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

[positrons]

I finished one channel of EQ and tested it but it dos not work
I am trying to find the problem and I have several questions and need your help.thank you for your helps friends.

1.I don't make the PSU yet and I used Calreq EQ PSU(jakob Calreq) for testing.the voltage is 18.has it any problem??

2.It doesn't have any sound even when it is bypass!!it should have sound in bypass mode even without PSU isn't it??like calreq EQ.if i am right,where is my first mistake??

3.I couldn't find the revers log 500K pots and I changed the taper of the 500k linear pot with soldering a 100K resistor between pins like this

which one can make problem in this project??if non of them,please help me to start troubleshooting.

 

[Harpo]

1.I don't make the PSU yet and I used Calreq EQ PSU(jakob Calreq) for testing.

Why do you want to change the PSU to a different PSU then?

the voltage is 18.has it any problem??

Depends on the type of fixed voltage regulators (78xx/79xx) you used and the secondary voltages of the center tapped or dual mains transformer. The NE5532 and NE5534 opamps will have no problem with your probably +/-18VDC supply (=36VDC between PSU out + and - with 0V reference voltage in between.)
Try to be more exact with your numbers, and signs matter. Your 'the voltage is 18' could as well be a +/-9VDC supply when you used 7809/7909 vregs.

2.It doesn't have any sound even when it is bypass!!it should have sound in bypass mode even without PSU isn't it??like calreq EQ.if i am right,where is my first mistake??

Your mistake simply is in assuming, any bypass circuit will behave the same and have the same circuit behind. If you would have taken a look at the schematic, you'd recognized that this unit doesn't come with a hard bypass.

3.I couldn't find the revers log 500K pots and I changed the taper of the 500k linear pot with soldering a 100K resistor between pins like this

Your pic shows a voltage dividing attenuator (3-legged device) to mimic a pos.log taper pot by paralleling a law bending/slugging resistor between wiper and the CCW end of the linear taper pot. This might work in some circuits that more or less are not depending on a defined total load value. (Sending device sees 500K with pot wiper full CCW and sees 83K3 with pot wiper full CW).
None of the pots in this circuit is wired as an attenuator. The pots in this circuit are wired as rheostats (2-legged device) with ~10% of its total value at half rotation. Unfortunately you can't mimic a rev.log taper rheostat from a lin.taper pot by paralleling a resistor between wiper and either end.

 

[peterc]

Some steps to fault find the problem.

1. Take out all the IC's. Power up and make sure you measure +18v on pin 8 of the IC sockets, and -18v on pin 4. Remember, U5 is a single opamp (NE5534) so +18v will be on Pin 7. Power down.

2. Put the ICs back in. to check the input/de-balancing stage is working, apply a balanced signal to the input. Use a scope to measure the output (pin 7 U4). If this is OK, then the input section is working.

3. To check the output/balancing stage is working.  Apply an unbalanced signal to Pin 2 of U5. Check for equal but out of phase signals on the output pins.


Peter

 

[positrons]

1.I don't make the PSU yet and I used Calreq EQ PSU(jakob Calreq) for testing.

Why do you want to change the PSU to a different PSU then?

the voltage is 18.has it any problem??

Depends on the type of fixed voltage regulators (78xx/79xx) you used and the secondary voltages of the center tapped or dual mains transformer. The NE5532 and NE5534 opamps will have no problem with your probably +/-18VDC supply (=36VDC between PSU out + and - with 0V reference voltage in between.)
Try to be more exact with your numbers, and signs matter. Your 'the voltage is 18' could as well be a +/-9VDC supply when you used 7809/7909 vregs.

2.It doesn't have any sound even when it is bypass!!it should have sound in bypass mode even without PSU isn't it??like calreq EQ.if i am right,where is my first mistake??

Your mistake simply is in assuming, any bypass circuit will behave the same and have the same circuit behind. If you would have taken a look at the schematic, you'd recognized that this unit doesn't come with a hard bypass.

3.I couldn't find the revers log 500K pots and I changed the taper of the 500k linear pot with soldering a 100K resistor between pins like this

Your pic shows a voltage dividing attenuator (3-legged device) to mimic a pos.log taper pot by paralleling a law bending/slugging resistor between wiper and the CCW end of the linear taper pot. This might work in some circuits that more or less are not depending on a defined total load value. (Sending device sees 500K with pot wiper full CCW and sees 83K3 with pot wiper full CW).
None of the pots in this circuit is wired as an attenuator. The pots in this circuit are wired as rheostats (2-legged device) with ~10% of its total value at half rotation. Unfortunately you can't mimic a rev.log taper rheostat from a lin.taper pot by paralleling a resistor between wiper and either end.

thank you for your response.
why do you say (Your mistake simply is in assuming)????????? ???

