Total Harmonic Distortion?

[SnowDrifter]

Could someone please explain to me how say... 1% harmonic distortion effects a sine wave? I know what THD is and that a lower amount is better - but not really the meaning of what percent it is.

And also: Does anyone know how I can produce a clipped sine wave of X% THD so I can hear what it sounds like?

Thanks!

[Wicks]

Could someone please explain to me how say... 1% harmonic distortion effects a sine wave? I know what THD is and that a lower amount is better - but not really the meaning of what percent it is.

And also: Does anyone know how I can produce a clipped sine wave of X% THD so I can hear what it sounds like?

Thanks!

It's hard to find a simple explanation but here goes:

http://en.wikipedia.org/wiki/Total_harmonic_distortion

THD is the ratio of the sum of the powers of the harmonic components compared to the power of the primary frequency.

Basically as you get distortion, harmonic components of the primary frequency are introduced.

If you're playing 40Hz, its harmonic components would be 80Hz(2x), 120Hz(3x), 160Hz(4x)... which would be incorporated into the original 40Hz.

Those higher frequency components would make the original sine wave look "fuzzy".

As you compare the ratio of the distortion components to the original, you look for 1% as that is considered barely audible.

If your primary 40Hz tone is 2W, then the distortion components would add up to 0.02W. 1% = 0.02W/2W

I believe the SMD DD-1 looks for 1% distortion (when the light turns on).

So without an o-scope and some complex calculations, the easiest way would be to buy a DD-1 and turn your gains up until the distortion light lights and then listen to the difference as you turn it back down.

It would probably be more noticeable using the 1kHz setting as 1% distortion at 40Hz is probably not audible as low frequency distortion is harder to perceive then at higher frequency's.

Make sense...

[SnowDrifter]

Could someone please explain to me how say... 1% harmonic distortion effects a sine wave? I know what THD is and that a lower amount is better - but not really the meaning of what percent it is.

And also: Does anyone know how I can produce a clipped sine wave of X% THD so I can hear what it sounds like?

Thanks!

It's hard to find a simple explanation but here goes:

http://en.wikipedia.org/wiki/Total_harmonic_distortion

THD is the ratio of the sum of the powers of the harmonic components compared to the power of the primary frequency.

Basically as you get distortion, harmonic components of the primary frequency are introduced.

If you're playing 40Hz, its harmonic components would be 80Hz(2x), 120Hz(3x), 160Hz(4x)... which would be incorporated into the original 40Hz.

Those higher frequency components would make the original sine wave look "fuzzy".

As you compare the ratio of the distortion components to the original, you look for 1% as that is considered barely audible.

If your primary 40Hz tone is 2W, then the distortion components would add up to 0.02W. 1% = 0.02W/2W

I believe the SMD DD-1 looks for 1% distortion (when the light turns on).

So without an o-scope and some complex calculations, the easiest way would be to buy a DD-1 and turn your gains up until the distortion light lights and then listen to the difference as you turn it back down.

It would probably be more noticeable using the 1kHz setting as 1% distortion at 40Hz is probably not audible as low frequency distortion is harder to perceive then at higher frequency's.

Make sense...

Perfect sense! Thanks!