Implementing a “Y Out” on an Oscilloscope - diyAudio
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Old 23rd May 2011, 08:51 PM   #1
gpapag is offline gpapag  Greece
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Default Implementing a “Y Out” on an Oscilloscope

Hi all

This thread is an offspring from these two posts.
LM317 experiments and measurements

LM317 experiments and measurements

I don’t find appropriate to divert the discussion away from the LM317 there.

I should have responded to Tony a few days back, but I was carried away the last 4 days by many manual–some unnecessary-, semi and fully automatic measurements from two X-Former (self made) implementations of the Symmetric to single ended idea for the oscilloscope “Y Out”.

I have some very small (30mmx25mmx21mm plus 6mm for connection pins) 220Vac/7.5Vac E-I power (core is 12.5x10mm) transformers bought for experimentation.
The first one was built just to see what comes out by unwinding the 7.5Vac secondary (outer winding) and keeping the primary as is. I name this X-former as “Old”
Then, I built a second one, this time with as many secondary turns as the coil window allowed (primary kept again intact). I name this X-former as “New”
After measuring both, it was found that that the two primaries were not identical.

Measuring apparatus used:
Inductance digital meter: Honeytek H623
Capacitance & Inductance digital meter: Mastech MY6243
Function Generator: Hameg HM8030-3
Bench Multimeter Keithley 175 (with 150MHz (X1) probe
Resistanse Decay Box: General Radio 1434-N plus a single 10X10K General Radio Cylinder.

Attached is the result of manual measurements.
I hope to continue tomorrow.

Regards
George
Attached Images
File Type: jpg meas.JPG (82.6 KB, 452 views)
File Type: jpg Linearity.JPG (98.1 KB, 440 views)
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Old 23rd May 2011, 10:10 PM   #2
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Hi George, take as much time as you want, the main thing is that you are enjoying it! Thanks for going to the trouble to do this as well. I'm sure it can be a useful addition to many peoples testing kit, not just mine.

It looks like you have quite a bit of test gear at your disposal!

Tony.

PS. I'm very slow to get things done The PS prototype I'm taking measurements on I first posted the design for over 12 months ago, and only just got around to building
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Last edited by wintermute; 23rd May 2011 at 10:13 PM.
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Old 24th May 2011, 09:59 PM   #3
gpapag is offline gpapag  Greece
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Now, here is one form of “Case 1” implementation of the “diy Y Out”.

This is implemented by using the diy x-former as the “differential to single ended converter” by connecting one coil of the x-former to the output of oscilloscope’s Ch1 Preamplifier Out and the other coil used as the single ended “diy Y Out”.

My oscilloscope (Hameg HM203-7) has already a “Y Out” . This, although I installed myself, it was actually per manufacturer’s specs and drawings (the pcb had the tracks ready, only the components were missing). It is not a great lie to say (for the economy of the discussion) that this “Y Out” is “manufacturer’s implementation”.
Attached Images
File Type: jpg Picture 002.jpg (371.8 KB, 413 views)
File Type: jpg Picture 003.jpg (396.8 KB, 395 views)
File Type: jpg Picture 006.jpg (403.9 KB, 376 views)
File Type: jpg Picture 009.jpg (403.9 KB, 125 views)
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Old 24th May 2011, 10:12 PM   #4
gpapag is offline gpapag  Greece
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Having this “Y Out”, it is quite convenient to check how this x-former idea performs and if it degrades the performance of the oscilloscope when it is connected to the Ch1 Preamplifier Out.

So I opened up my oscilloscope and started testing.
The first set of tests had to test for possible degradation of the oscilloscope performance, when the x-former is connected to the Ch1 Preamplifier Out.

In the attached figures you’ll see what configurations were tested.
Attached Images
File Type: jpg YOutwN.JPG (39.7 KB, 143 views)
File Type: jpg wCh1-H-L.JPG (47.1 KB, 98 views)
File Type: jpg wCh1-L-H.JPG (47.7 KB, 70 views)
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Last edited by gpapag; 24th May 2011 at 10:14 PM.
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Old 24th May 2011, 10:21 PM   #5
gpapag is offline gpapag  Greece
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These are with the "old" x-former.

First att.:frequency response
Second att.:Intermodulation distortion (60Hz & 7kHz)
Third att.: Noise
Forth att.: Total harmonic distortion
Attached Images
File Type: png fr.png (7.1 KB, 89 views)
File Type: png imd.png (9.2 KB, 59 views)
File Type: png ns.png (8.5 KB, 40 views)
File Type: png thd.png (8.8 KB, 40 views)
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Old 24th May 2011, 10:52 PM   #6
gpapag is offline gpapag  Greece
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I forgot to post these figures two post above
Attached Images
File Type: jpg Scope Diagr 1.JPG (19.6 KB, 57 views)
File Type: jpg Block diag HM203-7.JPG (88.2 KB, 56 views)
File Type: jpg HM203-7 CH1 Pre.JPG (112.7 KB, 70 views)
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Old 24th May 2011, 11:05 PM   #7
gpapag is offline gpapag  Greece
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And these are with the "new" x-former.

First att.:frequency response
Second att.:Intermodulation distortion (60Hz & 7kHz)
Third att.: Noise
Forth att.: Total harmonic distortion

It is really late. I hope I'll be here tomorrow.

Regards
George
Attached Images
File Type: png fr.png (6.1 KB, 67 views)
File Type: png imd.png (9.2 KB, 24 views)
File Type: png ns.png (8.6 KB, 16 views)
File Type: png thd.png (8.8 KB, 13 views)
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Old 25th May 2011, 04:06 AM   #8
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Hmmm big difference with the "new" transformer George, at least on the H - L orientation! It looks like it has minimal impact on the performance.

I'm not 100% clear on what you did with the old and new... old you reduced the number of turns on the secondary, and new you increased the number of turns on the secondary? Looking at how fine the wires are it must have taken a while!!

Tony.
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Old 25th May 2011, 08:49 PM   #9
gpapag is offline gpapag  Greece
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Tony, yes the “new” x-former has more turns on the secondary.
It takes time to wind the coils when I have to count the turns or when I have to wind overlapping sections and take out the leads. This was not the case with these two x-formers. It was an easy job.

The “new” x-former seems to perform better. You will notice this on the following measurements.
Attached Images
File Type: jpg Picture 006.jpg (379.8 KB, 114 views)
File Type: jpg Picture 007.jpg (400.6 KB, 115 views)
File Type: jpg Picture 004.jpg (391.0 KB, 91 views)
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Old 25th May 2011, 08:53 PM   #10
gpapag is offline gpapag  Greece
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Now, the x-formers are used to feed the R In of the soundcard. Their output is compared again to the original “Y Out”.

Edit: My Sound card is an external "M-Audio Audiophile USB"
All recordings here are 16 bit, 192kHz
Attached Images
File Type: jpg YOutwN.JPG (39.7 KB, 91 views)
File Type: jpg Ch1-H-L.JPG (45.6 KB, 35 views)
File Type: jpg Ch1-L-H.JPG (45.5 KB, 25 views)
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Last edited by gpapag; 25th May 2011 at 09:17 PM.
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