Amps for tri-amped HT setup


2001-12-26 9:04 pm
Hi all,

I'm new to the DIY game but I've been trying to do my research for the past 5 months on the web, etc. I've built a Pro 60 amp from seal electronics and a Foreplay tube pre-amp for practice, but now I'm itching to build my real project - the Phoenix speakers from The Phoenix are a pair of tri-amped open baffle speakers with a 3-way active crossover. I would like to build two full speakers and a "mini" for the center channel (minus one of the mids) for use in an HT setup.

Ideally, I would like to use a digital crossover and digital amps (ones that accept digital in). I'm using a computer as a scaler, DVD player, CD player and music jukebox. (I realize purists may be gasping at this point - using a computer as a CD player, but that's the next project...) Anywho, my point is that I would be happiest using a sound card with DSP chips and software to create and modify the crossover points, with the possibility of room correction. From the posts and research I've done on other sites, it seems that this isn't quite possible, yet. So, unless someone here can correct me, I may have to go with the electronic crossovers Mr. Linkwitz designed for the speakers, which means analog out, nullifying the need for amps with digital ins, at least for now.

I've been looking at amps from CAD Audio (PWM Amps), LC Audio and Tripath, primarily. I don't foresee myself being able to do listening comparisons... Does anyone have any direct experience with one or more of these (besides the 104s - those that have built with them seem very happy?) Another possibility is the TA2022 6-channel reference board from Tripath ( /Technology/Data sheets - available for $600 each, but I'm not sure what modifications are possible).

Are there any suggestions for an amp not mentioned above (preferably digital) which is:
1. high quality (at least THD <1%)
2. low cost - I need 9 channels!
3. capable of 200W per channel or more?

I've considered building the modified Tripath 104s as described in another thread here and on Chris Broderson's website, but I think that this solution may be a bit too pricey (~$900 for 2 channels, so close to $4000 for 9 channels). I'm hoping to keep this around $2000, especially since I would like to move to the digital crossover mentioned above as soon as it becomes practicable.


Well, $2000/9 channels = ~$222 per channel. Are you sure you need 200W per channel. That seems like major overkill for a tri-amped system. I can't imagine that you need 600W per speaker, if you do however you'll likely need to up that $2000 some. The power supply components alone will eat up a large chunk of that $$. Although effiecient amps like tripath will certainly help.


2001-12-26 9:04 pm
Actually, the 6-channel Tripath I mentioned is 90-100W per channel, depending on the power supply... That would be fine, I think. My concern with the Tripath is modification. From what I've read, people have felt the need to modify the 104s a great deal. I'm looking into which of those mods can be applied to the 2022 6-channel reference board, but, as a newbie, this is a long and confusing process....

I had an email conversation with Dave Reite who also built the Phoenix. He used the 40W version of the LM 3886 shown on the Linkwitzlab site. He said that the speakers were way underpowered and has since bought a couple of Adcom 6550's (if I remember correctly) to power them with a combined 12 channels of audio from those amps.

The bottom line is that I've never heard the speakers or the amps. I haven't even heard that many speaker/amp combinations in my life. So, I'm not quite sure how much power I need per channel. Tri-amping with the 104's at 400w / channel (at 4Ohms) definitely seems like overkill. But, I've also been told that 40W is insufficient. So, I guess I need something in-between.

I'm wide open to suggestions.

this is answer by email , i just menat it could have interest for others so i post it here.

i suggest the following:

you buy 3 stereo boards from us (they can be 3504 stereo or tripath 0103 boards) each board is 350w/ch.

you make (or buy) 3 a/b amplifiers for the high freqs , i think this is cost effective and gives you more power where its needed.(they could perhaps be lm 3886 amps)

you buy power suplies for the above and 3 cases if you dont allready have that.

the pwm amp boards are like $225 each , the a/b amps should be like $60 each and the power supplies (the parts) will be around $100 each , a round figure of $1100 should give you a high power (2200W +) and high quality 9 ch audio system.

k madsen - cad audio dk

ps. $2000 ?? where did that come from?


2001-12-26 9:04 pm

You were right - I was looking for about 200W per channel, but I think that that might be overkill, especially on the tweeters.


I've still got about a month to decide exactly what I want to do, but, unless somebody here talks me out of this, I think I'm going to go with the 6-channel TA-2022 reference board from Tripath (up to 90W per channel) for the mids and highs and 3 3504's for the bass. The 3504's come in mono, correct? Your website quotes $140 as a price, but you quoted $225. Is that for a pair?

The suggested tweeters have an impedance of about 4.5 ohms, the midranges 3.5 ohms and the woofers just over 6.5 ohms. So, to the best of my knowledge, and depending on the power supply, I should be able to get about 80W out of the tweeters, close to 100W out of the mids and about 250W from the woofers. This should be more than enough, no?

What about putting the power supplies in their own case(s) instead of in with the amps? Does anyone see a terrific advantage in doing so?

Thanks for all your advice.