secrets of the dangerous music bax eq

sorry to disapoint. im not revealing the secrets here. just inquiring as to what they may be?
http://blog.digitalcontentproducer.com/briefingroom/2010/09/01/dangerous-music-releases-the-stereo-bax-eq/

this unit has been getting rave reviews

there are a few baxandall circuit schematics available on the web.
http://gilmore2.chem.northwestern.edu/projects/equal_prj.htm

would this circuit work for pro audio applications?

any ideas what the differences are. the bax says inspired by the baxandall frequency curves? do they acheive these curves with a different topology?  any one have one they can take a look at?

seavote said:

there are a few baxandall circuit schematics available on the web.
http://gilmore2.chem.northwestern.edu/projects/equal_prj.htm

would this circuit work for pro audio applications?

Click to expand...

This circuit is certainly usable for professional applications; it's the same circuit used in Neve, SSL, Neumann, API,...

any ideas what the differences are.

Click to expand...

There are a few variations of the basic Baxendall circuit. Type 1 on the attached schemo is the closest to the original publication. Type 2 is a variant inspired by the passive treble n' bass EQ (I think it's a "White" EQ). The difference between type 1 and 2 is that type 2 has slightly superior slopes (so less audible interaction with midrange) at the cost of an almost unpredictable lower midrange interaction.

the bax says inspired by the baxandall frequency curves?

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Sales blurb...

do they acheive these curves with a different topology? 

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They may. From the 50's, the so-called Thordarson EQ (at least, that's the name I remember, correct me if I'm wrong) is capable of producing similar curves with similar phase response (a consequence of the fact that they are both minimum-phase).
The Baxendall EQ has degenerated slopes (less than the expected 1st-order 6dB/octave); as a consequence, its phase response is quite smooth. Some manufacturer take advantage of this simple fact of life to claim almost divine properties.

Response of Type 1 Baxendall

Response of type 2 baxendall

Marketing foo...

Baxandall was indeed a significant improvement over the former passive EQ with make up gain, but that was several decades ago and I would venture that 99.9% of shelving EQ that you encounter in modern designs are good old text book Baxandall.

JR 

It seems to me that a lot (if not most) of the creativity in the audio equipment industry is no longer associated with design, but with marketing.

johnR said:

It seems to me that a lot (if not most) of the creativity in the audio equipment industry is no longer associated with design, but with marketing.

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And so the music on radio, mirror effect?

JohnRoberts said:

Marketing foo...

Baxandall was indeed a significant improvement over the former passive EQ with make up gain, but that was several decades ago and I would venture that 99.9% of shelving EQ that you encounter in modern designs are good old text book Baxandall.

JR   

Click to expand...

I had the surprise to find that Yamaha and Tascam seem to distinguish themselves by using a Thordarson.

;;;

JohnR:

I have an idea for a compressor that would do something I don't know how to implement.

I'd like to make a compressor that is also an aural exciter, *generating* higher-order harmonics, maybe adding even a wide hi-shelf EQ component, the harder it compresses. I know some tube compressors sort of do this in ways.

This would not be just to correct for high-frequency rolloff, but as an additive effect.

The trick is, you would be able to adjust the amount of harmonics separate from the compression threshold/ratio/attack, and also have a sidechain EQ control right on the thing that would let you set the center freq and bandwidth of the sidechain. That, and be able to bypass that EQ for a "normal" full signal detector.

Eh sorry for the hijack...

abbey road d enfer said:

 
I had the surprise to find that Yamaha and Tascam seem to distinguish themselves by using a Thordarson.

Click to expand...

Good for them..  I've seen that topology used more commonly for GEQ and multi-band EQ. With the basic Baxandall there may be more interaction between the parallel feedback paths than with the "Thoradson", while there will be some interaction there too.  BTW I've never heard it called that, I learn something new every day.  
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FWIW and perhaps TMI, I got a patent back in '96 (US05509080) for a variant on the Baxandall EQ where I added a clamp diode across the bass boost leg to limit bass boost to a finite voltage level. This was useful in constant voltage background music systems where too much bass boost could make the output magnetics saturate sooner. With my bass only clamp the customer could get full bass boost at low levels, where they needed it most for loudness compensation, but still not overdrive the transformers at higher level.  It sounded better than you would expect for a simple diode clipper because the Baxandall EQ topology was steering only the LF content to the diode clamp (like a crossover) so the unmolested clean HF signals flowing thought the unclipped path masked most bass clipping artifacts. While i could have designed a cleaner bass only limiter with a frequency dividing network in front, then a HF/LF re-combiner after, this diode clamp was about a $0.01 incremental parts cost, in a market that counts every penny. THIS IS NOT A HIFI CIRCUIT. It could be audible operating on a pure tone, but for typical background music and speech it gave the customers  all the bass boost they wanted and protected the output side magnetics.

JR  

JohnRoberts said:

abbey road d enfer said:

 
I had the surprise to find that Yamaha and Tascam seem to distinguish themselves by using a Thordarson.

Click to expand...

Good for them..  I've seen that topology used more commonly for GEQ and multi-band EQ. With the basic Baxandall there may be more interaction between the parallel feedback paths than with the "Thoradson", while there will be some interaction there too.  BTW I've never heard it called that, I learn something new every day.  

Click to expand...

As I said, that's how I remember it in the french HiFi and DIY magazines of the 50's; I tried to google the name and it seems ther's a thordarson company making inductors, so the connection may be genuine.

