Barry Porter "Net EQ"

[skidmorebay]

I'm putting together a Mouser cart for my build. I'll share it here once I've got it assembled.

So, what was the final decision on C8, C9, C23, & C24? The BOM and schematic say 1000 uF/6.3V film caps, which is an error, right?
What's the real value? Gustav's pcbs have a round pad in those positions, like you would use for an electrolytic.

 

[Majestic12]

Those are 1000uf bipolar, electrolytic caps.

 

[skidmorebay]

Thanks.
Now I'm looking at C15, C16, C64.
C15, for example, is a 33pf cap in the feedback path for U2-B. The pcb has a 9mm leading spacing for these. I haven't found a 33pf cap in that size (WIMA's a 5mm lead spacing, for instance).
What cap have you used here?

 

[Majestic12]

Thanks.
Now I'm looking at C15, C16, C64.
C15, for example, is a 33pf cap in the feedback path for U2-B. The pcb has a 9mm leading spacing for these. I haven't found a 33pf cap in that size (WIMA's a 5mm lead spacing, for instance).
What cap have you used here?

Just a ceramic capacitor with long leads that can be bend to fit the footprint.

 

[skidmorebay]

Moving on... Transistors Q3 & Q1 are BC182's. They aren't stocked by Mouser any more. An internet search shows 2N3903 as substitute. The leads are reversed, though.
The NTE123AP is another possible substitute, but it isn't stocked by Mouser (which I would prefer).
Is there a better substitute?

 

[Majestic12]

Just use BC547. Those transistors only switch the relays and are not in the audio path at all.

 

[skidmorebay]

I put together a Mouser cart and a slightly updated BOM for the Barry Porter eq:

Bill of Materials spreadsheet, includes copies of Harpo's stepped switch calculators:
https://www.dropbox.com/s/1pq3trtareuc8ub/Barry%20Porter%20EQ_BOM%20AND%20STEPPED%20SWITCH%20CALC.xlsx?dl=0

Mouser Project:
http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=e2a0493bc6

This cart is for a build that uses pots for the frequency and Q controls (I'll add rotary switches later.) I'm using Grayhill switches for High Pass and Level, but I didn't include parts for them in the documents. But, I copied Harpo's calculators into the spreadsheet so you can decide how you want to set yours up.
Also, the BOM and cart don't include components for the input and output sections. I am going to use Collective Case's M/S matrix instead:
http://collectivecases.com/?product=mastering-grade-ms-matrix-pcbs

All told, I'm up to about $1,000. That includes a case with blank front panel from Collective and mostly pots instead of switches, and knobs I already own.

 

[trashcanman]

Thanks for the feedback. I just checked, and there is a dead-end trace, but that should be removed, not connected.

Gustav

How did things go with this layout? I'm looking at maybe getting some of your boards made at some point and was wondering if you managed to get your design working.

 

[Gustav]

How did things go with this layout? I'm looking at maybe getting some of your boards made at some point and was wondering if you managed to get your design working.

I havent tested it yet (life happened - won't have a bench to work at until february), but I do have a set you can get if you pay for shipping.

Gustav

 

[skidmorebay]

I updated my earlier post with a modified BOM and Mouser Cart.

 

[skidmorebay]

What is the purpose of J1 and J2? Why would I want to install this jumper?
Looking through photos on this thread, it seems like no one installed the jumper.

 

[Majestic12]

What is the purpose of J1 and J2? Why would I want to install this jumper?
Looking through photos on this thread, it seems like no one installed the jumper.

This jumper connects the Audio Ground to the chassis ground. You don't really need it. It's just there in case you want to connect both grounds together (which in most cases isn't a good idea)

 

[skidmorebay]

I got my Barry Porter eq working today. It's still a work in progress... stepped switches for Frequency and Q will come later. I'll also add mid/side capability with the Collective Cases MS Matrix soon.  (And a real faceplate, eventually.)

By using on-off-on switches with the gain controls I have boost/band bypass/cut all on one switch. Cool.

I used THAT 1200 & 1600 IC's for input and output instead of the I/O on the pcb. One problem now is that one channel is 0.8 db louder than the other. How could I balance them? I know I could adjust the feedback resistors on U2 (R13 & R14), but this would also change the amount of boost and cut on each channel (by changing the ratio of R13 & R14 to R77,82,86, &90).

Is there some way I could install a trimmer on each channel so I can fine-tune the channel balance? I could install a pad on one channel, but I think that would add a little Johnson noise from the extra resistors.

 

[Harpo]

...one channel is 0.8 db louder than the other. How could I balance them? I know I could adjust the feedback resistors on U2 (R13 & R14), but this would also change the amount of boost and cut on each channel (by changing the ratio of R13 & R14 to R77,82,86, &90).

A rheostat in series to R12 should decrease/fix it. A 1K trimmer in series to the 5K1 allows a 0...-1.55dB range, so will be dialed in about centered. Good luck

 

[skidmorebay]

Thanks, Harpo. I will order a trimmer to do that with.

Here's a pic. I've only played with it for an hour, but it sounds very nice. The low shelf sounded really nice across a mix, and the high is not grainy or harsh at all. Glad I built it.

 

[skidmorebay]

and the inside:

 

[AD797]

Hello Gustav!

Seem´s i am to stupid to download your attachment... how is it working? I get always just the website data.
Like to try this new version!

Thank you!

 

[Gustav]

Hello Gustav!

Seem´s i am to stupid to download your attachment... how is it working? I get always just the website data.
Like to try this new version!

Thank you!

Might be that you are clicking a link to an earlier revision that I removed - look at post 426 here - should be the "last" version attached.

I havent tested it myself yet, so feedback is welcome

Gustav

 

[Gustav]

Waiting for a few connectors to arrive to wire it up and see if theres any smoke to let out.

Did anyone try the design?

Gustav

 

[AD797]

Thank you Gustav, found it. But why do you use a 6u8 at the input of the 1646?  ???