Author Topic: gainclones diy anyone? (Read 381656 times)

joan2 · « **Reply #60 on:** Sep 07, 2003 at 06:42 PM »

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interesting comment. i also believe that the myth about the best solid state (amps) sounding close to tubes is also just that...a myth.

i know of no one claiming that solid state is superior to tube amps....there are good solidstate designs as bad ones, same with tubes, there are good deisgns and there are bad ones..i know one area where tubes are clearly superior to solid state, and that is the cost....it is never a question of one being superior to the other, there are many other factors to consider, the amplifying segment is just a third of the whole "music reproduction chain" we still have to look at the signal sources, and speaker systems....no one can win any arguments with subjectivism, after all your ears are the final judge, next of course to your wallet....music reproduction should be an enjoyable experience. the fun fades as one becomes more and more obsessed with wat they do not have!!!!

you see, it has nothing to do with solid state or tubes, it has a lot to do with the individuals' attitude!!!!!

john5479 · « **Reply #61 on:** Sep 09, 2003 at 07:51 AM »

stupid q. but I will ask it anyway, I am using caps with 35V rating, what is the max. voltage for tha trannie can i use?

Garp · « **Reply #62 on:** Sep 09, 2003 at 09:49 AM »

I think you should use 18v secondaries that gives you a dc of 25v on the rails. with 25v on the secondaries, you won't have much headroom. What caps are you using for filter and the input cap/dc blocking?

john5479 · « **Reply #63 on:** Sep 09, 2003 at 12:47 PM »

i'm using 1000 uF for the filter caps, no input cap, skipped that part. let's see 18v secondaries ~25 v which equates to ~12 watts, will try it out then. thanks

joan2 · « **Reply #64 on:** Sep 09, 2003 at 04:50 PM »

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stupid q. but I will ask it anyway, I am using caps with 35V rating, what is the max. voltage for tha trannie can i use?

not a stupid question at all, but rather a good question, to answer, any dc voltage developed from the secondary of your trannie should not exceed the rated cap dc working voltage, so in this case anything below 35 volts is safe.....to calculate, that's 35/1.4 or 25 volts ac, say 22 or 24 volts is fine....even if you use 25volts dc as rail voltage a capacitor rated at 35 or even 50 volts will do just fine....

john5479 · « **Reply #65 on:** Sep 10, 2003 at 05:00 PM »

thanks will just try 20v then i plan to do a dual mono even if it the power rating is just like ~15 watts per channel, just wanted to get an idea on how to construct an amp

arnoldc · « **Reply #66 on:** Sep 11, 2003 at 03:02 PM »

joan2, saan nga yung nag be bend sa aranque? yun ba malapit sa benavidez?

i will make a chassis with top and bottom acrylic sandwich yung bended aluminum kasi.

also, may pogi ka bang heatsink na pwedeng i-recommend?

joan2 · « **Reply #67 on:** Sep 12, 2003 at 06:30 AM »

arnoldc,
di ko alam yung exact address, per naroon lang yon sa vicinity ng aranque, you can buy your aluminum from sulimco cut to size, give some allowance, cause crude ang cutting methods nila, then there are nearby shops doing bending, there is one shop owned by " pio" a chinoy, then there's another one accros the steet from aranque, this one has a box bender.............last time i went there was in 1994, before i went overseas as an ofw....as to heasinks, we are only limited to what's available at either deeco or alexan, invensting in an extrusion die costs around 50thou...and another 50 thou for a minimum order so it is a costly proposition, wish i had that money.....

arnoldc · « **Reply #68 on:** Sep 12, 2003 at 06:05 PM »

thanks joan2, tingin ako ng heatsinks sa RS or Farnell.

joan2 · « **Reply #69 on:** Sep 16, 2003 at 11:45 AM »

i have several lm3386 and lm3875, lm4760 and lm 4780 inbound from hongkong......

rmpmla · « **Reply #70 on:** Sep 16, 2003 at 12:52 PM »

Quote from: joan2 on Sep 16, 2003 at 11:45 AM

i have several lm3386 and lm3875, lm4760 and lm 4780 inbound from hongkong......

bro, how much for a pair of lm3875 ? planning to build one

thanks

joan2 · « **Reply #71 on:** Sep 16, 2003 at 05:02 PM »

