| Lars Clausen |
What is the history of the GainClone?
Who 'invented' it, who invented the name, who is selling parts and PCB's for it?
Is any amplifier with a LM3875 chip to be called a Gain Clone? Or is there an official recipee?
What is considered to be it's prime qualities apart from low price? |
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| Pedja |
| quote: | Originally posted by Lars Clausen
...who is selling parts and PCB's for it? |
Are you interested exclusively to buy all the parts at one place?
| quote: | | What is considered to be it's prime qualities apart from low price? |
You shouldn't be an expert to build it.
Pedja |
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| uvodee |
and you have at least 8 options to build this thingy
I have right now a design for a non inverted, inverted, semi ultimate, pen ultimate, ultimate, a 3875, a 1875, a 3876 etc etc and then I have variation on each theme. ?????? with coupling caps, without, with carbon film resistors, with metal... , if you look at it, it is so incredibly confusing that one could give up before even getting the parts.
I kept with one design, and did not change anything after having ordered parts.
J-P |
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| Lars Clausen |
Thanks Peter.
What would be the estimated cost for a DIY'er to build a GC?
I understand that PCB's are not usual for the GC.... |
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| Peter Daniel |
I've been constantly playing with those amps for almost a year. While my first amp had about 65% of performance capability, I think I won't be far from truth if I say that the current design provides at least 85% of performance. Just yesterday I tested it against a custom built Aleph 2 and I can say it's a fair match (in some areas actually superior to class A amp)
Although the amp seems to be simple (only 7 parts involved in my setup) it is not that easy to make a top performer out of it.
We are attending this years CES in Vegas (although US custom restrictions prevent me from being there) |
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| Pedja |
| quote: | Originally posted by Lars Clausen
What would be the estimated cost for a DIY'er to build a GC? |
(oh my gosh) Jocko, are you here?
Pedja |
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| Peter Daniel |
| quote: | Originally posted by Pedja
(oh my gosh) Jocko, are you here?
Pedja |
I don't remeber Jocko's being ever excited about Gainclones.
I've been seeing the name 'GainClone' for a year on a forum, before deciding to investigate the matter more seriously. |
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| Peter Daniel |
I don't really care for his intentions here. He might know or might not. It's not for me to judge.
But I remember Phred mentioning once that he puts GC on a very short least of the best amplifiers he ever heard;) |
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| theChris |
well, to answer lars, gainclones is just a word now. there are trends in them. some people try many different variations because the parts are cheap enough and few enough, well, in general.
there are non-inverted and inverted gainclones, there are battery powered ones popular now. there are are "bridge-clones" which are used for subwoofers.
in any-case for PCB, there are few as most people will do a point-to-point wireing on the chip. the new 4780 and 4766 (i think) are 27 pins and are more difficult to p2p, though not impossible. |
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| Lars Clausen |
My intent of starting this thread is:
It could be fun to take this discipline of DIY audio even further. I mean:
Construction of Ultra Low Cost Amplifiers.
It shouldn't be too hard to construct something even cheaper and better than Gainclone .. I have been calculating last night, an amplifier with similar specs like the Gainclone (or better) can be built for around 10$ all parts and a nice PCB included.
Maybe less.......?
Could be fun.
Another example of Ultra Low Cost Amplifiers would be this Romanian built amplifier - yes based on old technology, but i am sure it works fine, and will be on level with other low cost solutions like the GC. And wait till you hear the price.
Take a look:
http://www.elmatrd.ro/amplificatoare.html
The 1 x 100 W RMS module cost 290.000 Romanian Lei that is equal to: ~ 9 US$ (Ready assembled and tested module).
How fun would it be to tweak a low cost module like this? |
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| peranders |
| quote: | Originally posted by Lars Clausen
My intent of starting this thread is:
It could be fun to take this discipline of DIY audio even further. I mean:
Construction of Ultra Low Cost Amplifiers.
It shouldn't be too hard to construct something even cheaper and better than Gainclone .. I have been calculating last night, an amplifier with similar specs like the Gainclone (or better) can be built for around 10$ all parts and a nice PCB included.
Maybe less.......?
Could be fun. |
You could also take a lot of money for it like Sakura Systems....
What do I get for 10 USD, heatsinks, PSU etc? A pcb + LM3886 + plus a few parts don't cost much. I guess you can get a pcb for 1 (not more than 2) USD even a double sided with plated through holes? |
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| Lars Clausen |
I see no reason to use a LM3886 for a project like that.
A discrete solution would be much better. And can be made at the same price. And is more fun to make. And has many more tweaking options than a chip amp.
For example: Try other output transistors in a LM3886 amplifier .. :cool:
The PCB's i have seen in here all cost 5$ plus shipping, and are mostly single sided low cost boards.
I would suggest a nice Dual Sided board (like the ones you make Per Anders).
