Author Topic: Requesting Assistance putting together a Second Amplifying stage (TL082)  (Read 399 times)

mrahc_jftd

Hiya!

So I'm working on an overdrive (Not my circuit/Schematic) and the issue I have is just that when Gain knob is all the way down and Volume knob is all the way up - I don't get any clean boost out of that. It's just a little quieter than my clean signal.

It was suggested to me that I run a second amplifying stage out of the second circuit in the TL082 chip.

Sounds like a good idea to me! Only issue is I'm not quite sure how I would go about putting that together.

Just wondering if anyone has any breadboard pics/schematics/explanations that would show how a second amplifying stage would be put together?

Thanks!

PS. Attaching schematic, it should be noted one thing I've done differently is add a 1k Resistor inbetween the TL082 output and Capacitor C3 (pps. I did see that C3 is backwards and have not placed it into the circuit that way!)



Vivek

Brother, did you see my post suggesting a method to get clipping and boost from the same one Opamp ?

With independent controls on amount of clipping and amount of boost

?

Vivek

SCALING RESISTORS at end of Opamp, to set clean gain of  that stage. You should be fine with clean gain of about 3 - 6 times.



Vivek

I request you to try this idea

I only simulated it in SPICE so far, did not try it in an actual circuit




or also try 2K and 470 Ohms to try and get lower added compliance = slightly harder clip

or 2K and 1K in case the Opamp goes into clipping


« Last Edit: October 29, 2020, 04:12:01 AM by Vivek »

Rob Strand

An answer was given in your other thread,

https://www.diystompboxes.com/smfforum/index.php?topic=125692.msg1198189#msg1198189

You need to add a resistor in series with the 500k pot.   Similar to R7 in this circuit,

TS-9 like first stage


Since you have 1k (R46)  to ground instead of 4.7k (R6) like the TS-9 you will need to use a resistor value around 10k instead of 51k (R7).

FWIW, your circuit has a 500k pot and a 1k resistor (R46) so that's going to produce a lot of gain.  If your pot is linear taper it's going to be difficult to adjust the gain at the clean end.

If you don't need a heap of gain when the gain is maxed out then you can increase your R46 value and decrease your C28 value.    The TS-9 values are fine.
« Last Edit: October 29, 2020, 05:55:36 AM by Rob Strand »
The internet:  answers without the need for understanding.

mrahc_jftd

Brother, did you see my post suggesting a method to get clipping and boost from the same one Opamp ?

With independent controls on amount of clipping and amount of boost

?


Just jumped back on here and caught up with everything!
So many suggestions, I'll have a lot to play around with.
Thanks everybody I really appreciate it. 💪

bluebunny

Please don't cross-post!  It makes things confusing for all us, including you.
Ohm's Law - much like Coles Law, but with less cabbage...

mrahc_jftd

Please don't cross-post!  It makes things confusing for all us, including you.


My bad everybody, I apologize ❤️
Thank you again for the assistance & patience!

mrahc_jftd

An answer was given in your other thread,

https://www.diystompboxes.com/smfforum/index.php?topic=125692.msg1198189#msg1198189

You need to add a resistor in series with the 500k pot.   Similar to R7 in this circuit,

TS-9 like first stage


Since you have 1k (R46)  to ground instead of 4.7k (R6) like the TS-9 you will need to use a resistor value around 10k instead of 51k (R7).

FWIW, your circuit has a 500k pot and a 1k resistor (R46) so that's going to produce a lot of gain.  If your pot is linear taper it's going to be difficult to adjust the gain at the clean end.

If you don't need a heap of gain when the gain is maxed out then you can increase your R46 value and decrease your C28 value.    The TS-9 values are fine.



This completely sorted it out! Took me a while to wrap my head around, still early days haha, but finally got there.
Thanks so much mate I really appreciate it.

I have another question if thats ok.

The moment of truth came whilst I was rearranging the gain pot wires - I still get kinda confused when I'm hooking them up, usually just jumbling up with lug leads where. I had the signal entering through the pot on the far left, Signal heading out to the rest of the circuit from the centre lug and finally I was initially placing signal leaving the remaining pot to ground.

When I was doing that it wasn't really working and when I went to rearrange it again I pulled out the wire heading to ground, at that point it was fine and I realised it was all working perfectly just using the two lugs (Or if I just run both centre and far right lug to the rest of the circuit it works still)

Is this normal to not always need all three lugs when wiring up a pot? Or am I doing something hell wrong?

I hope I'm making sense haha - any and all insight is greatly appreciated <3 Hope everyone is well!




Rob Strand

Quote
Is this normal to not always need all three lugs when wiring up a pot? Or am I doing something hell wrong?
For circuits where the pot wiper (the arrow) connects to the end of the same pot it's OK to leave that end unconnected ie. circuits like your gain pot.    It's slightly better to connect it though.  When the pots gets old and crackly the level of the crackle can be *much* less when you join the wiper and the end of the pot.
The internet:  answers without the need for understanding.