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bro, how much for a pair of lm3875 ? planning to build one

please call me at 6438957....

rmpmla · « **Reply #72 on:** Sep 16, 2003 at 05:28 PM »

joan2, nice talking to you. see you next week then

moonshow · « **Reply #73 on:** Sep 16, 2003 at 11:14 PM »

hi joan2

im also interested with a pair or 4x of you lm3875, if may naiwan pa.

im planning to build a lm3875 amp.

joan2 · « **Reply #74 on:** Sep 17, 2003 at 01:40 PM »

i have only a pair left, but will get more in two to three weeks time....

rmpmla · « **Reply #75 on:** Sep 17, 2003 at 02:31 PM »

Quote from: joan2 on Sep 17, 2003 at 01:40 PM

i have only a pair left, but will get more in two to three weeks time....

joan2, paki reserve na lang yung last pair mo. called you several times this morning but you were out. i got a chance kasi to pass by Shangrila around 12nn. thanks

joan2 · « **Reply #76 on:** Sep 17, 2003 at 04:50 PM »

rmpmla,moonshow,
i have a pair for each of you...no problem..btw, good caps, such as elna, rubycon, nichicon can be purchased at eleshop, the one besides oriental diagram center in raon.....

moonshow · « **Reply #77 on:** Sep 18, 2003 at 10:59 AM »

Yes! thanks joan2..

ill call you later for details and pickup.

homer · « **Reply #78 on:** Sep 26, 2003 at 09:36 PM »

sir joan, i'm interested in the lm3886 4pcs.

joan2 · « **Reply #79 on:** Sep 28, 2003 at 01:01 PM »

homer,
please call me at 6438957...

rmpmla · « **Reply #80 on:** Sep 29, 2003 at 09:24 PM »

joan2,

sent you a PM.

moonshow · « **Reply #81 on:** Oct 02, 2003 at 09:54 PM »

just finished my gainclone and its not a pretty sight! the sound was great, better than my old amp. but, my gainclone's life was pretty short, just less than two hours. it shorted after awhile, i clumsily mishandled a bunch of wires and it touched the heatsink, then kapoof, number 4 pin from my lm3875 chip exploded with a bright spark.

does anyone who has built a gainclone experienced echoed sound and sometimes the lack of voice? this is what i have experienced in my mono gainclone.

mang tony, pls reserve me the 3 lm3875 chips that you have.. thanks for your patience.

thanks to:
google.com
decibel dungeon
mang tony
jay gatchalian
and the various electronic shops at raon that have the most annoying salesladies that feels they own the store and we owe them.

joan2 · « **Reply #82 on:** Oct 03, 2003 at 06:55 AM »

well, we all learn from our mistakes, at least you got it working, being a newbie at that, so this just shows that this gainclone chip is the easiest first project to do, voltages involved are not that high..the important thing is that you incurred no injuries, i must and always have emphasized safety first when working around electronic circuits!!!!

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does anyone who has built a gainclone experienced echoed sound and sometimes the lack of voice? this is what i have experienced in my mono gainclone.

i was thingking about this last night as we speak on the phone, and i realized that this must have been due to the SPIKE circuit on the chip acting up...on normal use, meaning that installation is fixed up and sifficient heatsinking was provided, this should not happen...

joan2 · « **Reply #83 on:** Oct 03, 2003 at 07:00 AM »

Quote from: rmpmla on Sep 29, 2003 at 09:24 PM

joan2,

sent you a PM.

please call me na lang sa 6438957...i did not get your pm...thanks

Garp · « **Reply #84 on:** Oct 03, 2003 at 10:12 AM »

Quote from: moonshow on Oct 02, 2003 at 09:54 PM

just finished my gainclone and its not a pretty sight! the sound was great, better than my old amp. but, my gainclone's life was pretty short, just less than two hours. it shorted after awhile, i clumsily mishandled a bunch of wires and it touched the heatsink, then kapoof, number 4 pin from my lm3875 chip exploded with a bright spark.

does anyone who has built a gainclone experienced echoed sound and sometimes the lack of voice? this is what i have experienced in my mono gainclone.

mang tony, pls reserve me the 3 lm3875 chips that you have.. thanks for your patience.

thanks to:
google.com
decibel dungeon
mang tony
jay gatchalian
and the various electronic shops at raon that have the most annoying salesladies that feels they own the store and we owe them.

