## Scale signal in EQs to reduce quantization?

Sound synthesis techniques, DSP and related mathematics

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### Scale signal in EQs to reduce quantization?

Dont remember if i asked this once before. Sorry if i did. But, SM uses floating point... Is there any point in scaling the signal going into a biquad filter in a SM design considered the use of floating point precision? As I understandit is will not make any difference. But am I wrong here?
I guess the case in the article is a fixed system.
Any sufficiently advanced technology is indistinguishable from magic.
Arthur C. Clarke, "Profiles of The Future", 1961 (Clarke's third law)

http://www.audioteknikk.net

tor
essemilian

Posts: 462
Joined: Wed Apr 14, 2010 8:52 pm

### Re: Scale signal in EQs to reduce quantization?

they are talking about integers - with floating point i would guess its still preferrable to stay in -1/1 since float resolution is not equally spaced. you could try to add dc of say 500 000 and hear if it makes a difference.

MichaelBenjamin
smaniac

Posts: 1439
Joined: Thu Jul 12, 2007 3:26 pm

### Re: Scale signal in EQs to reduce quantization?

MichaelBenjamin wrote:add dc of say 500 000 and hear if it makes a difference.

Adding a large fixed number will reduce the resolution, as you would be confining the original +1/-1 to fewer bits in the mantissa of the float number. The bigger the number you add, the lower the resolution of the smaller part that you are interested in.
As a simple analogy, imagine I have a calculator that can only show 8 digits. The decimal point can be shown at any place across the screen - so it is a sinple form of 'floating point' maths.

so..
4.5 +
3.0002
=7.5002

No problem, the decimal place moved further left, and we can still see the whole result.
But...
10000000 +
3.0002
=10000003

Or
0.0000001 /
10
=
0.0000000

Something is lost with these examples because there are no more digits left or the decimal point couldn't move any further.
Float numbers work very much like this - there are 23 bits representing the 'digits' (matissa) and 8 bits representing the 'position of the decimal point' (exponent), plus a sign bit for +/-.

Scaling (multiplying) your input wouldn't alter the precision (same number of digits), but might allow a feedback loop to go on longer before the numbers got too small (run out of decimal places). But in practice those numbers are so small, that a soundcard could never represent them anyway.

The Wiki article about IEEE754 has a few useful explanations and tables about the limitations of float numbers.
Feel free to use any schematics and algorithms I post on the forum in your own designs - a credit is appreciated (but not a requirement).
Don't stagnate, mutate to create. Without randomness and serendipity the earth would be just another barren rock.

trogluddite
smychopath

Posts: 3024
Joined: Mon Oct 20, 2008 3:52 pm
Location: Yorkshire, UK

### Re: Scale signal in EQs to reduce quantization?

Thank you for the nice refreshing explanation and examples Trog. Some times i just start to doubt what i earlier have learned. You have the abilty to explain things so even my mother could understand. Are you or have you concidered becoming a teacher?
Any sufficiently advanced technology is indistinguishable from magic.
Arthur C. Clarke, "Profiles of The Future", 1961 (Clarke's third law)

http://www.audioteknikk.net

tor
essemilian

Posts: 462
Joined: Wed Apr 14, 2010 8:52 pm

### Re: Scale signal in EQs to reduce quantization?

tor wrote:explain things so even my mother could understand.

He he, I do provide a kind of '24hr telephone tech. support' for my mother, she decided to become a 'silver surfer' when she retired.
Thanks for the compliment doing the little examples often reminds me of things that I had forgotten.
Feel free to use any schematics and algorithms I post on the forum in your own designs - a credit is appreciated (but not a requirement).
Don't stagnate, mutate to create. Without randomness and serendipity the earth would be just another barren rock.

trogluddite
smychopath

Posts: 3024
Joined: Mon Oct 20, 2008 3:52 pm
Location: Yorkshire, UK

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