I don't want to change the PSU I Said for testing I used Calreq PSU because I haven't made PSU yet and I had one of those calreq PSU and the voltage is +18 and -18 and regulators are 7918 and 7818.

2.It seems that I should try to find rev log 500K pot and this method doesn't work here.my reference was http://music-electronics-forum.com/attachments/737d1181440399-pot_taper_amz.pdf but I don't know the difference between attenuator and rheostats resistors in circuits.

3.what do you mean by hard bypass?when in bypass mode I have no sound, which part of circuit can have problem??when I check connections between TRS jack pins with multimeter,they are not connected to each other.is it possible to explain it clearly for me??I am a beginner in electronics and not a pro like you

4.why do some people put jumper instead of 22u caps??peter said (
Input caps can be replaced for DC coupling) but i don't understand.
thank you for your patience. 

 

[positrons]

Some steps to fault find the problem.

1. Take out all the IC's. Power up and make sure you measure +18v on pin 8 of the IC sockets, and -18v on pin 4. Remember, U5 is a single opamp (NE5534) so +18v will be on Pin 7. Power down.

2. Put the ICs back in. to check the input/de-balancing stage is working, apply a balanced signal to the input. Use a scope to measure the output (pin 7 U4). If this is OK, then the input section is working.

3. To check the output/balancing stage is working.  Apply an unbalanced signal to Pin 2 of U5. Check for equal but out of phase signals on the output pins.


Peter

thank you peter.first of all,my problem is bypass mode now.I said to harpo in previous post.if you know that pleas help me.

 

[peterc]

The bypass is after the input stage.

Input XLR  -->  un-balancing stage  -->  bypass switch/EQ  --> balancing stage  --> output XLR

You can leave in the 22uF caps with no difference.

If you are a beginner, then build the circuit as is before changing it.

Peter

 

[Harpo]

why do you say (Your mistake simply is in assuming)????????? ???

Refers to your assumption 'it should have sound in bypass mode even without PSU isn't it??like calreq EQ.' The calreq EQ (different circuit) simply connects XLR-in with XLR-out by use of a DPDT switch. This will work without a PSU connected. If this calrec EQ bypass function would be made by a DPDT relais instead of a simple switch, the relais default setting would have to be wired for this bypass setting, else this wouldn't work either without PSU operating to activate the change over. This 3D-EQ circuit operates the bypass function different again. The balanced line receiver debalances the incoming differential voltage and instead of summing all bandwidth limited gain stages, the bypass switch now connects this audio voltage thru the 56K2 resistor R48 to the inverting summing stage. This requires the opamps to be working, what these wouldn't without working supply.

I don't want to change the PSU I Said for testing I used Calreq PSU because I haven't made PSU yet and I had one of those calreq PSU and the voltage is +18 and -18 and regulators are 7918 and 7818.

Whats wrong in using this already working psu. No need to build another for the same purpose.

2.It seems that I should try to find rev log 500K pot and this method doesn't work here.my reference was http://music-electronics-forum.com/attachments/737d1181440399-pot_taper_amz.pdf but I don't know the difference between attenuator and rheostats resistors in circuits.

A rheostat is a variable resistor between two pins, not referencing a 3rd potential.
The shown attenuator from your pic is a voltage divider with the incoming signal at one end, a 0V reference voltage at the opposing end and the attenuated signal at the pots wiper in respect to this reference voltage.

3.what do you mean by hard bypass?

Hard bypass is connecting device input to device output by a direct connection, leaving the function of this device itself disconnected. Soft bypass (FI the unity gain setting for the 3D-EQ or forcing a VCA in its current-in=current-out condition for a GSSL compressor circuit) requires the device powered on.

4.why do some people put jumper instead of 22u caps??peter said (
Input caps can be replaced for DC coupling) but i don't understand.

If you are sure, any sending device that might send signal to your 3D-EQ is free of DC offset voltages, you could leave out these DC-blocking coupling caps with -3dB cutoff set for 0.72Hz. Wouldn't change much because balanced line receiver operates at voltage gain of 0.5 and has a DC blocking cap connected to its output.

oops, Peter already answered.

