Barry Porter "Net EQ"

[abbey road d enfer]

The story of Q
http://www.collinsaudio.com/Prosound_Workshop/The_story_of_Q.pdf

Thanks for this document.
I can see that the concept drifted perniciously from the original meaning to EQ's without any caveat regarding the validity domain, which is an essential part of any scientific approach. I t is often stressed in this document that the notion pertains to circuits with a high "sharpness of resonance", a term I very much like.

 

[abbey road d enfer]

I looked it up and can be found here Constant-Q Graphic Equalizers

Attached are the graphs of what he is calling Q that varies with boost/cut vs constant Q.

The graph at fig. 4 is a typical example of deliberate misinformation. Photoshop can prove any assertion and its contrary.

 

[JohnRoberts]

The graph at fig. 4 is a typical example of deliberate misinformation. Photoshop can prove any assertion and its contrary.

I never put a RANE GEQ on a scope, but Dennis Bohn is a well respected engineer/businessperson and I'm inclined to believe him. His graphic artist may have exaggerated the curves.

JR

PS: Coincidentally when I was lobbying for an AES standard for Q in boost/cut EQs, Dennis was supportive of my effort.

 

[abbey road d enfer]

I never put a RANE GEQ on a scope, but Dennis Bohn is a well respected engineer/businessperson

I know, but however, the case for 3dB boost that shows non-asymptotic tails is hard to believe, unless a high-order filter is used, which would put it out of comparison.

 

[JohnRoberts]

Rane sold lots of those GEQ, maybe somebody here can get hands on one and scope it? A schematic would be instructive. I will speculate that it does not use high order filters inside a 30 band EQ, but I never checked under the hood of one.

JR

 

[moamps]

A schematic would be instructive.

https://www.ranecommercial.com/legacy/pdf/old/ge30sch.pdf

I will speculate that it does not use high order filters inside a 30 band EQ, but I never checked under the hood of one.

"The GE 30 is, as are all Rane equalizers, a constant bandwidth device. This guarantees that the Q (a measure of bandwidth) of all the 1/3-octave filters will be maintained regardless of the position of the filter’s slide control. This is accomplished by completely isolating the center frequency and bandwidth parameters of each filter from the variable resistor connecting the filter to the signal path. The sliders simply act like mixer faders
would; they sum the outputs of the filters to one of four different buses—two boost buses and two cut buses. This sort of careful attention to design allows Rane equalizers to perform as no others.
A further benefit of the constant-Q approach is the ease with which 0dB of boost or cut can be guaranteed when the control is set at zero. The filter slide controls feature a grounded center tap in the Boost/Cut mode and a grounded 0dB position in the CutOnly mode. This ensures that none of the filters will affect the
response of the unit when their contribution is unwanted."

 

[JohnRoberts]

Thanks, the bandpass sections look like what Burr-Brown called infinite gain multiple feedback or a fairly common bandpass filter topology with typical -6 dB/octave skirts.

Grounded center detent sliders are not uncommon and improve the metric of being dead flat when set to that (and shunting any residual filter noise).

The boost/cut approach is not common and no doubt responsible for the claimed bandwidth behavior wrt boost/cut. (This is why I asked Dennis Bohn to participate in my AES "Q/bandwidth" standards pursuit.)

Some people swear to the benefits of this.... I sold truckloads of Peavey GEQ with the more conventional bandwidth curves, but I had a secret weapon, my FLS invention with blinky LEDs over every slider showing which one to pull down to stop feedback was a desirable feature especially for Peavey level customers.

JR

 

[Darioricordi]

I'm wondering if anyone has any Gerber files for the Barry Porter "Net EQ" they wouldn't mind sharing/selling/trading for? Thanks in advance.

Steve

Hello. If anyone is looking for barry porter net eq gerbers, please send an email to me. [email protected] . I have those in a rare format .PHO so if someone knows how to convert, send an email too.

 

[porkyc]

I haven’t plotted anything out but it behaves like a constant bandwidth EQ. The bandwidth sounds independent of gain. A constant Q EQ is useful when there isn't a separate control for BW/Q.

API did a "constant Q" 550A-1 which they (API) said sounded exactly the same as the "proportional Q" 550A
Sunset Sound Recorders begged to differ with their jaws on the floor. Funnily enough, you can't buy the -1 version anymore.

But since it was me who said, "Don't bother with CT level pots", my work here appears to be done.........

 

[mikeyB]

Would it be ok to use a higher value pot for the cut/boost,( I have some 50k centre tapped pots) or would this introduce noise, loading problems?

 

[abbey road d enfer]

API did a "constant Q" 550A-1 which they (API) said sounded exactly the same as the "proportional Q" 550A

Due to varying opinions among designers, there is as much difference between two constant BW EQ's than between a constant BW and a constant Q, but there are probabilities that some of the settings will produce identical response.

 

[abbey road d enfer]

Would it be ok to use a higher value pot for the cut/boost,( I have some 50k centre tapped pots) or would this introduce noise, loading problems?

It would probably result in less noise, but the control taper will be different, more cramped towards the EOT's.

 

[mikeyB]

It would probably result in less noise, but the control taper will be different, more cramped towards the EOT's.

Ah, ok Abbey, thanks for the advice.

