Power Amps for Active Speakers

[Boaz]

Looking for a DIY design, parts lists and costs for power amps for Active speakers.

The main speakers are 3-way design, but I will want to bi-amp the center and surrounds as well in the future.

Costs are the main thing(!), as well as Class-A, high-end sound and ease of tweaking.

I thought of Aleph-X/Aleph-5/Mini-Alephs at least two of them (or six, one for each element). If it's 1500$ for two, 6 will be expensive...

I would like to hear your recommendations about what amps to build, costs, parts list and design schematics and other considerations.

Any commercial amps are more recommended than building (costs only as I don't have "problem" building)?

Thanks.
Boaz

[Ken L]

Originally posted by Boaz
Costs are the main thing(!), as well as Class-A, high-end sound and ease of tweaking.

I thought of Aleph-X/Aleph-5/Mini-Alephs at least two of them (or six, one for each element). If it's 1500$ for two, 6 will be expensive....... and other considerations.

Unless you've got 2 or 3 dedicated 20 amp circuits ( at 130 volt AC mains) to run them on, it could cost you a lot more than you're already thinking - Dependent on how much load you have room for in your panel - if you had to increase your service because you're already maxed out - it could be _very_ expensive

Not sure what type of mains current you have in isreal.

Biamping in Class A in a Ht quickly becomes not feasible for most folks.

Due to it's design, class A draws considerably more power from the supply circuit.. Also, there is a good bit of heat dissapation - Ever notice how large the heat sinks are on a class A amp?

It's been a while, so I'm not absolutely certain - but IIRC, five channels of Aleph's ( it will vary by the model) were going to pull about 15 amps total just for the power amps.

At the time, I knew I was going to pull 2 dedicated 20 amp circuits to my media rooom/HT. I shied away from the concept when I realized the power amps would take one of the circuits (code here stipulates that circuit size have a 25% safety margin factored in - which also makes good common sense)

I would think that no matter what type of mains current there is in various parts of the world, that class A HT may well overtax the mains supply in residential housing-

In addition, that much current draw would increase the actual cost of operation quite a bit -

It is not so noticeable in 2 channel, but quickly starts adding up in HT.

Regards

Ken L

[5th element]

Im not a huge fan of class A simply because of its massive waste of energy. But I can see that two high quality class A mono blocks in a passive speakers is a large attraction.

However in HT even with 5+ channels I wouldnt want class A of any significant power, least of all in an active HT. I wouldnt think wiring up dedicated high amp spurs would be the least of the problems. The electricity bill is going to be astronomical.

If you really want to build a class A behemoth then I suggest.

Class B amps on the centre the rears and any other extra surround channels.

Then a powerful class B amp on the bass in the main speakers.

Finally aleph two's or similar on the midrange and say a 30 watt class A amp on the tweeters, in the main left and right speakers.

I have not heard any aleph designs I wish I had, but until I do and am completely wowed by them Im not going to say deffo go for class A. The only technical advantage I can see with class A is the removal of switching distortion, but you can get class B amps with very low distortion so switching should be rendered inaudible. Others will dissagree.

[johninCR]

Why not use one of the new chip amps? The Tripath's are really clean and something like 98% efficient and are something different than the other class D chip amps (of course they call it a class T amp). You can get their evaluation boards really cheap and they would be perfectly suited for your kind of application.

[454Casull]

98% efficiency? ... Right.

[5th element]

Originally posted by johninCR
Why not use one of the new chip amps? The Tripath's are really clean and something like 98% efficient and are something different than the other class D chip amps (of course they call it a class T amp). You can get their evaluation boards really cheap and they would be perfectly suited for your kind of application.

Define cheaply? $335 at their website does not seem cheap to me.

[Mudge]

Class T is PDM not PWM like Class D, and their feedback circuit is somewhat unconventional. Other than that, I wouldn't say it's more efficient than most hi-end Class D designs.

[johninCR]

The suggested retail for a 2 channel board is $99 and the 6 channel is $229. http://www.tripath.com/TA2020_design_tools.htm

I was wrong about the 98%, 95% is their highest efficiency amp. Most are 88-92%. They're plenty efficient though. I know guys who are running their systems with rechargeable batteries to avoid the noise from the electric company's lines.

I have a Powerwave amp that uses one of their chip amps. It's the size of a 3"x5" index card and about a 1/2" thick. Once I got rid of the buzz caused by the wallwart power supply, it blows the SQ of my Denon 1804 away. Not bad for $80 .

[Boaz]

Thank you for your replies and advices.
I'm considering the Aleph's/Class-A's only for the main speakers.

Ken,

For the centers I want "cheap" but high-end amps.
On one of the threads I read about someone who builds his own amps for actives for 100-150$ each. In this case it can save.
I also considered to use an HT receiver for the center and rears at the start, but as far as I read here the sound isn't comparable even to 100-200$ DIY amps. Any ideas on that?
So:
1) Mains with Class-A's. At least for my main music I want superior sound. The question is if that would be noticeable compared to other type of amps/HT receiver (marantz/nakamichi) on active speakers?

2) Center and Rears including other excellent but cheap amps (One of my purposes is to define what is cheap enough but still has high-end sound).
I'm intended to use such amps for future DIY projects as well.
I know about the heat and efficiency of the Class-A's (I intend to put the amps in another room maybe) but I guess the best idea is to have Class-A's only for the mains mid and high.

5th element (Matt),
I haven't heard a Class-A amps yet (only tube one) but people are saying...
The question is if the amps in an active speakers should be at least of the same kind (like Aleph's and mini-Aleph's)? or can I use different amps with different power stats (I read a thread that says they should be the same)?
I got the info on your amps, of course, and that could be a very good choice. The question is if Aleph's on the mids/highs would give much better sound? A question I can answer only if I'll hear both choices.
I will have the mains with active Xover & amp for each component.


johninCR, Mudge,
Haven't read much about the chips & class -D amps (I guess I have homework...).
20W-4ohms isn't that much is it (maybe for the car?)?
I'll be looking for some designs in the chip-amp forum. It could be enough for some of the references in the future.
Any designs with those chips?

Can anyone recommend specific amps that I could get the design, parts lists and costs?

[johninCR]

Boaz,

After hearing the quality of the Powerwave, an amp designed for connecting to computer sound systems, I wouldn't even consider buying anything right now. I'm waiting until these little amps are incorporated into the things I buy. The future is a complete system in one package with true audiophile quality. Check out this thread, it's mostly tube enthusiasts, http://www.decware.com/cgi-bin/yabb/...540150&start=0

Unless you are using inefficient speakers, it's unlikely that you use more than one watt for normal listening, but Tripath has chip amps going as high as 500W/channel. The evaluation boards look like a simple DIY project. Make a cabinet, connect a power supply, I/O connections and a volume control.

http://www.tripath.com/audio.htm

At a minimum, invest $100 in a Powerwave to check out the quality. In the worst case, you'll have an audiophile quality amp for your computer.