Hi there. I'd like to piece together a 5 channel gainclone (perhaps based on the LM3875 Dual Mono Classic Kit from audiosector. I've looked at the guide posted on this forum and this is the list of parts I think I would need to order. I'm looking for input on what to get and help getting it all ordered and put together 
.
To get a 5 channel amp:
- Power cable http://www.parts-express.com/pe/showdetl.cfm?Partnumber=110-442
- Fuse + fuse holder (4A ?)
- Rocker switch http://www.parts-express.com/pe/showdetl.cfm?Partnumber=060-410
- Transformer http://www.parts-express.com/pe/showdetl.cfm?Partnumber=122-655
- Full wave bridge rectifier http://www.parts-express.com/pe/showdetl.cfm?Partnumber=050-060 is this one 'full wave' ?
- Reservoir caps http://www.parts-express.com/pe/pshowdetl.cfm?PartNumber=027-244 Not really sure on these ones.
- 3 LM3875 kits http://www.audiosector.com/lm3875.shtml
Any help would be greatly appreciated. Thanks.
. To get a 5 channel amp:
- Power cable http://www.parts-express.com/pe/showdetl.cfm?Partnumber=110-442
- Fuse + fuse holder (4A ?)
- Rocker switch http://www.parts-express.com/pe/showdetl.cfm?Partnumber=060-410
- Transformer http://www.parts-express.com/pe/showdetl.cfm?Partnumber=122-655
- Full wave bridge rectifier http://www.parts-express.com/pe/showdetl.cfm?Partnumber=050-060 is this one 'full wave' ?
- Reservoir caps http://www.parts-express.com/pe/pshowdetl.cfm?PartNumber=027-244 Not really sure on these ones.
- 3 LM3875 kits http://www.audiosector.com/lm3875.shtml
Any help would be greatly appreciated. Thanks.
This is http://www.audiosector.com/lm3875.shtml parts, for 2 channels.
Now, there are a number of other (more cheap) components you could buy
if wanting to build 5 x LM3875 amplifiers.
------------------------------------------
For example the 1500uF/50V supply caps.
you could use 2200uF or 1000uF caps, (as 1500uF value is not found everywhere)
Say this one would do fine:
An externally hosted image should be here but it was not working when we last tested it.
2200uF 50V Radial Mini Electrolytic Capacitor
There is no real need to use those fat recovery MUR860 rectifier diodes.
Ordinary silicon diodes OR bridge rectifier rated 6-8 Ampere would do well.
DigiKey USA has got many more components for a low price to select from.
http://www.digikey.com/
For example MR752-BP is one standard 6 Ampere, 200 Volt rectifier diode.
MR752-BP - digikey
You get >10 units for $1.225 a piece
------------
EDIT: .... but as the MU860 diodes are cheaper!!!
you may want to order here:
MUR860 - 8 Ampere diodes
$1.000 a piece, if you buy more than 10 of those.
Regards
The caps probably aren't worth skimping on. They're not a huge cost, and they do affect the sound. Resistors probably less so. Honestly, the easiest way is to just buy the inexpensive kit(s) from Peter Daniel or BrianGT.
If you're doing a 5-channel home theater amp, the LM3886 will probably be a significant improvement. They provide a lot more current, so they will handle the lower impedances that are typical of HT speakers. Plus, you tend to drive HT speakers a lot harder (read: louder) than music speakers, so they'll better cope with that as well.
Good luck! I still haven't had time to finish up my LM3886 and LM4780 HT amps
If you're doing a 5-channel home theater amp, the LM3886 will probably be a significant improvement. They provide a lot more current, so they will handle the lower impedances that are typical of HT speakers. Plus, you tend to drive HT speakers a lot harder (read: louder) than music speakers, so they'll better cope with that as well.
Good luck! I still haven't had time to finish up my LM3886 and LM4780 HT amps
Also, the caps that you linked to from Parts Express would probably be great coupling caps, though you can go down to 4.7uF instead of 10uF.
You might want to take a look at Antek Transformers here:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=370122753005
(This is a 300VA transformer, but they usually have 25+25 500VA transformers available, and they're cheaper than PE).
