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Old 27th September 2011, 10:01 PM   #21
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Here's a picture of the ugly, slouching beast, slouching in ugly surroundings (my office). It's about the size of a bread box - appropriate, for what amounts to an advanced breadboard...
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Old 3rd October 2011, 07:34 AM   #22
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Le Mutant spent some time at BA on Bill Berndt's system, and acquitted itself quite well. I had to shut it down to prevent self-immolation (I know it's Burning Amp, but you really don't want to toast an amp that has possibilities). The next immediate thing to do is to solve the thermal issues, as I want to give this amp some solid living room time. I have a promising bonded-fin heatsink and some heat pipe CPU coolers coming via E-pay. I also picked up a couple of the pictured heat sink/fan combos during a Weird Stuff excursion on Thursday. The fan is 120mm, and is pretty quiet when spun up with a 9V battery. The heat sink is not an extrusion, but was hogged out of a solid block of aluminum. With some sort of cowling to better direct the airflow from the fan, that rig has possibilities. Weird Stuff also had a small pile of the Cisco server supplies that I junked to provide the case for the mute.
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Old 4th October 2011, 05:25 AM   #23
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Yeats:

Turning and turning in the widening gyre
The falcon cannot hear the falconer;
Things fall apart; the centre cannot hold;
Mere anarchy is loosed upon the world,
The blood-dimmed tide is loosed, and everywhere
The ceremony of innocence is drowned;
The best lack all conviction, while the worst
Are full of passionate intensity.
Surely some revelation is at hand;
Surely the Second Coming is at hand.
The Second Coming! Hardly are those words out
When a vast image out of Spritus Mundi
Troubles my sight: somewhere in the sands of the desert.

A shape with lion body and the head of a man,
A gaze blank and pitiless as the sun,
Is moving its slow thighs, while all about it
Reel shadows of the indignant desert birds.
The darkness drops again; but now I know
That twenty centuries of stony sleep
were vexed to nightmare by a rocking cradle,
And what rough beast, its hour come round at last,
Slouches towards Bethlehem to be born?

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Old 4th October 2011, 05:50 AM   #24
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Actually, it sounded rather like a smooth and powerful beast, despite the rough exterior. The little box is pretty much lost on the table in any of the BA pictures I've seen that included it, especially compared to the tube amps in the same room. I just finished doing some simulations on a fully symmetric version of the amp, and now I want to go back and look at the simulations of the original to compare the two. I may be trying for too much closed loop gain in both versions.

What's interesting is this wasn't my favorite amp of the several I've been working with lately - that distinction goes to the SiC Puppy with the Semisouth 085 output stage. Once I get the hum exorcised from that hulk, I may want to prevail on Mr. Berndt to let me drag both of them up to his place for another go at his speakers. To my ears, the Puppy sounded more "incisive".

Last edited by wrenchone; 4th October 2011 at 05:54 AM. Reason: sp
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Old 4th October 2011, 11:12 PM   #25
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By the pricking of my thumbs...
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Old 5th October 2011, 12:56 AM   #26
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Ah,yes, the amp that would be king...
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Old 18th November 2011, 12:31 AM   #27
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I'm considering spinning a version of this amp with an SMPS, as I'm currently working on a project at my job that has fairly direct relevance. We're developing application circuits for a new line of hybrid ICs for use in power factor correction circuits and resonant half-bridge power supplies. The ICs are described at Welcome To Power Integrations | Power Integrations. Attached is a picture of a 150W, universal input 48V output resonant half-bridge supply with a PFC front end using the new hybrid chips. Conducted EMI is impressively low, and full load efficiency is high (91%/93% total efficiency for 115/230 VDC input). The supply itself is on a board approximately 2.5" by 7.7". It's a short step from this board to one with a bipolar (+/-) output. More developments as time and opportunity permit.
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Last edited by wrenchone; 18th November 2011 at 12:46 AM.
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Old 18th November 2011, 07:09 PM   #28
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I also have a variation of this circuit that is complementary from input to output, replacing the single N-channel diff pair at the input with a complementary diff stage. The boards are sitting around in the kitchen waiting for me to get to them. I plan to use Supertex small signal mosfets for the front end (VN0106N3 and VP0106N3), since I have them on hand. The rest of the major players will be your usual IRFXXX stuff. The complementary diff stage amp didn't simulate any better than the variant with the simple N-channel input stage, but Mr. Curl says that there's sonic benefits to be had from a totally symmetric architecture. After all, you can't listen to a simulation. I'll name the beast and put in in a seaprate thread once I stuff the boards and get the project in motion. That will be after I get my butt in gear and fix the thermal issues on this one. Maybe over the holidays...
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Old 30th November 2011, 04:59 AM   #29
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This is one circuit I'm considering for the symmetric incarnation of Le Mutant. I suspect it might not sound as benign as the original Mutant when pushed into clipping (it happens all too easily). The open loop gain is a whole lot higher, so understandably, the THD is a whole lot lower - as we all know, this may not be the whole game. Anyway, the way to go should be apparent after pushing the amp a bit with some difficult material. If it sucks at high volume, I can revert to a more mutant-like output structure to see if it improves the listenability.
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Old 5th October 2013, 03:58 AM   #30
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Le Mutant is now mounted down on the heat sink shown in post 22, so it can survive some extended play. The heat sink is cooled via a dialed-down DC fan, ducted into the sink with some flame-retardant polypropylene sheet (ITW Formex, very useful stuff) and some Kapton tape. The heat sink/fan is inside the case, so the overall amp should be pretty quiet once the lid is on. Sounds pretty nice...BA is go!
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