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Old 3rd January 2002, 04:51 AM   #1
abd is offline abd
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Question 6ch amp help ?

Hi all,

Warning, newbie. Bear with me as i don't know much, my cousin will be building it for me, im searching for a design for him to use.

I wish to build a 6ch amp for a home theatre system to power the speakers and sub.

I was hoping someone could point me to some successfull projects/kits/designs that i could use.

Thanks in advance
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Old 3rd January 2002, 06:16 AM   #2
djss is offline djss  United States
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Default Leach Amp

I know I know, I always push the Leach Amp. But I've built 3 and it's the one I know about.

Check it out at
http://users.ece.gatech.edu/~mleach/lowtim/

It's pricey, but powerful, high quality, stable.

Overall, it sounds great and I love it.

=The DJ=
(djss)(at)(mail.utexas.edu)
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Old 3rd January 2002, 07:13 AM   #3
abd is offline abd
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Thanks djss.

How much is pricey ? hehe

As I am not electronically minded. Would i be correct in saying that i need to build 3 of these amps to get 6 channels. The reason i ask is im trying to figure out roughly the cost it will cost me before i get my cousin to build it.

Oh, im in Australia, any1 know of some stores that supply these parts for the amp or any other amps for that matter.

Thanks again.
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Old 3rd January 2002, 07:13 AM   #4
Won is offline Won
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A simpler and cheaper to build alternative is Rod Elliot's 60-100W Hifi amp. He has plans and circuit boards available at www.sound.au.com, and he's very helpful over e-mail.

-Won
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Old 3rd January 2002, 08:43 AM   #5
abd is offline abd
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Cool, thanks for the info.

Has anyone got a rough price i would be looking at to build a 6channel amp based on Rod Ellliots or Leach's design. Please let me know which currency then i can convert it to AUD

Any tips/hints oyu can let me know of if i choose leach or rods design.


Any other info will be much appreciated.

Thanks again
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Old 3rd January 2002, 10:06 AM   #6
bawang is offline bawang  Malaysia
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Lightbulb Best of both worlds!

A suggestion from someone who has built both the Leach and ESP 60W amps. You said AV? Why don't you use the Leach for your subwoofers and the ESP 60W for the rest of the channels?

As said, the ESP amp is a snap to built, good sounding, compact and having the man himself (Rod) in your neighbourhood helps a lot.

The Leach Amp Ver 4.5 is powerful (up to 240W into 4 ohms) but relatively more difficult to build.

By the way, the ESP amp PCB available from Rod is a dual channel (ie stereo) design whereas the Leach Amp PCB as in Prof. Leach's website is a single channel design.

And then, 60W/8 ohm (100W/4 ohm) for the ESP amp is definitely not puny in a domestic/home theater environment. Remember, you are only getting an extra 3dB for each doubling of power (in watts) if the same loudspeakers (or loudspeakers with identical efficiencies) are used.
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Old 3rd January 2002, 11:06 AM   #7
Freddie is offline Freddie  Sweden
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Anthony Holton.. http://www.aussieamplifiers.com
Has a 6 x 300W/Channel Power MOSFET Amplifier.. Coming Soon it says on the webpage.. That looks like a really nice project. I think he will offer PCB for the amp too.

/Freddie
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Old 3rd January 2002, 03:17 PM   #8
tiroth is offline tiroth  United States
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Here is another vote for the ESP design. I'm currently building a 6-channel amp based on it (4 channels complete!), although I'm counting on my powered sub to pick up the LFE. 60W (100W with higher rail voltages) is quite sufficient for many people's needs, although you may wish to use an alternate design for the sub.

These amps can also be constructed with very cheap output transistors. (US$0.07-$0.60 for MJE2955) This is very comforting when you destroy them, and you can always use something like 2SC1302 (US$4) when you are more confident of your construction.

My suggestion is to buy 3 of Elliot's boards and build your 6 channels from them. They will make you happy, and you won't need to spend the same amount of time on heatsink fabrication that a monster amp would require. Very little of my amp construction time has been spent on wiring: it is mostly the mechanics that eat up time. (and you can always bug your cousin to build a more powerful sub amp in the future.)

ESP amp cost for 6 channels, USD. I warn you that I /invariably/ underestimate costs, so take this with a huge grain of salt. If you have access to lots of usable surplus parts, it may actually be cheaper, although I'm assuming you don't pay manufacturer prices for most items, and strike a balance between dirt-cheap construction and premium passives.

Output transistors: $6-$50
Other transistors: $30
Passive components: $50+
PSU
rectifiers: $18
capacitors: $36 for 35v rails, more for 42v
xforms: $120
Case: $30-$100
Sinks: $30-$100
I/O connectors: ??
Wiring, solder, tools, etc: ??
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Old 3rd January 2002, 09:28 PM   #9
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Hi abd, welcome to the forum.

I too am building a multi-channel amp for home theater use. I am shooting for a 5 channel amp. I originally thought I would go for six channels, but after looking hard at subwoofers, I realized that they need noticeably more power than the rest of your audio channels. Given my 5 surround's need for about 100W/8ohm, I reasoned that 100W for the sub just isn't going to cut the mustard. I plan on building a separate sub amp, which I would reccomend to you also if you are serious about performance.

I just hopped over to Rod Elliot's page and had a look at his 60-100W design. Looks pretty neat, but me personally, I am going with something a little more full featured. I suppose it depends on how far you want to go with your design. After deliberating for awhile, I decided I would rather have:
  • good power supply rejection
  • good noise performance (>100 dB)
  • short circuit protection
  • low DC offset
  • rugged lateral MOSFETs in the output stage

There is a design in Slone's book that does exactly that, so I am fairly convinced that is what I will build.

I also want to point out that for a 5 or 6 channel amp, the power supply starts to be a real sticking point. You are going to need a supply that is capable of driving all 6 channels at full power simultaneously. This requires a very big transformer, probably somewhere in the 1000VA + range (200 Wpc/4 ohm x 6) worst case. I myself have landed a badass 1500VA toroid off of Ebay, with many taps (including some low voltage taps; woohoo!).

Anyways, good luck with your project.
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Old 3rd January 2002, 10:05 PM   #10
tiroth is offline tiroth  United States
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At the risk of sounding defensive (^_^), I'll note that the reference P3 amp has THD+N of 0.0025% (-92dB) or less. I don't have filters (or a good enough scope) to measure this low, but I can say that the noise on a shorted input is -89dB or better. Of the four amps I've constructed, DC offsets are less than 30mV.

To each their own though. Nice grab on the toroid. I had to resort to three seperate trannies to get enough VA.
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