Tube Screamer Buffer

HydrozeenElectronics · Post by **HydrozeenElectronics** » 09 Sep 2013, 20:58

I have been bread boarding up the Tube Screamer Buffer as seen on this site: http://www.beavisaudio.com/techpages/blocksfragments/

only changes I have made are .1uf caps and I omitted the 1k resistor on the input.

Problem is this buffer is no where near close to Unity. I like the sound but for the life of me I can not figure why it is so quite. I have built other buffers and they where very close to unity.

I never noticed this problem with my old ts9 am I missing something here?

roseblood11 · Post by **roseblood11** » 09 Sep 2013, 21:01

Are you sure that all parts values and the orientation of the transistor are correct? 2sc1815 has a strange pinout...

HydrozeenElectronics · Post by **HydrozeenElectronics** » 09 Sep 2013, 21:17

roseblood11 wrote:Are you sure that all parts values and the orientation of the transistor are correct? 2sc1815 has a strange pinout...

Well I subbed in 2n3904 I forgot to mention that. I noticed that the bevis page has 100k on the voltage divider but I'm seeing other schematics that have 10k. I tested my voltage and I'm getting 4.5 with 100k voltage divider.

deltafred · Post by **deltafred** » 09 Sep 2013, 21:45

A voltage divider is just that, it divides the voltage into 2 parts determined by the ratio of the resistors, not the actual resistance. When the resistors are equal the voltage across each is half the supply voltage*.

The (V1) voltage across one resistor (R1) is given by

V1 = V supply * R1 / (R1 + R2)

* As long as you don't draw too much current which effectively decreases the resistor that the load is across, hence it decreases the voltage.

HydrozeenElectronics · Post by **HydrozeenElectronics** » 09 Sep 2013, 21:59

I swapped out my 100k divider for 10k and it is much louder now. the 2n3904 must need more current to bias even though the voltage is the same.

I do love the sound of this buffer though. Very transparent and plays well with other pedals.

Thanks

mictester · Post by **mictester** » 10 Sep 2013, 05:58

HydrozeenElectronics wrote:I swapped out my 100k divider for 10k and it is much louder now. the 2n3904 must need more current to bias even though the voltage is the same.

I do love the sound of this buffer though. Very transparent and plays well with other pedals.

Thanks

Correctly built, it will have no "sound" whatsoever - all it does is an impedance transformation from high to low. There's no Voltage gain at all, so what you put in comes out, but at lower impedance!

ChargerSG · Post by **ChargerSG** » 11 Sep 2013, 03:22

A 2N3904 facing towards you is EBC a 2SC1815 is ECB

Buffer is again unity gain as mentioned by people before above

Sometimes a 4k7 instead of 10k emitter has more gain, or even a lower 1k if the sound allows for it