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Old 28th February 2008, 07:37 AM   #1
wixy is offline wixy  Australia
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Default Aussies - Silicon Chip 20W Class A Amplifier opinions?

I'm just wondering if anyone had had any experience with the Silicon Chip 20 watt Class A amplifier available at altronics:

http://www.altronics.com.au/index.as...=item&id=K5125

Anyone have an opinion on the kit?
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Old 28th February 2008, 07:51 AM   #2
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hi wixy,

The standard kit sounds really good. If you mod it to SandyK's recommendations you will have an amp that will be hard to beat. Do search for other threads about the older 15W version.

If you have a Altronics account you will save $60.

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Old 30th September 2010, 08:56 PM   #3
imagios is offline imagios  Czech Republic
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Hi there, it catched my eye as well, did somewhone here already build it? Before I spend 500 bugs on a kit I rather would like to know how how das it really perform.
Looking at the picture I have my doubts about the pream and the capacitors it seems pretty cheap stuff for a 500bugs kit.
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Old 1st October 2010, 12:27 AM   #4
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Some good feedback on stereonet

Silicon Chip 20W Class A Amplifier

If you already have most of the parts then it should be cheap to build
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Old 1st October 2010, 08:20 AM   #5
imagios is offline imagios  Czech Republic
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Well I dont need much power for a single fullrange speaker therefore 20W are OK.

Never the less do you know what type of transistors do they use?

Im not only looking at the THD, but at the amp as it performs, therefore I would like to see an oppinion of somewhan who accualy did it and copared it with other A class amps.
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Old 1st October 2010, 11:58 AM   #6
imagios is offline imagios  Czech Republic
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btw . I found this page about the amp with a lot of details
Silicon Chip 20w Class A amp - Overclockers Australia Forums
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Old 1st October 2010, 08:09 PM   #7
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Hi Imagios
The trannys are MJL21193/4. The parts are certainly not boutique grade at that price but middle grade, all 1% MF resistors, MKPs and many 6.3 mm spade connections. Get a decent ratchet crimper unless you have a swage to suit or just mighty strong. The caps are as would be supplied in midrange commercial quality amps up to even $2,500 AU.

If you believe class A will be adversely affected by using such as Panasonic FC,M grade PSU caps, then replacing 6 x 10,000uF 50V will not be an obstacle for you.

I will say that distortion as low as claimed and without crossover artifacts is certainly distinct, dead quiet and genuinely the closest I have heard to studio production quality sound in the 20W design. If there is a problem, it is the specially wound toroid which is prone on some samples to a buzz at the constant 2.5 amps load which can be audible at close proximity. Resilient mounting has solved the problem for me in two builds.

The remote controlled preamp, incidentally, is buffered and amped with LM4562s which are amongst the very few opamps even in the running for the job.

I would not try to compare sonic qualities with any other amplifier as this is not a "musical" amp. However, if you need accuracy, IMHO, this is it for DIY. Frankly, I do like it very much because the imaging and soundstage is genuine, pin sharp, and absolutely stable. The rest is in the clarity to resolve massed voice sounds and and details that class AB generally struggles with. Try it with headphones, near field monitors or any decent, efficient speakers of 6 ohms and above and you will hear a difference to the rest....absolutely!

There are tweaks to the input pair balance, as mentioned here, which can make a significant improvement but its also impressive as it comes too. You will have to add your own little five button Philips RC5 code remocon and 230V power, however.
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Old 1st October 2010, 09:57 PM   #8
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sorry folks, error. line 1 read MKT not MKP
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Old 1st October 2010, 10:12 PM   #9
leo is offline leo  United Kingdom
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Quote:
Originally Posted by Greg Erskine View Post
hi wixy,

The standard kit sounds really good. If you mod it to SandyK's recommendations you will have an amp that will be hard to beat. Do search for other threads about the older 15W version.

If you have a Altronics account you will save $60.

regards
Agreed! I have the 15w version with Alex's mods, this amplifier has lots of potential . I've tried a lot of amps and this is one of my favourites
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Old 1st October 2010, 11:09 PM   #10
imagios is offline imagios  Czech Republic
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To be honest most likely I would order the kit just PCBs with a partlist and the case, and exchange some of the parts as you wrote. I mean look at a amp with that low distortion and on the in put site is a cich, just how much gets lost from the pream to the amp if insted of solderig wire from part to part, you solder the cinch socket and than make the cable and conect them...
Still I really concider the kit, but definately with changes in the area of capacitors and even I would like to change the resistors to for example Vishay resitors and so on. If the distortion is by design so low than it should be supported by matching quality of components and I mean they are not so much more expensive than the standart ones.
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