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Old 26th February 2007, 04:06 PM   #1
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Default BrianGT gainclone kit newbie- help me shop!

So far I've ordered the chipamp.com kit (dual mono) and a pair of the One Pi kits from Pi Speakers for my first real project.

I'm all set for speaker cabinets and will figure the amp chassis out afterwards--I have a friend with a machine shop and my father does architectural woodworking, so those I can handle.

What I need a little gentle for-dummies guidance on is getting together the rest of the parts for the amp/PSU. I know I need a transformer, but that's about it.

I would like to document this project end-to-end as a service to the other n00bs out there. The Web and this site are full of tons of great info, but I sort of need a little more direct hand-holding.

Thanks in advance!
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Old 26th February 2007, 09:39 PM   #2
Arx is offline Arx  Canada
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From a quick glance at that kit, it looks pretty complete. You'll mainly be needing all the external stuff.

Input jacks - I use XLR jacks, because I hate RCA jacks.

Binding posts - I get the mode electronics ones. They're cheap and solid. (Radio shack sells them under their own name)

Some sort of beefy connector for the power supply if it's not internal- I used a male xlr jack for this. I know better than to plug my power supply into my line outputs

Mains jack and fuse - If you want a detachable cord. You can get an iec jack, input filter, and fuse all in the same unit, so it saves some extra work.

if you're going for minimum $ you could just have a permanently attached cord and a panel mount fuse holder.

If you're not using a seperate preamp you'll need a volume control. I used a PEC brand pot that I bought from digikey (Part# KKA5031S28-ND) when I built mine. It was not cheap (~$35 Canadian), but it's nice and beefy and tracks well. It felt like a waste of money when I ordered it, but in hindsight I'd say it was well worth the extra cash. It doesn't have the typical imbalance at low volume, and I don't feel like it's going to get scratchy and quit working like the cheap $5 ones.

That's about all I can think of other than whatever you're building the chassis out of, and some wire for internal connections, etc.

I don't really believe that the parts make any significant difference in sound, but sometimes spending a little more $ on the plugs and whatnot will get you something much more solid and reliable.

-Nick
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Old 26th February 2007, 10:37 PM   #3
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Thanks! I'm still a teeny bit at sea on the PSU parts--mainly the transformer, but I'll dig through some more threads there.

In general I like to do things right--tools don't make the carpenter, but I'd rather do something the right way the first time. Anyway the whole point (for me anyway) of the DIY approach is that you get to choose the compromises. I like equipment that feels solid and well-constructed. At Best Buy that volume knob might cost you $300 more.
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Old 26th February 2007, 11:44 PM   #4
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OK, so looking at this Tx here:
http://www.partsexpress.com/pe/showd...number=122-625

Avel 250VA 25+25... I've ordered the One Pi speakers which are 8-ohm, so the 25 isn't pushing it, I take it? Or should I go for the 18s?

I was thinking about altering this to use one of the valve-buffered designs, but on reflection I suppose I might just start that from scratch after I get this one to work. The designs for those that I've seen (mainly the Joe Rasmussen one) seems to call for 35V which I guess is more than I want here.
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Old 27th February 2007, 05:01 PM   #5
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Default Re: BrianGT gainclone kit newbie- help me shop!

Quote:
Originally posted by sansbury
I would like to document this project end-to-end as a service to the other n00bs out there.
Please do. I'd like to have ago at one of these kits and and 'end-to end' overview would really help.
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Old 27th February 2007, 05:43 PM   #6
Arx is offline Arx  Canada
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I'd guess that transformer should be alright. It's at the high side of the spec, but should be okay.

I'm building a 6 channel right now (for tri-amping) and am going to run it off of a 600VA 25+25

My current one is running off of a pair of EI core transformers that I think were meant for battery chargers. ~14.4v output unloaded. I ran them off of a second input tap which I beleve is meant for Japanese 100v AC. It gave me around 18v no load. It works just great. Runs cool, plenty of output for my liking.

So, either way I think it'll be fine. The 18v secondaries will probably give you a little more versatility for lower speaker impedances, but the 25v will give you more power if you're sticking to 8 ohm loads.

-Nick
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Old 27th February 2007, 06:04 PM   #7
thegeek is offline thegeek  Norway
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From another noob; the information is already out there. I've built other amplifiers (m3 headphone amp + steps power supply) but I don't really know the electronics very well and I was not sure if I could handle a a bigger project. But; I've just successfully built/started the myref c (twisted pear audio kit), kookaburra and some other stuff:P
Have not yet wired up the kookaburra, and I've only tested one of the channels on the myref but so far so good;P
I had to do some searching to find all the info I needed, especially since I felt I had to be _very_ sure how to wire up the transformer and high voltage stuff in general; Everything works great so though, just need to do the final assembly and test;P (+ read up even more on "proper" grounding;P)
The biggest challenge for any noob is probably just finding all the info that is needed, the most important(and dangerous) stuff should probably be collected and documented on the wiki. (on the other hand, one of the greatest satisfactions is knowing you had to work hard and learn new things in order to build it)
I could go on rambling, but I think I'll stop since I fear I'm not really making much sense;P
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Old 28th February 2007, 07:42 AM   #8
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I'm pretty noobish to the gainclone expperience too lol,

figured i'd hyjack you're noob thread instead of cluttering the forum with more,

I want to buy a kit from BrianGT's site but i'm a little unsure of what exactly i should be getting??

Only want a stereo amplifer, so i'm presuming all i need is the;
Non-Inverting LM3886 Stereo Kit,
Snubberized Stand-alone Power Supply Kit,
A single 25V-0-25V 160VA Toroidal Transformer,
and all the fittings for the case ie. RCA's, power connection, volume pot, etc.


http://www.chipamp.com/supply.shtml
http://www.chipamp.com/lm3886.shtml
http://www.jaycar.com.au/productView...Max=&SUBCATID=

Is that the lot?

Cheers guys,
Ashlin.
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Old 28th February 2007, 10:48 AM   #9
thegeek is offline thegeek  Norway
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I'm not going to comment on wether that is all you need as far as electrics go, just wanted to say that you are going to need a _lot_ more to get a finished "amp".
There are soo many hidden costs in the enclosure++ so just be prepared to pay;P
Also, try to think through and consider every last little part you are going to need, since you are probably going to end up ordering several times from the same place ( atleast I did ).
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Old 28th February 2007, 02:57 PM   #10
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I was under the impression that the PSU kit on Brian's site was optional or not required for new kits, but I could definitely be wrong.

I'm going to build it on a block of wood or something to start with. I have a friend who runs a large machine shop so after I'm happy with the results I'll work with him to build a nice case. I've talked with him about manufacturing them, but I wonder how many people here would be willing to pay real money for "just a metal box," even if it was a really nice one.

It would be really nice if someone put together a truly complete kit, or at least gave a canonical list of parts to make it easier for first-timers. Anyway, I might try to do at least the latter. I know the whole point of DIY is, well, DIY, but it can be a steep learning curve for first-timers.
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