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Old 22nd January 2013, 03:57 AM   #1681
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Join Date: May 2011
Location: Quebec
bonfis, I replaced the VAS for a 2SC1819 and the CCS for a 2SA1837. The drivers are still MJE15030 and MJE15031. The dent is still present, and when the baker clamp is absent, the sticking is also still there. The VAS and CCS replacement has changed nothing on the scope about these two behaviors.

In the VAS position, aside the MJE15030, I tried only the 2SC1819. I left it there as it's the best component for that role, in theory at least, with a Cob of 5pF.

In the CCS position, aside the MJE15033, I tried only the 2SA1837. I left it there as its specs are a closer match with the 2SC1819, although it's likely irrelevant...

These two guys changed nothing on the dent and rail sticking behavior.

In the drivers position, i tried:
- 2SA1930 & 2SC5171
- 2SA1837 & 2SC4793
- 2SA968B & 2SC2238B

All of these drivers gave approx the same result: the ringing that surfs on the positive sine wave, similar at what you had prior increasing base-stopper resistors. Remember that I have increased these to 100 Ohms on my circuit... These drivers all got rid of the dent going out of clip though... so, I guess I would need to adjust other values elsewhere if I want to keep 'em without ringing.

At the end, I'm back to square one, and I will accept that dent. I've replaced my clamping diode from a UF4004 to a NTE177, it's a BAV20 equivalent with a low TC of 5pF.

But because I've replaced the VAS with something theorically better, as a perfectly human human, I feel better now hahaha (hi Carlos).

I cannot pretend to hear any difference though.

I feel good about the amp. But I got to stop buying hard to find pieces, they're not cheap. The only drivers I would have love to try are Sanyos 2SA1011 & 2SC2344. But I feel that replacing these drivers will present the same result as the previously tried ones.

The amp is back in my listening room... I missed it while it was on my bench...

The Hx amplifier is awesome... see mine here: http://www.diyaudio.com/forums/solid...ml#post2796303

Last edited by canonnica; 22nd January 2013 at 04:01 AM.
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Old 23rd January 2013, 01:22 AM   #1682
bonfis is offline bonfis  United States
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Location: Land of 10,000 Lakes
Hi Mart
I'm glad you're back to listening. For my part the cover is back on my MK III and likely to stay there. The sound quality is very satisfying and I don't see any obvious prospects for improving it. Should you to get the bug to be back at the bench and there happen upon a modification of merit please let me know. In the interim my best to you and thanks to all the builders and contributors to this most varied and interesting thread.
"I tend to believe that the absence of evidence is evidence of absence" - Christopher Hitchens
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Old 29th January 2013, 12:21 AM   #1683
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Join Date: Oct 2009
This is an attractive amp to build and I have a few questions if anyone can answer them so I do not have to search the entire two years of posts.
What is the wattage on this amp? Did I read 150 watts per channel?
How does it sound? I think I read where Carlos stated it sounded glorius but say you?

Carlos thank you so much for making your design available to the world.If not for guys like you,guys like me would have nothing to build.
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Old 29th January 2013, 07:09 AM   #1684
AndrewT is offline AndrewT  Scotland
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Location: Scottish Borders
The maximum output power depends on the load impedance you drive and the power supply rail voltage.
There is no single maximum power for this, nor any amplifier.

You choose how to implement the build.
You could end up with anywhere between 40W and 300W depending on who you believe and how you assemble.
regards Andrew T.
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Old 29th January 2013, 12:28 PM   #1685
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Location: Recife - Brasil Northeast
Default You are welcome Gyrene.... i do not remember the power, but i will search

I do think i have made a chart about it.


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Old 29th January 2013, 12:35 PM   #1686
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Default Here you have power specifications

This depends on your supply voltage...was measured in the simulator and there the voltage do not drop.

Real world you have voltage drop and will not achieve all that power.

To achieve you must have stable voltage, this depends on SMPS or a series pass regulator that will have higher voltage at the regulator input.... doing this way, having stable voltage when loaded, then you will achieve this power shown in the chart.

Attached Images
File Type: png 1 power.png (35.1 KB, 340 views)
File Type: jpg 2 power.jpg (88.2 KB, 333 views)

Last edited by destroyer X; 29th January 2013 at 12:55 PM.
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Old 17th February 2013, 08:35 PM   #1687
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Carlos, a question for you.I've four 6 OHM sub woofers is it possible for the MKIII-HX to drive 2 woofers per channel?I'm talking about 3 OHMS per channel
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Old 18th February 2013, 11:05 AM   #1688
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Default Yes.... the amplifier can drive 3 ohms loads....can drive even 2 ohms

but cannot drive lower than that.

Impedance depends on the speaker impedance graphic.... you should check if it goes below 3 ohms in some frequency.... sadly they usually go lower...and this is dangerous.

If it is really 3 ohms and do not reduce the impedance in any frequency..them no problems.

In the real world it may have valleys of impedance, and 3 ohms is just nominal and at 1 Kilohertz only.


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Old 6th March 2013, 10:05 PM   #1689
mcd99uk is offline mcd99uk  United Kingdom
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Location: UK
Hello all,

I have read this thread from start to finish and have learnt a lot from other peoples experiences.

My only decision still to make is what output transistors to use. I will only be using 4 output pairs due to space.

I have come down to a short list of two the MJL1302/3281 pair of the MG6331-R/ Mg9412-R. Both have similar specs. I prefer these over the MJL4302/MJL4281 pair due to PNP and NPN Hfe matching and the linearity.

What do people think?
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Old 6th March 2013, 10:14 PM   #1690
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Location: Recife - Brasil Northeast
Default Please...for safety reasons, use MJL4281A

Watch the S.O.A and you will see that it can hold more current when operating 55 or 65 volts compared to the most common competitor.

In special this advice is for you, because you will use only a few transistors.... do not use 2 ohms...use only 8 and 4 ohms loads if your supply is the suggested or lower voltage...if higher..then use only 8 ohms.

In this video you can see a picture of a beautifull Blame MKIII Hx:



Attached Images
File Type: jpg 2SC5200 SOA is 3A to 50V.jpg (201.5 KB, 201 views)
File Type: jpg MJL4281A SOA to 50V.jpg (223.7 KB, 180 views)

Last edited by destroyer X; 6th March 2013 at 10:22 PM.
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