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Old 7th November 2007, 10:48 AM   #1
Dr_EM is offline Dr_EM  United Kingdom
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Default Commercial or DIY amps

I am planning a 3 way tri-amplified system. My drivers will be:

Bass - Monacor SPH-275C, 8 ohm, 91db sensitivity, up to 420Hz

Mid - Audax HM100Z0, 8 ohm, 93db sensitivity, up to 4.3Khz

Treble - Hi-Vi RT2E-A, 8 ohm, 93db sensitivity (more like 96 up to 10Khz)

On amplifier choice I was originally considering the ESP P101 amp for bass and mid, with lower supply rails on the mid (to give about 180WPC and 80WPC respective powers). For treble I was considering the ESP DOZ class A amp with 40v rail (about 15W RMS).

Now all of this together costs a lot in parts and in time (and construction of the chassis is going to be difficult without a known source of cut 4mm aluminium panels). I have seen these commercial amps which seem to respesent great value, the Alesis RA series:

http://www.alesis.com/product.php?id=32

With the RA500 on bass, RA300 on mid and RA150 on treble I can have a full amplification system for a great price. My question is how much worse (if at all) would it be? Would there be a more optimum combination of amps (like the studio amps for bass and mid and the class A on treble)? Any input welcome
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Old 7th November 2007, 11:11 AM   #2
ttan98 is offline ttan98  Australia
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There are many nice amps(these amps receive good reviews ) around see these sites:

http://www.aksaonline.com/
and
http://www.ska-audio.com/diy/index.html

I don't think there are expensive, they reasonably priced, furthermore, your speakers are fairly effcient, and you are tri-ampling.

you don't need heaps of power. 100watts per channel is plenty.
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Old 7th November 2007, 11:15 AM   #3
AndrewT is offline AndrewT  Scotland
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Hi,
the treble and mid have the same sensitivity, therefore they need the same peak drive voltage from the amplifier.
The bass is only 2db lower so needs approximately 25% more drive voltage.
On the basis that 45W satisfies the treble, then the mid should be the same and the bass 70 to 80W.
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Old 7th November 2007, 11:18 AM   #4
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The best amp I have ever used on my HM100Z0s is MikeB's Symasym.
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Old 7th November 2007, 12:22 PM   #5
Dr_EM is offline Dr_EM  United Kingdom
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Thanks for the replies!

With Tri-amping I was under the impression that higher frequencies required less power since music signals have diminishing energy content above about 3Khz? Also the baffle step effects act to boost these frequencies futhermore (meaning less required power again with an active compensation)? I don't know, I get mixed views on this.

Perhaps the very best combo would be the class-A DOZ on top, the Symasym on mid and the P101 or RA500/300 on bass? Thats at least 2 DIY amps though, not a problem so long as I can figure out the panelling for the chassis.

Is this the Symasym you used Pinkmouse?:

http://www.lf-pro.net/mbittner/Sym5_...ymasym5_3.html

It fits the bill but I'd need a PCB. You don't happen to have any left over or know where to get them? I can drill them myself if I need. Did you use ON-Semi devices or Toshiba at the output?
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Old 7th November 2007, 12:53 PM   #6
AndrewT is offline AndrewT  Scotland
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Quote:
Originally posted by Dr.EM
With Tri-amping I was under the impression that higher frequencies required less power since music signals have diminishing energy content above about 3Khz? ..........(meaning less required power again with an active compensation)? I don't know, I get mixed views on this.
we continue to disagree on this. I say that peak SPL is the criterion. It is certainly not the energy content of time averaged music. This energy content can have a bearing on your choice of smoothing capacitance and heatsink size for each of the amplifiers.
Quote:
Originally posted by Dr.EM
It fits the bill but I'd need a PCB. You don't happen to have any left over or know where to get them? I can drill them myself if I need. Did you use ON-Semi devices or Toshiba at the output?
you just missed a group buy on AAK's PCB.
try asking Mike if he knows where some suitable PCBs are.

The 50W to 70W available from a 1pair Symasym would be ideal (economic build) for all six channels of a tri-amped system.
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Old 7th November 2007, 01:14 PM   #7
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Sorry, but I have no spares. My original two channel version used home etched boards to the design on Mike's site, with Onsemi outputs. It was a very easy job with toner transfer process. If you like, I can print off a couple of glossy prints for you to do yourself.

The next project is 10 channels for an active system using the Toshiba devices, with AAK's GB boards. I'm getting the parts together as we speak.
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Old 7th November 2007, 01:52 PM   #8
Nordic is offline Nordic  South Africa
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There is still one or 2 sets of the first run from the DXAMP groupbuy left if you are interested, at $20 a set it may be worth looking in to.... I got some nice caps for my boards yesterday... the four caps cost $30... which is more than the boards... of course it can be built with scheaper/smaller stuff too.

I guarantee it is miles better than P3.
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Old 7th November 2007, 02:03 PM   #9
Dr_EM is offline Dr_EM  United Kingdom
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With regards to energy content i'm only going by what Rod Elliot says in his articles, I haven't actually experimented with it much myself. The only real experiment I conducted was playing a 15W amplifier with 24db highpass at 3khz unclipped (viewed waveform on scope) into a speaker around the same 93db sensitivity. By itself it was horribly loud and I had to wear ear protection in the same room as it, it was heard clearly downstairs. With the full frequency range it'd probably be just be heard as "loud" but still louder than I tend to play music.

Shame I missed that group buy . I haven't made boards myself but I could experiment with it easily enough. Can get press-n-peel and a "student etching kit" cheaply enough. Thanks for the offer on glossy prints, I may take you up on that if I do decide to do it.

Your project sounds very interesting, though I trust your getting a great sound already from your 3 way with HM100Z0 mids? You planning a 5 way stereo or surround setup with all those amps?

Finishing these in an attractive way will still be the biggest problem, which is a part of why those commercial amps are an attractive option (and cost of course).
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Old 7th November 2007, 02:12 PM   #10
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HT setup triamped, though I still need to sort out bass amps. If I'd had any sense, (and more spare cash), I'd have bought another 5 boards and run the bass amps as Symasyms on the higher rails that the AAK variant allows.
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