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2stageEF high performance class AB power amp / 200W8R / 400W4R
2stageEF high performance class AB power amp / 200W8R / 400W4R
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Old 5th December 2018, 02:53 PM   #2801
astx is offline astx  Austria
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2stageEF high performance class AB power amp / 200W8R / 400W4R
Default ASTX LABS - SA2017 VMOS IXYS - Measurements

Noise measurements with closed case. Nearly the same results as on testbed with regulated supply and without case.

Output ÁV noise is a bit lower if I short circuit the inputs instead of using 600R resistor.

BR, Toni
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Old 5th December 2018, 03:27 PM   #2802
astx is offline astx  Austria
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2stageEF high performance class AB power amp / 200W8R / 400W4R
Default ASTX LABS - SA2017 VMOS IXYS - Measurements

Heavy overload with connected speakers. Amplifier has very good control and there are no signs of oscillation. Rail sagging good viewable. This amp is all but not a treble speaker killer!
Will move the amplifier now to my home cinema and change SA2017 IXYS status from testing to production ready.

BR, Toni
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Last edited by astx; 5th December 2018 at 03:44 PM.
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Old 5th December 2018, 05:01 PM   #2803
diyralf is offline diyralf
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Thanks for the detailed measurements! It is normal that the distortions increase very much at low levels. AP's new anaylzer lives somewhere at 0.0002%. But the VP7723D seems to be an older kit.
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Old 5th December 2018, 05:12 PM   #2804
astx is offline astx  Austria
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2stageEF high performance class AB power amp / 200W8R / 400W4R
You are welcome!
And yes - the VP7723D is old but good. Of course not as good as a newer AP which is way too expensive for diy.

The automatic modes via GPIB bus are working very good. I'm using gpib tools/libs/kernel modules for linux and perl as scripting language.

One channels full plot takes about 40 minutes to check (fetching THD and noise data as presented the latest posts), but is running full automatic.

Have fun, Toni
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Old 6th December 2018, 03:31 PM   #2805
astx is offline astx  Austria
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2stageEF high performance class AB power amp / 200W8R / 400W4R
Default MyDOA 4.1 protoboards

... got today new MyDOA V4.1 prototype boards for the preamp ...

Have fun, Toni
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Old 6th December 2018, 05:23 PM   #2806
Carl_Huff is offline Carl_Huff  United States
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Quote:
Originally Posted by astx View Post
... got today new MyDOA V4.1 prototype boards for the preamp ...

Have fun, Toni
MyDOA v4.x?? What changes from your v3.1 design?

I have built your v3.1 and it works and sounds great! I have used your v3.1 DOA successfully in two DIY projects:

#1) In a legacy audio preamp that include switchable baxandall tone controls and ...
#2) At the heart of a headphone amp.

I find it very competitive with John Hardy's 990C implementation of the classic Deane Jensen circuit.

In fact I think that I might well prefer your DOA over the 990C as I find it less fatiguing during long listening sessions.
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Old 6th December 2018, 09:05 PM   #2807
astx is offline astx  Austria
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2stageEF high performance class AB power amp / 200W8R / 400W4R
Dear Carl,

- your results are very close to my findings. IMHO it is extremely important for diy'ers if one can repeat the results! Many thanks for spending your time testing the MyDOA V3.1! It would be very nice if you could post some pictures of your setup!

The MyDOA v4.1 is a rework of the pcb to make room for some small modifications:
  • allow adding a series resistor in TMC compensation for better GM and PM at unity gain
  • room for a VAS diode for reducing sticking on overload
  • allow TPC compensation with simply soldering the TMC resistor R7 to ground using a dedicated gnd-pin
  • allow replacing the current mirror trim-pot using fixed resistors (added 2 extra pins)
  • higher output currents to drive 75 - 100R loads
Now I can start testing the modifications using the new pcbs... but no need to replace the MyDOA v3.1. The MyDOA v3.1 is well tested and stable at unity gain and above.

The new pcb I have mostly designed for one reason: to speed up the assembling, because I can easy solder 10, 20 or even 30 pieces in one step due to the tab and v-routed pcbs in 2x5 col/row.
The new tower amplifier will get active crossovers for bass/mid/treble and needs many DOAs...

BR, Toni
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Last edited by astx; 6th December 2018 at 09:10 PM.
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Old 6th December 2018, 10:28 PM   #2808
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Hi astx,
What will the PreAmp look like? Can you sketch the blocks roughly?
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Old 6th December 2018, 10:42 PM   #2809
astx is offline astx  Austria
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... sorry - meant active crossover for the 3 channel tower amplifier.
Currently I have no plans to build a preamplifier.


BR, Toni
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