# Horrible Squealing From TC Integrated Preamp



## guitarfreak2105 (Apr 3, 2021)

Let me start off by saying hello and that I am new here. So, Hi!

I purchased a RullyWow ChuggaPre PCB (I know it isn't PedalPCB but they were out of stock and I have bought a few from PedalPCB but haven't started them yet)

I built this preamp and it works in the sense that it boosts the crap out of the horrible squeal that is coming out of the amp. One thing I did notice is that the TL071 (I believe I am using a TL072CP) got extremely hot when I plugged it in and tested it for the first time. I switched it out for another and it does not get hot anymore.

There is no other reason the squeal would be happening other than the pedal. Tested with Mesa Boogie Mark V and Peavey 6534+ and both have the same results.

Is this possible something power related? Like DC getting somewhere it is not supposed to be?

I have double checked all of my solder joints, cris-crossed wires, things touching that shouldn't be, I/O jacks are wired properly, I used 3PDT board (could it be something on there?) and I am damn near positive I didn't install anything in the wrong place or with the wrong value. I really took my time verifying everything was going in the right spot however, it still is possible I screwed up. I checked parts placement but could have missed something.

I am very new to this (this is my very first build).

You guys owe me absolutely nothing so I appreciate any help or advice given.

I am happy to provide any more information or details needed.

Thank you!

Edit:

Link to what is happening:


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## BuddytheReow (Apr 3, 2021)

You'll need a TL071. There's a difference between the 71 and 72. I cannot see the pictures very well. They are quite small


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## mnemonic (Apr 4, 2021)

Yep, tl072 is a dual op amp, you need a single op amp, TL071 or lm741 work well.

different pin outs is the main issue











You’re currently attaching +24v from the charge pump to the output of the second op amp stage, and taking the output from its inverting input.

it would be possible to make use of half a TL072 in this circuit but you’d need to take account of the pinout. Also TL071’s are extremely cheap.

also your pictures are really small so can’t see if there are any other problems.


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## music6000 (Apr 4, 2021)

As noted above
TL071 is a Single OpAmp.
TL072 is a Dual OpAmp & not compatable with this circuit as shown above, different pinouts!
Always check OpAmp listed for Build for alternatives which no Dual OpAmps are for TL071!
Also, their is a small pad for the other OpAmp that requires a small dob of solder if you use TC1044S or 7660S chip between pins 1 & 8 on the PCB!


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## guitarfreak2105 (Apr 6, 2021)

mnemonic said:


> Yep, tl072 is a dual op amp, you need a single op amp, TL071 or lm741 work well.
> 
> different pin outs is the main issue
> 
> ...


You are the man. Thank you so much! I will get the correct IC and report back!


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## guitarfreak2105 (Apr 6, 2021)

music6000 said:


> As noted above
> TL071 is a Single OpAmp.
> TL072 is a Dual OpAmp & not compatable with this circuit as shown above, different pinouts!
> Always check OpAmp listed for Build for alternatives which no Dual OpAmps are for TL071!
> Also, their is a small pad for the other OpAmp that requires a small dob of solder if you use TC1044S or 7660S chip between pins 1 & 8 on the PCB!


Noted. I will check that and make sure there is a dab of solder if needed. Thank you so much for your reply!


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## guitarfreak2105 (Apr 6, 2021)

BuddytheReow said:


> You'll need a TL071. There's a difference between the 71 and 72. I cannot see the pictures very well. They are quite small


Thank you. I will replace with the correct IC and report back. Thanks for your help!


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## guitarfreak2105 (Apr 7, 2021)

Alright folks. IT WORKS! Holy crap thank you so much to all of you! I did not have the pad under the IC2 soldered and I went and picked up a TL071 from my local electronics store and 5 minutes later viola! It worked! Thank you so much for the help this pedal is awesome! I will have to post pictures once the build is complete!


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