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previous: Mike Maki Hi,Can someone tell... -- 2/8/2000 6:32 PM

Re: Tone Controls

2/8/2000 7:15 PM
SteveR	Re: Tone Controls Hi Mike, I think you don't find four or five band passive eqs because the falloff of passive tone circuits is so gradual that you would either have controls that extended beyond a useful range (for a guitar amp) or the controls would stomp all over each other and would be difficult to use. To get a tight bandwidth (steeper falloff) of a specific control you need to have an active cicuit. People usually use SS components for these because they are smaller, cheaper, and easy to implement. They don't require high voltages. And because the tone circuit isn't supposed to generate clipping or overdrive distortion, they sound just fine within their linear range. You don't necessarily want the active component of the tone circuit to color the sound. That's what the inductors, caps, and resistors are for. They usually include a standard passive tone stack because these shelving types will essentially take care of ALL the lows below a certain point and ALL the high above a certain point. This provides very general tone shaping, and then the mid controls more actively allow detailed "voicing". For a tone stack alternative check out Duncan's web site at: http://duncanamps.simplenet.com/technical/technical.html He's got some great info on the Baxandall circuit which has a lot of versatility for just two controls. I know that years ago I ran across both a tube-based five band fixed EQ and a two band parametric in an old HAM ammature radio book, but it has long since disintegrated. I think it was Ken Gilbert who posted a link for a semi parametric EQ that used four tube stages (or was it four tubes? I don't remember!) Ken? Hope this helps. SteveR

2/8/2000 7:15 PM

SteveR

Re: Tone Controls

Hi Mike,

I think you don't find four or five band passive eqs because the falloff of passive tone circuits is so gradual that you would either have controls that extended beyond a useful range (for a guitar amp) or the controls would stomp all over each other and would be difficult to use.

To get a tight bandwidth (steeper falloff) of a specific control you need to have an active cicuit. People usually use SS components for these because they are smaller, cheaper, and easy to implement. They don't require high voltages. And because the tone circuit isn't supposed to generate clipping or overdrive distortion, they sound just fine within their linear range. You don't necessarily want the active component of the tone circuit to color the sound. That's what the inductors, caps, and resistors are for.

They usually include a standard passive tone stack because these shelving types will essentially take care of ALL the lows below a certain point and ALL the high above a certain point. This provides very general tone shaping, and then the mid controls more actively allow detailed "voicing".

For a tone stack alternative check out Duncan's web site at:

http://duncanamps.simplenet.com/technical/technical.html

He's got some great info on the Baxandall circuit which has a lot of versatility for just two controls.

I know that years ago I ran across both a tube-based five band fixed EQ and a two band parametric in an old HAM ammature radio book, but it has long since disintegrated.

I think it was Ken Gilbert who posted a link for a semi parametric EQ that used four tube stages (or was it four tubes? I don't remember!) Ken?

Hope this helps.

SteveR