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Old 9th December 2016, 03:29 PM   #1
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Default Matching transistors & measuring the results

OK folks!

I built up version II of the Beta matcher. It works very nicely!

Here are the Gerber and drill files.
http://www.mv-makoto.com/adcom/Matcher.zip

Here is a photo of my unit in operation,

Click the image to open in full size.

...here are some PDFs of the schematic and board,

http://www.mv-makoto.com/adcom/MATCHER-SCH.pdf

http://www.mv-makoto.com/adcom/MATCHER-BRD.pdf

...and here are the raw Eagle files.

http://www.mv-makoto.com/adcom/Matcher-Eagle.zip


Have fun!

Scott

Edit: split from this thread:Yet Another Adcom GFA-565 Thread

Last edited by cogeniac; 9th December 2016 at 03:32 PM.
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Old 9th December 2016, 06:57 PM   #2
anatech is offline anatech  Canada
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That looks much nicer than any of my prototypes! Well done Scott!!

-Chris
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Old 10th December 2016, 06:18 PM   #3
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The new board configured with Phloodpants' surface mount Stabistor diodes...

Click the image to open in full size.

Last edited by cogeniac; 10th December 2016 at 06:24 PM.
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Old 10th December 2016, 09:03 PM   #4
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I'll take two once they are available.
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Old 10th December 2016, 09:25 PM   #5
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Nice!!

Yeah, I'm interested in a matcher board too.
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Old 16th December 2016, 12:50 AM   #6
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OK, I've just received a pile of MPSA42/92 variants. Here's the Hfe from a cheap multimeter, about 1ma. I really wish I had a curve tracer, but the Hfe differences between these devices is pretty clear, and these trends should hold at higher currents.

I sampled 10 of each brand, and got Hfe's in these ranges:

Central Semi MPSA42 - 96-120
MCC MPSA42 - 135-170
Fairchild KPS42 - 150-190

Central Semi MPSA92 - 116-126
MCC MPSA92 - 150-174
Fairchild KPS92 - 225-266 (Woo!)

The Fairchilds seem to be winners! They seem to fall well within range of the "L" grade 2SC3478/1376" (135-270 Hfe 135@10ma). I see mostly L's used in the 565's, sometimes K's. (200-400)

Interesting how the Central Semi's have lower gains, but fall within a tighter range. I wonder if that's good in some way.
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Old 16th December 2016, 02:41 AM   #7
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Hi Phloodpants,
Tighter parameter control is a very positive thing. One thing that will spread your groups is temperature. Even the warmth of your fingers will throw the results out. So experimental error is huge here.

-Chris
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Old 16th December 2016, 03:49 AM   #8
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Quote:
Originally Posted by anatech View Post
Hi Phloodpants,
Tighter parameter control is a very positive thing. One thing that will spread your groups is temperature. Even the warmth of your fingers will throw the results out. So experimental error is huge here.

-Chris
I use small plastic cover over the matcher board when I am testing devices. The air currents tend to change the temp and the devices often react differently tot he change. Ideally we should measure the temp of an operating amp,a nd test them all there..
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Old 16th December 2016, 05:34 AM   #9
anatech is offline anatech  Canada
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Hi Scott,
Yes, but you are testing in diff pairs, and once your shielded devices settle, they tract thermally.
Quote:
Ideally we should measure the temp of an operating amp,a nd test them all there..
I have measured various equipment. The temperatures vary widely from 25C to 50C. The hotter temp is ridiculous while the lower temperature was from a Marantz 2225. Most Marantz amplifiers ran the diff pairs in clean air with vertical air currents from bottom to top. The worst offenders were newer amplifiers designed in the 90's and later were air came in the bottom and came out the top - eventually. No clear shot from bottom to top. A Nikko Alpha 450 was up there too, as well as other amplifiers that ran the voltage amp board upside down.

I'm pretty sure our members can look at their equipment and visualize the air flow path.

No matter what the temperature is, matching transistors the way you are doing it is the best way. Pretty much the only sane way unless you have multiple jigs set up in environmental chambers to control the ambient temperatures. Even then, chances are good that pairs matched at ambient room temperatures (20 ~ 22 C) will fare as well as the one matched at various elevated temperatures. Remember that they are most likely from the same production lots from the same manufacturer and the doping levels will match (by definition). Therefore the two parts will track each other as long as you can keep them at the same temperature. A little thermal compound and some heat shrink tubing will help there, and you could also stick foam around that if you want to go crazy. (don't do that, it's stupid for audio). You could even stick your bonded pair in a chamber with a heater, leaky thermal insulation and temperature servo. That way you could set the pair to run at 40C for example. In most homes and lab environments, they could be relied upon to stay at the set temperature. Overkill if all you want to do is listen to music.

Why leaky thermal insulation? So you can drop the temperature to take into account the heat generated by the matched pair within a reasonable time frame. That means your oven is always generating some heat (excepting "bang-bang" controllers). You really want a proportional temperature controller!

-Chris
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Old 16th December 2016, 05:43 AM   #10
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I must say that matching these suckers is a very time consuming task. My observation is that some devices settle right away, and some start drifting as soon as you insert them, and can take about a minute to settle down. When they drift past 20 mV I just note the 20+ offset and move on. Some settle for a while than take off again for a few more mV and then settle back to some stable value. It is tempting to try to rush things, but they are going to settle on their own time....
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