The £60 Amplifier

[istari_knight]

I got bored at the weekend so decided to throw this together...

http://farm8.staticflickr.com/7432/9223803033_e8bc2cbafc_c.jpg (http://www.flickr.com/photos/87920837@N06/9223803033/)

Thats a 300va transformer > 1000v/15a Bridge rectifier > 40000uf cap bank into a pair of Naim "Nap 140" clone boards from our dear friends in China.

It sounds damn good considering it only cost £60 to put together... Blasting out the tunes through it now :cool:

[Puffin]

Excellent work. I was always tempted by those boards. I also have some Hackernap boards I bought from a group buy on PFM, trouble is you have to source all the parts yourself and my desire to hear a NAIM style amp is not so great that I can be arsed to go through the ballache of it all. I suppose having built a load of amps of which I only use 2 means it could be a costly exercise of just getting it done for the record.

[brian2957]

Wish I could do something like that James . I'm afraid I'm limited to building my own cables . Looks very nice though, hope it sounds the way you want it to :)

[Ali Tait]

Nice job.

[John]

Nice work James

[shane]

Nice job, James. What chassis did you use?

[DSJR]

How wonderful to have this easy skill at your fingertips. Well done :)

[istari_knight]

Cheers guys :) I just wanted to show what could be achieved for such a low budget.

Shane, I won the case in auction on eBay for £5... It was originally a rackmount DC power supply so it did have the odd hole in it from a previous life but nothing that cant be blanked off.

The heatsink is 6mm copper sheet with a 3mm ally U section coupled for extra [unnecessary] dissipation... I picked them up from a local sheet metal shop as off-cuts for £6. The coloured hook-up wires are from a 8 core caravan towbar cable which cost £1.50 for 2m.

I'm such a cheapskate :D

Ugly but purposful:

http://farm4.staticflickr.com/3781/9240857495_fd87b717a8_c.jpg (http://www.flickr.com/photos/87920837@N06/9240857495/)

[walpurgis]

Well, you can't knock that for a value for money project James. Looks like you had fun, that's what it's all about.

I keep seeing interesting parts on far eastern eBay listings. Must have a bash.

[Stubies]

Very nice James - i wish i had the time and knowledge to try it.

Let us know how it sounds after a few days burn in :)

[Oldpinkman]

Love it. Brilliant idea. Will do a quad for myself while oj fannies around with mine. I can easily do the input gain, opamp, wiring loom and power supply mods, and just put up with the standard bridge. Case & heatsink ideas are inspired. Thin copper sheet bent in a vice will let me mount to some conventional fins.

[istari_knight]

Very nice James - i wish i had the time and knowledge to try it.

Let us know how it sounds after a few days burn in :)

Its definitely getting better the more I use it :thumbsup:

The only problem with buying amplifier boards from china is they always come with the cheapest possible components so I do need to change all of the ceramics for polystyrene's but wanted to make sure the things actually worked before splashing out £10 on new capacitors... Also beware of fake output transistors, I assumed the Sankens included with the boards would be fake considering the boards including all components cost £22 & the Sankens should cost £40 for 4 but lo and behold they arrived 100% genuine :eek:

[Puffin]

James, can you give a link to the site you purchased your kit from. Can you also let me know what voltages the tranny secondaries need to be. Thanks.

Rob.

[istari_knight]

James, can you give a link to the site you purchased your kit from. Can you also let me know what voltages the tranny secondaries need to be. Thanks.

Rob.

I got them from "zoe_tsang" http://www.ebay.co.uk/itm/1pc-140-Classic-NAIM-CLONE-AMP-CLONE-KIT-70W-Mono-/200801089657?pt=UK_Sound_Vision_Amplifier_Parts&hash=item2ec0ad7879 Although there's currently none in auction [buy it now only] they do occasionally have 99p start auctions. Took 3 weeks to arrive & unlike other clones out there the silkscreen is correct.

Just done another search & there's a pair on eBay UK: http://www.ebay.co.uk/itm/Naim-NAP140-clone-circuit-boards-unused-from-Krescendo-HiFi-/111106450628?pt=UK_Sound_Vision_Amplifier_Parts&hash=item19de75e4c4

Transformer wise, I'm using a 300va 25v-0v-25v :)

[Puffin]

Thanks James. The Krescendo hifi boards could be good, but as they have been made up the screen printing will be obscured by the components and one would have to assume that the builder did it correctly. Please don't take this as a gripe at your link, but simply an observation. Were your Zoe Tsang bought boards mono (i.e you bought two) and out of interest if they were an auction, how much did you get them for. Thanks Rob.

[istari_knight]

My thoughts exactly on those Krescendo Boards, they do appear to have different driver transistors to mine... Anyway, populating the boards is half the fun !

Mine were won in auction as a stereo pair for £22 inc p&p.

If populating the boards yourself you can decide how you want them to sound, if you want a Naim presentation then just replace C1 with a tantalum drop, C5+C6 with dry tantalum/tantalum drop, C40 with stacked film & C2, C7, C8, C9, C10 & C12 with polystyrene. If you want a more refined less "prat" presentation replace C1 with MKP, C5 & C6 with Elna Silmic & C2, C7, C8, C9, C10 & C12 with silver mica.... Or a mixture of whatever floats your boat - Theres lots of options to play with !

I'm certainly noticing Naim traits with mine, it delivers basslines like little else... I think the sheep call it "boogie factor" :eyebrows:

[Puffin]

Excellent, thanks for that. I think I might take a punt. Oh yea, sorry one last Q. How do you know the Sankens are genuine?

[istari_knight]

Excellent, thanks for that. I think I might take a punt. Oh yea, sorry one last Q. How do you know the Sankens are genuine?

:thumbsup:

If in doubt the outputs can be substituted for Toshiba 2SC5200.

This picture shows a fake [left] & genuine [right] Printing is much better quality on the genuine, The batch code is central on the genuine & to one side on the fake, the genuine has moulded letters/numbers shown with the red arrows whilst on the fake these are missing... Lastly, a genuine one will weigh approx 18.4g but a fake will almost always be much lighter due to the comparatively tiny die inside.

http://img269.imageshack.us/img269/8604/fakeoriginalsanken.jpg

[Puffin]

James, thanks for taking the time to provide such a detailed explanation. Much appreciated.

Rob.

[istari_knight]

My pleasure :)

For anyone looking & thinking "I need an integrated not a power amp" I've found simply fitting a 50K pot at the input works perfectly. This one's sounding so good I'm seriously considering building another in a proper case with a decent DIY DAC... Could make for a very nice integrated with digital inputs, something I've wanted for a while.

[istari_knight]

Just replaced all of the ceramic caps for films... Wow ! Huge leap forward in HF resolution & detail retrieval.

I'm impressed :eek:

[stupinder]

Very cool. I wish I had the skills to do thins kind of thing. Sadly my DIY extends to putting picture frames up...and that's not always a success!