Barry Porter "Net EQ"

[Bonsaimaster]

I hope to get some help before starting this project. Sorry for the newbie questions but I have tried to collect all the data that is out there. But some missing pieces do exist. Any help would be great!

Will be purchasing two Barry Porter NETEQ boards for a Dual mono unit from PCB Grinder.

Will use PCB 1815 to power the two boards. I will be building a USA version and need suggestion for a 2x18V toroidal transformer. Can I use this Dual Primary (115V/230V) Toroidal 2X25 30VA Power Transformer?

http://www.hairballaudio.com/shop/product_info.php?cPath=33&products_id=37

I will provide all the information I get or have to anyone.

1. The "current" BOM and board overlay seems to have some mistakes. I am trusting the schematic on this one. Please any corrections welcomed.
Ex.
Board overlay shows
R6-10K
R7-10k

Schematic shows
R6-10R
R7-10R

2. Can someone verify the BOM I made.
http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=7cd513ac77
I have not included the R500 and the NE 5322 they will come from other sources.
I have swapped out resistors and caps as per HARPO excel sheet so I can use rotary switches.

3. I am unable to find a source for a 10-47pf variable capacitor. Any suggestions?

4. Does anyone have suggestions for rotary switches? My possible suggestions included.
For the
Q Band
http://www.ebay.com/itm/180931177387
1pc,1 pole 12 positions PCB Rotary switch NEW,1P12L

FREQ
http://www.ebay.com/itm/251292325032
2pole 24 step Rotary Switch Attenuator Volume Control DIY Pot Potentiometer New

FREQ with selfing
I have no source

GAIN
http://www.ebay.com/itm/251292325032
2pole 24 step Rotary Switch Attenuator Volume Control DIY Pot Potentiometer New

HIPASS
http://www.ebay.com/itm/170880281315
1,2 pole 6 positions PCB Rotary switch NEW,2P6L

I don't know much about rotary switches. Therefore excuse my ignorance if these suggests are wrong.

5. Will be using switches for bypassing each channel should I use (sorry newbie questions) DPDT ON-ON?

6. Any suggestions on how to wire the bypass switch for each channel?

Thanks for any help in advance!

 

[voitto]

I was able to find the trimmer capacitors from http://www.banzaimusic.com/Trimmer-Caps/

 

[Harpo]

..but I don't realize about Wye Delta in Barry Schematic, Thank You for pointing that, my newbie common stupidity  ;D, I still build using Your calculator but need to know how Mr. Barry calculate this filter.

Maybe some 'hops', but not the final version and looking at another forum building a commercial version from Barry's work, I won't share this file.
From his readme file Barry used a simulator to get the results. He could have calculated it as well this way.
(Part numbers used are related to your last question for the 2K..20K band)

And about the shelfing, from the schematic it doesn't have any relation with peaking band right? So if I using 2 deck for peaking freq and switch to another 1 deck for shelf freq it will be OK?

As drawn in Barry's schematic and using lin.pots, the peaking and shelfing bands have no relation and will have different cutoff points at same pots rotation angle (he already said so in his readme file). Using switched resistors you can build them for same cutoff point for correct frontpanel labeling.

 

[Majestic12]

Hi Bonsaimaster,

1. The "current" BOM and board overlay seems to have some mistakes. I am trusting the schematic on this one. Please any corrections welcomed.
Ex.
Board overlay shows
R6-10K
R7-10k

Schematic shows
R6-10R
R7-10R

I will buy both value and try, but I prefer the value on the schematic (10R)

10R (as in the schematic) is the right value.

 

[Bonsaimaster]

Thanks for the info. Very helpful. Can I use a 4 pole 24 step switch for the high shelf?

Also I got the excel spreadsheet for wiring the pots. However, I am unclear on the 2 pole pot wiring. Does anyone have a picture of one?

Thanks
Bonsaimaster

 

[Nescafe]

Hi Bonsaimaster,
yes You can use 4P 24S for the high freq selector, and please see the post by Harpo in page 6 for the wiring.

 

[Nescafe]

5. Will be using switches for bypassing each channel should I use (sorry newbie questions) DPDT ON-ON?

6. Any suggestions on how to wire the bypass switch for each channel?

I'm not sure, but I will trying the same thing and using SPDT ON-ON using Harpo Calculator last bottom in the spreadsheet and switch the wiper out from the circuit but if You build using Harpo sheet that use all step for boot or cut rotary switch gain, You will need rotary 2P3P (2P: ground and wiper, 3P: boost, cut, bypass).

Hope that will help.

Thank You.

Edited, see the bold section.

Also I just thinking about toggle 3PDT/4PDT also can be use (ala MANLEY Massive Passive) but make sure the switch is have On-Off-On configuration for taking out the wiper.

Thank You.

 

[Nescafe]

Harpo,
could You please explain the formula for Q from original schematic?

I try to analyze from Your excel file
=(1/(1/(D$218)+1/(SUM(K$218:K218)+G$218))+E$218)/(2*(1/(1/(D$218)+1/(SUM(K$218:K218)+G$218))))

but still don't have clue and cannot find the right number.