 

[peterc]

No problem, Harpo, thanks for the input

 

[positrons]

Some steps to fault find the problem.

1. Take out all the IC's. Power up and make sure you measure +18v on pin 8 of the IC sockets, and -18v on pin 4. Remember, U5 is a single opamp (NE5534) so +18v will be on Pin 7. Power down.

2. Put the ICs back in. to check the input/de-balancing stage is working, apply a balanced signal to the input. Use a scope to measure the output (pin 7 U4). If this is OK, then the input section is working.

3. To check the output/balancing stage is working.  Apply an unbalanced signal to Pin 2 of U5. Check for equal but out of phase signals on the output pins.


Peter

Peter I checked IC voltage and they are correct.but I don't have scope,how can I check (the input/de-balancing stage)???
before soldering,I checked all component except inductors,how can I check them?also I checked back of the PCB and there is no shorts and soldering problem,I don't change the pots yet and they are 500K liner with 100k resistor soldering between 2 pins,are they problematic parts or not???I have no sound in active and bypass mode!!!!

 

[Harpo]

I don't have scope,how can I check (the input/de-balancing stage)???

Feed the input XLR with a balanced or unbalanced signal at a frequency your multimeter can handle (maybe 300Hz sine). Amplitude doesn't matter much, as long as its peak value is below the supply rail voltages and more than zero V (maybe 100mV ... 1V). Take your multimeter, set for measuring AC voltage and measure between XLR-pins2/3. Confirm same value ariving at J1-pins2/3. Write down this measured voltage. Now measure AC voltage between U4-pin1 and 0V reference voltage. This measured voltage will be half the value of previously noted voltage (this stage has voltage gain of 0.5=-6dB).

I don't change the pots yet and they are 500K liner with 100k resistor soldering between 2 pins,are they problematic parts or not???

If the pots are connected as shown in your previously shown pic (without the black wires), you don't have a 100k resistor between 2 pins, as the leftmost CCW pin and wiper connection are joined on schematic and pcb, so your 100k resistor is shorted out as well. The pot, wired as rheostat, varies resistance between wiper connection and rightmost CW pin (between the red wires from your pic), setting the amount of gain of the inverting summer for the frequency band it controls (rheostats highest resistance value gives lowest gain and vice versa). With your linear taper pots you'd have to dial them in for ~90% of rotation for the otherwise +/-0dB center position of pots with rev.log taper.

From 3. of Peters reply, DON'T apply a signal to U5-pin2 directly (will most likely kill the opamp, missing a current limiting/gain setting input resistor). Apply this at the junction R5/R25/R48/C1 and switch the unit to bypass, so R48 is in circuit as this required resistor. Otherwise as Peter posted.

 

[Sammas]

Just "for a laugh" I put the Nite EQ in a 500 series module last year;

Faceplate looks like this;
http://www.audiomaintenance.com/downloads/5003d_front.jpg

and I even did a transformer output option PCB;
http://www.audiomaintenance.com/downloads/5003d_eq_transformer_option.jpg

It worked just fine, but slightly differently from the original in that when you boost a band it brings the "out of band" level down as well so it makes it difficult to overload (consequently the "Sub" band has the effect that the signal gets quieter when you increase the level..... because the "out of band" is basically every thing audible)...

There was one very small error on the PCB which I have now corrected.... but did not get any made.... I was thinking about getting a few boards made and then sending the gerbers to Gustav.....

... does anyone want these ?

Colin
www.audiomaintenance.com

I am gearing up to make a pair of these bad boys... but have hit a bit of a hurdle when ordering parts.
Most of it is pretty straight forward - the bits I have zero experience with is the ferrite beads.

CL1      EMI Filter - Murata  Ferrite Bead          DSC
CL2      EMI Filter - Murata  Ferrite Bead          DSC
--------------------------------------------------------
F1        Ferrite Bead  Ferrite Bead          DSC
F2        Ferrite Bead  Ferrite Bead          DSC

Can anyone give me a hint which type I am ordering? The Murata ferrite beads in particular look pretty unique as they have 3 legs!

 

[Indecline]

They are plain jane ferrite inductors that look like a thick resistor. I grabbed a couple Vishay's for mine, although you could probably use a wire link and get by just fine.

 

[Anthropic]

Hey everyone,

I just completed four channels of the Night EQ.  However, when a signal is sent through them, I'm getting an enormous amount of hum on all four channels (2 channels in each 1-space rack).  The (1kHz at 0dB) signal I'm sending it gets through, but it's very quiet and masked by the hum.

