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Old 28th March 2008, 05:15 PM   #1
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Default 41Hz.com AMP8 - Output power when bridged

41Hz.com have updated their site http://41hz.com/

If you look at the overview page, you will see that they claim the AMP8 will do 2x1000W into 2ohm (I'm going to assume ~600W low THD). Unfortunately they are out of stock, but I'd like to see if this will work for what I want before I order...

Now, they also state that the amp can be bridged, but they do not state the power when bridged... I'm guessing this would be 1x2000W into a 2 ohm load (or would it be 4 ohm)? I know there are a few people here that run an amp 2, so I was hoping to hear how this amp works when bridged.

Basically, I want to drive 4 x 8ohm subs, they are each rated for 500w but I plan to run no more than 200-300W into each. The amp8 seems perfect for this.

Finally, for the PSU I plan to use 1 x 1500VA toroid, plus 2 x 10000uF caps for each rail. Each rail will be 65v DC. Will this be enough, or will I need more capacitance or a bigger toroid... Bare in mind this will be used for PA.

As for heat, I plan to use a 2U PA amp chassis with actively cooled heatsinks... This should enough I would have thought? Does anyone know how many output FETS the AMP 8 uses (8?)?
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Old 28th March 2008, 07:05 PM   #2
luka is offline luka  Slovenia
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Hi

This data is from tripath, almost the same board for TK2350, but it has TA3020 chip for driving and input stage, everything else is the same...and from this pdf tripath said 1350w @THD+N =0.1%, R= 4R, with +/-60v supply. each channel will provide about 600w into 2R @ same THD+N...on 41Hz you will find dynamic, music or something that is not RMS and not MAX.

Amp can be bridge and DjQuan has done so...
Which amp do you want to hear how it works when bridged, AMP2 or 8?

Toroid should be fine, I would just add 2 more 10000uF, so you will have 4 in total...

Be carefull, you will have to find/buy such toroid, that when not loaded(idle), DC will be up to 65V, one or two volts lower wouldn't hurt, even if you get only 60v, trust me it will be more than enough

2HE, with heatsinks outside will be too much (read enough), and AMP8 uses 8 fets, 4 per channel
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Old 28th March 2008, 07:51 PM   #3
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Thanks for the info, by the sounds of it it will be able to drive 2 out of my 4 subs ok when bridged.... 4 x 8 ohm subs in parallel will be a 2 ohm load, will will be too much really (when bridged at leaast).

I may have a look into mounting 2 amp8's in 1 chassis, but it may be too much of a squeeze, as my caps are huge. I've had a look and building an amp8 with 8 fets per channel would be difficult also, as you would have to build a new PCB.

I've check my toroid specs, it outputs 45vac on the secondaries, which will give 63v before it hits the rectifier... I guess it will lose 2v after the rectifier, so 61v seems like a good value. I'll just have to hope the mains doesn't go too much above 230v...
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Old 28th March 2008, 08:01 PM   #4
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Hi

I won't say nothing, but you could build 2 AMP2's, each bridged will do about 950 into 4R, say 900 to be sure THD is really low

If you want you could drive each sub on its own channel, boards are small, so you will/should have enough space for everything
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Old 29th March 2008, 12:04 PM   #5
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That's a good idea, plus it would be much less of a squeeze as I would only have to have half the FET's to cool... 8 per heatsink = squeeze, 4 per heatsink = less of a problem. I didn't know that the AMP2 will work with a 4ohm load when bridged... Will it do this with +-60v rails or will have to be +-45v?

I'm going to pick up the chassis today, so I'll get measuring... Also, the AMP2 is in stock which is a bonus. Unfortunately the AMP2 section on the 41hz site is missing.
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Old 29th March 2008, 12:13 PM   #6
luka is offline luka  Slovenia
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Hi

Any amp can work in bridge, AMP2 does too, even if with 4R, you will just have to set overcurrent, which I hope you will set to 22A for this reason. And you won't even need +/-60 for this, as you said +/-45v will be enough, which means only 50v caps...
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Old 29th March 2008, 12:43 PM   #7
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Quote:
Originally posted by luka
Hi

Any amp can work in bridge, AMP2 does too, even if with 4R, you will just have to set overcurrent, which I hope you will set to 22A for this reason. And you won't even need +/-60 for this, as you said +/-45v will be enough, which means only 50v caps...
Well the bad news is I've already bought the toroid, but I'm sure I'll find another use for it...

The good news is a have loads of 63v caps, and they are so much smaller than my coke can sized 100v caps, meaning I can stuff loads more in the chassis and end up with more capacitance...

I'll see if I can get hold of a good toroid with 30v secondaries, and give the amp2 a whirl...
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Old 29th March 2008, 12:59 PM   #8
luka is offline luka  Slovenia
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Hi

I know this is hard, something I wouldn't want to do, but you can unwind some of the secondary from trafo off, to get voltage you need
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Old 29th March 2008, 01:47 PM   #9
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Quote:
Originally posted by luka
Hi

I know this is hard, something I wouldn't want to do, but you can unwind some of the secondary from trafo off, to get voltage you need
Well that is an option, and I've already done this in the past with car SMPS toroids and it's worked... This toroid is a little on the huge side tho!

I think the best option will be to buy another toroid really, so I'll go for that. When it comes to mains powered things, I don't like to cut corners...

I may build an amp8 (if they even come back in stock) as well just for the hell of it, seeing as I already have the caps and toroid...

I'm not really in any rush to get this finished, and I'd like to get it right the first time.

I've also looked into using an SMPS, but there isn't really anything available right now apart from the coldamp kit, and I'm not really a fan coldamp... I may go over to SMPS eventually if a new one arrives.
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