Author Topic: gainclones diy anyone? (Read 381629 times)

john5479 · « **Reply #30 on:** Aug 27, 2003 at 02:03 AM »

ramble_on pm me naman where you got the mur860s or if you have some spare ones you can sell..thanks

Garp · « **Reply #31 on:** Aug 27, 2003 at 07:10 AM »

Quote from: ramble_on 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...

Hey may I know how to get samples? Do you just go to National Semicon site? Guess will just try it. Now the you have the chips maybe you can try prototyping one using the cheapest available capactors. I did with mine yesterday just to see if I could make it work, using P20 caps, P1 resistors, and a P170 3 amp transformer 12-0-12, and P10 4amp rectifiers available at my local shop. I put the whole thing in an Amazon box. It works alright and no hum.

john5479 · « **Reply #32 on:** Aug 27, 2003 at 08:35 AM »

Quote from: Garp on Aug 27, 2003 at 07:10 AM

Hey may I know how to get samples? Do you just go to National Semicon site? Guess will just try it. Now the you have the chips maybe you can try prototyping one using the cheapest available capactors. I did with mine yesterday just to see if I could make it work, using P20 caps, P1 resistors, and a P170 3 amp transformer 12-0-12, and P10 4amp rectifiers available at my local shop. I put the whole thing in an Amazon box. It works alright and no hum.

tried it out with speakers already? comments on sound quality?

ramble_on · « **Reply #33 on:** Aug 27, 2003 at 12:31 PM »

sory for the late reply. @ garp and john, sent you both pms

ramble_on · « **Reply #34 on:** Aug 27, 2003 at 01:34 PM »

garp, was your transfo (12v-0-12v, 3a) able to power the lm3875t without difficulty? how did it sound? thanks.

john5479 · « **Reply #35 on:** Aug 27, 2003 at 05:15 PM »

thanks for the link ramble_on will try my luck there

hope the three of us working on these projects will be able to post up some pics of these amps here

Garp · « **Reply #36 on:** Aug 28, 2003 at 07:24 AM »

Quote from: john5479 on Aug 27, 2003 at 08:35 AM

tried it out with speakers already? comments on sound quality?

My first impression was that sound was clean and clear with no hum even from a one meter distance--that's really good considering my ground bus is only a 22awg magnet wire from RShack. I immediately noticed the bass which seemed more prominent here than using my Onkyo receiver. I can't yet make a more detailed comparison because the transformer melted after an hour of play and I used a very old pair of sony speakers (dunno impedance and sensitivity). The chips though and the heatsink were not even warm to the touch.

I initially tried using a 1 amp 12-0-12 but this one can't even cope with moderate listening levels.

Garp · « **Reply #37 on:** Aug 28, 2003 at 07:27 AM »

Quote from: john5479 on Aug 27, 2003 at 05:15 PM

thanks for the link ramble_on will try my luck there hope the three of us working on these projects will be able to post up some pics of these amps here

Will do that. My workmanship though will be screaming newbie! to anyone who will have the unfortunate chance of viewing it.

john5479 · « **Reply #38 on:** Aug 28, 2003 at 08:28 AM »

Quote from: Garp on Aug 28, 2003 at 07:24 AM

My first impression was that sound was clean and clear with no hum even from a one meter distance--that's really good considering my ground bus is only a 22awg magnet wire from RShack. I immediately noticed the bass which seemed more prominent here than using my Onkyo receiver. I can't yet make a more detailed comparison because the transformer melted after an hour of play and I used a very old pair of sony speakers (dunno impedance and sensitivity). The chips though and the heatsink were not even warm to the touch.

I initially tried using a 1 amp 12-0-12 but this one can't even cope with moderate listening levels.

well its consistent to what the builders say about gainclones..clean clear and has bass...might want to try a heftier power supply then.

ramble_on · « **Reply #39 on:** Aug 28, 2003 at 01:22 PM »

@garp, pics pics pics

Garp · « **Reply #40 on:** Aug 28, 2003 at 02:49 PM »

I actually took pics already but don't know where to upload--if you want I can send thru your email? I'm a little shy about showing it (not showing it off) because its got the words "newbie" and "amateur" written all over it

---I've seen the insides of Rene's 300B and the workmanship just makes me want to weep.

I bought another 3 amp 12-0-12 transformer (Star Vox brand for P215) this morning and within 2 minutes of connecting it to my system I can smell plastic burning, so I figured there must be something wrong with my connection, maybe a short somewhere so I simplified things: I disconnected the other bridge and decided to use only a single bridge this time and rewired the thing. Maybe a faulty diode is causing it. This cured it and the transformer just goes warm not hot. I tested the amp again---I get 15+ and 15- DC on the rails this time and 0.5 millivolt dc offset.

