The last few replies I entered to clarify the performance differences between the LM3875/Lm3876 and the 3886.
the differnce between the LM3875 and LM3876 are simply that at a critical point of the voltage amplification stage the Lm3876 has a seperate -ve rail input that allows the flexibility of mute control. In reality the performance difference between the 3875 and 3876 is really quite negligable.
the Lm3886 has a beefed up output stage (Bigger output transistor junctions), which translates to reduced total harmonic distortion, greater efficiency and more short term power dissipation capacity.
I have no idea why the 3875 and 3876 have lower noise stats but it does show in the 20kHz graph as an improvement in high frequency performance for these chips at low output power(<10W).
When you look at all of these graphs as a whole it is quite clear that the LM3886 is considerably better in a number of ways, so I would suggest to use the 3886 unless availability or cost is an issue.
the differnce between the LM3875 and LM3876 are simply that at a critical point of the voltage amplification stage the Lm3876 has a seperate -ve rail input that allows the flexibility of mute control. In reality the performance difference between the 3875 and 3876 is really quite negligable.
the Lm3886 has a beefed up output stage (Bigger output transistor junctions), which translates to reduced total harmonic distortion, greater efficiency and more short term power dissipation capacity.
I have no idea why the 3875 and 3876 have lower noise stats but it does show in the 20kHz graph as an improvement in high frequency performance for these chips at low output power(<10W).
When you look at all of these graphs as a whole it is quite clear that the LM3886 is considerably better in a number of ways, so I would suggest to use the 3886 unless availability or cost is an issue.
Looks like the LM3886 has bigger output transistors than the Lm3875 but the output transistor capacitance has increased as a function of die area so the high frequency performance is not so good
A similar thing can be seen with the ST parts TDA 2030 through to the TDA2051. If you look at the zobel network needed for the TDA devices the resistor goes down while the capacitance goes up as the current increases.
In other words the output needs to be slugged heavier with high current devices for stability.
Some people here seem to get away with no zobel networks on the national parts. I think their amplifiers are probably oscillating albeit at a low level.
A similar thing can be seen with the ST parts TDA 2030 through to the TDA2051. If you look at the zobel network needed for the TDA devices the resistor goes down while the capacitance goes up as the current increases.
In other words the output needs to be slugged heavier with high current devices for stability.
Some people here seem to get away with no zobel networks on the national parts. I think their amplifiers are probably oscillating albeit at a low level.
Sorry to "ask a question and disappear" but each time I went to respond more data arrived! Thank you all for your thoughts, it has been enlightening for someone with limited chip experience. I will be spending more time with the data sheets.
As I said at the outset, the 3886 kit from Brian realy sounds wonderful and for someone with a preference for tubes that's quit an admission.
The bottom line for me are the last comments regarding the Hi-Freq performance of the 3875/6 as I am planning on using the next amp in triamp to drive a Vifa XT tweet. probably from 5-6 K Hz and up, and certainly within the 10 watt range.
Again, thanks to all for your information.
Pete
As I said at the outset, the 3886 kit from Brian realy sounds wonderful and for someone with a preference for tubes that's quit an admission.
The bottom line for me are the last comments regarding the Hi-Freq performance of the 3875/6 as I am planning on using the next amp in triamp to drive a Vifa XT tweet. probably from 5-6 K Hz and up, and certainly within the 10 watt range.
Again, thanks to all for your information.
Pete
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