Author Topic: gainclones diy anyone? (Read 381642 times)

joan2 · « **on:** Jul 24, 2003 at 05:41 PM »

for those with no budget for tube amps but whould like to try their hands at soldering, then this may be for you:http://www.diyaudio.com/forums/forumdisplay.php?s=&forumid=40
http://www.diyaudio.com/forums/forumdisplay.php?s=&forumid=40

these amps are based on national semiconductor single chip power amps, the LM3875,LM3886 and its cousins.
the adavantage of these amps is simplicity, no need to use pcb as point to point wiring can be done....the chip is available thru rs electronincs phils as an order item and cost around 450 per chip for the LM3886, thus for a budget of around 5000 pesos, you can have a 200watt stereo amp....
i can guide anyone wishing to biuld these amps thru my [email protected]

arnoldc · « **Reply #1 on:** Jul 24, 2003 at 05:51 PM »

the toroidal transformer for this project is P2,000 each already from Farnell or RS Components.

since you meantioned P5,000 pesos for stereo, i assume you have another source. will you share that?

i know somebody who assembled an aksa amplifier and used a pair of these toroids.

john5479 · « **Reply #2 on:** Jul 25, 2003 at 02:32 AM »

hmnnn interesting...sir joan2 you got mail!

I checked the link...what can you say about the gainclone design using tubes? thanks!

joan2 · « **Reply #3 on:** Jul 25, 2003 at 05:46 AM »

power transformer need not be torroid type an EI core would do....at a low cost compared to torroids which had to be imported....this is available from alexan, same as with metal film resistors...if you need more power such as when you are paralelling chips and/or brdging them, then go for a bigger va capacity, i can help you with the design for that...these amps are not level gain stage types and as such can use an EI core type, i have worked on many amps with an EI core as well as a torroid, sonnically to me they are the same....consider these:
http://www.soundstage.com/maxdb/maxdb071998.htm
http://www.diyaudio.com/forums/showthread.php?s=&threadid=16337

arnoldc · « **Reply #4 on:** Jul 25, 2003 at 09:30 AM »

joan2, exactly what i want to hear! dumping the toroid in favor of EI makes a lot of sense and will bring you to sub 5K or even less.

Philander · « **Reply #5 on:** Jul 25, 2003 at 09:49 AM »

I have a toroidal transformer, PM me if you want.

ramble_on · « **Reply #6 on:** Jul 25, 2003 at 10:24 AM »

check this out

http://members.ozemail.com.au/~joeras/index.html

seems like good value for the money. could this be the middle ground in the great tube / ss shootout?

sir tony, sent you mail. thanks.

arnoldc · « **Reply #7 on:** Jul 25, 2003 at 11:23 AM »

USD1,200

ramble_on · « **Reply #8 on:** Jul 25, 2003 at 12:15 PM »

sir arnoldc, i meant that it might be feasible for a diy project...

arnoldc · « **Reply #9 on:** Jul 25, 2003 at 12:22 PM »

sorry. by all means it could be.

joan2 · « **Reply #10 on:** Jul 25, 2003 at 01:01 PM »

for those bent on doing one, here is where you can buy the ic LM3886:
http://ph.rs-c.dk/toc/produkt-tocframes.html

the metal film resistors can be purchased from alexan, the capacitors from deeco, choose the name brands, like rubycon or elna, or nichicon....

the power transformer can be purchased from alexan, it's the one they used for a 40 watt per channel amp. shoudln't cost that much, u can use one transformer per channel so you can have more room for expansion later on...

the chasis can be made out of ga.13 aluminum and can serve as heatsink also.....i purchase my aluminums from sulimco metals in binondo area, aranque market.. lots of sheet metal shops that can do bending for you....
i still thinks this project can be built on a 5k budget...

jackryan · « **Reply #11 on:** Jul 25, 2003 at 01:17 PM »