======

FWIW and perhaps TMI, I got a patent back in '96 (US05509080) for a variant on the Baxandall EQ where I added a clamp diode across the bass boost leg to limit bass boost to a finite voltage level. This was useful in constant voltage background music systems where too much bass boost could make the output magnetics saturate sooner. With my bass only clamp the customer could get full bass boost at low levels, where they needed it most for loudness compensation, but still not overdrive the transformers at higher level.  It sounded better than you would expect for a simple diode clipper because the Baxandall EQ topology was steering only the LF content to the diode clamp (like a crossover) so the unmolested clean HF signals flowing thought the unclipped path masked most bass clipping artifacts. While i could have designed a cleaner bass only limiter with a frequency dividing network in front, then a HF/LF re-combiner after, this diode clamp was about a $0.01 incremental parts cost, in a market that counts every penny. THIS IS NOT A HIFI CIRCUIT. It could be audible operating on a pure tone, but for typical background music and speech it gave the customers  all the bass boost they wanted and protected the output side magnetics.

JR  

Click to expand...

Very clever.

> Baxandall was indeed a significant improvement over the former passive EQ with make up gain

Disagree, kinda. Bax with linear pots and high-gain amp will give a flat response when centered and symmetrical up/down slopes. The James needs 10%-taper pots, is a pain to get flat, and is asymmetrical. But to my ears nothing beats a good James. Try the old Heathkit mono preamp. Try my modified Stromberg-Carlson.

Bax with a single 12AX7 is always slumpy; nearly any Fisher.

> the so-called Thordarson EQ (at least, that's the name I remember, correct me if I'm wrong)

Plausible. I think this would have been published as a Cathodyne, as in your Yamaha clip, not a triangle-amp, but same idea.

Great feature is it uses an inductor. Great for Thordarson!

The Dove console essays call this a Swinging Input. I think.

It is very popular in 3 to 9 band graphic EQs.

Your Yamaha plan appears to be Swinging Outputs.

> degenerated slopes (less than the expected 1st-order 6dB/octave)

Any simple 2-corner plan with less than 20dB between corners is doomed to <6dB/oct slope.

The "Thordarson" with an L-C tank (a la Yamaha PM1k) can hit greater slopes.

PRR said:

> degenerated slopes (less than the expected 1st-order 6dB/octave)

Any simple 2-corner plan with less than 20dB between corners is doomed to <6dB/oct slope.

The "Thordarson" with an L-C tank (a la Yamaha PM1k) can hit greater slopes.

Click to expand...

Both the Thordarson and the Baxendall have degenerated slopes because the frequency selective network is applied simultaneously to the input and feedback paths. The transfer function is not a simple biquad.
Using center-tap pots is the solution for interaction-free paths, which improves this aspect of performance, but anyway the self-imposed limitation on boost/cut amplitude imposes a restriction on the slope.

PRR said:

> Baxandall was indeed a significant improvement over the former passive EQ with make up gain

Disagree, kinda. Bax with linear pots and high-gain amp will give a flat response when centered and symmetrical up/down slopes. The James needs 10%-taper pots, is a pain to get flat, and is asymmetrical. But to my ears nothing beats a good James. Try the old Heathkit mono preamp. Try my modified Stromberg-Carlson.

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While I make a point to not argue with people about what they hear, my basis for considering the Baxandall EQ topology an improvement is for purely technical reasons. With lossy passive EQ and fixed makeup gain, the signal is always subjected to the full noise and distortion of the wide band fixed gain stage.

With the Baxandall approach the effective closed loop gain for the path only approaches the passive EQ example when commanding full boost and then only in the bandpass being boosted. For all other settings the loop gain margin and therefore performance (all things equal) will be better.

I consider this significant. but opinions vary...

JR

You can put "James" into the NFB loop of an (edit: NON-inverting) opamp (i.e. has HI input Z, unlike the "normal" baxandall which in practical use most often demands TWO opamps - one as a "driver", another the actual tone-control). You will to some extent circumvent the noise-at-makeup situation, but it has some other problems.

Blade guitars use(d?) such.

I had similar in 80's.. (homemade)

Imho, it's not for hifi purists and audiophiles, but it has almost-better fit for instrument electronics. One-opamp wonder.

riggler said:

JohnR:

I have an idea for a compressor that would do something I don't know how to implement.

I'd like to make a compressor that is also an aural exciter, *generating* higher-order harmonics, maybe adding even a wide hi-shelf EQ component, the harder it compresses. I know some tube compressors sort of do this in ways.

This would not be just to correct for high-frequency rolloff, but as an additive effect.

The trick is, you would be able to adjust the amount of harmonics separate from the compression threshold/ratio/attack, and also have a sidechain EQ control right on the thing that would let you set the center freq and bandwidth of the sidechain. That, and be able to bypass that EQ for a "normal" full signal detector.

Eh sorry for the hijack...

Click to expand...

Drawmer did this with their Spectral Compressor, I may have a scan of this.

Yes I do - sent to GroupDIY with a couple of other Drawmer rarities!!

Were the Drawmer circuits of interest?

Hi,


  I lashed together a James passive eq on some veroboard, using the DI input of a preamp to make up the gain. The response is far from flat, the skewed potentiometer response sucks, BUT . . . it sounds so damn good, I built a second one right there and then on the other end of the same piece of veroboard! They are in daily use, and I love them on vocals, drumbus, and kickdrum. You can just pile on the top or bottom! They are great in a mastering context to gently tilt a bit. I wish the top wouldnt roll off when set flat . . . .

  I will be building more of them, but looking into switches instead of pots, and switchable frequencies. I will also be trying a DOA as input buffer and as gain makeup. I hope to iron out the lumpy frequency response a bit . . .


  Simplicity rules!


  ANdyP

riggler said:

I'd like to make a compressor that is also an aural exciter, *generating* higher-order harmonics, maybe adding even a wide hi-shelf EQ component, the harder it compresses. I know some tube compressors sort of do this in ways.

Click to expand...

riggler, PM sent. I think this would make a good subject for a new thread.