this LM4702 has found a new home in a Crown DC150 -- for some reason the driver board in the crown was fried but the power supply in good shape:
An externally hosted image should be here but it was not working when we last tested it.
My LM4702 Integrated Amplifier
It use LM4562 and LM4702
Aiming at improving on the defects of sound effect and circuit of the LM4702 original machine, I apply the latest voltage current feedback technology to this product and achieve a better stability and tone quality than the original current feedback circuit.
It use LM4562 and LM4702
Aiming at improving on the defects of sound effect and circuit of the LM4702 original machine, I apply the latest voltage current feedback technology to this product and achieve a better stability and tone quality than the original current feedback circuit.
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Hi all,
I made a LM4702 amp with renesans MOSFETs three months ago. And listening it for three months. This is the schematic I use;
And this is the PSU and output delay circuit for it;
If I want to cirticise it (with my poor ear experiences of course) It is a really good amplifier. In fact its the best amplifier I did.
Mid and trebles detail are ver very clear.. I have three more gainclones (LM3886, LM3875, LM4780) however I cannot make a comparison it with them. Because theyre not in the same league!
I use 120mA BIAS current and 0,5°C/W heatsink gets very hot after 10 minutes! But I am very happy with it.
Except; Its very big and there is no place to put it in living room.
.......
I made a LM4702 amp with renesans MOSFETs three months ago. And listening it for three months. This is the schematic I use;
An externally hosted image should be here but it was not working when we last tested it.
And this is the PSU and output delay circuit for it;
An externally hosted image should be here but it was not working when we last tested it.
If I want to cirticise it (with my poor ear experiences of course) It is a really good amplifier. In fact its the best amplifier I did.
Mid and trebles detail are ver very clear.. I have three more gainclones (LM3886, LM3875, LM4780) however I cannot make a comparison it with them. Because theyre not in the same league!
I use 120mA BIAS current and 0,5°C/W heatsink gets very hot after 10 minutes! But I am very happy with it.
Except; Its very big and there is no place to put it in living room.
.......
It's a simple Vbe multiplier, it is reliable. You will want to spend some time optimizing the values for your required performance. For example, you can make it over compensating so that at the heat sink gets hot the bias current goes down more. How much down, or down at all, is all dependent on the value of the resistors. It takes time but what is shown in the note should get you started.
-SL
-SL
And,
They gave no optimal gate resistor values for IRFP240/9240 pair. However its the best alternative for 2SK1058/2SJ162 because, they can give 40W @ 0.0009% THD with only 25mA bias current..
Anyway, I have some questions;
- In AN-1645 figure27 shows a gate driver idea to have a better slew rate.. Has anybody tried that? May it cause any significant sound difference?
- Also in AN-1645, example circuit the gain resistor values 6K19 and 200R. And in AN1490 theyre 68K and 2K7. Is there any special reason to select these values in 6x and 2x ranges? Means if I use 47K/1K pair to have a higher gain (then I wont need a preamp) and to use just a unity gain buffer before it, does it cause any bad result or a sound difference?
....??....
They gave no optimal gate resistor values for IRFP240/9240 pair. However its the best alternative for 2SK1058/2SJ162 because, they can give 40W @ 0.0009% THD with only 25mA bias current..
Anyway, I have some questions;
- In AN-1645 figure27 shows a gate driver idea to have a better slew rate.. Has anybody tried that? May it cause any significant sound difference?
- Also in AN-1645, example circuit the gain resistor values 6K19 and 200R. And in AN1490 theyre 68K and 2K7. Is there any special reason to select these values in 6x and 2x ranges? Means if I use 47K/1K pair to have a higher gain (then I wont need a preamp) and to use just a unity gain buffer before it, does it cause any bad result or a sound difference?
....??....
Yes but theyre in AN-1645 advicement list for the output stage..
They also tested and had very near results to lateral MOSFETs..
In fact, the bias need of that MOSFETs (~100-150mA for lateral MOSFETs and just 25mA for IRFPs) supports your idea.
So under that situation; do you think we should use a different driving method for that MOSFETs? If so how?
They also tested and had very near results to lateral MOSFETs..
In fact, the bias need of that MOSFETs (~100-150mA for lateral MOSFETs and just 25mA for IRFPs) supports your idea.
So under that situation; do you think we should use a different driving method for that MOSFETs? If so how?
The IRs used in AN-1645 were for example of other FETs besides laterals. If you want to use these FETs then use the LME49830 instead of the LM4702. You cannot eliminate cross over distortion with the IRs. Do as you wish but I'd recommend determining which output devices you can get and what prices then choose what is best for you. The LME49830 is only mono but is better for driving FETs than the limited output current with the LM4702. You can use a buffer stage to increase output current, as shown in AN-1645.
-SL
-SL
1) Any comment to Application note
AN-1850: LME49830TB Ultra-High Fidelity High Power Amplifier Reference Design at http://www.national.com/an/AN/AN-1850.pdf
2) Any comment to LM4702, LME49810 or LME49830 with output stage using BJT or MOSFET, which sound will be better: BJT or MOSFET?
AN-1850: LME49830TB Ultra-High Fidelity High Power Amplifier Reference Design at http://www.national.com/an/AN/AN-1850.pdf
2) Any comment to LM4702, LME49810 or LME49830 with output stage using BJT or MOSFET, which sound will be better: BJT or MOSFET?
I have tested the 4702 with lateral MOSFETs (2SK1058/SJ162) for over one year. All I can say is with a suitable (may be a LM4562) preamp it sounds very good.
However, my project was not made from audio grade parts, especially I am not sure on Ci capacitor. I will try to run it without Ci...
I have another LM4702 sample in my drawer, and planning to use it with some SAPs... So I will see which is the best configuration, BJT or MOSFET?
However, my project was not made from audio grade parts, especially I am not sure on Ci capacitor. I will try to run it without Ci...
I have another LM4702 sample in my drawer, and planning to use it with some SAPs... So I will see which is the best configuration, BJT or MOSFET?
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