Hi
I have a small question regarding the power supply:
As far as I understand the front end gets higher supply voltage in order to operate not too close to its limits (linearity issues, distortion etc). But if I use the same supply voltage (using linear regulators (LM338 e.g.) and limited total power (80W am)) for both (front end and mosfets) and do not exceed the voltage limit: is there a difference?
Example: Using +-36V power Supply for both but only run it up to +-25V on the mosfet output using matched gain settings. Of course power is less than maybe possible with that voltage and more heat is generated....but what else?
Thanks!
I have a small question regarding the power supply:
As far as I understand the front end gets higher supply voltage in order to operate not too close to its limits (linearity issues, distortion etc). But if I use the same supply voltage (using linear regulators (LM338 e.g.) and limited total power (80W am)) for both (front end and mosfets) and do not exceed the voltage limit: is there a difference?
Example: Using +-36V power Supply for both but only run it up to +-25V on the mosfet output using matched gain settings. Of course power is less than maybe possible with that voltage and more heat is generated....but what else?
Thanks!
if you use different voltages for the front end and the rear end, you should look carefully at what happens when the amplifier starts to clip.
Clipping of the rear end generally sounds quite nasty and this is mostly due to the time it takes for large area devices to come out of saturation.
Clipping recovery in the front end can be made to sound less nasty and even inaudible with special "soft clipping" measures.
This has led me to consider that the "best" way to operate the LME series is with the same voltages on front and rear ends.
There is some advantage to using regulated, or ultra stable/smooth, supply for the front end, but at the same voltage.
Clipping of the rear end generally sounds quite nasty and this is mostly due to the time it takes for large area devices to come out of saturation.
Clipping recovery in the front end can be made to sound less nasty and even inaudible with special "soft clipping" measures.
This has led me to consider that the "best" way to operate the LME series is with the same voltages on front and rear ends.
There is some advantage to using regulated, or ultra stable/smooth, supply for the front end, but at the same voltage.
I would think that it would be nice to adjust the front-end ps voltages just to the point where the front-end clips before the back-end does or the other way around. This allows for the full dynamic range of the outputs, especially for the fets. Who knows there might be a sweet spot in there somewhere.
I always thought it was a good idea to have a clip detector in a power amp. Not too many of them do. 49811? i think has the clip detector circuitry.
I always thought it was a good idea to have a clip detector in a power amp. Not too many of them do. 49811? i think has the clip detector circuitry.
Hi there. I'm starting to finish the amp. Have made the boards. As for it is hard to lay my hands on the 20 pF mica capacitor, I found this one: 08052U220GAT2A (AVX microwave cap. Ultra low ESR.) What do you guys think of this capacitor? It's not mica but it looks like it has good quality. (I'm new here and will post in time some pictures of the project.)
Absolutely! I have measurements in this thread somewhere with 1A of bias current and pretty much exactly the rail voltage you describe. Performance is phenomenal with that setup. I ran mine for quite a while like that driving a small pair of full range speakers that didn't need much power.
The datasheet also has distortion info for a variety of bias currents, and it tracked quite well with what I saw in practice.
As a side note, the lateral FET amps will be back in stock in three weeks.
Regards,
Owen
Ordering details are in this thread - http://www.diyaudio.com/forums/vend...jects-available-here-bal-bal-se-se-lpuhp.html There are no kits anymore, too much hassle for almost zero return for Owen and no volunteers have put their hands up for arranging group buys of parts, but the order lists are pretty clear and easy to get parts for yourself
.Chris
I have few doubts
1. what if we want to scale the number of output mosfets? Im thinking to add a driver but can that be a transistor or it needs to be a mosfet if mosfet then which one do you suggest. If transistor which one is best suited to drive as many as 12 mosfets per rail.
2. The output stage of the LME49830 is not biased in class A hence this is not pure class A even if its output stage is biased in class A?
3. I thought of using LME49811 but its DC output is about 5V which after the VBE multiplier it might be about 4.5V. As checked the datasheet of the ALF16P20W for VGS 1.5V the drain current is 1Amp and I feel thats more than sufficient. Are the calculations right?
There are 2350 replies!!!!!!!!!!!!!!!!!!!!!!!! on this thread cant search it as it will take few days to traverse all of them to find out the distortion figures. I think it might be on your pc please post the figures to see the graphs if possible.
what about the bias stability of the circuit as I dont see any VBE multiplier and I agree these are lateral mosfets. I think it might take more time to settle the bias than with the VBE?
Searching for posts containing the word "measurements" by opc using advanced search to search this thread only will find the posts you're after.
One bunch of measurents here -there are others if you use method above and variations of it - http://www.diyaudio.com/forums/soli...lme49830-lateral-mosfets-107.html#post3016816
From memorythere were two batches of measurements with linear supplies (one with lme at same voltage as latfet other with higher voltage to lme). One batch of measurement for each DPS400 and DPS600 smps and another set looking at the clipping characteristics.
Since I have taken the time to explain this I hope at some point you take the opportunity to help someone else learn about the search features.
Chris
One bunch of measurents here -there are others if you use method above and variations of it - http://www.diyaudio.com/forums/soli...lme49830-lateral-mosfets-107.html#post3016816
From memorythere were two batches of measurements with linear supplies (one with lme at same voltage as latfet other with higher voltage to lme). One batch of measurement for each DPS400 and DPS600 smps and another set looking at the clipping characteristics.
Since I have taken the time to explain this I hope at some point you take the opportunity to help someone else learn about the search features.
Chris
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Thank you i just thought of searching from the member specific and just got reply from you.
The results seems pretty interesting and despite of the class AB output drivers of 830 the results seems pretty good but one thing which bothers me is the crossover distortion in HF because of the class AB stage.