Active crossover guys.....what amps do you use?

[demon2091tb]

This is a vague question i know, but i was wondering what kind of amps, and array of channels you guys are running with, if i can find a set of nice budget used amps for the home, PA or home really, then i could go active with a dcx2496. This seems to be the best route to go, but amplification is the trouble for me, finding cheap amps in the home audio world that are bareboned and straight power. I'm ideally looking at 100-200rms@4ohms.

[Drew Eckhardt]

3 x Adcom 545ii into my Linkwitz Orions. 100W x 2 into 8 Ohms, 150W x 2 into 4 Ohms, about $200-$225 and change used.

Bought the first one new for ~$600 10+ years ago; still works fine.

[sreten]

Originally posted by demon2091tb
.
...finding cheap amps in the home audio world that are bareboned
and straight power. I'm ideally looking at 100-200rms @ 4 ohms ...

Hi,

You won't find them in a hi-fi shop. However if you head towards your
nearest musician / home recording emporium you will be relatively spoilt
for choice, go figure....... e.g. the Beheringer A500 @ ~ $200.

Go for quality over quantity for your midrange and treble amplifiers.

/sreten.

[wigginjs]

Parasound HCA-1206. 6 Channel, 120W/channel. Weighs a TON, but it takes up less shelf space than 3 2-channel amps. I paid about $700 used on audiogon.

[BobEllis]

I use a pair of modified Pass/Thagard A75s (total ~125W x 4) for the mains and a Hafler DH500 on sub duty in my main system. A quad of Leach amps (125W x 4) power my bedroom system and a pair of LM4780s (60W x 4) wired point to point power my son's. Can you tell I like DIY active systems?

If inexpensive is important consider building amps for your mains. Symasym by MikeB looks to be a good sounding amp (haven't built any yet) that can be fairly inexpensive to build, but only 60W. Professor Leach sells circuit boards for his amp. As designed it is ~125W, but can be scaled up fairly easily if you really need more power. Four channels sharing a common power supply can be built for around $400 excluding a case if you use surplus parts like transformers and heat sinks. The case can be as plain or elaborate as your budget allows. My Leach amps originally resided in an MDF box.

DIY is more fun, but the PA amp route is probably the way to go for subwoofer duty. However, if you can live with "only" 500W, Parts Express has the BASH 500 plate amp on sale for $160. ($70 off regular price)

[demon2091tb]

Thanks guys, as far as i know my sub amplification is taken care of, got a single 250rms PE plate amp, pretty nice i think, gonna get another or will most likely buy a PA amp like suggested and keep my current plate amp for a small job in the future.

Substage is looking very defined as a pair of Tempests 8cf sonotube tuned at 16hz. Midbass is going to be a pair of RS225's sealed, RS52 midrange, and a nice tweet, i have LPG 26nafm, and the Neo3's, but wanted to try a new tweet specifically for home, possibly a seas.

I think i really would only need a good 150w @4ohms to get everything moving really well, possibly a tad more on the midbasses. But someone suggested that i up the quality on my midranges and tweets, i had planned to just get 3 of the same amp.

Inexpensive is my current route, which way it would go, but finding suitable amps at low prices i find is the difficulty to starting the active way.

[nilsomat]

Originally posted by demon2091tb
Inexpensive is my current route, which way it would go, but finding suitable amps at low prices i find is the difficulty to starting the active way.

I could recommend Tripath-based class-d amps by
http://www.41hz.com
if you look for inexpensive but high quality kits. For example Amp9 will deliver up to 4x100W for just 49 $, you just have to add a transformer (and build it). Or consider 2x Amp2 for 164$ which gives you 4x300W.

Regards,
Nils

[Drew Eckhardt]

Originally posted by demon2091tb
I'm ideally looking at 100-200rms@4ohms.

Since you're listening to music rather than trying to meet FTC advertising requirements, you don't need 100-200 W RMS; just the peak voltage and current implied by that.

This came across the bass list some time ago; it includes RMS to peak measurements for rock, jazz, and classical music as well as the power spectrum for a 3-way with 300Hz and 3KHz XO frequencies -

http://www.silcom.com/~aludwig/EARS.htm

This is great news since iron and heat sinks are the most expensive part of an amp.

Along those lines, you might look at SL's Pluto:

http://www.linkwitzlab.com/Pluto/electronics.htm

Active 2-way, LM3886 for the tweeter, bridged LM3886s for the woofer, all run off +/- 30V rails fed by a 50VA transformer with 22KuF per rail. SL states 150W peak woofer output, 50W tweeter and says nothing about RMS output.

I finished stuffing my Pluto boards last night, and got curious about the thermal analysis.

Assuming 1 degree/W thermal resistance between junction & case per National specs, .5 degrees/W for the heat sink interface via a thermal pad, and a 4 degree/W heat sinks you have a 5.5 degree/W thermal resistance between chip die and air. Using a 150 degree limit at 25 degrees ambient you get a maximum thermal disipation of 23W per chip.

Eyeballing the power dissipation curves from the LM3886 data sheet it looks like that's enough heat sink to hit the flat part of the curve for the tweeter amp (~45W RMS) but the bridged woofer amps are on the hockey stick part of the 30V / 4 Ohm curve where it looks like I hit 25W dissipated @ < 5W output each for 10W total. Looks like trading -6.5dB of RMS output for +6dB peak.

Getting rid of the insulating washer would require something like a 1.7 degree C/Watt heat sink with 30V rails.

Definately an interesting design. Costs about ~$12/side for the tweeter amp, ~$25/side for the bridged woofer amp, ~$40/side for the power supply. Each LM3886 takes just 6 passive components.

[demon2091tb]

Specifically nilsomart, those kits look very intresting, i'd like to ask what comes with them, the board.....Do i have to pick out all of my resistors, and capacitors, etc, or do they send them all as well. If they send them all i could easily do that, How would i mount them into a chasis, and how would i attach my heatsinks and all that goodness.

More info on the subject would be nice, and your experience with them would be ok?

I would love to take a few of the 2ch amps and put them all together in a single amp chassis, i would still need some sort of volume pot for the level matching controls if i use the behringer unit for processing 6ch's.

[nilsomat]

@demon2091tb: I am just about to build my 3rd amplifier kit from 41hz and i am very pleased with them. They include almost everything you need, you just have to add a pot (if you want), transformer, fuses, cables and connectors, and thats about it.
Have a look around at the shop, there you will find detailed information about all the kits.
Some of the kits are smd, some of them are with through hole parts (which are easier to solder).

@Drew Eckhardt: good link! Very interesting topic.

Regards,
Nils