A simple 10$ amp (parts and PCB) can be made to accept supply voltages up to +/- 80V Almost twice that of LM3886. Also 10-15 Ampere output current is possible, almost 5 times that of LM3886, so outputs of:
50 W in 8 Ohms and
100 W in 4 Ohms
is possible without stacking chips.
I would use IRF540 / IRF9540, a set of drivers, about 10 SMD mounted transistors, and some fair quality caps. All can be easily tweaked and scaled (unlike LM3886 solutions). Replace the output devices with ones that cost a couple of Dollars more (IRFP140 / IRFP9140) and you have 100 W in 8 Ohms / 200 W in 4 Ohms. Or with IRFP240 / IRFP9240 you can even make something like 200W in 8 Ohms. Still around 12$ price tag.
Who knows maybe it can be made even cheaper than my suggestion?? |
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| peranders |
Lars, it's not very complicated to make a good MOSFET amp with few parts. Maybe you shall start a project called ClausenClone :D
It's a good thing because there aren't that many good high quality power amp projects with good pcb's. As you know I'm also into SMD at the moment. It would have been very fun with a cute little driver board.
I have talked to Fred and he feels that you should go for 0604 parts or smaller.... :no:
BTW: have you checked the swedish project XTF at www.hififorum.nu All SMD with error correction(!), very interesting so far, not a minimalistic design though. It's a monster in fact :nod:
http://www.hififorum.nu/forum/topic...earchTerms=,xtf
http://www.faktiskt.se/modules.php?...viewtopic&t=566 |
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| ronc |
I once built a SE class A mosfet amp for about the cost of the GC, but IMHO didnt sound near as good as the GC.Also had to use the biggest H/S i had in my parts box.
ron |
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| Peter Daniel |
| quote: | Originally posted by Lars Clausen
A discrete solution would be much better. |
I very much doubt it.
Coming back to your initial question (as I didn't know what you really meant), the cost of building GC is about $10 per channel;) |
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| Lars Clausen |
Thanks for this info, Peter.
I guess i will have to prove my point :) |
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| peranders |
The advantage of LM3875, 3886 is the simplicity and all protection schemes. I think this is the main advantage.
Eventually I will make pcb's but so far I haven't heard a LM3886 live yet but I have no doubts that it's quite good. Technically it's also interesting because I believe it's the best monolithic non-class D power amp around. Apex is possibly better. |
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| zygibajt |
| quote: | | The biggest cost is transformer, but even using exotic components the total cost shouldn't exceed $150 (not including chassis |
Peter how much does the Piltron transformer cost?
Let's say 400AV ,2*20V.
And where can they be bought (via internet)?
Bartek |
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| Peter Daniel |
A transformer like that cost $89,59 CAD (plus 15% taxes if bought locally). Shipping weight is 4kG. The lead time is probably 4 weeks. http://www.plitron.com/
There was a recent price increase, as I remember those were sold at around $ 70 previously. |
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| Morse |
Hi Peter;
>>>A transformer like that cost $89,59 CAD (plus 15% taxes if bought locally). Shipping weight is 4kG. The lead time is probably 4 weeks.<<<
How about the Avel Lindberg trafos? I see that Parts Express in the US has a 36vct, 250VA rated job for $42.26USD that's available without delay. Are the Plitrons really that much better (not stating an opinion, since I don't have one!), or could one "get away with" the Avel Lindberg toroidals?
Thanks in advance!
All the best,
Morse |
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| Peter Daniel |
I was buying 250VA transformers from Apex Jr for $25. They were pretty good and initially I thought they were even better than Plitron, but more tests shows 400VA Plitron was preffered.
I don't think Avel Lindberg would be a bad choice, it will work perfectly well in a GC. It's only if you want to gain tha last few percent of performance, you should become fussy about transformer chouces. I'm almost sure that 400VA vs 250VA toroid would be better.
I would assume that 400VA Lindberg converted to Canadian funds wouldn't much different regarding the price (comparing to Plitron). And then you add higher shipping cost when dealing with States vs local Canadian.
I would also assume that good quality R-core would be even better than toroid. |
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| Morse |
Thanks Peter;
Good point about currency conversion and shipping - 'course if the USD keeps dropping, you guys north of the border may be buying cheap US goods soon! :)
BTW, my TDA2030's and LM4766's have all shown up, so it's just a question of finding enough 'quality time' in my workshop to wire up a little chipamp.
Do you think that a 4"x6" sheet of 1/8" thick aluminium will suffice as a heatsink for a (approx) 12wpc chipamp? I'll need to use a mica spacer with these, so that will cut into heat transfer. My current plan is to use the top plate of the chassis to mount everything (so it's going to hang upside down in there) and use it as a heat sink. Then the bottom plate can just be some thin alloy sheet stock I have laying around. Good or bad idea?
Thanks in advance!
