Power Amps for Active Speakers

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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
 
If you have to pull new circuits to run them, they're more expensive yet _grin_

Boaz said:
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
 
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.
 
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.
 
johninCR said:
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.
 
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 .
 
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?
 
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/YaBB.cgi?board=General&action=display&num=1080540150&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.
 
The requirements in terms of IMD, THD and output power are more relaxed when used for active speakers.
Many active studio monitors (that are used to record/mix our highly audiophile recordings) use chip amps !!!!

You can of course go for different amps in order to match the specific requirements of the different frequency ranges. While you can get the max performance/cost ratio that way, it may not be that easy technically.

Regards

Charles
 
gainclone

gainclones are perfect for this assuming that you like the sound of them. They are relatively cheap, require minimal power supplies, so simple to built that they are often wired p2p, finally they are very small and produce minimal heat.

Build or buy one and see what you think of it. I haven't personally built one but looking at various designs it doesn't get any simpler. There are dozens of kits available.
 
Hi boaz, glad you posted a thread. How much power do you need? If you can get by with 25W or so for the mid+hi I think it is doable. How much power do you need for bass?

I think the cheapest possible solution from U.S. supplier is via Steve @ ApexJR. I do not know how terrible shipping will be, but the prices are so good it may be worth it. Something like

4x tunnel heatsink $50
Signal transformer $8
68,000uF caps x 4 $24
Bridges $5

This is about $90 for the complete PSU and heatsinks, which are probably the most expensive parts. He might even cut you a deal if you were buying six sets of these. ;) You'll still need to finish the cases in some way, plus all of the amplifier components, but since you only need four output devices/channel, this won't be too expensive.

Are you totally committed to Class A on the bass? I am with you up to that point, but IMHO it is a bit wasteful in terms of cost and heat, unless you are really going for that last 0.1% of quality.
 
johninCR ,

Interesting info. I already contacted the tripath dealer here about the evaluation boards (6x100W!). It can save time and money maybe. Evaluation boards are very "heavy" meaning they're expensive next to a board designed only for the specific purpose.
Of course that in the "end" manufacturers will sell such boards/amps more expensive than the current evaluation boards.
I didn't quiet understand who are powerwave (tripath?)...
But it is worth investing a little bit (100$) just to check if the sound is as promised. good idea, thanks.

phase_accurate,
Yep, I know (read about that, of course). The question is what kind of amps I should put together? Chip amps for the bass, Class-A for the mid & highs?

SWhite,

Which designs do you think can suit each element (bass, mid, highs)?

Tiroth (Tyller),

How are you?
Well, I'm not committed to Class-A for the bass. I think that clear sound is important mostly to the mids and highs. After the advices here, I still am thinking if in active speakers we really need class-A's at all?
ApexJR sounds good, I still have to read about it, and of course, I'll check the prices.
It's very hard for me to say how much power do I need. Usually a 120W per one passive speaker is enough in power, but I don't know how it behaves with peaks. That's a question one should ask: How much power does any element in actives (for home use) need?
I think that 150W for the bass is enough, but I'm not sure.

A little summarize:
2 mains: Class-A/Chips amps for the mids and highs. Chip/Class B amps for the bass.
Center: it's a two way that produces bass, so maybe two chips/one chip and one little Class-A.
Rears: I'll active them only in the future.

At first I'll active the mains and see what goes, then I'll probably be smarter and know better.
I'm also thinking to build one Class-A, one Chip, one Class B and check the differences. The question here are costs only (I'm not lazy you know...).

Thanks,
Boaz
 
I think a good chip amp is all you need for your non-class-A amps, provided the power is great enough. If you need really huge power, one of the digital amps is probably the way to go.

If you can use ~50W amps on the centers/rears eventually, I think BrianGT's LM3875 boards are the way to go. Very quick that way. I know he is working on a LM4780 board too. How much power you can get depends in part on your speaker's impedance.
 
