3D "AIR" EQ - "Night EQ" PCB's Complete!

[Dr nEon]

..One Final Question!


Would it be a good idea to use a dpdt switch on each channel , to select the bal/unbal jumper positions ?


I can see myself using the night eq in a couple of ways in my studio..either on channel insert via my unbalanced patchbay...or sometimes over the mix bus , using short balanced leads to run into a mix compressor . So I'd need to have the flexibility of selecting bal or unbal modes ,rather than committing to one or the other by soldering those jumpers.

Maybe someone has already tried this , or can verify that this idea makes sense...

Cheers!

nEon.

 

[Harpo]

Not new but working idea (mine is wired this way). See schematic (2nd link from the 1st post @ pg1 from this thread).

 

[[silent:arts]]

best way is to use an output stage where this doesn't matter ...
not the best idea if YOU (or ME) have to think about it in witch position a switch is set.
I would either go balanced with a balancing chip, or a cross coupled pair output.
(same way for some other projects here)

 

[Dr nEon]

Thanks guys,

Harpo , that schematic is the one that got me thinking , since it's drawn as a switch ,but I'd only seen people doing it a wire link jumpers. So it's good to hear you have done it as a switchable thing.

I would put the switches on the back of the unit.  I presume you had to keep the cable length as short as possible.


I've had to implement 0dB / +6dB switches on my other stuff  too .  I always put xlrs on the back , altho' the gear spends half it's life in my home studio , where the soundcraft2400 p/bay is unbalanced..unfortunately!

Cheers

nEon

 

[Dr nEon]

Hey everyone!

New question re the night eq..

After tweaking the various resistor values , using the excel calcuator for accurate pot centres, it looks as though I have to change the 22pF capacitor down to 18pF , since my R30 has now become 64,000..

I don't have np0/c0g type in that value , which the bom calls for , but I do have standard 18pF ceramic disc in stock , or  polystyrene (or ,rather,a combination of styrene to get the correct value..).

Would either of these be ok to use in this position?

Or do I really need to find a c0g/np0 cap?

cheers

nEon.

 

[keefaz]

C13 with R30 form a lowpass filter with -3db point at 118kHz with 22pf cap and at 144kHz with 18pf cap
Now if you can hear a difference in sound with -3db attenuation at thoses frequencies, you're not an human 

 

[Jed]

Hey, does anybody have a photo showing how the lorlin is wired?

I think I understand, but the photo from the link here (http://www.groupdiy.com/index.php?topic=19789.520) seems to be gone...

 

[giltmastering]

i just found this thread for the first time.  i've wanted to build one of these as well.  we have an original 3ru  NTI EQ3 here at the studio.  this unit sounds amazing.  i don't know the differences between this and the 3d but we can use ours to figure it out.
i opened it up to post some pictures here. sorry the quality sucks, it's off my phone. 

 

[Anthropic]

Those are some rare pictures!  Thanks for posting them!  Anything you can do to find out more would be fantastic (especially concerning any input or output transformers).  If you can get some clearer/closer pictures, that would be fantastic also.  This is what we've been waiting for, in relation to this particular EQ project.  Thanks again.

 

[giltmastering]

i'm ready to help with this project.  i would love to build one myself.  this unit belongs to a friend in the studio here and he's willing to let me dissect his unit. i don't see any input and output transformers near the XLR connectors. the might be elsewhere hard to see.  i will look again.  i will try to post better pictures.  he also has a mic pre that he loves.  it has the air band as well.

 

[okgb]

the schematic kev made has no signal xfmrs
but what are the concentric pot functions
on the pix you posted
gain & what ?

 

[khstudio]

but what are the concentric pot functions
on the pix you posted
gain & what ?

Yes... what are they for?

The 3RU's basic circuits aren't any different (from what I've been told) but as you can see they use the POWER ONE's for the power supply as opposed to the "Switching PS" in the smaller unit + all those Grayhill switches for "Recall"... which is nice but doesn't make the circuit or "sound" different. I do think the better PS would help the sound though.

That second pic you posted is the Pre, which I've never used.

 

[briomusic]

I am currently trying to breadboard just the switchable shelf part of the night eq and it's not working too well, yet 
The circuit is passing audio, but it sounds very thin, and the pot acts as a level control.
I have basically just used the top row of this schematic:
http://www.khstudio.us/DIY%20PICs/3D%20EQ%20-%20FULL.bmp - ignoring the bypass arrangements and making the shelf fixed at 5khz (I don't mind switching the capacitors/frequency manually while this is on the breadboard)

Do I need to have all the sub circuits going to get a full frequency signal?

Thanks in advance!

(edited as I respect Kevin's decision to hold back air eq schematic)

 

[Harpo]

I am currently trying to breadboard just the switchable shelf part of the night eq and it's not working too well, yet 
The circuit is passing audio, but it sounds very thin, and the pot acts as a level control.
I have basically just used the top row of this schematic:
http://www.khstudio.us/DIY%20PICs/3D%20EQ%20-%20FULL.bmp - ignoring the bypass arrangements and making the shelf fixed at 5khz (I don't mind switching the capacitors/frequency manually while this is on the breadboard)

Do I need to have all the sub circuits going to get a full frequency signal?

It would help to have a look at the air eq schem (as opposed to the full 3d eq) but unfortunately I get a "permission denied" error when following this link:
http://www.khstudio.us/DIY%20PICs/3d%20%20AIR%20EQ.bmp

Would anyone be willing to share the air eq schematic with me?

Thanks in advance!

