Class-A bias EF output stage
I use bias the EF output stage in Class-A for up to 18 W/8 Ohm (49810+MJE15031/30+ThermalTrak). The DC rail is +/- 24V. The performance is very very good!!! Here are some curves. This is a nice (affordable) 10 W Class-A amp!
I use bias the EF output stage in Class-A for up to 18 W/8 Ohm (49810+MJE15031/30+ThermalTrak). The DC rail is +/- 24V. The performance is very very good!!! Here are some curves. This is a nice (affordable) 10 W Class-A amp!
Attachments
Although 49810 and 49811 are "very" similar, 49811 has better PSRR over frequency (from data sheet and my measurement). Does it contribute to better sonic performance?
As pointed out by Mark/audioman54 that 49811 output is Class-A whereas 49810 output buffer is Class-AB biased. I recently measured Vee and Vcc current of the chips. Does 49811 Class-A operation contribute to lower THD compared to 49810?
Are the chips being used in any products?
As pointed out by Mark/audioman54 that 49811 output is Class-A whereas 49810 output buffer is Class-AB biased. I recently measured Vee and Vcc current of the chips. Does 49811 Class-A operation contribute to lower THD compared to 49810?
Are the chips being used in any products?
I believe it can be this. A better, cleaner power does attain results that are often beyond what the instruments says.
Panson,
Are you putting the 3 pair boards up for sale on your website yet?
With the added width of the thermal trak chip it seems we should have better cooling with the increased contact area.
What number thermal trak diodes are you having to use to attain proper Vbe in the circuit?
Does anyone know if the LME49830 is using a class A driver?
Nice work Panson. The specs on these chips is quite exceptable.
Tad
Are you putting the 3 pair boards up for sale on your website yet?
With the added width of the thermal trak chip it seems we should have better cooling with the increased contact area.
What number thermal trak diodes are you having to use to attain proper Vbe in the circuit?
Does anyone know if the LME49830 is using a class A driver?
Nice work Panson. The specs on these chips is quite exceptable.
Tad
Hi Tad,
I can measure the Icc and Iee current of 49830 to "know" whether its output is class-A or not.
Yes, the new boards will be added to my website. For the ThermalTrak diodes, I will do some tests (for 3-pair, 4-pair) and present the results.
Carl,
Aavid Thermalloy 530101B00150 Digikey or Mouser
See national semiconductor app note AN-1850 bill of materials
Ken
LME49811 and LM4702 heatsinks
If you run the LME49811 at 50VDC you don't need a heatsink. I have run the exact amplifier in AN-1490 (the LM4702 chip which is in a Bigger Package than the LME49811) in my sound room for 3 years at 50VDC without a heatsink along with the 10 or more prototype demo units at National Semi when I was still there. I have also run the LME49811 (smaller package than the LM4702, i.e. cheaper) mono blocks built in the same enclosure as the stereo LM4702 amps at 50VDC without a heatsink for a lesser time period as well... However at 75VDC rails you will need a heatsink! (The heatsink listed in the BOM on AN-1850 was the only one that we found that fit the LME49811 and 810 and is a pain to mount!) Please if anyone who is heatsink savvy out there knows of one that is a better fit please let us know, as that would be wonderful! I also wanted a hole in the packages to be able to screw on a heatsink but was unable to get that!
In addition I also wanted it in a metal can but that turned out to be quite difficult! We did actually try and get the packaging folks to do it. They spent a great deal of effort on the project but it turned out they had lost the ability (People?) to do a multi-lead TO-3... without it leaking!
Mark / Audioman54
If you run the LME49811 at 50VDC you don't need a heatsink. I have run the exact amplifier in AN-1490 (the LM4702 chip which is in a Bigger Package than the LME49811) in my sound room for 3 years at 50VDC without a heatsink along with the 10 or more prototype demo units at National Semi when I was still there. I have also run the LME49811 (smaller package than the LM4702, i.e. cheaper) mono blocks built in the same enclosure as the stereo LM4702 amps at 50VDC without a heatsink for a lesser time period as well... However at 75VDC rails you will need a heatsink! (The heatsink listed in the BOM on AN-1850 was the only one that we found that fit the LME49811 and 810 and is a pain to mount!) Please if anyone who is heatsink savvy out there knows of one that is a better fit please let us know, as that would be wonderful! I also wanted a hole in the packages to be able to screw on a heatsink but was unable to get that!
In addition I also wanted it in a metal can but that turned out to be quite difficult! We did actually try and get the packaging folks to do it. They spent a great deal of effort on the project but it turned out they had lost the ability (People?) to do a multi-lead TO-3... without it leaking!
Mark / Audioman54
Mark,
Here is URL to the part "Clip On" Heatsinks, HS Type, HS-010, HS-011, HS-012
I think it looks ideal. What do you think?
Here is URL to the part "Clip On" Heatsinks, HS Type, HS-010, HS-011, HS-012
I think it looks ideal. What do you think?
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