Discussing the EQ

[BJF]

So in the Studiomaster EQ schematic, is the Mid Frequency dual ganged control changing the center frequency with a fixed width, or is it changing the bandwidth with a fixed center frequency? I suppose the thing to do is to build it up and try it.

At a previous job I had regular access to one of these bad boys http://ap.com/products/2700 which would be perfect for analyzing changes to EQ circuits visually. Anyone use any similar hardware/software measurement tools that are available to the DIY'er?

Hi,

What Studio Master Schematic?

I could comment if I knew what it was......

Ah, that's a piece of work- I wonder what it would preform at 1V square

just kidding

Well one can see but then also hear but what does it mean?

The hard part in this is that music and sound is not an exact science or at least not viewed that way.
It can get very complicated since sound can be said to have travelled through generations and exact studies on the uses are lacking while still it could be said that the impact of fuzz guitar on people's minds is greater than man walking on the Moon!

But still yes it is fun to see and in these days when sound must be kept low especially for sound technicians it is a magic tool.

Ah no, I haven't I'd confess to being oldschool again.

Have fun
BJ

[ibodog]

Well, of course the meaning to the sound will not be had from a pretty picture alone. However the mind has evolved quite a complex system for dealing with visuals and I think it is good to be able to tap that as well as the auditory system and to create some connections between the two. You have to use your judgment/taste to create the meaning. The visuals (and even audibles to some degree) are cues to help in the remembering and communicating. Creating the language is even harder...

[BJF]

Hi,


Yes the language......




The two questions

What is the Studio Master that you asked for?

What does it mean?

The latter is wide as it asks what is it that needs eq?
It is one thing to eq a guitar sound in the system so to say and another when recording the system..
And now just talking in the system one could say there would be about half as many sounds as there are guitarists....
but anyway eq for guitar or eq for recording by all means why not both in a thread about eq?
Actually language is the key and this with the visual represetation is also important as it has also led to recordings of sausage form......again it is important to understand and interperate just as you say.

As a not for guitar eq's those can often be used to compensate for set filtering in amplifiers or pedals as noted above.
One drawback as I see with many pedal eq's is that many use a noise reductionfilter that boosts treble at the input and cuts treble at the output and these curves can never meet also so depending on the accuracy of these filters sound can be slightly dulled passing through the EQ trying to compensate for this can often bring up the wrong treble........
Watch this with squarewave and see what happens...........
Whenever you try an EQ visually you pass it with square as it would show clearly what it does.

Have fun
BJ

[ibodog]

Like this? Check the link for explanation of the test conditions. At my previous job dealing with recording equipment I used to run tests like this with a burst generator to also check that the signal was not inverted and to validate any other odd measurements that may have been noticed.
http://ap.com/products/2700/analog_performance

[BJF]

Hi,

Ah not really you'd look at things like that with poweramps if you'd be talking audio and not digital and I'm going of on a tangent here. You've got some overshot and some ringing on channel B.
You can go into the specific design to correct that as far as possible and for guitar use ahum we'd not exactly be talking linear amplification.........but nonlinear amplification.

I meant more like if you'd take an EQ and feed that with square and watch the output on a scope you'd see ......
However that maybe more a service trick to check EQ's ahum but as I recall it was also on the curricullum
electronics degree like what kind of filter is this?

Doesn't really mean anything

What did you want to know about that Master EQ?


Have fun
BJ

[ibodog]

What did you want to know about that Master EQ?

The bottom trace is a DSP generated square wave through a 96kHz DAC showing the effects of the DAC's filters versus the high quality analog square wave generated by that Audio Precision measurement instrument. I suspect that even on really good monitors that 99.99% of people could not tell the difference in a blind listening test. Only sensitive equipment like this is good at finding and showing the difference. Anyway, like you said it shows the effect of a filter on a square wave input.

It must be that the schematic I linked is not showing in my post? Here is a direct link:

I suppose this EQ would need in/out buffer for use in a pedal? Also would like to fix the Bass frequency appropriately for guitar but be able to vary the Treble frequency instead. Also the dual-gang mid control - is it changing the bandwidth of the mid band or the center frequency of the mid band? If it is changing one of these, how to change the other?

[BJF]

What did you want to know about that Master EQ?

The bottom trace is a DSP generated square wave through a 96kHz DAC showing the effects of the DAC's filters versus the high quality analog square wave generated by that Audio Precision measurement instrument. I suspect that even on really good monitors that 99.99% of people could not tell the difference in a blind listening test. Only sensitive equipment like this is good at finding and showing the difference. Anyway, like you said it shows the effect of a filter on a square wave input.

It must be that the schematic I linked is not showing in my post? Here is a direct link: http://www.fortunecity.com/tinpan/humpe ... 3/stma.gif

I suppose this EQ would need in/out buffer for use in a pedal? Also would like to fix the Bass frequency appropriately for guitar but be able to vary the Treble frequency instead. Also the dual-gang mid control - is it changing the bandwidth of the mid band or the center frequency of the mid band? If it is changing one of these, how to change the other?

Hi,

Oh, If you posed a schematic it didn't show and neither does the the link it just shows an icon that has a webb address.

More later

have fun
BJ

[ibodog]

Ah, that host must not like outside links in to the images... http://www.fortunecity.com/tinpan/humpe ... effect.htm then scroll down to STUDIOMASTER EQ for the correct link to the schematic. Or this for the time being:

[VacuumVoodoo]

P1a & P1b is a dual gang pot for midrange center frequency adjustment. Dual gang antilog can give a frequency change in octave per equal rotation angle but antilog duals with good tracking are very difficult to make and thus expensive. Poor tracking on dula antilogs will cause varaiation of Q over pot rotation. You can always substitute a dual rotary switch with pairs of equal resistors for a selection of fixed center frequencies. You can get dula 12 position quality switch from Greyhill.

To change the Treble eq onset frequency you can have a switch for different values of the capacitor that is 1nf in the schematic.

I need to dive into my old design notes and post a nice fully parametric EQ I once made....sometime in the early 1980s, there's a small chance I still have PCB artwork for it

[Donner]

hmmm this could be an interesting project Alex - everyone needs a parametric EQ whether they know it or not