Weird square wave when measuring transformer

[AUDIO FREQ]

I got curious on these transformers Tamura GA02310 inputs. They are stated to be (600ohm: 3Kohm).

I put a 6k square wave on the primary with my computer and measured the secondary with my handheld oscilloscope.

The square wave looks like a lopsided sine wave. Is this transformer malfunctioning?

 

[JohnRoberts]

How does it look with a sine wave?

JR

 

[AUDIO FREQ]

looks like a noisy sinewave

 

[JohnRoberts]

How clean is the sine wave at the input to the transformer?

JR

 

[Brian Roth]

How is the secondary terminated?

Bri

 

[AUDIO FREQ]

The secondary is connected to the handheld oscilloscope, white wire hooked up to the red lead of the scope, yellow wire hooked up to the black lead of the scope.

The input sinewave is coming from Logic Pro on my macbook.

The transformer came from my PM400 mixer, which is made by Yamaha. It looks like the secondary is terminated by 22k ohm resistor + 1k ohm resistor, parallel to....a 100k ohm resistor? I never seen anything like this before.

 

[Brian Roth]

Try terminating that secondary with 22K.....would be quite close to the original design.

Also, use your scope to examine the input signal in the circuit with the 22K termination.

Bri

 

[AUDIO FREQ]

How clean is the sine wave at the input to the transformer?

JR

Wow, so without the transformer....the square signal at 6kh is wobbly also. This is straight from the computer output, using a stereo male to stereo male 3.5mm headphone cable right into my handheld oscilloscope.

 

[Brian Roth]

Wow, so without the transformer....the square signal at 6kh is wobbly also. This is straight from the computer output, using a stereo male to stereo male 3.5mm headphone cable right into my handheld oscilloscope.

Garbage in, garbage out <g>.

Bri

 

[AUDIO FREQ]

Garbage in, garbage out <g>.

Bri

At 15khz, it looks like a sine wave completely. Not a square in sight! I did some googling, and ran across a bunch of articles talking about there is no such thing as a true square wave. And as higher the frequencies go, they start to look more and more like sinewaves, due to cable capacitance acting as a low pass filter. That's as far as I got to reading about it, but what do you mean Brian? And again, thank you guys for taking the time to help me learn this stuff.

 

[Khron]

Audio DACs need and always DO have a low-pass filter on their output, usually set to just above the audio range 25-40kHz. That's gonna have an infinitely greater effect on rounding off that squarewave coming out of Logic, than any amount of cable capacitance.

It helps to know the tools you're trying to use, and be aware of their limitations etc.

If you want a squarewave, try using the calibration signal from a bench oscilloscope (1kHz at 0.5-1Vpp, depending on the model). Or an actual physical / "independent" signal generator.

Why exactly did you feel the need to use a squarewave to test that transformer, though?

 

[AUDIO FREQ]

Audio DACs need and always DO have a low-pass filter on their output, usually set to just above the audio range 25-40kHz. That's gonna have an infinitely greater effect on rounding off that squarewave coming out of Logic, than any amount of cable capacitance.

It helps to know the tools you're trying to use, and be aware of their limitations etc.

If you want a squarewave, try using the calibration signal from a bench oscilloscope (1kHz at 0.5-1Vpp, depending on the model). Or an actual physical / "independent" signal generator.

Why exactly did you feel the need to use a squarewave to test that transformer, though?

I was reading Jensen notes on finding out how to load the secondary, the values for the RC network needed for the transformer secondary to eliminate ringing. I have no idea what I am doing, I am just going by what Abbey linked me to read over. Trying new things.

My tools for measuring are as follow:
Logic Pro X Signal Generator > Macbook Pro 2011 headphone out > 3.5mm cable split ends into > Transformer primary > Transformer Secondary > Handheld Oscilloscope.

The handheld oscilloscope has a little notch for 1khz Square Wave, I will give it a shot!