Boaz said:
johninCR ,

I didn't quiet understand who are powerwave (tripath?)...
But it is worth investing a little bit (100$) just to check if the sound is as promised. good idea, thanks.

Boaz

Powerwave is a little amp marketed for computers with retail price of $100. It has a tripath amp in it. The little thing is amazing not even considering that it's the size of a 1/2" thick 3"x5" index card.
 
I'm currently building Active 2.5 ways for the front three speakers in my HT. I'm going to drive them with three LM3886 chip amps. The two woofer amps will be run of a 32v PS for 68 + watts each and I'm thinking of running the tweeter at lower PS voltage to get ~ 35 watts. This 175 watts is a LOT of power with an active amplified speaker. 175 watts with an active speaker is equivalent to probably 250 watts per speaker, or more, with a passive crossover (depending on the crossover frequencies). I'm considering the idea of swapping out the tweeter amps for a small class A amp (maybe DOZ from ESP). Unless you go with some of the more esoteric parts, you will find that the biggest expenses will be heatsinks (especially for Class A), transformers (if you go with Torroids - I'm using much cheaper surplus transformers) and the boxes in which to put the amp. Everything else is pretty cheap (maybe $25-35 per channel).

I'm eventually going to build 2 way surrounds (four of them) but I can't decide if they are worth the trouble of building 8 more amps and four more active crossovers.
 
Boaz said:


Ken,........

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?


Back up, slow down - reorganize your thinking -

You must decide - which is the highest priority - 2 channel or multichannel - it determines your approach - While they seem like common goals, they really are not

FWIW, there is one school of thought that if you go truly high resolution and great 2 channel - that the center channel will collapse the sound stage. Somewhat like it is a lot easier to get a 3 legged stool stable than a 4 legged stool. These folks set their receiver to a "phantom" center

The main 2 channel approach is in keeping with Aleph's and class A

Quoting Nelson Pass " go for killer two channel and put the crap with it that you need in order to go 5.1

If HT or multichannel is a priority then you need to look at different amplification and do a different configuration. Although gainclones might serve for some users.




Boaz said:


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).

While not DIY - you really ought to consider using an XR45 Panasonic digital amp (or two) or whatever the new model equivalent will be - they are no longer shipping xr45 to the US and are shipping newer models

It would meet your needs, be relatively inexpensive - hard to beat without spending more money.

For a good explanation go to Newform Research at

http://www.newformresearch.com/ click on expert advice, then click on digital - the way the frames are I can't paste a full link

More than several people are using these amps for audio and _biamping_ with them

with two of them you would have ten channels to use for active amplification - in the US these would be about $300 each.

Biamping or tri-amping with these will probably compensate a good bit for their relatively minor weaknesses.

Very probably, you could not build chip amps for the parts costs - They have the reputation for being very good for the money even without tri-amping -

It's something you should seriously consider

Regards

Ken L
 
Ken,

I already gave to that a lot of thought.
First of all, of course that I will want to own two Nelson's Pass Aleph-X's with my speakers (passive) - who wouldn't?
Still, I don't forget my first aim is to get a superior sound especially in the mains (like Aleph's sound with the passives).

Two channels is my main goal at first with addings to 5.1.
In the future, when SACD/DVD-AUDIO will be common as discs (5/7 channels...) the center and the rears will be important too
So the goal is that the system can be upgraded.
The idea is to have two speakers with the-best-I-can-afford sound and a high-end amps for bi-amping all the other speakers.
I won't build everything now of course but in stages (first of all I'll tri-amp my mains).

For HT, the sound of an HT receiver is usually enough for me, except for the mains which give the music & songs. Most of the music I hear is in two channels (in the future with four-way stereo).
Some shows in dts have the voice in the center and then it's very important to have a good sound from the center, but I don't watch shows a lot.

Speaker impedance is 8ohm in general (~8ohm drivers). Of course it varies with the frequency....

Another thing you all mentioned, is the power consumption (and heat) with Class-A's, a thing I haven't thought of somehow...
 
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