check out the Technology of the Tube screamer at GEOFX and also the TS articles at AMZ in the lab notebook section.

If the pedal is working well for guitar and not bass it's got to be a frequency issue with the clipping section.
Try the 1K/.22 that soulsonic mentioned above.
Putting in germaniums will give you much more clipping but it will really clamp down the output of the pedal.
You can raise the 1K between pins 6 and 7 a bit and get some more volume output in that case.

john

[jlullo]

thanks fellas... i'll play around with it this weekend and let you know what i find.

I'm also having my roommate bring home his G&L to try as i have a hunch it's going to sound significantly different over his mexican jazz bass

[wavenator]

man look here
http://www.tonepad.com/getFile.asp?id=81

where there is a 47 nano which goes to the 2nd leg of the opamp
change it to a 100 nano one


good luck

[jlullo]

Just wanted to let you guys know that i figured this out!

i'm an idiot and had the vol and gain pots switched...... so that was the problem.  thanks for all the input!

[Sir_Ian]

Just wanted to let you guys know that i figured this out!

i'm an idiot and had the vol and gain pots switched...... so that was the problem.  thanks for all the input!

The simplest things are always the problem.

I buit a TS for my brother. Couldn't get any response out of the tone control. I had a wrong resistor going from the tone control to ground. Instead of 220 ohm or whatever it was....I had a 220k ohm. So the pedal produced sound, but not the right tone.

[jlullo]

the funny thing is is that the tone was great for it on guitar, which is what made it so hard to tell what was wrong!  it definitely has more gain now (obviously), but i finally realized what it could be when i was laying in bed

[Meanderthal]

 LOL! Glad ya figured it out, because I was going to say it was his amp!    Sometimes a TS just don't have enough balls on some amps for some purposes. Also, a B-15 is a... different sounding amp than most. At least the old fliptop ones were, I haven't heard the newer ones. But, as I recall, the B-15 was very 'dark' sounding, and had maybe a little too much tube mush going on(and was severely underpowered for bass at only 35 watts), so I could see how it could be harder to notice what a TS does on a bass thru it.

But, since that ain't it, and ya got it figured out, ummm... nevermind....