Same experience here. I blew up one of my chips after a resistor accidentally touched the heatsink---I forgot to unplug the thing before working on it. I'll will make sure I use an isolation pad and washers for the chip in the final version. I got it to work nicely the first time I built it---none of the echo that you noted. The sound was expansive and dynamic and for a 160VA trafo and it gets really loud. The only thing I don't like about it is that it can get pretty edgy at the top but the detail is really superb IMHO. I'll be adding a tube buffer in the final version.

One thing I noticed is that everytime I noticed any problem with the sound, the heat sink temp rises dramatically within 20 seconds of play even if the volume is just enough to hear the sound squeak. It gets so hot that you won't stand touching the heat sink longer than 10 seconds.

The working prototype I built which worked did not hum at all even at full volume (the cd is in pause and I jack up the volume to max level), no transient noises at switch on or off and gets just moderately hot after 2 hours of play at my listening levels. I hope I'll get as lucky with the final version.

I

Garp · « **Reply #85 on:** Oct 03, 2003 at 10:37 AM »

Quote from: moonshow on Oct 02, 2003 at 09:54 PM

and the various electronic shops at raon that have the most annoying salesladies that feels they own the store and we owe them.

Oo nga eh. Was at Raon last Tuesday and I was looking for LM3875 although I found some at the store near Eleshop they're selling it almost twice the price I got my first pair. I got me a pair of SK18752 in Raon from NS also which is rumored to be the one used for the Gaincard. When I got home I fired it up but it sounds really bad--almost like the ones used for portable radios. I'll definitely use LM3875 although I still have a pair of 1875s which I haven't tried. I'm quite curious however about the SK3875. Its a 5 pin chip like the 1875 and sells for P400 each at Newport. A lot of guys at the DIYaudio.com have been looking to try this chip.

Oh Joan2, sorry for misleading info about TDA7294. But its true its available locally although I don't know where in Raon. I do know the local store here in Cavite has them because I've inspected them myself and they're selling it for a little over P200. Farnell is selling these at P716 each.

Thanks for the tip Joan2 on eleshop although I didn't buy any caps there. I was able to buy from them two huge heatsinks. They also have knock down casing suitable for gainclone but made of thin aluminum. The smallest one sells for P350.

joan2 · « **Reply #86 on:** Oct 03, 2003 at 02:28 PM »

garp,
no problem....from the web the tda7294 is not as good as the lm3875, that is why most diy'ers choose the ns chip over the sgs one, the tda afaik has mosfet ouput devices while lm3875 have npn bjt's in a quasi-complimentary mode....

guys,
i must emphasize you all that while the amp is live, do not touch anything!!!, if you must do something, turn off the power and give 5 secs or so for the caps to fully discharge....this way we can minimize loss of the chip...

moonshow · « **Reply #87 on:** Oct 03, 2003 at 07:17 PM »

grap, where did you buy your insulation pads?the pads i used was mica and not really for ic chips.

i also noticed the heating of the heatsink after every tweak i did. the only time it normalized was when i perfected the grounding of the cicuit. btw. how big are your heatsinks? and what chips are you using? thanks

ramble_on · « **Reply #88 on:** Oct 04, 2003 at 09:06 AM »

are insulation pads the same as the ones they have at radio shack? i passed by radio shack in ali mall the other day and they have thermal pads. are they the same?

also, i was looking at scrap stuff we had at the office and i came upon some unserviceable motherboards (not the pc type). they had chips much like the 3875s and there were these small stamp-sized grey things (rubbery cloth-like) which were in between the chips and the heatsinks. i was wondering if these were the same insulation pads mentioned.

btw, congrats to moonshow on your first successful outing.

joan2 · « **Reply #89 on:** Oct 04, 2003 at 12:30 PM »

if you are reffering to the grey colored insulation pads, they work the same as a mica insulator, except that you do not have to use silicon grease, therefore easier to use...btw, when using mica insulators, just smear a thin film of grease just enough to make it opaque, otherwise too much grease is also no good....keep it coming guys!!! there's more lined up....