"The Wire AMP" Class A/AB Power Amplifier based on the LME49830 with Lateral Mosfets - Page 91 - diyAudio
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Old 13th March 2012, 03:17 AM   #901
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Quote:
Originally Posted by IanAS View Post


With 68 we might run into clipping with friends with bigger low efficiency speakers in their soundproofed listening rooms but for my other pals and myself that might do (in a mono block driving a passive crossover) as these days I have keep the volume down a bit. If I get the active cross over sorted then I'd have to get another pair of SMPS I guess.

85 would be better though. Is that too much?
Sounds to me like you or your friend or whoever would ideally want a different amp for those speakers. Its not totally diy, its off topic but it is made by forum sponsor and could fit your needs - HPA-NXV1200 1200 watt MOSFET Audio Amplifier Module

FWIW. I have a regulated 800W smps by coldamp to power two of the nxv203 amplifiers by aussie amps. The sound is quite enjoyable. Those amplifiers have 40ma bias current though so obviously don't run into the startup condition issues that have been discussed here with opc's amplifier.

Last edited by hochopeper; 13th March 2012 at 03:24 AM.
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Old 13th March 2012, 03:24 AM   #902
opc is offline opc  Canada
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Hi Guys,

Wow... lots of excitement. I'm going to sit this one out for a bit and see where it goes.

I would like to clarify though:

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Originally Posted by exp4nder View Post
Owen, can you please clarify the reason for the removal of the temperature compensation network (that is present in the datasheet) ? Will it not be unstable without it? Excuse me if i am wrong, i haven't read many data...
The temp comp is not needed because I'm using lateral mosfets. This is very important, as any other sort of output device, mosfet or BJT, is going to need temp comp to work properly. This board and circuit is only suitable for use with lateral fets, as they posses a negative temperature coefficient above a very low bias point, which prevents thermal runaway.

It's also the reason there are no emitter resistors.

If you build this up with BJT or standard mosfets, it will quite literally melt itself within 30 minutes.

As for bias, I have always been referring to the pair of dual-die lateral fets needing 360mA total bias. If you want to break it down to a per-die amount, it's roughly 160mA per pair of dies (one P and one N die) if you use discrete devices.

Regards,
Owen

Last edited by opc; 13th March 2012 at 03:27 AM.
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Old 13th March 2012, 09:49 AM   #903
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Ok guys, i understood, thanks!!

Last edited by exp4nder; 13th March 2012 at 09:59 AM.
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Old 14th March 2012, 12:59 PM   #904
back is offline back  Greece
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i have a question.

in case i want to add one more pair of mosfets is it better

to mount both pairs on the heasink and hardwire them to the pcb?
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Old 14th March 2012, 01:22 PM   #905
IanAS is offline IanAS  England
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You should fit each gate resistor as near as you can to each MOSFET, ie, don't have the gate resistors on the PCB and run wires to the gates.

I suggest using small pieces of VERO type board and solder the MOSFET pins to those. This contains the pins and prevents them touching the heat sink. You can then easily attach a gate resistor to each, and if using older lateral mosfets such as the 2SK1058 and 2SJ162, you can solder a 22pF polystyrene across the gate and drain pins to stop high frequency stuff.

You could, if you wanted, also attach a small capacitor or two onto there between supply rail and ground. But that adds the complexity of taking a ground wire to each.

Last edited by IanAS; 14th March 2012 at 01:26 PM.
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Old 14th March 2012, 01:29 PM   #906
IanAS is offline IanAS  England
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Originally Posted by hochopeper View Post
Thanks, I'll have a look into that.
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Old 14th March 2012, 01:36 PM   #907
qusp is offline qusp  Australia
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sounds like you 2 should get together, you seem to have the same goals =D
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Old 14th March 2012, 01:37 PM   #908
qusp is offline qusp  Australia
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i'm just joking btw
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Old 14th March 2012, 01:38 PM   #909
IanAS is offline IanAS  England
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Quote:
Originally Posted by opc View Post
...sit this one out for a bit...
My plan is to wait for your good self to complete your SMPS work and for a few people buy and try these and give their repost with their various setups. Then it appears I and some others have an option for a higher bias and slightly higher supply rails SMPS with the 500S (which I can only assume will sound the same?) which will do for a somewhat higher power amp with more output devices like a couple of my pals could just now do with before their upgrade need has them buy a commercial product.
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Old 14th March 2012, 01:52 PM   #910
back is offline back  Greece
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Quote:
Originally Posted by IanAS View Post
You should fit each gate resistor as near as you can to each MOSFET, ie, don't have the gate resistors on the PCB and run wires to the gates.

I suggest using small pieces of VERO type board and solder the MOSFET pins to those. This contains the pins and prevents them touching the heat sink. You can then easily attach a gate resistor to each, and if using older lateral mosfets such as the 2SK1058 and 2SJ162, you can solder a 22pF polystyrene across the gate and drain pins to stop high frequency stuff.

You could, if you wanted, also attach a small capacitor or two onto there between supply rail and ground. But that adds the complexity of taking a ground wire to each.
thanks for the info.

i was talking for this amp with these ADD alfets.
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