 

[Khron]

https://xiph.org/video/vid2.shtml
Reconstruction Filters For Dummies • Audioreviews.org (no offense )

https://www.audiosciencereview.com/...ficient-reconstruction-filter-in-a-dac.19167/
https://www.ti.com/lit/an/sbaa322/s...40616&ref_url=https%3A%2F%2Fwww.google.com%2F

 

[AUDIO FREQ]

https://xiph.org/video/vid2.shtml
Reconstruction Filters For Dummies • Audioreviews.org (no offense )

https://www.audiosciencereview.com/...ficient-reconstruction-filter-in-a-dac.19167/
https://www.ti.com/lit/an/sbaa322/s...40616&ref_url=https%3A%2F%2Fwww.google.com%2F

Lol, no offense taken. I will gladly take all the help I can get. More reading material!!! Thanks

 

[aurt]

A square wave is a sign wave, plus the odd harmonics. The first difference will be the third harmonic, which at 6k would be 18k. You can see that as the wiggle. If you start them at the same 0, when they add, the 18k will start steepening the initial slope of the sine. Then as it drops, it will take the peak of the sine down, as we see. The next difference would be the fifth harmonic, at 30k. Most converters will filter that out. If it’s there, you’ll see more wiggles. The middle trough of the positive part would gain a slight peak, and the flanking peaks would get troughs. Keep going, and you get a square wave.

Try starting at, say, 100Hz, and sweeping up. You can watch the harmonics drop. Or start at 10-15k and sweep down, and watch the square wave build.

 

[Brian Roth]

At 15khz, it looks like a sine wave completely. Not a square in sight! I did some googling, and ran across a bunch of articles talking about there is no such thing as a true square wave. And as higher the frequencies go, they start to look more and more like sinewaves, due to cable capacitance acting as a low pass filter. That's as far as I got to reading about it, but what do you mean Brian? And again, thank you guys for taking the time to help me learn this stuff.

The point I was making is that if you feed in a "less than pristine" test signal into any device, then the output of that device will also look funky on the 'scope.

Bri

 

[Hubbub]

The secondary is connected to the handheld oscilloscope, white wire hooked up to the red lead of the scope, yellow wire hooked up to the black lead of the scope.

The input sinewave is coming from Logic Pro on my macbook.

The transformer came from my PM400 mixer, which is made by Yamaha. It looks like the secondary is terminated by 22k ohm resistor + 1k ohm resistor, parallel to....a 100k ohm resistor? I never seen anything like this before.

It is a 2.2K resistor, which would give a proper 10dB attenuation. So the secondary load is 3.2K. Give that a try.

 

[Hubbub]

I was reading Jensen notes on finding out how to load the secondary, the values for the RC network needed for the transformer secondary to eliminate ringing. I have no idea what I am doing, I am just going by what Abbey linked me to read over. Trying new things.

My tools for measuring are as follow:
Logic Pro X Signal Generator > Macbook Pro 2011 headphone out > 3.5mm cable split ends into > Transformer primary > Transformer Secondary > Handheld Oscilloscope.

The handheld oscilloscope has a little notch for 1khz Square Wave, I will give it a shot!

You headphone out is designed to drive a load about 32 Ohms. A fair test of that output would possibly require a load of 100 Ohms or less, DC coupled.

 

[tayeb keraoun]

I got curious on these transformers Tamura GA02310 inputs. They are stated to be (600ohm: 3Kohm).

I put a 6k square wave on the primary with my computer and measured the secondary with my handheld oscilloscope.

The square wave looks like a lopsided sine wave. Is this transformer malfunctioning?

hello,maybe you need to load the secondary with a 3K resistor to have a correct measurement
regards
Tayeb

 

[abbey road d enfer]

hello,maybe you need to load the secondary with a 3K resistor to have a correct measurement
regards
Tayeb

The measurement is correct, within the equipment's limits.
A 6kHz square wave contains a good dose of 6khZ and a smaller dose of 18kHz, and smaller and smaller doses of 30kHz, 42kHz...
Sin,ce the response of the soundcard drops abruply afeter 22 or 24kHz, only the 6kHz (fundamental) and the third harmonic (15kHz) are passing througn. The picture is one of a a perfect rendition of a fundamental summed with its third harmonic.

Check post #15.