I finally connected it to my Missions and listened...whoohoo!!!! I just could not believe that something costing not more than P1,500 (P800+ for the chips) can sound as good as this! Maybe I'm biased but the amp really blows away my Onkyo TXSR500 (ok fine maybe I'm coming from a low standard, mid-fi you might say) at least on two counts: clarity and bass. The bass is more defined and I can hear things I never heard with my Onkyo bass-wise--and I'm using only 1000 uf per rail (I'll be using 2,200 per rail in the real version). I played the Chicago soundtrack and the low end oomph is just amazing. The thing that struck me also within a few seconds of play is the soundstage---the speakers sound bigger. I simply can hear more if the instruments.

The amp can sound really loud but at almost max volume and without any signal you would here a nasty hum. At my preferred however listening levels however I don't hear hum even without a signal. There is however a lot of room for improvement as I'm using only a 22awg ground bus connecting my signal star ground and power star ground. In fact everthing in the amp--signal and power wires--are just 22awg magnet wires from Rshack. I just used "sphagetti tubes" to isolate the wires. The limitation on the power supply however showed when I played a Ray Brown CD: at very loud listening levels enough to for our glass windows to vibrate, the clipping becomes audible. Sometimes you can hear soft ticks at loud listening levels.

Here's what I used for my ultracheap prototype:

ST or SV 1000 uf 50 V filter cap (P20 each, P80 total)
4.7uf Y.c. bipolar (P15 each, P30 total)
resistors 10K, 18K, 22K, 220K (P1 each, P8 total)
4amp 600v ST diodes (P10 each, P40 total)
3 amp 12-0-12 trafo (P215)
Radioshack magnet wire (P130+ a pack)
Binding posts (P30 pair, P60 total)
RCA sockets (P30 pair)
IEC outlet (P59 at Rshack)
terminal block (P20 each, P40 total)
Perfboard (P80 at Rshack)
Fuse 2A slo blow (P30 a pack I think)

joan2 · « **Reply #41 on:** Aug 28, 2003 at 04:00 PM »

glad to be back,
congrats to you on your gainclone sortie, i also got my samples of 5pcs lm3875 and lm4701....i have given my deisgn for power traffos to podmoon in legarda, you can ask nelia about them, sizes available are 150va, 250va, 350va and 650va...
as for my own gainclone, this is how i plan to proceed,
1. 4pcs lm3875 to be wired paralled/bridged mode to give me 200 watts into 8 ohms and about 300 watts into 4ohms, this will drive a sub-woofer in mon,then,
2. 4pcs lm4701 to be wired in parallel to geive me 60 watts into 8 ohms with two channel,
3. a built in electronic crossover network with crossover frequency of 120hz.
will use this setup for my pc sound system to replace my altec lansing acs33 system... i'll be using the 650 va, power traffo, 16pcs mur860 rectifiers, filter banks consisting of 22,000ufd/63v nichicon filter caps for the subwoofer, 4700ufd/50v for the satellite amps...

ramble_on · « **Reply #42 on:** Aug 28, 2003 at 08:34 PM »

@garp, sent you pm. thanks...

joan2 · « **Reply #43 on:** Sep 01, 2003 at 02:02 PM »

just talked to nelia of podmon, prices range from 300 to 900 bucks, the 650va is actually a 750va one, you can order any va rating you desire, from between 150 to 750va...using my basic design with a 50volts center-tapped secondary....or any addittional secondary windings you may need....

there's another good link at diyadio:
http://www.diyaudio.com/forums/showthread.php?s=e3f40dc1ef73cc521b4f24e068a7d690&threadid=19593&perpage=15&pagenumber=1
please check this out...it is very informative indeed...

Garp · « **Reply #44 on:** Sep 02, 2003 at 01:37 PM »

Hi Joan2,

Thanks for the great link above. I really like the chassis but my question is is: How important is keeping the signal path really short? The chassis in the link you provided looks really neat but I noted the very long signal path. I've seen the images of the PD Amp that was reviewed by Sixmoons and the signal path seems 3-4 inches only?

And oh, thanks for starting this topic.

joan2 · « **Reply #45 on:** Sep 02, 2003 at 05:01 PM »

reason for short signal path is to minimize stray coupling effects, ie less noise, sheilded wire can be used if the signal path can not be made very short...if you are reffering to the sselector, and volume control wires, you can use shaft extenders so that the signal path can be made shorter......i started this thread to give readers an alternative to tube amps...i am of the opinion that good sound need not be expensive...and i believe the the myth about tubes being superior to solid state is just that..a myth....

arnoldc · « **Reply #46 on:** Sep 02, 2003 at 05:32 PM »

Quote from: joan2 on Sep 02, 2003 at 05:01 PM

reason for short signal path is to minimize stray coupling effects, ie less noise, sheilded wire can be used if the signal path can not be made very short...if you are reffering to the sselector, and volume control wires, you can use shaft extenders so that the signal path can be made shorter......i started this thread to give readers an alternative to tube amps...i am of the opinion that good sound need not be expensive...and i believe the the myth about tubes being superior to solid state is just that..a myth....

first of all congratulations to those who made it. DIY is great and I'm a supporter of DIY whether solid state or tubes. I have made transistor-based and chip amps too.

joan2, you should get credit for supporting the people in this thread, kudos to you.

however, joan2, what you called a 'myth' are people's choices. if a person prefers tubes over solid state, do you call that a myth? if a person says solid state is better than tubes, will you call that a myth?

