Help Coupling 2 cicuits

Thread Starter

DCent

Joined Sep 21, 2012
20
All I need is a way to keep the 2nd circuit powered as it is and be compatible with a separate (pot controlled) gain circuit.
 
Im sure i could have helped you overcome your problem but unfortunately you are not able to converse effectively as to what you want both circuits to do to the signal.

Im afraid i wont be able to help you further,

Good luck with your circuit!!

thanks
 

Audioguru

Joined Dec 20, 2007
11,249
Why can't you post the complete circuits with part numbers like everybody else does?
I use Microsoft paint program to copy whole schematics or parts of them then paste them together. Straight lines are easy when the Shift key is held down. I can easily type part numbers onto a Paint schematic.

I suspect that your "amplifier" in the second part is an LM386 little power amp that has internal biasing and internal negative feedback and its inputs work fine at 0V.
 

Thread Starter

DCent

Joined Sep 21, 2012
20
Im sure i could have helped you overcome your problem but unfortunately you are not able to converse effectively as to what you want both circuits to do to the signal.

Im afraid i wont be able to help you further,

Good luck with your circuit!!

thanks
I'm not sure you can help as you've gone through this cycle of dangling assistance and then becoming a dick twice(?) now. This thread must be important to you (as you've been here three days in a row) so feel free to continue alluding to how helpful you could be if you had people skills and/or lacked personality disorders.
 

Thread Starter

DCent

Joined Sep 21, 2012
20
Why can't you post the complete circuits with part numbers like everybody else does?
I use Microsoft paint program to copy whole schematics or parts of them then paste them together. Straight lines are easy when the Shift key is held down. I can easily type part numbers onto a Paint schematic.

I suspect that your "amplifier" in the second part is an LM386 little power amp that has internal biasing and internal negative feedback and its inputs work fine at 0V.
The OPamp is a NE5532P.

There's nothing else going on with the rest of the circuit that would have an impact. As someone else pointed out I omitted it because I didn't want it to distract from the power problem... which has backfired because even without the rest of the circuit, everyone is asking about the rest of the circuit. :p
 

liquidair

Joined Oct 1, 2009
164
Ok, you have two options in this case.

1. Use another opamp in place of the transistor stage. If this is for guitar, the higher input impedance of the opamp vs. transistor will be a welcome advantage. Drop a 1Meg resistor from the + input and set the inverting input to whatever gain you like. You could even place the pot there for variable gain. Power hookups are the same as circuit 2 and you are compatible.

2. Put those 2 resistors I showed you in the pic on the opamp input. 2 x 1Meg will do the trick. 1 from pin8 to pin3, 1 from pin3 to gnd. Then rewire the transistor to be supplied from the positive side of the battery. If you place a pot between circuit 1 and 2 then the transistor stage needs a coupling cap on its output and the opamp stage needs one on its input and output, pot in between those caps to keep DC off of it.

Either one of those will solve your power problem. I'd prolly go for option 1 as it is easier and you don't run through 2 caps.

That's it. Let me know what happens.
 

Thread Starter

DCent

Joined Sep 21, 2012
20
Ok, you have two options in this case.

1. Use another opamp in place of the transistor stage.......

2. Put those 2 resistors I showed you in the pic on the opamp input......

That's it. Let me know what happens.
Oh, awesome. I think I'll try the first option and see how that works.

The second idea is very helpful as well as I have another idea for something that could benefit from that setup. I have lists of things I want to try but this powering issue has been confusing me to no end. Hopefully this will free me up a bit.

Thank you for helping me. I have monday set aside for experimenting. I'll report back!
 

Ron H

Joined Apr 14, 2005
7,014
An op amp won't work unless the power supplies are returned to signal ground. A floating power supply will not work.
 

Thread Starter

DCent

Joined Sep 21, 2012
20
If a floating power supply for one won't work, why would you think it would work for two, or four?
I have circuit two working now with a floating power supply and it has 2 opamps in it. If a quad opamp were used instead it should work as well (I think.)

I have to dive a bit more into my single supply opamp readings. I'm over my head.
 

Ron H

Joined Apr 14, 2005
7,014
I have circuit two working now with a floating power supply and it has 2 opamps in it. If a quad opamp were used instead it should work as well (I think.)

I have to dive a bit more into my single supply opamp readings. I'm over my head.
What is the part number of your dual op amp?
 

Ron H

Joined Apr 14, 2005
7,014
I have circuit two working now with a floating power supply and it has 2 opamps in it. If a quad opamp were used instead it should work as well (I think.)

I have to dive a bit more into my single supply opamp readings. I'm over my head.
You might think it's working, but I don't.:eek:
If you post a real, complete, accurate schematic, I 'll tell you why I don't think it is working.
Otherwise, I'm outta here.:rolleyes:
 

Thread Starter

DCent

Joined Sep 21, 2012
20
You might think it's working, but I don't.:eek:
If you post a real, complete, accurate schematic, I 'll tell you why I don't think it is working.
Otherwise, I'm outta here.:rolleyes:
Depends how liberal you are with the word "working."

It's definitely changing the signal.
 

Ron H

Joined Apr 14, 2005
7,014
Depends how liberal you are with the word "working."

It's definitely changing the signal.
Wow. You wouldn't believe how many circuits I have built that changed the signal, but didn't work (don't ask, I lost count).:eek:

EDIT: Oops, I was supposed to be outta here.

Oh well.
 
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