"The Wire AMP" Class A/AB Power Amplifier based on the LME49830 with Lateral Mosfets

[igor0203]

Originally Posted by AP2

One dps-600 supplies both voltage eg. +/-68V and 85V for lme (or other difference,that Owen advice)
yes, one dps-600 for one amp (independant of power)
Is possible VADJ (trim on board) +/-5% Vout (lme follow in proportion)

Great, than I'm definitely buying it. Just waiting to see if there will be GB or not (I hope it will )

[opc]

Hi Guys,

Just a quick heads up to say that I tested the DPS-600 with a 600mA bias current, and it did start up. It seemed to take a little longer than at 400mA, but it did work.

Regards,
Owen

[qusp]

Originally Posted by igor0203

Great, than I'm definitely buying it. Just waiting to see if there will be GB or not (I hope it will )

yeah we will, should we start a list somewhere today? we have 2 options, see if we can arrange for the bulk purchase to be made, but still have the supplies sent out individually, or find a reputable (not new, it'll be a fair chunk of change) member of the GB in the EU to accept the package and redistribute them to the rest of us. the second one also complicates the tax/vat scenario, as we would be charged tax on all of them and then possibly a second lot of tax on delivery to the final owners. the second option also complicates ownership and support somewhat, as it could be said that person is the person who bought them.

Originally Posted by opc

Hi Guys,

Just a quick heads up to say that I tested the DPS-600 with a 600mA bias current, and it did start up. It seemed to take a little longer than at 400mA, but it did work.

Regards,
Owen

excellent! have you run it higher than this by adjusting after start up? so we just need to work out a way to delay the connection to the amp, though that would also delay the loading of the PSU wouldnt it? so may not actually achieve what we set out to do.

is the linear regulator (headamp PSU) still used, or omitted when using these supplies?

[QRikard]

Hi again, i'm back with a few new stupid questions...

I have read the last few posts a few times but there are a few things that i'm not completely following. I'm aiming for a bit over 100W in output power because i think that should be sufficient to drive any "conventional" speaker to reasonable volumes with some headroom. If i'm mistaken here please tell me asap so i won't find out the expensive way...

1. Would it be helpful to use some circuit to detect if the power cord is connected and when it disconnects draw the shutdown pin of the SMPS and the mute pin of the LME? Or do the noise go trough the rails so it's useless to mute the LME?

2. When you start the amplifiers is that without input signal? In that case what happens if there is music playing at startup (and shutdown)?

3. Do the DPS600 benefit from the PBTU-2? It is listed as a related product on the website but if i understood owen correctly it wasn't used for the DPS600 measurements does that mean it provides no significant improvement?

4. If i understood correctly AP2 you can easily lower the output voltage of the DPS600 without loosing any performance right? Say about +/-50V for the mosfet rails just to reduce the temperature of the amp.

So i think the DPS400 looks nice in terms of power and price but i'm a bit scared of the transients on startup and shutdown. I can accept 3-400mA of bias which seems to work nicely after the updates.

But if my estimate is correct the price difference between dps400 and dps600 is only around 50€ and in that case i can definitely consider the dps600 if that's where the group is heading.

In the end i'm still up for some SMPS, as least 2 maybe a third. I'm having problem to decide because active woofers seem to be a lot more common and then includes filters to set the breakfrequency in an easy way, and my main problem still stands because the dac only provides stereo output...

[qusp]

the PBTU-2 is not used in any of the measurements and it is not used with the dps600, it is a stand alone linear supply, it would only make matters considerably worse if used in conjunction. we are already working on the shutdown behavior, for the 600 it doesnt matter a great deal as there is nothing to be scared of in the transients and I gather the 400 isnt as bad as it appears. do remember the output is scaled higher than the rails if you read the graphs properly. the start up behavior presents more of a challenge than the shutdown, but should be easy enough to solve regardless

we cannot set a multitude of different Vout levels for the supplies, particularly if we expect to take advantage of bulk pricing. the supplies are adjustable +/-5% from the voltage that comes factory set, no more. we should decide on 1 or 2 voltage options for each 400 and 600

I have no solution for your stereo dac issue, so you are still pursuing multiple channel output with only 2 channels?

[AP2]

I hope that Owen contact me fast. becouse:
DPS-600 have 1 output pin (optoiso) action=(low to gnd after startup is complete)
1 input pin (optoiso) action=(if close to gnd,smps break fast)
is possibile that someone can use this in good way.
----------------------------------------------
problem in startup/shuntdown, even scale is 1V, is apparent mistake.
i have sended email to Owen, just for understand action of mute in lme.
i think that mute switch off, while voltage pump at 20V.
after i ceck it, is possible as professional application, that amplifier is "enabling" from smps (after startup sequence, if all is ok)
now, exist many way for this, we find a simple..very simple.
if we see well measure at startup/ shuntdown, dps-600 not emit spike
-----
I mean,if Owen send me measure with mute fix on, then is simple. ruote same component used on mute, for obtain a treshold. eg. mute switch off when voltage =>30V. this solve all. amplifier is in mute condition while voltage is 20V, even i want adjust this time a 3-4 sec

[opc]

Hi Guys,

Attached is the startup and shutdown plots for the DPS-600 at 600mA.

Startup takes 16 seconds from "plug in" to full rails.

I connected a Behringer Truth passive monitor to the output of the amp to see how the transients actually sound. On startup, there is absolutely no audible click, pop or anything else. The amp and PSU are dead quiet at startup with or without the LME muted.

On shutdown, I captured both with the LME muted and with it unmuted. Not surprisingly, it makes no difference between the two states since the off transients are being caused by the + rail of the supply pulsing on and off, which completely bypasses the amp through the output mosfets.

Based on the above, I can assure everyone that this is not an instability issue with the amplifier, and is definitely the supply. I can check tomorrow by measuring just the supply driving a 250 ohm resistive load, and I would imagine that I will see the same behaviour on the positive rail.

With the Behringer hooked up, these transients are audible, but not detrimental in any way. I could see it being a little obnoxious, but it won't damage anything.

Regards,
Owen

[AP2]

Thank Owen, just for be clare, my word "instability" I did not want to refer to the amplifier, but in the particular circumstance that was emerging. but you are right, positive rail contain pulse.
it is clear that we are in an extreme condition (startup lasts too long) then you must reduce that time to about 3 sec at 400mA.
Now i understand that "mute" not have action on driver, as enable /disable circuit.

[qusp]

Chris (hochopeper), can we use xBEE to set the bias you think? start at 200ma and ramp to 600-650ma after 10 seconds?

[hochopeper]

Originally Posted by qusp

Chris (hochopeper), can we use xBEE to set the bias you think? start at 200ma and ramp to 600-650ma after 10 seconds?

Was wondering how long till you to asked! Need to have another look at the amp [I haven't looked at it in much detail yet and it has been months since I've read owen's manual or looked at the schematic] and what interface options we've got. I'm not confident the xbee is the right tool for that job, but I'll look into it.