Thank You.

 

[Harpo]

??? is this some kind of a trick question or an Excel question ?
just picking one band, Q=(R99 || (P4+R104)+R95) / (2(R99 || (P4+R104)))
As already said, P4 isn't a pot but a variable resistor/rheostat with wiper and CW position joined to the opamps non-inverting input.

 

[Nescafe]

Hi Harpo,
it's more on excel question, actually my question is how ro calculate the q of the state variable filter 
I cannot find the formula and try to analyze from Your excel table, but still don't find the right formula.
Most of the SVF input is on the inverting amp and feed back to the non inverting that also controlled the Q, but BP using non inverting input and Q control, so how is actually the Q formula for the SVF?

And in the BPEQ if I take out the rheostat connection, is that correct that the Q calculation will be using wye configuration again (like in the attached picture)?

Thank You.

 

[Nescafe]

Harpo,
maybe the previous pic in my post is not clear, so I just draw and is that correct:

Q=(((R99+RU||(RL+R104))+R95)/(2((R99+RU||(RL+R104)))

RL is Lower Section of P4
RU is Upper Section of P4

edit: I just read Barry articles in ETI and the equation is the same, just different placement, of the pot but if I calculate using Barry choosen value the Q range is not 1 to 3 but 1.169 to 0.928 and that confusing me  ???

 

[petermontg]

With regards to switches, don't skimp

http://www.goldpt.com/prices.html

 

[Harpo]

With regards to switches, don't skimp

2 pole 34 pos or 2 pole 46 pos shorting with adjustable tension for the click stops 
http://www.partsconnexion.com/SEIDEN-74750.html
http://www.partsconnexion.com/SEIDEN-74751.html

 

[petermontg]

With regards to switches, don't skimp

2 pole 34 pos or 2 pole 46 pos shorting with adjustable tension for the click stops 
http://www.partsconnexion.com/SEIDEN-74750.html
http://www.partsconnexion.com/SEIDEN-74751.html

Wished I'd known of those Harpo. Cheers for that :'(

I used the 6 row Elma for stereo ganged. So I used all the Elma goldpoint.

 

[Nescafe]

Hi,
from Barry schematic, if I want to implement bypass switch for each band, what is the most ideal way to take out the filter?

I have drawn a circle in the attached schematic for 1 band including the shelf.
1. On gain wiper only is enough
2. On Input of each filter including the shelfing of each band if available
3. Both of point 1 and 2

And the drawback, like DC noise from switching toggle switch????

Thank You and any reply will be very appreciated

 

[Harpo]

1. On gain wiper only is enough

This. The other options change connected load to the driving stage.

And the drawback, like DC noise from switching toggle switch????

C55/R63, C34/P14 and C24/P14 already bock DC. Switching AC might cause a pop, depending on snapshot moment.

 

[Harpo]

Anybody here know why in the BOM in the high filter section, C8, C9, C23, C24 are using electrolytic bipolar but have (Film) mark? Is that means I must bypass with film cap there? And why only in the high filter section?

Typo/whishful thinking and wrong section label ? (try to source 1000uF film caps and -if you doubtfully could get them- make these fit on pcb/inside your 19" box. The 6.3 voltage rating isn't a film cap rating as well).
For your bypass question a single pole 3 throw for boost/bypass/cut at wiper position should be enough. If needed at all, two permanently connected maybe 100K resistors between rails boost/gnd and cut/gnd will keep C23 and C24 at reference voltage for your stepped 5K level switches for the case, all boost/bypass/cut switches are at the same setting.

 

[Harpo]

..at some point I have some thinking & feeling that it's not a typo but intended by Mr. Barry Porter..

The .V0 BOM isn't from Barry and there isn't even a placeholder on pcb for these caps.
http://groupdiy.com/index.php?topic=33256.msg628044#msg628044
The DC offset blocking 1000uF caps set a HPF with FI the paralleled 10K center tapped level setting pots. Your -maybe fitted from traceside- paralleled 33nFs and ignoring parts tolerances will give a 1000.033uF cap on paper..., but you could always try it (a croko-clip might come handy for an A/B test) and listen to the result.

 

[assrael]

Hi,

I’m planning to build a NetEQ. After thinking about some build options I’m thinking about to make my one with separate controls for the shelving bands.
That means 4 bands of peaking filters, 2 bands of shelving filters and the high pass filter for one channel. This would be at least a unit with 4U in height.

Has somebody built such a version? Do you think that this is useful? Some concerns about that?

Greetings,
Assrael

 

[Nescafe]

Hi,

I’m planning to build a NetEQ. After thinking about some build options I’m thinking about to make my one with separate controls for the shelving bands.
That means 4 bands of peaking filters, 2 bands of shelving filters and the high pass filter for one channel. This would be at least a unit with 4U in height.

Do You mean it will be 6 band both the shelving and peaking can be boost/cut simultaniously? I think no one try that yet but looks like that possible