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-   -   Multi purpose multi channel gainclone PCB: Team project - group buy (http://www.diyaudio.com/forums/chip-amps/12641-multi-purpose-multi-channel-gainclone-pcb-team-project-group-buy.html)

rick57 19th March 2003 06:40 AM

Multi purpose multi channel gainclone PCB: Team project - group buy
 
Multi purpose multi channel gainclone PCB: Team project - group buy

Who’s interested in a flexible PCB design and group buy, useable for either:
- a cost and time effective active 3 way (or 4 way) power amp, or
- a home theatre power amp, with say two (or more) channels bridged to drive a single sub.
Even entry level eg Marantz integrated home theatre receivers have pre-outs on all channels. It wouldn’t take much of an amp to better most built in power amps (or get similar or a little better quality to many HT dedicated power amps, for fewer $ even than second hand).
IMO it’s not worth spending too much on HT power amps. Better to put the money into speakers or other things.


The opamp based stereo power amps – the commercial Gaincard and Monarchy Audio SM-70; Linkwitz’s simple diy design based on the National Semiconductor LM3886, the “Gainclone” and variations, etc:
Better than eg many Rotel etc amps, certainly the Rotel home theatre power amp.
The Monarchy has been rated by some better than Aragon!

Simple, cheap, not "SOTA” but very good, especially for the cost and ease of construction.
Big attractions are:
- Depending on design, components total only 9-12!
- Dependent on components, *total* cost of a gainclone 2 channel power amp, is around $US 40-60.

The other day at Madisound Doug posted about the 8 amps needed to drive the active 3 way Linkwitz Orion.
To drive this, the mid and tweet each get an amplifier, and each of the two woofers get a channel– an 8 channel amp.
Other DIYers are doing other active 3 ways (I’m considering the Linkwitz Phoenix, and my own active 3 way).

Doug’s suggestion was combining 8 channels of power amplifier based on the LM3886, with SL’s Orion filters with the eight 3886s all onto ONE board.
SL doesn't think there would be much demand for a specific unified board.

(I’m not an amp designer, and not (just yet) an amp builder).
Some opamps (including the LM3886) are bridgeable.

There are newer opamps (eg the TDA 7293) that sound better.

Although the trigger for my idea was a post on Madisound, diyAudio seems to be the place for this. Need to agree:

(A) Number of channels (maybe 10 is better) and how much flexibility about what is bridgeable, to make either:
1. Stereo 3 way with more grunt in the bass,
2. For the more ambitious, a stereo 4 way
3. Stereo 3 way with dual subs (much the same)
4. 5 channel with all channels bridgeable
5. 6 channel with double power to the L/ R/ C and sub.
6. Etc

(B) The chip & design
Exact design, the power supply, how many power supplies, etc.
Multiple power supplies, maybe 4? 5? would be good.

(C ) Who to do the group buy - mailout. I would be prepared to do this.
I’m in Australia, so freight would be a little higher (though weight will be low).
Aksa boards are locally made, so this should be competitive. And eg for our US participants, the USD is worth about $A 1.70!

Dependent in interest or opinion, it could be posted at the DIY section of AVS:
http://ww.avsforum.com/avs-vb/forumd...?s=&forumid=28
(would boost economies of scale)

As we sometimes say here, whatya reckon?

NB: I only get the chance to check the site 2-3 times a day.

Richard

deandob 19th March 2003 09:18 AM

Hi Rick,

Isn't the idea behind the gainclone to do p2p wiring rather than PCB?? Also everyone interested in this group buy would need to decide on what spec, chips, topology, parts etc. to use.

I have just received my LM3875 samples from NS (Thanks NS - I will be paying for more NS parts on another project) and keen to get my gainclone going.

I'm looking for a home theatre amp with the following specs:
- As high as possible 2 channel quality
- 3 x surround sound using similar but lower quality parts to keep the costs down.
- Based on the Peter Daniels tweaked up recipe.

A group buy on the components as well as the PCB would be useful. I am also based in Australia and having a tough time sourcing components like Riken resistors, Alps pots & Black Gate caps without paying ridiculous prices in US$$$$. There is a group buy on Black Gate on this site's WIKI but it seems to be dead.

rick57 19th March 2003 11:50 AM

p2p. Peter Daniels tweaked starting point
 
Although maybe_ all gainclones are p2p, I dont think this is critical to sound quality.
Anyone feel free to correct me.

It is sensitive to quality of components. Short distances are beneficial so circuit design should be done carefully.

I expect this project to take a while to get going. If youre in a hurry, component selection will realistically take a while, preceded by circuit design.

Peter Daniels tweaked recipe would be a good starting point. I hacvent followed recent gainclone threads. Do you have a quick or direct link


Richard

ThorstenL 19th March 2003 12:38 PM

Re: p2p. Peter Daniels tweaked starting point
 
Koinichiwa,

Quote:

Although maybe_ all gainclones are p2p, I dont think this is critical to sound quality.

Think again. Or even better, build one stereo Gainclone P2P and another on PCB. The results will surprise you quite a lot. In low level circuits it is even greater of a difference.

Plus, P2P allows a lot tigther layout.

Ask Jonathan Carr.

Sayonara

sonnya 19th March 2003 02:08 PM

Not Really.. Make use of some fine SMD resistor in 1206 house, Double sided board and you can place a circuit board on top of your output terminal's.

A benefit is no microphonic effect! :clown: Just my thoughts

Peter Daniel 19th March 2003 02:39 PM

With a carefull layout and attention to detail, PCB may produce satifying results as well. I'm in a process of building my commercial GCs, which are p2p, but it is really time consuming task and when I imagine countless orders coming in, I don't know how I would manage with a demand.;)

fedde 19th March 2003 03:39 PM

I never liked the idea of pcb for gainclones until recently. I realized that pcb's make it easier to connect both channels in the exactly the same way (length of connections) and ensure good connections. Also, the components can be mounted very rigid to the board. As long as the feedback resistor is soldered directly to the chip and the pcb is as SMALL as possible I do not see a problem. The original gaincard also uses a very small pcb and sounds great! :nod:

Though I wouldn't use pcb's larger than say 5x5 cm...

Fedde

vo_guy 20th March 2003 04:37 AM

The man's a freakin* genius!
The man's a freakin* maniac!
The man's a freakin* glutton for punishment!
Ah what the hell, I'll take 10 channels. Out of small seeds may come the patter of little Krell feet.

Nisbeth 20th March 2003 07:21 AM

This sounds like an interesting idea, Richard. Just wanted to remind you (and others) that Tim Harrison (trwh in here) has already done a small board for this range of IC's (link) which might be of interest.

/U.

rick57 21st March 2003 01:38 AM

integrated stereo amplifier
 
Thanks Nisbeth, though this is an integrated stereo amplifier . .

I was thinking that much of the very recent learning/ development that has been done by gaincloners (eg Peter fedde and others) could be translated without a huge effort into a multi-channel.

If someone here doesn't do it, I'll bet London to a brick that someone will. If I had the experience and time to do the design.

Doug thinks that the audio community regards projects such as this with distain. He's proably right. But I think they will be proved wrong, when it's done and listened to.

Whoever does it first (and well) would win a lot of kudos, and if they did it commercially, I suspect a lot of moola. I wish it could be me!


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