Quote from: joan2 on Jul 25, 2003 at 01:01 PM

for those bent on doing one, here is where you can buy the ic LM3886:
http://ph.rs-c.dk/toc/produkt-tocframes.html

the chasis can be made out of ga.13 aluminum and can serve as heatsink also.....i purchase my aluminums from sulimco metals in binondo area, aranque market.. lots of sheet metal shops that can do bending for you....
i still thinks this project can be built on a 5k budget...

a slight bit of digression, do you have sulimco metal shop contact info... can these guys create customized 19" slim-type cabinets similar to the photo below but for other purpose?

please kindly pm me back.

joan2 · « **Reply #12 on:** Jul 25, 2003 at 05:01 PM »

sulimco metals sells cut to size sheet metal plates, in copper, aluminum or brass, you have to take it to nearby metal shops for bending and forming, i used to buy cut to size 1/4 in alum metal plates and have a mchine shop finish it for me as front panel facia....i used to have them make one cabinet just like yours which i use for electronic active crossover network.....fyi i made all my amplifier cabinets from ga14 aluminum sheets with a ga16. aluminum sheets as covers....

joan2 · « **Reply #13 on:** Jul 31, 2003 at 05:26 PM »

i have been going around looking at prices of parts so here is a partial breakdown:\
1. 2pcs LM3886 @460 each
2. 500va power transformer @ 600
3. filter caps at 200
so partial amount is 1720 for above three major parts, this project can still be had for about 5,000...

Garp · « **Reply #14 on:** Aug 01, 2003 at 10:54 AM »

Hi Joan,

Just want to know if by experience you know that LM3886 is better than either LM3875 or LM1875. I noticed kasi that the latter 2 are the most commonly mentioned chips for first time gainclone DIYers. I can look at the datasheet but I'm not sure I'd know what to look for.

Where can you get that 500VA transformers? I'm tempted to try after reading the review on the AMP-1 at 6 moons and considering its really cheap--I reckon that even with toroids (2K for 225 VA) and quality capacitors (Panasonic FC 2200 35v) and Welwyn resistors (RC55 series), Hexfreds (MUR860), the cost is just about 6-7K. LM3875 goes for a little over 400 apiece at Farnell and LM1875 is almost half of that.

joan2 · « **Reply #15 on:** Aug 01, 2003 at 06:16 PM »

garp.
truth to tell. i haven't built one yet, but i have lots of experience with leach super amps, and other bipolar transistor amps..from what i know so far the lm3886 has muting and the lm3875 has none, this is no problem really...the selling point of gainclones is that of simplicity, even a newbie can do with point to point wiring..see the work of peter daniels at diyaudio....i have 5 lm3875 chips coming in from hongkong and i intend to build a subwoofer.satellite speaker system with those chips, the sub will be powered by a bridge iteration and the satellite on normal single chips, so this will give my pc an honest to goodness 200watt power amps, i have an electronics crossover to be integrated with the gainclone amps....i may even use a tube buffer for inputs....the 500va transformer is my own design using locally available materials, i overated it for future expansion needs, as gainclone is easily scalable....

joan2 · « **Reply #16 on:** Aug 03, 2003 at 07:05 AM »

here are links you might find usefull:
http://www.decdun.fsnet.co.uk/gaincloneFAQ.html
http://www.decdun.fsnet.co.uk/gainclonesl.html

national semicon has a free samples program wherein they give away up to 5pcs of these chips, unfortunately, they can not service the philippines at the moment, so if you have friends and relatives in other parts of asia, then you can avail of this, this is how i am getting my gainclone chips....

ramble_on · « **Reply #17 on:** Aug 03, 2003 at 10:11 AM »

sir joan2, thanks a lot for the very fast reply (and the attachment you sent) last friday.

anyway, i was poring over the document and i was just wondering that the three projects (bridged, parallel and bridged/parallel) might be a tad difficult for my skill level.

i was just curious; except when built as monoblocks, are gainclones supposed to be built as integrated amps? i've been going over the threads at diyaudio and i came across this...

http://www.diyaudio.com/forums/showthread.php?s=&threadid=17556&highlight=legit

comments or suggestions would be most welcome. thanks a lot...

joan2 · « **Reply #18 on:** Aug 04, 2003 at 07:04 AM »

ramble_on,
regarding that article, it shows how easy it is to buid that amp, even as a newbie....don't worry much about the offsets...a +/-100mv is acceptable...a big offset will cause noticeable cone displacement at idle....