You might want to take a look at Antek Transformers here:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=370122753005
(This is a 300VA transformer, but they usually have 25+25 500VA transformers available, and they're cheaper than PE).
lineup said:Ordinary silicon diodes OR bridge rectifier rated 6-8 Ampere would do well.
DigiKey USA has got many more components for a low price to select from.
http://www.digikey.com/
For example MR752-BP is one standard 6 Ampere, 200 Volt rectifier diode.
MR752-BP - digikey
You get >10 units for $1.225 a piece
------------
EDIT: .... but as the MU860 diodes are cheaper!!!
you may want to order here:
MUR860 - 8 Ampere diodes
$1.000 a piece, if you buy more than 10 of those.
At those prices you can buy a complete 8 A bridge rectifier for the price of a single MUR860 diode.
Or, if you want something more robust, spend the money for two diodes on this.
pacificblue said:
Hi PacificBlue! I really like your ideas.
I enjoy the sturdy standard rectifiers that can be used along with 4 tiny value caps (per each rectifier unit) when I'm after a bit cleaner DC and/or less interference for my radio.
I think that I would use the bridge rectifier unit for a chip amp style amplifier -or- the MR/MUR specialty diodes for a gainclone style amplifier.
For some reason that I can't find documented, owners of gainclones tend to favor the MUR and other specialty diodes. Why is this?
pacificblue said:
Good option, pacificblue
There will be, in my opinion, no difference in performance.
But using one Bridge Rectifier (including 4 diodes in one package) instead of separate diodes
is much more simple in practical terms.
Just drill one hole.
And fasten your Bridge.
Solder the wires to terminals.
danielwritesbac said:
The name reveals it. The Gainclone is a clone of Lab47's Gaincard and that uses MUR860. Gaincloners derive from that fact that they must have been chosen for sonic reasons.
The real reason however is probably that you can skip the snubbers on the rectifier, if you use fast-recovery diodes. Standard diodes with snubbers generate about the same amount of noise as fast-recovery diodes without snubbers. While there may be little to no difference from a sonic point of view, Lab47 as a commercial manufacturer has to comply with certain standards on interference. And while a bridge rectifier may be easier to use for a gaincloner, using snubbers on it will be so much more expensive for a commercial manufacturer that the people at Lab47 may have found the MUR860 solution more economic.
Hmm, 5 channels. This is a surround sound amp?
Well that's like. . .
One audiosector stereo amp exactly to spec for the two main speakers.
One stereo buffer + adder circuit (or inverted duophonic interpolator) with one LM3875 chip and rolled off bass to spec for center channel. The output of the little buffer + adder would also normally operate a sub woofer with a LM4780 and rolled off treble. They work as matched pair, somewhat like an active crossover, except easier. Its a very small input filter cap for the center channel. Its a cap over the nfb of an op amp (makes only bass) for feeding the sub amp.
The rear channels can be either mono or stereo, but its like a stereo or quad buffer plus princeton delay chip(s) (or really any sort of delay or reverb) plus LM3875 chip(s) and slightly rolled off bass. If I remember correctly, this (these) channels use the right+ and left+ into the LM3875's + and - inputs in a way that is similar to a bridged amp. But, the point is different in that the amplification and therefore the output is mostly differences between the left and right. For stereo rear channels, its the process of adding left+differences for the left channel and right+differences for the right channel. That takes the quad op amp chip in the buffer/pre role.
And, presto! There's 5.1 surround sound that also works for music.
Plan "B" follows. . .
But, there's a much easier way:
Drive the main two channels with a hifi amp's clean signal.
Drive the rest with a mass market theater noise amp.
Drive both amplifiers from a single preamplifier (unified volume control and unified source selection).
As Linkwitz found out http://www.linkwitzlab.com/surround_system.htm
the method is fast and generally satisfying, but it doesn't buy you a clean center channel. I think this is due to the mass market amplifier having a simple adder (makes grotesque muffled mono sound) rather than inverted duophonic (makes the clear mono sound of a 50's era hifi). There's quite the difference there. So, you may be omitting the center channel with this easier method.
A look at his speakers tells me that there's not much need for a center channel speaker, and this is because they are the "wideband style" which has a full-range/wideband speaker covering the majority of the audio frequencies with great cohesion of information, while a woof and tweet add bass and treble for "room accommodation" (actually its for personal taste when I do it). And since the imaging with this class of speaker is already pinpoint accurate, then a center channel is unnecessary anyway.
