Lemonade more gain

[natezaps]

I am looking to get more gain out of my Lemonade OD. Is that possible?

 

[BurntFingers]

Lower the values of r6 and/or r8.

I think.

 

[Sturdag Lagernathy]

Changing those would change bias to Q1 or Q2, the bias is set for them to operate properly. Have you tried a clean boost in front of the OD? Seems like a great excuse for more pedals!

 

[Feral Feline]

Ahh all is a web and whatever strand you touch affects the whole...

So if you mess with R6 and/or R8 you could re-bias the Qs with R4 and R10.

You could also get a dribble more output if you lower R9, but I suppose that too would change the LPF action of C10 and output impedance.

 

[Chuck D. Bones]

Lower the values of r6 and/or r8.

I think.

Nope. Q1 is pretty well maxed out. Fiddling the bias on a BJT to get more gain is a zero-sum game because anything you do to increase gain takes away headroom. To get more gain out of Q2, you have to make R10 bigger, which means making R8 proportionately bigger. You can increase both of them 10x (no lie) and get about an 8dB gain increase.

I am looking to get more gain out of my Lemonade OD. Is that possible?

Howe much more gain do you want? Why not put a booster in front of it? You can get more low freq gain by increasing C2 and/or C4.

 

[Sturdag Lagernathy]

Thanks for explaining what I couldn't, Chuck!

 

[Mark]

What about replacing the BC108 with a Darlington pair transistor or use two BC108’s to make a Darlington pair. This would yield higher current gain.

Regards

Mark

 

[Chuck D. Bones]

That will increase the current gain, but it will not increase the voltage gain, which is the thing we care about.

Check out this article I wrote:

https://forum.pedalpcb.com/threads/another-way-to-measure-transistor-gain.4590/

 

[Mark]

Thanks for your link. I did read your article, though if you have greater A/C current flow though the collector resistor, won’t you get a greater voltage drop across the resistor and thus greater amplitude of the signal?

Regards

Mark

 

[Chuck D. Bones]

Yes, but increasing the collector current without changing the collector resistor moves the average collector voltage toward saturation. Usually, the collector is biased somewhere near 1/2 Vcc for maximum headroom. We could double the collector current and get a 6dB gain increase, but then we'd have zero headroom. So if you're after a small gain increase and can give up some headroom, then sure, increasing the collector current is an option.