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Old 18th September 2013, 08:36 PM   #1341
all212 is offline all212  United States
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I understand why the laptop power supplies are used and I like the idea as it keeps the build and cost simple and keeps me from electrocuting myself. Someday I'd like to build a non-switching power supply for these amps but in the meantime - is there a circuit that can be used to smooth that voltage out without changing the voltage or current?
I'm not an engineer - just a guy who can figure out which end of the soldering iron gets hot.
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Old 18th September 2013, 10:23 PM   #1342
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I reckon the power-suppliest feelings towards switch mode power supplies is a little bit over the top sometimes. Nelson uses switch mode supplies on quite a few of his products, if they were that bad he wouldn't use them in the first place.

To answer your question you could put a RC filter inside the chassis if there is room for it, but you have to be careful not to cause the supply to go into oscillation.

Maybe .1R and 4000uF could work well. Someone dumber than me could probably give you better advice though.
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Old 19th September 2013, 05:57 PM   #1343
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I am skeptical you'll hear a noticeable improvement with a linear power supply over a pair of properly rated laptop bricks (I use 19V, 3.4A). I've owned tube amps and tube preamps and vinyl (and tape!) playback, so I'm no anti-analog, pro-digital-only kind of guy. Note I'm not saying it's impossible you can make the amp sound significantly better-sounding with a good linear power supply. I'm just skeptical. I have used beefy linear supplies that sounded awful (transformer physically vibrating being the most common problem) and have also used SMPS's that introduced hash. The ACA sounds great as designed.

That said, I'm thinking about going bi-amped with an active XO (miniDSP). I think I can use some more oomph in the bass. My subjective impression is that the sound quality of the MF/HF is a 9, and the bass is a 7 in my system. With proper futzing around, I think my Classe (100 wpc @ 8 ohms, 200 wpc @ 4 ohms) to the bass drivers and the ACA to my Radian compression drivers ought to sound pretty, pretty, pretty . . . good.
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Old 23rd September 2013, 11:28 PM   #1344
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Well, crap--and surprise!: I have to sheepishly confess that hum (more like a modulated buzzing noise) from my Classe cut short my active XO plan. With the two amps, extra wiring and the miniDSP, there was probably a ground loop introduced, and I was in no mood to mess with all that, especially since I found the sound a little "off," which I could never pinpoint. Dynamic and detailed, yes, but not very musical.

The surprise is that I decided to try the ACA on my venerable Large Advents with upgraded crossover caps and employing a BSC circuit. I was pretty sure they wouldn't sound too good with the ACA's measly 5 watts. But I was wrong, they sound damn near superb to my ears. I have always loved how seamless and refined the LA's sound, never mind that they aren't the most detailed or slammin' speakers around. The ACA contributes to the Advent's strengths and really highlight their luscious sound, unlike a p-p 6V6 I had that made the LA's sound a little too luscious--more like syrupy. But since the speakers are only about 89/dB/1w (perhaps even less with the BSC's -3 dB midband "correction"), they won't get rockin'-out loud. But I can certainly live with the sound: velvet smooth and closer to my ideal of "musical." In fact, right now they're close enough.

Anybody have any ideas about good matches for this amp? I'm thinking a Fostex BLH might work. And I've heard an F5 make magic through a pair of 605's in 9 cu ft cabinets.
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Old 24th September 2013, 07:39 AM   #1345
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soldersmoker F6 time ?
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Old 24th September 2013, 01:25 PM   #1346
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soldersmoker, I am pretty sure that the cornu spiral horns (or the thread of speakers made with foam core board) will sound as good or even better.
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Old 24th September 2013, 01:53 PM   #1347
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Those horns have always intrigued me. They seem to combine backloading with a bit of open baffle. I'm a crappy woodworker, but I have a friend who has some skills and tools. Hmm.

F6? One amp at a time!
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Old 24th September 2013, 03:56 PM   #1348
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I think that a lower than expert level of woodworking skills is required, just a lot of glue and patience. And Cal (quite the speaker guy) and xrk971 both believe that they sound very good (depending on the driver).

I wanted to try them out on my ACA, but timing was bad between my making the ACA and the speakers, that my pair went to a friend of mine has "borrowed" them permanently (from the looks of it) and those were old rescued from satellite speakers drivers. Lucky I have two more of those satellite speakers for an even better cornu and ACA pairing.
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Old 25th September 2013, 02:46 PM   #1349
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The FC threads are fascinating, but now I'm fixated on Karlson K15's. Reasonably sensitive with the right drivers, prodigous bass, wide dispersion: that sounds like my kind of sound.
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Old 26th September 2013, 02:19 AM   #1350
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Default Up and running...

All - Just wanted to follow-up and say thanks to the diyAudio team, as I got a replacement heatsink direct from Italy last week. I was so excited I stayed up late to finish the build, and the amps sound and look great!

The pictures are a little dark, but here they are hooked up to the Squeezebox Touch / Berkeley DAC / Epos speakers. Yes - the speakers are a bit too inefficient for these amps, but my project for next week is to build up the Audio Nirvana 15" speakers into the cabinets below the amps.

I'm still in the process of building up my Bottlehead amps, and am looking forward to comparing the sound of the two different amps. I will say right now that what I love about the ACA is that you can build it up in a few hours and start enjoying the music. The Bottlehead isn't rocket science either, but it takes a bit more time to put together - will be interesting to compare the sound.
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