Tube Screamer Schematic confusion / help ....

[griff10672]

going to try to breadboard the above schematic .... I'm little confused on a couple of things ...

The IC pinout  says 6 , 2 , 3 on both of the symbols ..... now I'm a total noob with schematics ... but have breadboarded a few things already ... but the IC always showed 1 ,2 , 3 , 4 , 5 ,6 , 7 ,8

2nd confusing issue are the resistors RA , RB , RC ( at least RC says 10k )    on the BOM for this build they are listed as RA 0Ω      , RB 100    ,   RC 10K

wondering why they are titled that way ...  at least the RC has a value I understand .... RA and Rb though

and the distortion pot ..... leg three goes to nothing

[bluebunny]

That's a poorly-drawn schematic, so far as the op amps go - there are lots of better examples.  There is only one dual op amp (a 4558), so "U1" and "U2" is confusing.  And the pin numbers are completely wrong!  The first op amp has pin three as the non-inverting (+) input, pin two as the inverting (-) input and pin 1 as the output.  The corresponding pins on the second op amp are 5, 6 and 7.  It doesn't matter which op amp in the IC you choose to be "first".  Power (9V) is pin 8 and pin 4 is 0V or GND.  That's your expected complement of eight pins.

You'll often see RA, RB and RC shown in Tube Screamer schematics because the difference between a TS-808 and TS-9 is basically the value of these resistors.  See the "Technology of the Tube Screamer" article at GeoFEX for more information on this.

Finally, the gain pot is just a variable resistor.  It might be safer to tie the unused end to the wiper, just in case the wiper ever goes open-cuircuit.

[griff10672]

thanks a ton ...... !!!

[PRR]

RA and RB may be low-value resistors. RA is very reasonably zero, or some designer may have put a few Ohms there for some other version. RB could be zero if the output cable were short, but a hundred or a thousand Ohms is more stable with very long output cables.

And yes, someone took the image for a single opamp (and pin numbers) and pasted it twice for a Dual opamp. Those pin numbers are wrong. Learn to look-up data and pinouts to verify, guard against hasty schematics.

[amptramp]

What are these guys doing with the battery?

The negative terminal should not be connected to the input jack as shown.  It is shown connected to a capacitor on the input.  Most people use a mono plug with a stereo jack and the battery is connected to the ring terminal of the jack so when the plug is inserted, the negative of the battery is connected via the barrel of the plug to the ground of the jack.  When the plug is removed, there is no connection.

[thermionix]

Yeah, wow, not the first erroneous schematic I've seen from Electrosmash.  What's up with R4?  In an actual TS, that runs to Vref, some people run it to ground, looks like they're trying to do both.  Or just sloppy.

[duck_arse]

I second this ^: I've found some odd errors in their chorus/bbd docs.

[griff10672]

Is there a Stock TS808 schematic I can trust     I googled the hell out of it ... they all seem different ...

and a Ce-2 clone was going to be my next build . lol ....... Oh Joy !!   

[FiveseveN]

Is there a Stock TS808 schematic I can trust

Like bluebunny said,

See the "Technology of the Tube Screamer" article at GeoFEX

they all seem different ...

Different how? Maybe some omit the bypass switching (or show a true bypass version), but the essentials should be there.

[GibsonGM]

Is there a Stock TS808 schematic I can trust     I googled the hell out of it ... they all seem different ...

and a Ce-2 clone was going to be my next build . lol ....... Oh Joy !!   

Geofex will be one you can absolutely rely on.

[thermionix]

Is there a Stock TS808 schematic I can trust

From the original Ibanez service manual:



BYOC version with true bypass:

[ElectricDruid]

Agree with what's said before. That schematic is ropey. The power connector section isn't connected to ground.

It's pretty easy to read and work out what they meant, but that's not exactly the point. It's sloppy, and it won't work as written.

Tom