 

[Bernardo]

Hello, I was thinking of building a "neteq" equalizer, I know that pcbgrinder sells pcb, but I can't find diagrams to know what psu, toroid and potentiometers this machine has. If someone could tell me where to find them it would be a great help. thank you

 

[MerlynMetal]

This is a redraw of the Porter netEQ PCB to replace the exotic format Gerber files circulating around. I tried those at 2 local PCB shops and 2 major Chinese PCB manufacturers and all of them said files were useless. After spending hours trying to make use of these files I concluded that myself but decided to ask companies that are in the business as well. I assume those were deliberately manipulated so that couple of people can sell their PCBs but that's just an evil conspiracy theory of mine.
Fortunately the archive included PCB tracing and schematic which is plenty enough to redraw the whole thing. Now I offer it as a compete and free Sprint Layout PCB project for everyone interested to use as they would like and to modify it to their needs.

Changes I made:
1/ some PCB traces have been optimized and don't exactly overlap the PDF file tracing
2/ included option to use THAT1246 and THAT1646 for input and output instead of the unnecessarily complicated original stages
3/ included is an option for a LM317/337 regulated onboard power supply section
4/ optimized are positions of the onboard 9mm pots in case one wouldn't use stepped attenuators including a footprint for a 10k center tapped 16mm pot available from Aliexpress
5/ all mounting holes and pots/switches distances are in mm of course

ATTENTION: as of August 10, 2022 this PCB is to be considered UNTESTED!

Check the PCB against the schematic and PDF tracing and layout files before you order these somewhere!
I'll be also doing some more checks and post corrections if any.
If you find any mistakes let me know so I can correct them and post corrected files.
To view the files you can download a free Sprint Layout viewer from here:
https://www.abacom-online.de/updates/Sprint-Layout60_Viewer.exe
or get the full software temporarily for educational purposes from...well, you know how.
Note that ground planes are not visible in the viewer.

Last archive update 13.08.2022

 

[skidmorebay]

This is fantastic. Thanks for putting it out there. I've built one BPEQ, getting ready to build another. I built an off-board THAT I/O board for mine, and a few other mods I wish had been incorporated into the pcb's.

I'd love to see a version someday that held resistors for stepped freq, gain, and Q, and could accept Grayhill pcb pin rotary switches.

I wish I had a dozen channels of this EQ. It's known as a mastering EQ, but it is also so useful on a lead vocal, bass, acoustic instruments, just about anything.

 

[capacitorless]

I'd love to see a version someday that held resistors for stepped freq, gain, and Q, and could accept Grayhill pcb pin rotary switches.

I'm just getting my feet wet with diy projects, so please bear with a newbie question

Could it make sense to have a separate front panel board, set up for the Grayhill rotary switches + resistors, and jumper that to one (or two) EQ boards?

 

[ruairioflaherty]

This is a redraw of the Porter netEQ PCB to replace the exotic format Gerber files circulating around. I tried those at 2 local PCB shops and 2 major Chinese PCB manufacturers and all of them said files were useless. After spending hours trying to make use of these files I concluded that myself but decided to ask companies that are in the business as well. I assume those were deliberately manipulated so that couple of people can sell their PCBs but that's just an evil conspiracy theory of mine.

Welcome to the forum Merlyn. It's a nice place and I'm going to suggest that you reconsider your "conspiracy' theory.

A little history on the Porter EQ and Group DIY. My mentor and friend Dave Collins brought this circuit to my attention back in the day, before even he had a working build. This was before anyone had really heard of this project. Dave liked the elegance of the design, and as I learned more about electronics and compared it to other designs I found myself agreeing,

Frank Lacy was an early builder of some custom units, including the one I use daily here but he was not commonly selling his pcbs separately (a few people did manage to purchase). So I located the Gerber files that were made by Barry Porter himself before he died and asked Gustav who is a long-standing member her to consider manufacturing some.

The Gerber did indeed have some issues that Gustav was able to correct and he stepped up, solved those issues and has made boards available for many years at a fair price. No one corrupted the Gerber file set you've found, that's how they were coming from Barry Porter himself.

Obviously the Porter has become quite a cult item over the past 10 years, I think deservedly so. Credit goes to Barry Porter for the design, Dave Collins for championing it, and Gustav for making it available to the DIY masses.

 

[MerlynMetal]

Could it make sense to have a separate front panel board, set up for the Grayhill rotary switches + resistors, and jumper that to one (or two) EQ boards?

Please provide the part/s number/s and how this looks in an actual build and I'll let you know.

Welcome to the forum Merlyn. It's a nice place and I'm going to suggest that you reconsider your "conspiracy' theory.

I'm sorry if someone got offended by my evil conspiracy theory.
I'm not aware of the project history in detail however the fact is those files in the archive distributed were useless and it was very suspicious to me that all those years a corrected version was not posted.
Now a full PCB project is available and everyone can modify it according to their needs.
I'll be building this in the next month or so and will be able to test the and troubleshoot the board if necessary so if you're not in a hurry you might want to wait some time before you order the boards from somewhere or if you do let us know if you find something that needs to be corrected.

 

[ruairioflaherty]

I'm sorry if someone got offended by my evil conspiracy theory.
I'm not aware of the project history in detail however the fact is those files in the archive distributed were useless and it was very suspicious to me that all those years a corrected version was not posted.

Offended is a strong word but I don't think it's cool to come into a longstanding community like this and speculate in that manner.

I gave you the defacto history, the files Gerber distributed all these years are the work of Barry Porter himself. They were not useless to a skilled operator who was able to modify the Gerber and make boards.

Gustav has made PCBs available to the forum as long as I can remember (I'm here 17 years) at fair prices. He has no obligation to give away a Gerber file that he did corrective work on.

That said I commend your work and sharing, I hope it helps more people discover the project.