DIY Amplifier Suggestions - on a tight budget

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elizard

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Joined 2003
#1
Hey,

Well, I'm going to have enough money soon enough to buy some amps, and I need some suggestions.

My original idea is two K8040's from Velleman http://www.velleman.be/Product.asp?lan=1&id=345697

Those run at $300/piece, so in total they're just under $700 after tax/shipping.

So, my budget is CAD$700 (USD$480)
I'm on a tight budget, no more than that, school is a priority!

So, I'd like some suggestions for amps. I'm open to both tubes and solids.
I listen on low-moderate levels, so I don't need a 200watt beast, but >50watt is preferred.

Btw, that $700 would need to include the amp/supply/chassis and everything else that might cost me for the project, except tools.

Also, another requirement is I'd prefer it to be easy-medium difficulty, I've only done one project so far from a kit, and although I've had little problems with it, I'd prefer not to take a bigger bite than I can handle.

Thank You 🙂
 
#5
If I was on a tight budget and still wanted to build a substantial amplifier I´d definitely go for a gainclone with a LM3875.
This chip cost about 6-8€ here in Europe.
The expensive parts would be the heatsink, transformer, some decent capacitors and the chassis of course.
If you build the chassis yourself you won´t spend more than half of your budget.
Have a look here : Gaz included a pricelist for his monoblocks
(first page).http://www.diyaudio.com/forums/showthread.php?threadid=12981
The chip is good for up to 50W but you can bridge/parallel if you need more power.
If you need more info : Do search for "gainclone" or "LM3875".

Regards
Jens
 
#6
yeah, i've considered gainclone, however from what i've read is unless you use some high-grade components, you're bound to be dissapointed 🙁

also rarkov's list isn't complete for me .. for some reason it cust off after 2 cases for the monoblocks

but that's what i'd be looking to make .. preferably monoblocks ..

or should i just go for the vellemans?
 
#8
yeah, i've considered gainclone, however from what i've read is unless you use some high-grade components, you're bound to be dissapointed
Click to expand...
I built a LM3886 amplifier about 3 years ago.
At that time I haven´t heard about the "famous" gainclone.
I used a PCB-layout from a magazine which has twice as much parts on it than the layout most use here.
No hypercautious and supertight layout and neither so called high-grade components.
I still haven´t modified it and I have to say I really like the amp.

Which high-grade components do you mean by the way?
The only thing you could go so crazy with that it exceeds your budget are the capacitors and my personal opinion is that you can build it without Black Gates for example.
Most good companies for capacitors should be within your budget.

Regards
Jens
 

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#9
What sort of caps should I use then, if not BG?
Something that digikey preferably carries 🙂

Thank you for the help though! 🙂
I just want to price out the gainclone monoblocks today preferably 🙂

I can get the cases pretty cheap locally, and I could probably order MOST parts (if not all) from a local electornics store. But I'd still want to price them on digikey first.
BTW .. any actual digikey#s are welcome for the caps/transformers
 
#10
If you like Digikey then order the Panasonic FC 1000uF/50V for the filters. I do recommend you use a 4.7uF BlackGate N type for the input capacitor and a Mills 10K ohm for the input resistor. You can order them from Parts Connexion in Toronto. These components will cost you about $20US total vice $5-10 for other brand components but they are worth it. I use a Roederstein 220k resistor for the feedback but a good Dale-Vishay NH65 from Digikey will be work too. Don't spend to much on heatsinks use a 8" piece of 2"angle aluminum screwed to case will be sufficient. Stick with 18-24V transformers 120-180VA per/chan or a 225-300VA for both. The case depends on how good your metalworking skills are or buy one like cheap aluminum project box and paint it for super cheap. With the kind of money your willing to spend you could get a nice rack mount case 1U or 2U size and put everything in it. Good luck. It's a great project to cut your teeth on. 😀
 
#12
well i think you just sold me for a gainclone 🙂

any recommendations for a transformer?
where i can get a cheap-er one from canada? specs for the transformer?
I'd stick to 2 monoblocks, each with a separate power supply i suppose (so long as its not twice the cost!)
 
#13
eLizard,
You should read through the "This is not just another Gainclone" thread. I know it's huge and gets off track once and awhile but has just about all the info you need. Check around with local suppliers for some transformers. I would stick with toroidals as they are more efficient and generally quieter. Victoria Magnetics and Plitron are excellent manufacturers if your surplus search comes up empty. A Google search will find them. Call them up for a quote. Peter Daniel, the forum's Gainclone King, can probably help you with local Canadian sources, as well..
 
#15
Can you live with 38watts per chan? Unless your speakers are less then 86db sensitivity or you play your music really loud, you don't need more IMO. A 180VA toroidal transformer with dual 18 volt secondaries for each monoblock would be perfect. I use even less (120VA-18VAC/chan) for my main amp and it drives my 89dB B&Ws more than loud enough. Pics are @post 81 in the big thread.
 
#16
yeah i can live with 38watts 🙂

i've 91db crap speakers, and my new set will be 89-90 .. so 38 will be great 🙂

gonna price it all .. as long as its under $200 w/o chassis (i can do that myself with some aluminum or wood) its all good 🙂
 
#17
The transformers are your biggest expense and you'll get under $200 easily. Just pay particular attention to the ground paths and keep your signal path as short as physically possible. Those have been most people's biggest headaches.
 
#19
A 10 amp (5/winding) 18VAC transformer (10*18=180VA) 😉
A 50k resistor to ground instead of the pot would be the obvious solution but I have had some extra noise in my experiments using that configuration so I just made my amp an integrated version.
Peter, any suggestions?
 
#20
hmm. well i can point out a few suggestions and i'm sure others can shoot them down.

apexjr.com may still have one of those 48Vct -7A transformers (E I core) for $10, and they also have lm3886 chips and heatsinks.

www.goldmine-elec.com has the lm3875t chips for like $4.75 or $5. they also have lm837n opamps 4 for $1 (and they're quads). no resistors or caps to speak of. well, mylar 1uF 5 for $1, but that's not much better than local for me! also they have some 3pdt (actually 4pdt if you look at the diagram...) for 70 cents each, 6v coil thoguh... oh and they have cool magnets which aren't really related but still cool.

www.newark.com always has stuff, and they pack insanely. if you need extra boxes just order 50 each of differenet values of resistors... i now have like 13 small boxes...
 
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