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

[Whoops]

I 'm asking about c1, c14, c15 because of the voltages of capacitors. In bom they're labelled 63v to withstand phantom... but I use any phantom power.

Well this unit should never receive phantom power, only condenser mics should receive p48V from a mic pre.
The unit sould be always connected to a Line input (line inputs dont have phantom)

Capacitor voltages will not affect the audio.
It just says an aproximate max limit of the voltage the capacitor can withstand

 

[Whoops]

I'm finishin an unit at the moment,
just giving the final calibration touches.

There is something that I would like to call attention for.
In Harpo tweaking Excel sheet it says
"The C13 cap (actually 22pF) in the feedback loop of this summing stage for bandwidth limiting, set for -3dB cutoff at 128kHz, may be lowered to 15 or 18pF to get similar results in case R fb is upped. (-3dB lpf = 1/(2*pi() * R30 * C13)"

In my case R fb had to be upped in both channels, the original value was 56.2K, and I had 63.8K and 61.6.
So I did what Harpo suggested in the sheet and lowered the value of C13 to 18pf and 15pf.
Well I don't advise doing this as with both 18pf and 15pf I had low end loss when I turned the EQ on (compared to bypass mode).
With the original 22pf value the Low end stays the same when you change from bypass to EQ on, so I would stick with the value and not lower C13 even if you have to increase the vaue of R fb.

Or maybe there was something I didnt got right and Harpo can step in and help

Thank you Harpo for the great document and thanks everyone

 

[Harpo]

everythings look ok...
unity gain with no jumper (bypass) and -6db with j7 unbalanced. j3 changes nothing...
I use 470uF 25v... could this be the problem?

I don't think so.
You seem to be measuring VAC output level between XLR-pins 1/2 and/or pins 1/3.
XLR-pin-1 is not involved in this measurement. You measure AC voltage between XLR-pins 2/3.
With your 'no jumper' version, XLR-pin-3 is not connected at all ...
For your 470uF/25V for C14 and C15 these would need a voltage rating of 35VDC in order to withstand a reverse kick in the butt from accidently activated phantom voltage.
48VDC * 1,1 for +/-10% phantom tolerance / (6k8 + 10k) * 10k = 31.4VDC
Some AD/DA converters come with built in mic-preamps and phantom supply that might be activated, so this isn't an only academic problem, but as always YMMV.

 

[Harpo]

..."The C13 cap (actually 22pF) in the feedback loop of this summing stage for bandwidth limiting, set for -3dB cutoff at 128kHz, may be lowered to 15 or 18pF to get similar results in case R fb is upped. (-3dB lpf = 1/(2*pi() * R30 * C13)"

This 22pF cap (I'd put in an additional 22pF cap) better would be connected between U5-pins 5/8 (a pcb has a backside) for unity gain compensation, because a NE5534 isn't unity gain stable. Unstable opamp in this context would be the only reason for low end loss I could forsee. An increase/decrease of C13 would mainly change the >100kHz high end perception of bats, as long as you don't operate this stage beyond its GBW and power bandwidth limits.

 

[mrdarwin]

Hi!
A last question...My unit is powered with the green psu and two +15/-15v...
The original is 18v, Maag is 18v etc...
Datasheet of ne5532/34 says these can be powered with 12 to 20v if I remember correctly...
Does the value of  the rails affects the sound? I can easily change the resistors of lm317/337 on the psu pcb if its necessary...
Thanks again

 

[Whoops]

A last question...My unit is powered with the green psu and two +15/-15v...
The original is 18v, Maag is 18v etc...
I can easily change the resistors of lm317/337 on the psu pcb if its necessary...

Yes, you should do that and run the unit from +-18v

I installed 2 trimpots to adjust the regulators output to + and - 18v, other people have done the same.

 

[steves.mastering]

Hi,

I'm now hooking up my LM317/337 PSU, and for some reason I cannot achieve more than +/- 10V.

I am using this toroid - Triad - VPT30-830. Connected Primaries in series. secondary's parallel.  (Black and Orange tied together and Red and yellow tied together).

Any suggestions why the adjustable PSU seems to stop as soon as I reason +/-10v? thought these went up to 37V?

I have another Toroid I'm tempted to try but wasn't sure if I was missing something obvious.

cheers.

 

[druu]

Hi,

I'm now hooking up my LM317/337 PSU, and for some reason I cannot achieve more than +/- 10V.

I am using this toroid - Triad - VPT30-830. Connected Primaries in series. secondary's parallel.  (Black and Orange tied together and Red and yellow tied together).

Any suggestions why the adjustable PSU seems to stop as soon as I reason +/-10v? thought these went up to 37V?

I have another Toroid I'm tempted to try but wasn't sure if I was missing something obvious.

cheers.

You need to have the secondaries in series with centre tap (CT) for 0V reference. This should provide you with the right voltages.

 

[dasnevestheo]

Hi there,
been poking around this thread for a while and gather loads of great info 
But i'm still looking for some panel info. I suck at DIYing panels so i'm looking for a FPD file or someone i could buy a panel.

Thanks !

 

[Le Roux]

Awesome EQ!

Dead quiet, sounds great!

Thanks for the project!

 

[lautamei]

This 22pF cap (I'd put in an additional 22pF cap) better would be connected between U5-pins 5/8 (a pcb has a backside) for unity gain compensation, because a NE5534 isn't unity gain stable. Unstable opamp in this context would be the only reason for low end loss I could forsee. An increase/decrease of C13 would mainly change the >100kHz high end perception of bats, as long as you don't operate this stage beyond its GBW and power bandwidth limits.

Hi, my build it's working fine, but my bypass it's not a real "bypass". It's cutting of some low end. You think that the problem it's on C13 cap?

 

[Whoops]

Hi, my build it's working fine, but my bypass it's not a real "bypass". It's cutting of some low end. You think that the problem it's on C13 cap?

Which pots did you use?
Did you use Harpo's doc to get the resistor values to adjust the center values of your pots?

 

[weiss]

does someone own a .fpd frontpanel file which fits the pcb print? 
don't want to buy from purusha

 

[Whoops]

don't want to buy from purusha

Yes, Nice!

A friend of mine did a great looking front pannel for his unit, I will ask him the files and send it to you

please pm me your email

regards

 

[weiss]

Yes, Nice!

A friend of mine did a great looking front pannel for his unit, I will ask him the files and send it to you

please pm me your email

regards

thanks a lot! your mailbox is full  ;-)
sent you a mail

 

[dasnevestheo]

so did I

 

[weiss]

Yes, you should do that and run the unit from +-18v

I installed 2 trimpots to adjust the regulators output to + and - 18v, other people have done the same.

Hi,

Could you help me which ones you used and where exactly to put it?

Appreciate your help!
Ansgar

 

[Whoops]

I don't have the schematic here with me,
please post the schematic of the green psu and I will tell you.

 

[weiss]

I don't have the schematic here with me,
please post the schematic of the green psu and I will tell you.

here the schematic: http://fucanay.fischerworks.com/diy/_Green_PSU_Schem.GIF
here is the layout of the pcb

 

[Whoops]

HI Weiss,
LM317 and LM337 are adjustable voltage regulators.

Check their datasheet on how to install a trimpot

check also the implementation of these regulator in the JLM PSU:

http://www.jlmaudio.com/ACDCVer2sch.pdf


I think in mine I just replaced R1 and R5 for a 5K Multiturn Trimpot