THATCorp 4315 One Knob Squeeze help!

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AVA

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Hi All, I hope you're well...

I'm adapting THATCorp's One Knob Squeeze circuit (pdf attached) to use their 4315 instead of the 4316, the only difference is the 4315 can take a 9V single supply, and the 4316 cannot...

I'm also using TL072/4 instead of the recommended MC33178 op amps because thats what I have on hand, and I'm not concerned about power consumption just yet.

I've breaboarded the circuit (attached) a couple times, and it's just not working out. I've combed through it a zillion times, changed just about every component, and still I cannot get it going.

Can anyone spot anything glaring that needs to change?

I circled the first opamp, because while there is voltage signal going into it, there is no signal coming out. I realize this opamp is used to convert it to a current signal, but I'm not getting any signal output.

Any ideas?

Are TL072/4 a poor choice for this application? So poor that they're somehow crippling it? I can't image there's anything wrong with them...

I've attached my schematic along with THATCorp's schematic in case you're curious.

Ignore the balanced line receiver and line driver output, I'm not including them in the breadboard.

Thanks in advanced!
 

Attachments

  • 4315 One Knob TEST.png
    4315 One Knob TEST.png
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  • 4316 Battery-Powered One Knob Squeezer.pdf
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Bo Deadly

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Schematic is too small. Maybe try zooming in on the important part.

If the op amp is wired vaguely correct and you can see a voltage on the input but nothing on the output, then maybe the op amp died. It's easy to burn out an op amp when breadboarding. I reversed supply on a TL082 once and it exploded. Literally. I mean it popped and a chunk of it when flying across the table.

TL0X vs just about any other amp is not the problem. For this application just about any op amp will do.
 

AVA

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Messages
47
Location
Canada
Hey Bo Deadly, Thanks for your reply and your time, I appreciate it.

Good suggestion with zooming in, I attached a new image that should be a little better. Apologies for the poor initial image.

I thought that it might be the op amp burning out too, I switched it with another TL072 and even tried a TL052 as well, but no dice.
The original schematics from THATCorp call for a MC33178, but I don't have any on hand...in my brain, this shouldn't make any difference at all. Perhaps the 33178 has better current handling abilities? I'm not seeing anything that reflects this in its datasheet, but I'm not datasheet expert either lol
 

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  • 4315 One Knob TEST Op Amp 1.png
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Newmarket

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Firstly - I see that on the THAT schematic the two caps that are attached to the opamp output (C10 C20) are both 10u whilst yours are 470n (C5) and 100n (C16). Is that intended ? Won't stop the opamp working anyway. And I can see some other component value changes too so guess that's all intentional.
I think of it as : either the opamp isn't working or it is 'trying' to work but something is holding the output still ?
Apologies if this sounds obvious but check the obvious:
Short Circuit at output ?
Voltage rails present and properly decoupled. (so 9V there and 0V properly connected)
Is the chip getting hot ?
Is there a Vcc/2 bias voltage at the other end of R6 ?...
 

AVA

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Joined
Jun 7, 2021
Messages
47
Location
Canada
Firstly - I see that on the THAT schematic the two caps that are attached to the opamp output (C10 C20) are both 10u whilst yours are 470n (C5) and 100n (C16). Is that intended ? Won't stop the opamp working anyway. And I can see some other component value changes too so guess that's all intentional.
I think of it as : either the opamp isn't working or it is 'trying' to work but something is holding the output still ?
Apologies if this sounds obvious but check the obvious:
Short Circuit at output ?
Voltage rails present and properly decoupled. (so 9V there and 0V properly connected)
Is the chip getting hot ?
Is there a Vcc/2 bias voltage at the other end of R6 ?...
Thanks a lot for your help. I appreciate your time.

I'll give it another run in the morning and see if there's something common about the various methods I used to troubleshoot, maybe something will be revealed.

Whether the op amp is converting voltage to current is irrelevant as far as my troubleshooting methods are concerned, right?

Apologies for all the questions. This thing has been frustrating me for days. It's humbling my knowledge of the circuit, but happy for the opportunity to learn more about it nonetheless.

Cheers
 

Newmarket

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Joined
Oct 10, 2016
Messages
723
Location
Brighton Sussex UK
Thanks a lot for your help. I appreciate your time.

I'll give it another run in the morning and see if there's something common about the various methods I used to troubleshoot, maybe something will be revealed.

Whether the op amp is converting voltage to current is irrelevant as far as my troubleshooting methods are concerned, right?

Apologies for all the questions. This thing has been frustrating me for days. It's humbling my knowledge of the circuit, but happy for the opportunity to learn more about it nonetheless.

Cheers
Well that's not really what the op amp block itself is doing ie it's not a "Voltage to Current Converter". It's a simple non-inverting amplifier with 6dB gain at audio frequencies. The 10u in the path to GND means that its dc gain is kept at unity.
 

AVA

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Joined
Jun 7, 2021
Messages
47
Location
Canada
Well that's not really what the op amp block itself is doing ie it's not a "Voltage to Current Converter". It's a simple non-inverting amplifier with 6dB gain at audio frequencies. The 10u in the path to GND means that its dc gain is kept at unity.
Thanks a ton.

It sounds like im going to need a reread of all those analog circuity books haha.
Definitely not something I thought this circuit would push me to do when I first embarked on this journey. But always glad to identify some knowledge gaps.

Thanks for your help!

Cheers pal
 

Bo Deadly

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Dec 22, 2015
Messages
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Location
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It's not the op amp and it's not the circuit and it has nothing to do with the VCA. My guess would be that your breadboard is just miswired. It's easy to do and very easy to do if you're trying to wire together 3-4 different chips. Unless you're using those assorted length U shaped jumpers and not regular wires, I would be surprised if you get it working at all. And the noise will probably be horrendous because grounding will be wonky for sure.

What is the voltage on the output? Is it 4.5VDC as it should be or is it high / low? If you left out the cap in the feedback network and just connected minus to earth ground for example, that would send the output high.

Check your ground lines. Check all of the points that are supposed to be connected to the virtual ground vs regular ground. If you get virtual ground and regular ground mixed up, that would definitely break things.
 

MidnightArrakis

Well-known member
Joined
Sep 25, 2015
Messages
104
Hi All, I hope you're well...

I'm adapting THATCorp's One Knob Squeeze circuit (pdf attached) to use their 4315 instead of the 4316, the only difference is the 4315 can take a 9V single supply, and the 4316 cannot...

I'm also using TL072/4 instead of the recommended MC33178 op amps because thats what I have on hand, and I'm not concerned about power consumption just yet.

I've breaboarded the circuit (attached) a couple times, and it's just not working out. I've combed through it a zillion times, changed just about every component, and still I cannot get it going.

Can anyone spot anything glaring that needs to change?

I circled the first opamp, because while there is voltage signal going into it, there is no signal coming out. I realize this opamp is used to convert it to a current signal, but I'm not getting any signal output.

Any ideas?

Are TL072/4 a poor choice for this application? So poor that they're somehow crippling it? I can't image there's anything wrong with them...

I've attached my schematic along with THATCorp's schematic in case you're curious.

Ignore the balanced line receiver and line driver output, I'm not including them in the breadboard.

Thanks in advanced!
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!!!

/
 

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