I know a lot of different buffers have been discussed in quite a lot of those forums, but I've been wondering if anyone has experience with the latest and the greatest that is out. What good, chip buffers are there and still available nowadays? The latest mentions for chips that I've seen talk about the LME49600. How does that compare to other commonly used buffers, compared to people's experiences with it? For example, compared to BUF634.
How about trough-hole buffers, for all those SMD-weary? (I'm sure I can solder a TO-263 allright, but just wondering)
They all have a catch somewhere though, the LME49600 is hard for me to find, the BUF634 has definitely worse specs and costs quite a lot of money...
Is anything else worth the try?
How about trough-hole buffers, for all those SMD-weary? (I'm sure I can solder a TO-263 allright, but just wondering)
They all have a catch somewhere though, the LME49600 is hard for me to find, the BUF634 has definitely worse specs and costs quite a lot of money...
Is anything else worth the try?
LME49600 seems to be a slightly better version of BUF634 and you can choose the package according to your own preferences. Since the buffer is a big part it's rather easy to solder even in SMD verision. If you want to solder the one in the picture, just burn for some time and two soldering irons will of course help but it's not necessary.
The LME49600 is actually quite excellent as a buffer. I measured the THD+N
of it and there is no difference between it and going strait into my ADC.
THD+N at a level of around 1.7v RMS is < .0006% (the limit of my DAC/ADC)
with a load of 5k ohms. Also to note, the higher order harmonics didn't seem to
change, which means that the output transistors on the chip are very closely
matched and don't seam to be adding any crossover distortion. Same spectral
content at about 5mv RMS both with and without the buffer. The noise floor
was also about the same. All this without any negative feedback!
of it and there is no difference between it and going strait into my ADC.
THD+N at a level of around 1.7v RMS is < .0006% (the limit of my DAC/ADC)
with a load of 5k ohms. Also to note, the higher order harmonics didn't seem to
change, which means that the output transistors on the chip are very closely
matched and don't seam to be adding any crossover distortion. Same spectral
content at about 5mv RMS both with and without the buffer. The noise floor
was also about the same. All this without any negative feedback!
LME49600 seems to be a slightly better version of BUF634 and you can choose the package according to your own preferences. Since the buffer is a big part it's rather easy to solder even in SMD verision. If you want to solder the one in the picture, just burn for some time and two soldering irons will of course help but it's not necessary.
Made with a Macintosh? Does that make it prouder?
Yes, open loop (that's why I said "without any negative feedback").
I also measured the IMD and there was no difference with or without the
buffer, but my setup seems to have high IMD, so maybe there is a tiny
difference that I could not see.
And how was the sound with and without the buffer? That's the interesting part
Sorry, haven't gotten that far yet. Still don't have all the bits together.
I will post my opinion after I get everything put together.
Made with a Macintosh? Does that make it prouder?
Not many pcb's are made with a native pcb software. I used a 15000 USD software the german RUN Electronic Design System. The software was a bit special, the only software in the world with "real"-annotation. The project was in a single file with 100% synchronisation between schematics and the layout and it happened in real-time. If I inserted a resistor in the schematics, boom you have a resistor in the pcb.
Just wanted to give an update on my measurements of the LME49600 as an
open loop buffer (no feedback). Sorry, still no listening tests yet...
I got my measurement setup working quite good now. It was just some settings
for the audio interface and the software. I still don't think it is optimal, but there
is nothing I can do further (may be a software bug).
Anyway, my setup resolution is THD+N = .00055% and IMD = .0005%
With the buffer in the circuit, the THD+N = .0006% and the IMD is the same.
I noticed a small peak of 2nd harmonic with the buffer added. This is at full scale
signal level (about 1.7v RMS). At lower signal levels, the THD+N is the same
with or without the buffer.
Circuit configuration is + and - 15v supply using Linear Tech adjustable regs.
Buffer input resistor is 100 ohms and output resistor is 100 ohms. AC coupling
on the input is 1 uF with 100k bias resistor to ground and the output coupling
is 33uF.
I also made distortion measurements with a simple single pole low pass filter
on the output... 1k resistor with 6800pF cap (about 23.4kHz) and there was
no change in distortion performance.
The LME49600 really is a great buffer chip. I can't wait to actually listen to it!
open loop buffer (no feedback). Sorry, still no listening tests yet...
I got my measurement setup working quite good now. It was just some settings
for the audio interface and the software. I still don't think it is optimal, but there
is nothing I can do further (may be a software bug).
Anyway, my setup resolution is THD+N = .00055% and IMD = .0005%
With the buffer in the circuit, the THD+N = .0006% and the IMD is the same.
I noticed a small peak of 2nd harmonic with the buffer added. This is at full scale
signal level (about 1.7v RMS). At lower signal levels, the THD+N is the same
with or without the buffer.
Circuit configuration is + and - 15v supply using Linear Tech adjustable regs.
Buffer input resistor is 100 ohms and output resistor is 100 ohms. AC coupling
on the input is 1 uF with 100k bias resistor to ground and the output coupling
is 33uF.
I also made distortion measurements with a simple single pole low pass filter
on the output... 1k resistor with 6800pF cap (about 23.4kHz) and there was
no change in distortion performance.
The LME49600 really is a great buffer chip. I can't wait to actually listen to it!
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At first, I didn't think I had any BUF634 chips laying around... but yes, I have a
couple.
All circuit connections are the same as with the LME49600 measurement.
At full scale, the THD+N is .0007%. Only slightly worse than the LME49600. It is
mainly 2nd harmonic as you can see in the plot (Spectrum3.pdf). With a 220
resistor, the THD+N gets slightly worse at .00085%. Again, an increase in 2nd
harmonic (Spectrum4.pdf). IMD was the same for both BW pin settings at
.0005%.
Although not as good as the LME49600, it is still excellent for no feedback!
Also, my baseline IMD is .0004%, not .0005% as I previously stated.
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