6ch amp help ?

abd

Member
2002-01-03 5:46 am
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 :)
 

abd

Member
2002-01-03 5:46 am
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.
 

abd

Member
2002-01-03 5:46 am
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
 
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.
 
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: ??
 
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.
 
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.
 
Hey tiroth, what is the reference P3 design you are referring to? I can't find anything resembling that on Rod Elliott's pages :confused: .

You are probably right about the noise spec though. Anything better than about 90 dB is pretty much gravy. In the spirit of overkill, the design I will probably build has a SNR of -110 dB :D .
 

abd

Member
2002-01-03 5:46 am
Hey Gals/Guys

Thanks for all the input

I will most likely go with Rod's design and mabye Leach's or some other complex design when i can convince my cousin to build one for himself :) hehe

Any recommendations for some more complex designs when i manage to convince him.

Also, what do you think of this design http://www.aussieamplifiers.com/ as posted by Freddie. I know there aint much detail there yet.

Tiroth - i can get wholesale prices but there isn't much difference between the retail prices on most parts :(

Thanks again, much appreciated
 
abd,

I haven't seen the schematic of the 6 channel mosfet amp...
The information I have about it can be found here.
http://members.optusnet.com.au/~aussieamps/what's.htm

I think it's based on the N-channel amp, which from what I've heard is a really nice amp..
It's much more powerfull than the ESP amp.. However it is also more expensive to build. I think it all depends on how much you are willing to spend.

/Freddie
 
Silverpike said:
Hey tiroth, what is the reference P3 design you are referring to? I can't find anything resembling that on Rod Elliott's pages :confused: .

There are actually two versions of the project: the original Project 3, and the updated 3a (plus an even older design). Project 3 includes some test info and comments that 3a does not...very good reading for P3a constructors.

ABD-surplus is the way to go if you can find places that have the parts you need.