All the best, |
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| Peter Daniel |
| I would say it should be enough. The amps usually run only slightly warm and only when you really push them they can become hot (but this also in a case when 40W pc is expected). |
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| ronc |
Good to see you trying a chip amp
Morse.If done right you wont be displeased.More like startled.
ron |
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| Morse |
Thanks Peter!
Sounds like it's a 'go' on my current chassis design....
BTW, IIRC I can freely use a 115VAC 60cps rated PS trafo for 100VAC 60cps, right? In which case I can expect a reduction in Vout from the thing, but so long as I stay above +/-10VDC on the rails the 4766 should be happy. I'd like it to work on either power standard, so if need be I could wire in a 6.3VAC trafo and use it as an autoformer with a DPDT switch to select between the two configurations.
Or is any of that wrong? Thanks in advance!
Hi Ron; you wouldn't happen to be "Ron" at the Fullrange Forum, would you? Anyway, yep, I'm looking forward to getting something up off the ground (pun intentional) - it's been too long since my last new amp was finished and I'm going through "DIY amp withdrawl"! ;)
Thanks again!
All the best,
Morse |
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| ronc |
Yea the same ron here, OK i confess,LOL.
ron |
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| Morse |
Hi Ron;
Good to see you here too! :)
All the best,
Morse |
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| PRR |
> Do you think that a 4"x6" sheet of 1/8" thick aluminium will suffice as a heatsink for a (approx) 12wpc chipamp?
VERY ROUGH rules of thumb:
A surface runs about 100°C per watt per square inch.
So 4"x6" with both sides exposed is about 100/(2*4*6)= 2°C per watt.
A class B amp at full sine power dissipates about half its output power (and much less with unclipped speech/music signals).
Two 12W amps is 2*(12/2)= about 12 watts. I would round-up since chip-amps sometimes have 4-7 volt losses, so working at lower voltage they are not near theoretical efficiency. 20 watts dissipation is surely conservative.
20W*(2°C/W)= 40°C temperature rise. Is that OK?
The old habit for glass-seal transistors in commercial class B music service was to keep temperature rise down to 50°C rise, because the constant hot/warm/hot/warm cycling with the musical beat would fatigue the seals even though the continuous-duty rating was 100°C or so. Seals are better now, and the epoxy seals seem to beat the old glass-seal TO-3, and you are probably not going to abuse your amp as hard as a commercial sound system. 40° rise is quite safe. (And the National chips have a thermal-cutout to control temperature cycling, and IIRC it is set much higher than 50°C. I'm sure they thought about this and tested their seals, so my old 50°C rule is old-dog trivia.)
If the heat has to flow a long distance, it needs a fat conductor. The thickness to length ratio of heatsinks should be held to 1:10 or maybe 1:20. 1:10 is nice for parallel-flow as in fins; 1:20 is OK with radial-flow as for a small chip in the middle of a large area. With 0.125" plate, you would like the longest heat-path to be 20*0.125= 2.5".
Optimal chip location and heat-flow distance: To a rough approximation, you locate two chips as-if you had sawn the plate in half and centered each chip on its plate. So draw a line down the center of the 6" dimension (2" from each long edge), then divide it in quarters. Put a chip at the 1/4 and 3/4 mark, or 1.5" from each short edge. Each chip is then 2" from a long edge and 1.5" from a short edge, and 3" from a corner. We see that the corners are less effective because they are more than 20*0.125=2.5" from the chip, but not much more, and a lot of area is inside the 1:20 thickness/length rule of thumb, which is only a crude guide to begin with. (And if other layout factors suggest off-centered location, it will still be pretty good.)
I think you could get away with half this area. But if you have the plate and it fits your box, use it. It is always better to over-cool than under-cool. |
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| fmak |
[QUOTE]Originally posted by peranders
[B]The advantage of LM3875, 3886 is the simplicity and all protection schemes. I think this is the main advantage.
Eventually I will make pcb's but so far I haven't heard a LM3886 live yet but I have no doubts that it's quite good.
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I have just built the LM3875 with dual 22 V dc supply. Clips at about 11V into 8 ohms and rings on a sqaure wave into resistive load. Distortion at 4V is only about -63 dB thd+N. I will make the other channel and listen.
What I don't like is dc shift with ramp change in input signal level, about 60mV on a digital meter with quite slow response. This evenyually settles to about 5mV. |
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| Morse |
Thank you very much PRR!!
That is a lot of REALLY useful info - just what I was looking for, in fact!
To maximise cooling along the length of the heat sink, I could mount a separate sheet of .125" stock underneath (frankly I've got enough plate stock left to double 'em up to .25" for the whole top deck, if that's desireable...).
Do you think there'd be a problem with using a mica spacer between the chip and the heat sink (i.e. will it change the numbers on heat transfer significantly)? I was planning on using some Radio Shack heat sink compound.
Thanks again! Your help is greatly appreciated!
All the best,
Morse |
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