EDIT: Single preamplifier? Sure. But perhaps it should be a quad op amp in order to insure isolated output. The hifi on the front two channels gets its own signal. The theatre noise amp gets its own signal. The point for a "Y" type connection is the input of the quad op amp. Its just a thought.
EDIT2: The setups mentioned above all do work for music, owing this feature to the hifi amp on the main two channels. So, if one isn't too busy watching television, then its possible to also use the same room for quality music.
Well that's like. . .
One audiosector stereo amp exactly to spec for the two main speakers.
One stereo buffer + adder circuit (or inverted duophonic interpolator) with one LM3875 chip and rolled off bass to spec for center channel. The output of the little buffer + adder would also normally operate a sub woofer with a LM4780 and rolled off treble. They work as matched pair, somewhat like an active crossover, except easier. Its a very small input filter cap for the center channel. Its a cap over the nfb of an op amp (makes only bass) for feeding the sub amp.
The rear channels can be either mono or stereo, but its like a stereo or quad buffer plus princeton delay chip(s) (or really any sort of delay or reverb) plus LM3875 chip(s) and slightly rolled off bass. If I remember correctly, this (these) channels use the right+ and left+ into the LM3875's + and - inputs in a way that is similar to a bridged amp. But, the point is different in that the amplification and therefore the output is mostly differences between the left and right. For stereo rear channels, its the process of adding left+differences for the left channel and right+differences for the right channel. That takes the quad op amp chip in the buffer/pre role.
And, presto! There's 5.1 surround sound that also works for music.
Plan "B" follows. . .
But, there's a much easier way:
Drive the main two channels with a hifi amp's clean signal.
Drive the rest with a mass market theater noise amp.
Drive both amplifiers from a single preamplifier (unified volume control and unified source selection).
As Linkwitz found out http://www.linkwitzlab.com/surround_system.htm
the method is fast and generally satisfying, but it doesn't buy you a clean center channel. I think this is due to the mass market amplifier having a simple adder (makes grotesque muffled mono sound) rather than inverted duophonic (makes the clear mono sound of a 50's era hifi). There's quite the difference there. So, you may be omitting the center channel with this easier method.
A look at his speakers tells me that there's not much need for a center channel speaker, and this is because they are the "wideband style" which has a full-range/wideband speaker covering the majority of the audio frequencies with great cohesion of information, while a woof and tweet add bass and treble for "room accommodation" (actually its for personal taste when I do it). And since the imaging with this class of speaker is already pinpoint accurate, then a center channel is unnecessary anyway.
EDIT: Single preamplifier? Sure. But perhaps it should be a quad op amp in order to insure isolated output. The hifi on the front two channels gets its own signal. The theatre noise amp gets its own signal. The point for a "Y" type connection is the input of the quad op amp. Its just a thought.
EDIT2: The setups mentioned above all do work for music, owing this feature to the hifi amp on the main two channels. So, if one isn't too busy watching television, then its possible to also use the same room for quality music.
If I get this PSU kit - http://www.chipamp.com/supply.shtml - with an appropriately sized transformer, would I be able to run 5-7 amp kits off of it? Or is it impossible to wire it in such a manner? Can you only run one or two kits off of a PSU kit?
There is nothing mentioned about max Current output.
Or any other specification of ratings.
It is simply intended to supply max 1-2 Channels. I think.
Main factor for how much a supply can do:
1. Transformer rating.
Bigger transformer (VA-rating) at same voltage (VAC) = More current out.
2. Rectifier diodes (or Bridge) rating. Current out.
3. Those 2 Big filter capacitors.
More capacitance = better filtering for higher currents.
More filtering gives cleaner supply. Less ripple.
Or any other specification of ratings.
It is simply intended to supply max 1-2 Channels. I think.
Main factor for how much a supply can do:
1. Transformer rating.
Bigger transformer (VA-rating) at same voltage (VAC) = More current out.
2. Rectifier diodes (or Bridge) rating. Current out.
3. Those 2 Big filter capacitors.
More capacitance = better filtering for higher currents.
More filtering gives cleaner supply. Less ripple.
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