You'll need R48 in parallel with the air band amp and the R24/R25 common attenuator in front ('bypass' at R48 now connects to 'to sum' instead of 'bypass' at sw7), so the air band can add up to your (actually missing) program signal.
Another way is, to build a derived lowpass from program and air band to also make boost/cut for the air band possible.
Just my 2ct.

 

[khstudio]

I am currently trying to breadboard just the switchable shelf part of the night eq and it's not working too well, yet  
The circuit is passing audio, but it sounds very thin, and the pot acts as a level control.
I have basically just used the top row of this schematic:
http://www.khstudio.us/DIY%20PICs/3D%20EQ%20-%20FULL.bmp - ignoring the bypass arrangements and making the shelf fixed at 5khz (I don't mind switching the capacitors/frequency manually while this is on the breadboard)

Do I need to have all the sub circuits going to get a full frequency signal?

It would help to have a look at the air eq schem (as opposed to the full 3d eq) but unfortunately I get a "permission denied" error when following this link:
http://www.khstudio.us/DIY%20PICs/3d%20%20AIR%20EQ.bmp

Would anyone be willing to share the air eq schematic with me?

Thanks in advance!

Sorry but I asked everyone to NOT share the "AIR" schematic. Not very many even have it.
I shared the FULL version with everyone

You can't just build the hi shelf sections... you won't get any other (or Lower) frequencies except the hi shelves.
What I did wasn't too difficult. But I did spend some time tweaking & listening.

Try making one of the other bands - FULL Band.

 

[briomusic]

Hi Kevin,

thanks for your response, I completely respect your decision re: the air eq.
since posting the above, I have had a read through the patent application someone posted earlier in the thread, and I understand the circuit much better now

I also appreciate your little hint - glad I am still on breadboard at this stage  ;D

Very curious about your air eq product, make sure to let us all know!

Thanks for your help, I am going to edit the schem request out of my original post.

Harpo, just saw your message, I tried your first solution, but then the air band control didn't seem to have any effect. Now moving on to the "everything-BUT-air"-band approach, which I think both you and Kevin alluded to.

 

[briomusic]

Hmmm, after two more days of experimenting I am closer, but not quite there yet.
I have tried the "bypass-wire + air" method as well as the additional "full-band with its own opamp" approach, and everything sounds great and seems workable after juggling some resistor values around, but there are still some operational hangups...

First of all, is the air band supposed to be boost only? I noticed the scales on the faceplate are +/-5 for most pots, but 0-10 for the airband, what gives?

ETA: just read the SOS review...so boost only it is

Secondly - for me (fully) boosting the airband results in a +5dB boost for the entire frequency spectrum down to 500Hz (and below), then at about 2.5Khz I get a 7dB boost and finally a 15dB boost @ 20kHz (this is with the .47uF cap for '20kHz' air).

I am not sure if the latter problem is connected to my struggle with the "program" band, but I observed this phenomenon in both of the setups mentioned above.

 

[Whoops]

Hi,
I'm just starting to gather the parts to build my Night EQ project.

I read this full thread, so I know that Kevin used 15V rails instead of 18V.

I would like to ask what are all you guys using, 15V or 18V?

anyone else noticed a sound difference?

is that I can't really think , of why it would sound better at 15v, it seems to me that technically it should sound better with higher voltage.

thanks

and Congratulations to Kevin, for all the hard work in bringing this project,
and Peter C also for the PCB's.

 

[khstudio]

Hmmm, after two more days of experimenting I am closer, but not quite there yet.
I have tried the "bypass-wire + air" method as well as the additional "full-band with its own opamp" approach, and everything sounds great and seems workable after juggling some resistor values around, but there are still some operational hangups...

First of all, is the air band supposed to be boost only? I noticed the scales on the faceplate are +/-5 for most pots, but 0-10 for the airband, what gives?

ETA: just read the SOS review...so boost only it is

Secondly - for me (fully) boosting the airband results in a +5dB boost for the entire frequency spectrum down to 500Hz (and below), then at about 2.5Khz I get a 7dB boost and finally a 15dB boost @ 20kHz (this is with the .47uF cap for '20kHz' air).

I am not sure if the latter problem is connected to my struggle with the "program" band, but I observed this phenomenon in both of the setups mentioned above.

I think your observations are correct concerning the boosting of lower frequencies when boosting the AIR... YES it's boost only (for that section) & it does reach pretty far down = large/smooth shelf.

 

[khstudio]

Hi,
I'm just starting to gather the parts to build my Night EQ project.

I read this full thread, so I know that Kevin used 15V rails instead of 18V.

I would like to ask what are all you guys using, 15V or 18V?

anyone else noticed a sound difference?

is that I can't really think , of why it would sound better at 15v, it seems to me that technically it should sound better with higher voltage.

thanks

and Congratulations to Kevin, for all the hard work in bringing this project,
and Peter C also for the PCB's.

You may have gotten confused... I'm using 18v rails!
What I may have mentioned is liking a LOWER AC voltage TX, going into my PS.
To me, when I used an 18-0-18 TX (which measured more like 20-0-20) the sound of the unit was "Stiffer", which I Personally didn't like.
It was subtle but there, for me at least... When I used a 15-0-15 (which measured more like 16-0-16) the sound was less restrictive.

Keep in mind this could have been due to the larger current/Amps TX I used & I would NOT sweat it too much.

To be safe... the rule is to use an AC TX with the same output voltage as your regulated DC output.

Running the rails anywhere from 15v to 18 volts will be fine.
The original unit was 17v rails.

Good Luck.