Garp · « **Reply #19 on:** Aug 04, 2003 at 10:27 AM »

Joan2 thanks for the reply. May I know what schematic you're using? I've seen the one at http://www.decdun.fsnet.co.uk/ and he seems to be following Peter Daniel's circuit. There's another one at Chip AMP DIY which I think is Thorsten's and this is the one I think i'll use. Can you also point me to the schematic for the bridged or parallel amps? Thanks.

ramble_on · « **Reply #20 on:** Aug 04, 2003 at 11:07 AM »

garp, sent you pm.

ramble_on · « **Reply #21 on:** Aug 04, 2003 at 12:30 PM »

garp, pmd you.

Garp · « **Reply #22 on:** Aug 04, 2003 at 01:06 PM »

Replied to your PM.

joan2 · « **Reply #23 on:** Aug 04, 2003 at 04:21 PM »

i favor the inverted clone type, to me it's simpler, you can use many values for the input and feedback resistors as long as the ratio is about 19 to 22, lower values of input resistor means lower noise, but if using an input capacitor, means higher low freq. cutoff, meaning you will have to use a bigger size input cap. the application notes i gave ramble_on should fill you in on any information you require...fyi i have many stock of 0.1ohm 2 watt resistor which can be used for output ballast resistor in case you want to do a parralel,bridge iteration of this amp...btw, the lm3875is aboult half the price of the lm3886...

john5479 · « **Reply #24 on:** Aug 10, 2003 at 07:57 AM »

I'll be constructing a 20 watt "gainclone" using a pair of lm1875's (I have four chips at hand). if anyone can help me in adding a tube buffer input stage I would gladly appreciate it

here is the schematic: http://sound.westhost.com/project72.htm

I'm a total newbie but if i'll be given a schematic then I can follow somewhat with the circuit. thanks!

ramble_on · « **Reply #25 on:** Aug 10, 2003 at 02:15 PM »

i'm also planning of putting one together. i've got almost everything in place and my chips are due in two weeks time (a pair of lm3875's).

hope this helps...
http://www.diyaudio.com/forums/showthread.php?s=&threadid=9557

btw, in case you're interested in diagrams using the bridged, paralleled and bridged/paralleled configurations, i've got something you might be able to use (courtesy of joan2). i suggest you try to give joan2 a holler.

keep us posted. good luck...cheers

john5479 · « **Reply #26 on:** Aug 10, 2003 at 10:48 PM »

I just plan to build the low powered one, might just use a simpler circuit but still add a buffer if possible. The tricky part here is what design for the power supply will I use

I've got data sheets for lm3886, lm3875 and lm1875, might just do the one in the lm1875's data sheet though sinc eI have 4 l1875's at hand already

Garp · « **Reply #27 on:** Aug 26, 2003 at 10:46 AM »

Updates anyone? Hey John5479 have you got that tube buffered gainclone up and running yet? I'd be interested to know if anyone's finished theirs. Thanks.

john5479 · « **Reply #28 on:** Aug 26, 2003 at 02:40 PM »

nope aint doin the tube buffered one...almost got all the parts to start building...just need a pair of torroids. I'll be using typical carbon resistors and nichicon capacitors (1000 uF 50v) which I bought from radio shack. Good luck to me i guess hehe.

ramble_on · « **Reply #29 on:** Aug 26, 2003 at 04:52 PM »

a pair of lm3875t's and mur860's just came in this afternoon. transformers to follow...

btw, in case anyone's interested. i got the mur860's as samples. pm na lang for details.

cheers...