I'd like to hear you comment on this post:

Quote

I just could not believe that something costing not more than P1,500 (P800+ for the chips) can sound as good as this! Maybe I'm biased but the amp really blows away my Onkyo TXSR500

you see, i understand people being passionate, as i am as too. but i know how to respect other people's choices and opinions.

i hope your comment is just a slip of your fingers...

joan2 · « **Reply #47 on:** Sep 03, 2003 at 07:03 AM »

Quote

you see, i understand people being passionate, as i am as too. but i know how to respect other people's choices and opinions.

i am sorry to touch your sensibilities, but i am expressing my opinions too.....there was a time tube amps died from maintstream audio....now only monied poeple can afford tubes, here in the phils...i am just pointing out a cheaper alternative.....

arnoldc · « **Reply #48 on:** Sep 03, 2003 at 08:54 AM »

joan2, i think we're on the same boat as far as offering cheaper alternatives go, undoubtably.

i also share the same opinion as yours that good sound need not be expensive, as you stated.

i started the cheap tube projects at wiredstate, and it caught some serious attention i would say.

you also stated your belief, and a belief is not an opinion, so i called your attention. and no, you have not touched my "sensibilities" as what i'm merely pointing out is what is fair.

so going back to the project, you have some nice lineup ahead i can see.

i also wish i have the tools, materials and talent as that of peter daniel, he he he.

joan2 · « **Reply #49 on:** Sep 03, 2003 at 01:12 PM »

arnoldc,
let us build up on our common beliefs then.....
peter daniel has imagination, lots of tools, resources readily available to him....but talent, i believe we are not far behind....
anyway, a good machine shop with vertical milling, possibly cnc, box benders, guilotine shears, bench drill press, a small lathe machine and we are in bussiness...

GC · « **Reply #50 on:** Sep 03, 2003 at 04:22 PM »

Hello!

Is the LM4780 available here in manila? If not, i'll use the LM3886.

thanks!

joan2 · « **Reply #51 on:** Sep 03, 2003 at 04:46 PM »

you can try farnell, or rs components, but these ics can not be purchased in raon as of the moment,

GC · « **Reply #52 on:** Sep 03, 2003 at 06:04 PM »

Quote from: joan2 on Sep 03, 2003 at 04:46 PM

you can try farnell, or rs components, but these ics can not be purchased in raon as of the moment,

Thanks for informing me that these ICs are not available in raon at the moment.

I'm planning to use the gainclones for my HT setup. I don't have enough budget to buy myself a decent 5.1 or 6.1 channel amp/receiver so my alternative is to build myself a 3 channel amp for the center and surround channels.

What I need is something like between 60 and 200 watts per channel. If a single LM4780 (bridge) is cheaper than four LM3886s (BPA-200 circuit) per channel, then that's what i'll use...that's if its available here.

If not, i might as well use one LM3886 per channel. That'll be 60 watts per channel into 4 ohm load.

Its good to be back in this hobby again.

Suggestions are welcome.

joan2 · « **Reply #53 on:** Sep 04, 2003 at 07:14 AM »

afaik, LM4780 (bridge) is likewise unavailable here, the device is just two chips encapsulated into a single package, so construction wise it should be the same as the single chips such as lm3875 and lm4701...

ramble_on · « **Reply #54 on:** Sep 04, 2003 at 04:00 PM »

sir joan2, sent you pm. thanks.

john5479 · « **Reply #55 on:** Sep 05, 2003 at 11:09 AM »

got 16 pcs of mur860's thru onsemi's samples program, now I just need the trannies and off I go!

Garp · « **Reply #56 on:** Sep 05, 2003 at 11:22 AM »

Hi John5479,

How long did it take to get the mur860's. I had them ordered at onsemi last Thursday.

john5479 · « **Reply #57 on:** Sep 05, 2003 at 11:25 AM »

roughly a week..they came in a fedex box shipped from hong kong..but guess what? the diodes are assembled here in pinas ! now to use a torroid or not? hmmnnn

joan2 · « **Reply #58 on:** Sep 07, 2003 at 08:10 AM »

ramble_on
i did not get your pm, how then may i help you?

vintage_dog · « **Reply #59 on:** Sep 07, 2003 at 09:40 AM »

Quote from: joan2 on Sep 02, 2003 at 05:01 PM

...and i believe the the myth about tubes being superior to solid state is just that..a myth....

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