xerxes
Been here a while!
Posts: 1,115
|
Post by xerxes on Apr 14, 2012 2:38:59 GMT
I've had a set of LM3886 Gainclone boards made up for about 5 years and have finally got around to making them into a completed amp: 2 x 300VA with 2x22V secondaries, earthed electrostatiic screens and EMI/RFI shields. I drilled and tapped the heatsinks so that the boards coould be mounted directly to them. The extra board on what will be the rigt hand heatsink is a soft-start module to limit inrush current and prevent blown fuses. It also allows the use of a nice momentry on push-button switch. Some thermal paste between the chip and the heatsink. No matter how carefully I plan these things, the wiring always seems to be fairly messy in the end. I'm quite pleased with the simple push button and a very subtle green power LED. I powered it up without any dramas, no smoke, no blown fuses - a good start. Measured the DC offset on the outputs - no problems. I've had it up and running for about an hour and it sounds pretty good, but it's late and I've got it very low, so I haven't had a proper listen. I was worried that the aluminium sides of the case wouldn't be large enough for heat sinking, but at low level they're not even warm, so they may be enough.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Apr 14, 2012 5:34:01 GMT
|
|
|
Post by szoze on Apr 14, 2012 6:30:40 GMT
Really nice.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Apr 14, 2012 8:02:37 GMT
Ah... the famous gainclone project. I like that... it kicks against every sacred house in the high-end business and managed to stay afloat in the audiophile DIY scene (they were even sold for ridiculous prices while containing just a few cheap parts) on name/hype and the inability to be discern it from high-end amps in every test done with it (except sighted tests ofcourse after what was revealed what's in there) that was flung at it. Originally intended to 'show' you don't need fancy power supplies (the original was even underpowered), boutique parts or high slewrates/ultra low distortion and extremely light bandwidths or difficult designs and a single (rather simple with asymmetric A-B output stage) 'power opamp' was enough. These power amps were originally intended for the lower to medium quality cheap audiosets and not intended for serious HiFi. No discrete parts needed aside from a few resistors. Same kind of thing with class-T. Originally designed for low cost/size multichannel amps that could deliver enough power. It doesn't measure well at all but some where in awe about size and power and couldn't believe something could sound so good. Same as the gain-.... project(s) a hype with cult followers was born. I love it ! ;D It 'validates' everything I know and value to be true. I hope it sounds every bit as good / you enjoy it as it looks like. nicely build, beautifull cabinet.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Apr 14, 2012 9:17:43 GMT
That case front is superb! I'm so impressed with how neat you got the hole for the LED, after my efforts. How is mounted, or is that a trade secret Syd
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Apr 14, 2012 10:23:17 GMT
Hi Xerxes great work and very nice build i think the Chipamp boards are pretty much the same as my Audio sector boards with a few extra parts. i must say that i was pleasantly surprised by the sound quality I've had from mine. i terms of bang for the buck these amps are pretty hard to beat and not tooooo hard to build. I've seen some people get a little sniffy about these chip amps but it's really not warranted. I've moved on to something else but I'd not part with my LM3886. well done I found that mine (in my system to my ears) sounded warm, round but pretty detailed. now some reports on SQ would be interesting. what pre are you thinking of to drive it? i have a spare DC1B board if you'd like to build one. my DC1B sounds great with the audiosector. let me know and I'll hook it out for you. take care
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Apr 14, 2012 11:44:19 GMT
Is the power button latch or momentary? If latch where did you find it?
|
|
xerxes
Been here a while!
Posts: 1,115
|
Post by xerxes on Apr 14, 2012 11:48:53 GMT
Thanks guys. The LED is mounted really simply. I drilled a small 2mm hole in the face plate, then on the back/inside I countersunk the hole. I then held the small 3mm LED in the countersunk hole with some hot melt glue. It actually looks quite messy from the inside, but I'm pleased with how it looks from the outside. I wanted to keep it plain and simple as I believe power amps should be heard and not seen. I think the main difference is the "snubberised" power supply. I think it's supposed to make the amp work better with a wider range of speakers. I've had a longer listen today and I'm very pleased with the sound. It's nice and clean, no harshness (which I hate), nice presence on the vocals, imaging, separation etc. All the stuff that you want an amp to do. I have now tried and/or built all the "new" amp variants. I have a pair of Hypex Class D mono amps, I've got a little 15W/C TA2020 T amp and now a gainclone. All of them sound considerably better than the commercial class A/B amps I've bought and owned in the past. The little Topping TP20 I have: playitclear.blogspot.co.uk/2010/10/topping-tp20-mark-2-audiophile.html is ludicrously good fo the £45.00 I paid for it. And apart for it's rather low power output, I reckon it would put a lot of "mid-fi" stuff from Arcam, Cyrus, Audiolab etc. to shame.
|
|
xerxes
Been here a while!
Posts: 1,115
|
Post by xerxes on Apr 14, 2012 11:57:08 GMT
|
|
xerxes
Been here a while!
Posts: 1,115
|
Post by xerxes on Apr 15, 2012 12:33:56 GMT
Hi Shaun, I'm currently using a Hypex MiniprE: www.hypexshop.com/DetailServlet?detailID=1982. It's the only preamp I have. I've got an 50K Alps RK27 pot in my parts box and did think of putting that in a box to make up a very basic passive preamp, because I'll want the MiniprE back in my main system at some point. I'm not familiar with the DC1B, what is it?
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Apr 15, 2012 15:15:48 GMT
|
|