to snubberize or not to snubberize

[jberends]

I am fairly new to this subject and I am wondering if anytone could point me to a good source that explains clearly about the whole thing on snubberization. I am fairly lost in searches on diyAudio and Google.

So basically: What is snubberize? Why does it make the world a better place.

[moving_electron]

Originally posted by jberends
I am fairly new to this subject and I am wondering if anytone could point me to a good source that explains clearly about the whole thing on snubberization. I am fairly lost in searches on diyAudio and Google.

So basically: What is snubberize? Why does it make the world a better place.

The Carlos' snubberized Gainclone Power supply thread is probably the best discussion of what is going on electrically. There was some pretty interesting network analyser measurements posted. You have to search for "snubberized" to find it.

The short form is this:

In order to have a good power reserve that can be utilized by an amp you tend to need a fairly high capacitance on the power supply smoothing caps. 10,000uF per rail for example.

This high capacitance has two main benefits.
1) It smoothes out the rectified power to produce low noise DC by reducing 60Hz hum to a sufficiently minimal level (for many amp designs)
and
2) You have a power reserve held by the caps that can discharge to cover large transient demands such as needed by a large bass sound or higher volumes.

But alas, nothing comes for free in audio except part spec improvements and clever design improvements. So there is a trade off with the high cap. They have a high inductance as well and their effective "capacitance" effect falls as the frequency rises.

Whatever the reason for the effect on the chip amps, the following has been the experience related to the LM chip amps: High capacitance has not sounded particularly good.

This was overcome with the original Gaincard commercial product which used a fairly low capacitance power caps. This design spawned the Gainclone designs. It was found that 1500uF provided enough smoothing that the hum was sufficiently low for the chip amps, given the chip amps designed in ability to reject the hum to a great extent. It has been proposed that LM chips don’t perform well to high inductance in the power supply and are therefore more sensitive to this than other amp designs. Lower value supply caps have a lower inductance value presumably and the focus on putting the caps very close to the chip pins presumably reduces the inductance even further.

This “gainclone classic” (1500uF supply caps) configuration is regarded as sounding quite good and many DIY amps have been built to the satisfaction of the builders.

But the lack of reserve can produce detrimental effects on the highs and mids when there are large bass or volume demands. The bass can be “loose” or otherwise lacking depending on how demanding the speakers or volumes are.

The snubberized supply uses high capacitance power supply caps but via a series of resistors, caps, and cap and resistor combinations between the supply caps and the chip amp, which changes the inductance seen by the chip amp at different frequencies.

The result is currently regarded as a way to get the benefits of both the high capacitance supply as well as get the benefits of the 1500uF supply. So it appears to be a best of both worlds for most systems even if it lacks the simple elegance of the “gainclone classic”.

Gainclone "classic" work continues as well though and has good reported results with higher efficiency speakers and particular part selection.

But for the general case of building an amp and hooking it to speakers with normal or lower efficiency the “Snubberized” appears to be the best way to go currently.

[x. onasis]

Nicely said Moving_Electron, this gets my vote as the most lucid post on the subject.

[jberends]

Thank you very much for make it this crystal clear. Very helpful.

Jochem

[peranders]

Originally posted by moving_electron
The snubberized supply uses high capacitance power supply caps but via a series of resistors, caps, and cap and resistor combinations between the supply caps and the chip amp, which changes the inductance seen by the chip amp at different frequencies.

This is not completely correct.

This is what happens: The impedance of the power supply is decreasing with increasing frequency and at a certain point you have a minimum (series resonance) and very close you will also have a small impedance peak (parallel resonance) caused by the inductance between the big cap and small one. This small peak (yes it isn't very big at 1 MHz or so) can be reduced by inserting losses in form of a resistor, 0.5-5 ohms.