THAT4315 One Knob Squeezer for Line Level

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AVA

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Joined
Jun 7, 2021
Messages
47
Location
Canada
Hi Folks! Alex here, first time poster...
Hopefully I don't insight a riot or something lol.

I searched the forum but couldn't find anything that my feeble brain could translate into a solution for my project...

I'm trying to take the "Battery Powered One Knob Squeezer" from THATCorp (link below), and adapt it in a few ways:

Use the 4315, operate at line level, and use TL072/4 Op Amps...

Again, I apologize in advanced for the noob questions. I'll take all the eye rolls with salt...on the egg shells that I'm already walking on.

I've breadboarded this circuit two separate times, and combed through everything over and over. So I'm hoping you fine folks will spot something. I've been staring at it for days, so I'm bound to miss something, as it often goes.

The op amp that I circled is meant to take the voltage signal, and put out a current signal. It's outputting current, but no signal

However, using an oscilloscope (dc coupling), and putting a 1kHz sine wave @ 1V pp, I'm not seeing anything other than a straight current output...
Could be an amateur measurement fault, but I also get no sound with a test speaker if I poke the signal lines all the way to the end, of course.

Obviously I don't expect you to comb through my (albeit, eye bleeding) schematic, but just if there is anything glaring, please, please god, let me know lol.
Sorry for the aneurysm of a schematic, I can't seem to make it any more visible :/ ...I used Eagle...

Are the TL0xx opamps to blame here? Have I screwed the pooch completely in other ways? Should I recluse?

Thanks all! I hope you're well.

THATCorp Link: http://www.thatcorp.com/pedals/4316 Battery-Powered One Knob Squeezer.pdf
 

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  • 4315 One Knob TEST.png
    4315 One Knob TEST.png
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JohnRoberts

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the op amp you called out is a simple non-inverting voltage gain stage. Trouble shooting op amps is relatively straight forward. With a VOM measure the voltages at the different IC pins and look for something incorrect.

JR
 

AVA

Well-known member
Joined
Jun 7, 2021
Messages
47
Location
Canada
Hey John,
Thanks for your reply.

I agree, troubleshooting this simple opamp should be a breeze, but absolutely nothing comes up wrong...aside from the fact that I don't get any waveforms on the other side, and therefore nothing through the rest of the circuit.
It's supposed to convert voltage to current, so I set my oscilloscope to DC coupled...is this wrong?

Perhaps something later in the circuit is causing it?

I don't see how, considering it basically goes straight into the 4315 as per the datasheet.

Truly baffling.
 

JohnRoberts

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Staff member
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Nov 30, 2006
Messages
20,478
Location
Hickory, MS
I am not going back to the schematic again, but over the decades I have looked at lots of op amp gain stages. If audio is coming in and not out, there will be one or more IC pins with invalid signals/voltages. It is always possible to encounter a faulty op amp but i will ASSume you already tried that.

JR
 

MidnightArrakis

Well-known member
Joined
Sep 25, 2015
Messages
68
Hi Folks! Alex here, first time poster...
Hopefully I don't insight a riot or something lol.

I searched the forum but couldn't find anything that my feeble brain could translate into a solution for my project...

I'm trying to take the "Battery Powered One Knob Squeezer" from THATCorp (link below), and adapt it in a few ways:

Use the 4315, operate at line level, and use TL072/4 Op Amps...

Again, I apologize in advanced for the noob questions. I'll take all the eye rolls with salt...on the egg shells that I'm already walking on.

I've breadboarded this circuit two separate times, and combed through everything over and over. So I'm hoping you fine folks will spot something. I've been staring at it for days, so I'm bound to miss something, as it often goes.

The op amp that I circled is meant to take the voltage signal, and put out a current signal. It's outputting current, but no signal

However, using an oscilloscope (dc coupling), and putting a 1kHz sine wave @ 1V pp, I'm not seeing anything other than a straight current output...
Could be an amateur measurement fault, but I also get no sound with a test speaker if I poke the signal lines all the way to the end, of course.

Obviously I don't expect you to comb through my (albeit, eye bleeding) schematic, but just if there is anything glaring, please, please god, let me know lol.
Sorry for the aneurysm of a schematic, I can't seem to make it any more visible :/ ...I used Eagle...

Are the TL0xx opamps to blame here? Have I screwed the pooch completely in other ways? Should I recluse?

Thanks all! I hope you're well.

THATCorp Link: http://www.thatcorp.com/pedals/4316 Battery-Powered One Knob Squeezer.pdf
Send me your EAGLE schematic file. I have a PCB design program that can import EAGLE schematics (my program has a specific EAGLE schematic translator) and then I could output a nice PDF file for you. Should you also have a PCB file, you can send that as well, as my program also has an EAGLE PCB translator.

Attached are 2 PDF files that show two versions of the same schematic. One is a hand-drawn schematic created by another member on this board and the other schematic is how it turned out after I captured it within my schematic program. Just sayin'.....

Is your schematic a re-drawn copy of the schematic shown in the THAT 4316 Application Note? If not, what's different?

I am - NOT - a circuit design guru as the other members on this forum are. I am just an "Equipment Designer" who takes schematics and performs all of the mechanical and PCB designs necessary to come up with a piece of physical gear. You can reach me here: [email protected]

I hope to hear from you shortly!!!

/
 

Attachments

  • 1954 Limiter Hand-Drawn Schematic.pdf
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  • 1954 LIMITER AMPLIFIER B-Size Schematic.pdf
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