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Old 21st October 2006, 12:53 PM   #1
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Default Building my first "Gainclone"

Hi all,

I've commited to building my first power amp and decided to go with a "Gainclone". I'm sort of a n00b but I know how to use a soldering iron, I've recapped a motherboard and fixed it, recapped my current amp (Cambridge Audio A5.... cheapo I know, shh!), done some volt-mods on a couple of motherboards, fixed more than enough xbox's etc etc. I've been wanting to build an amp for a long time, looking at Rod Elliots stuff, but the parts for most of his stuff seem hard to find / quite expensive over here in the UK.

So anyway, I have bought myself four LM3886T's on FleaBay for £7 (which is what has basically commited me to building it!). I did a day's worth of reading Gainclone stuff yesterday, and think I have it pretty much sorted. I intend to build carlosfm's regulated / snubbed power supply (I don't really understand what a snubber is or why it helps but hey), and also following his schematic for the amp (v4).

I've decided to go with a single transformer and two regulated supplies, one for each channel. From what I have read I should be able to do this. I'm mainly only doing it because it seems (from the spec sheet) the LM338 "only" puts out a guaranteed (constant?) 1A when regulating to 30v. I figured that's not really enough to power two channels all that well.

My current amp has a preout, so I can just use it as a preamp. I will start off by hooking the Gainclone to this and powering the speakers (a lowly pair of Celestion 7's) from the Gainclone. I have a Rane MX23 active crossover sitting here doing nothing, so in the future I intend to go bi-amping or tri-amping, all depending on how well the first Gainclone goes really

I have absolutely no idea how I am going to actually wire it all up. I bought some blank PCB's, but have nothing to actually produce the PCB's at home (intelligent idea I know). I'm not sure a PCB can be produced without all that etching stuff can it? I read someone someone just used a scalpel and did it manually, how would that work? Just scratch away at the copper creating the traces?

At the moment I'm thinking about trying to get it all on prototype board / veroboard / whatever you want to call it. I haven't really seen any Gainclones built like this though, apparently because the LM3886 is awkward to mount on such board. I am not sure I would be happy doing it P2P. I would be constantly worrying about shorts and things!

I couldn't find a 300pF MKT cap for carlosfm's amp schematic. Am I able to leave this out? Or perhaps go with a 1000pF MKT instead? Also finding a 0.1R carbon film is impossible. I'm thinking about going with a 0.22R there and a 2.2uF cap instead.

Think that's all for now. Mainly just posting because, well, I don't really know To let the world know there's someone else attempting a Gainclone and to thank carlosfm for the schematics, and everyone else for all the general info and discussions
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Old 21st October 2006, 06:02 PM   #2
Nuuk is offline Nuuk  United Kingdom
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It honestly isn't difficult to build a GC using P2P!Take your time and do one componets at a time and you shouldn't go wrong.

May I suggest you have a read through this before you start as it should give you some good guidelines and answer at least some of your questions.

A system using an active crossover and GC amps will sound pretty good but start simple and get two channels working OK first!
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Old 21st October 2006, 06:08 PM   #3
Nordic is offline Nordic  South Africa
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Thats where I started... sadly Nuuk hasn't fixed the 4uF7 input cap on the diagrame yet in the year or so since :P
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Old 21st October 2006, 06:42 PM   #4
Vikash is offline Vikash  United Kingdom
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Default Re: Building my first "Gainclone"

Quote:
Originally posted by markiemrboo
I intend to build carlosfm's regulated / snubbed power supply and also following his schematic for the amp (v4).

I have absolutely no idea how I am going to actually wire it all up. I bought some blank PCB's, but have nothing to actually produce the PCB's at home (intelligent idea I know). I'm not sure a PCB can be produced without all that etching stuff can it? I read someone someone just used a scalpel and did it manually, how would that work? Just scratch away at the copper creating the traces?
Yup, I guess you could draw the design on the copper and then just scalpel it away but that's bordering on insanity Else you will need 'that etching stuff'. I assume you've seen the PCB's available. I believe they are what Carlos uses as a basis and mods it to implement his design

Quote:
Originally posted by markiemrboo

At the moment I'm thinking about trying to get it all on prototype board / veroboard / whatever you want to call it. I haven't really seen any Gainclones built like this though, apparently because the LM3886 is awkward to mount on such board. I am not sure I would be happy doing it P2P. I would be constantly worrying about shorts and things!
It's not too difficult.

P2P LM3886 Power Amp with Hi-Cap PSU (snubberised)

A good DMM to check the connections and patience is all you need. Probably wise not attempting it for a first effort though.
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Old 21st October 2006, 07:00 PM   #5
Nuuk is offline Nuuk  United Kingdom
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Quote:
sadly Nuuk hasn't fixed the 4uF7 input cap on the diagrame yet in the year or so since
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Old 21st October 2006, 08:16 PM   #6
Nordic is offline Nordic  South Africa
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Reffering to the basic ICG, which would not affect him with those chips..
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Old 21st October 2006, 08:34 PM   #7
Nuuk is offline Nuuk  United Kingdom
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Quote:
Reffering to the basic ICG, which would not affect him with those chips.
Yes, but what exactly are you referring to?
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Old 21st October 2006, 08:41 PM   #8
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Nick

Not often I the surf chip room I was a little confused, but I think Nordic is refering to your diagram showing 47uF input cap not 4.7uF

http://myweb.tiscali.co.uk/nuukspot/...ecircuits.html

A simple error in the vast Decibel Dungeon
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Old 21st October 2006, 08:51 PM   #9
Nuuk is offline Nuuk  United Kingdom
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Well Pete, when the chips are down as they say!

Now, if you read the statement to the right of that circuit diagram and it is not plain enough, please let me know and I will re-phrase it!
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Old 21st October 2006, 09:22 PM   #10
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Quote:
Now, if you read the statement to the right of that circuit diagram and it is not plain enough, please let me know and I will re-phrase it!
Looks fine to me but folks often just look for pictures and diagrams by searching the image function of search engines the pictures show without the parent page they reside in that's when mistakes happen

That single page on building a basic IGC is not a too difficult read is it.easier than "the little red lorry books"
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