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Class D Switching Power Amplifiers and Power D/A conversion

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Old 4th October 2008, 12:09 AM   #11
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Depends, mostly, on how loud you want to go - if the Insignia's genuinely are 90dB/W, then 1 watt gets you 90dB max, 10 watts gets you to 100dB max, 25 watts gets you to 104dB max, and 100 watts gets you to 110dB max.

Assuming you're listening to modern rock/pop, you can assume a dynamic range of only 10ish dB, so if you want to listen at an average 90dB (which is already quite loud) with transients up to 100dB, 10 watts (or 25 watts) will be sufficient. Going to 100W would allow you to listen at an average 100dB with corresponding dynamic headroom.

Add 3dB to all the above figures to get the numbers for a stereo pair.

I can't see you having many opportunities, in a small apartment, to be going to 100+dB, so I'd suggest the 25W model.

However, I just read through the 41hz site, and their specifications are rather dishonest. Their rated power outputs are for 4 ohm loads at 10% THD. When you assume an 8 ohm load at a more realistic 0.1% THD, Amp6 is only good for about 2 x 8 watts.

Amp5 is much more honestly specified, and is good for 2 x 50W at 0.015% THD, which is far more acceptable. So despite the advice above, I would recommend either: going for the Sure-electronics board, which turns out to be not-so-different from the Amp6 in real power output, or going for Amp5.

At 2 x 50W, you're looking at 107dB max from each speaker, or 110dB total, ie. sustained listening at ~100dB.
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Old 4th October 2008, 01:04 AM   #12
Davet is offline Davet  United States
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Default AMP6 power supply

The AMP6 has voltage regulation built on the board. You will still need either a transformer that provides 12 to 15 VAC or a power supply that provides 16-20VDC.

As to power required; it has been my experience that the T-Amps provide a lot more music power than traditional solid state. I replaced a 200-WPC solid state amp with my AMP6. I have found myself listening at lower and lower volume levels with the AMP6.

I would attribute this to what I call music power. The noise floor on these amps allows more music to come forth. Thus requiring less power. It is my experience that performances sound more life like with a fraction of the power that the AMP6 can provide compared to my 200-WPC SS amp with tube pre-amp.

If you are trying to melt the paint on the walls then go for greater power, else you will find the AMP6 more than adequate. YMMV.
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Old 4th October 2008, 01:10 AM   #13
dweekie is offline dweekie  United States
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Quote:
Originally posted by TheSeekerr

However, I just read through the 41hz site, and their specifications are rather dishonest. Their rated power outputs are for 4 ohm loads at 10% THD. When you assume an 8 ohm load at a more realistic 0.1% THD, Amp6 is only good for about 2 x 8 watts.
I find class D chip ratings to be very difficult to compare. A lot of them are rated for 4ohm 10% THD. Some are rated at 0.1% THD. Others rated at 8ohms, but you have to be careful to make sure they have the current capability to support 4ohms at the same voltage. What's even more confusing is that manufacturers (e.g. Phlips) don't even standardize ratings within their own product line
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Old 4th October 2008, 01:31 AM   #14
col is offline col  Australia
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why limit yourself to 2 channels? go for an amp9 and get an extra 2. If you are at uni you will want to have a party with your friends sooner or later. 4 channels of amp9 will power a couple of subs too.

Headroom is your friend.

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Old 6th October 2008, 04:27 AM   #15
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Quote:
Originally posted by col
why limit yourself to 2 channels? go for an amp9 and get an extra 2. If you are at uni you will want to have a party with your friends sooner or later. 4 channels of amp9 will power a couple of subs too.

Headroom is your friend.
How does that work with stereo inputs? Outputs 2 channels of L input and 2 channels of R input? And would I have problems with impedance or sensitivity matching b/t the Insignias and the sub if I added one?
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Old 6th October 2008, 04:48 AM   #16
col is offline col  Australia
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I divide the signal up using a preamp and a electronic crossover:

http://minirig.org.au/2008/07/25/min...anced-outputs/

another good way of doing it is to get a small mixer that has 2 lots of outputs. Some DJ mixers have a "booth out", the little Behringer UB1002 are good value .

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Old 7th October 2008, 09:41 PM   #17
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hmm, I'm wanting to keep it simple for now. Is there any reason I can't just use 2 channels of the Amp 9 till I get around to getting subs and a mixer or something? And what does it mean by "for 12-24V"? The power supply? It also says for low impedance loads, which I don't think 8 ohms is considered low, is it? Will this be a problem, or will it make it easy to blow my insiginas? Maybe I'll just stick with the Amp 5 for now. I can always sell it later if I want to get a 9
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Old 7th October 2008, 11:58 PM   #18
col is offline col  Australia
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you can just use 2 channels of amp9 and then use the other 2 later on when you want to add subs or even another pair of fullrange. Having the 4 channels gives you the flexibility.

the range of the input voltage is 12-26v so it will work within that range giving you max power using a 26v supply.

using a 24v 6A power supply into 8ohm will give you around 40W RMS into each of the 2 channels. Using a 24v 14A supply into 8ohm will give you the same but into 4 channels (approx figures). If you drop the load to 4ohm, say by adding another pair of 8ohm speakers to the same outputs, the amp will supply more power into the lower impedance load, around 80-100W.

These little amp9s prefer lower impedance loads. I run mine with 4 x 2ohm loads playing at maximum power

some photos of my setup before a party:

http://pix.minirig.org.au/main.php?g2_itemId=661

I'm using amp9 to power 4 x JBL GTO937 (high sensitivity car speakers)

In that photo I have the subs on a different amp. Sometimes I just run one pair of JBL GTO937s and the subs off the other 2 channels.

a good power supply for amp9:

http://cgi.ebay.com.au/350W-24V-14-5...QQcmdZViewItem


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Old 8th October 2008, 12:07 AM   #19
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"For low impedance loads" just means that it CAN drive low impedances, not that it has to. It can actually drive all the way down to 1ohm loads, which is fairly impressive.

"For 12 - 24V" is mostly a set of numbers for those who want to use batteries to drive it, as the real maximum voltage specification is 27V. Since it includes a bridge rectifier (well, some versions do), it seems that it would be best to run it from an 18V transformer.

Yes, you could just use only 2 channels of the amp-9, but the power supply needed for the amp-9 is different from that needed for the amp-5, so keep that in mind.
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Old 8th October 2008, 12:24 AM   #20
col is offline col  Australia
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I'm using amp9-basic with a SMPS. shown in earlier post.

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