Actually, the hum sounds very similar to the sound you'd get if you had an unterminated input to a high-gain amp.  I'm a pretty experienced builder, so I don't think I made any resistor/capacitor value errors, but it's possible.  I'm leaning to the cause being some sort of grounding problem.  Does anyone have any special grounding "tricks" for this project?  I've simply attached a lead from the GROUND connection on the AC input side of the Green PSU to the chassis ground lug (where the AC ground from the wall jack is also grounded).  The EQ boards get their grounds from the GROUND connection on the other side of the Green PSU board (where the -+18V is supplied).  The XLR inputs/outputs have their PIN 1 connected to the GROUND connection area on the EQ boards.  This (from pictures I've seen) seems to be the way everyone else is wiring theirs. 

Any ideas?  I've tried swapping OP AMPs, etc., but since the problem is common to all 4 channels I assume something else has gone awry.  Thanks!

Dan

 

[Indecline]

Hey everyone,

I just completed four channels of the Night EQ.  However, when a signal is sent through them, I'm getting an enormous amount of hum on all four channels (2 channels in each 1-space rack).  The (1kHz at 0dB) signal I'm sending it gets through, but it's very quiet and masked by the hum.

Actually, the hum sounds very similar to the sound you'd get if you had an unterminated input to a high-gain amp.  I'm a pretty experienced builder, so I don't think I made any resistor/capacitor value errors, but it's possible.  I'm leaning to the cause being some sort of grounding problem.  Does anyone have any special grounding "tricks" for this project?  I've simply attached a lead from the GROUND connection on the AC input side of the Green PSU to the chassis ground lug (where the AC ground from the wall jack is also grounded).  The EQ boards get their grounds from the GROUND connection on the other side of the Green PSU board (where the -+18V is supplied).  The XLR inputs/outputs have their PIN 1 connected to the GROUND connection area on the EQ boards.  This (from pictures I've seen) seems to be the way everyone else is wiring theirs. 

Any ideas?  I've tried swapping OP AMPs, etc., but since the problem is common to all 4 channels I assume something else has gone awry.  Thanks!

Dan

It's possible there's a ground loop in there. Try removing audio ground (eq board) off of the PSU ground to a star grounding scheme. IIRC, XLR pin 1 ties to chassis ground by the IEC inlet. Do a search for 'star ground' on the forum, you'll find plenty of threads on the topic.

Let us know how it works out!

 

[Anthropic]

Thanks INDECLINE. 

I did a few tests today.  My problem definitely seems to be grounding-related.  Running Pink noise through the EQ and turning the knobs, I'm able to cut/boost all of the frequencies with no problem (as intended).  Also, the frequency selector switch is fully functional.  Still, the test tones are nearly completely obscured by the "ground loop" hum I described in my previous post. 

In attempt to find a quiet ground scheme, I did the following:

- disconnected the grounds from the EQ board to the IN/OUT XLR jacks.  This added a loud buzz to the output signal.
- unscrewed the XLR jacks from the chassis (to remove the possibility of a loop through the chassis).  This did little, if anything to the hum.
- disconnected the ground wire that ran from the Green PSU to the EQ board's -+18V input area and connected that EQ board Ground input directly to star ground.  This produced a significant reduction in hum, but a large portion remains.
- I've also run PIN 1 on the XLR jacks directly to star ground (rather than to the Ground connection on the EQ Board XLR IN/OUT).  This did nothing to reduce the hum.

Some hints:

- the hum seems output-based (rather than hum induced at the input).
- the volume of the test tones (in relation to the hum) is louder when the EQ is in BYPASS. 


Does anyone have a grounding plan that has produced reliably quiet results with this EQ?  Since the grounding between individual portions of the EQ is set by the construction of the board (and presumably works well), the ground wiring of the boards/XLR jacks must be critically important. 

Thanks for the help so far!

 

[peterc]

Dan

Do you have a scope to check the ripple on your PSU rails?

Getting back to the grounding issue, can you take the PCB out of the chassis, to eliminate that component.

Start simply, connect one channel to the PSU.

Peter

 

[Harpo]

The (1kHz at 0dB) signal I'm sending it gets through, but it's very quiet and masked by the hum.

Your signal connects between XLR-pins2/3 (the balanced line receiver exclusively operates the differential between these pins 2/3). XLR-pin1 connects to the cable shield and case by a shortest possible connection. When using shielded cable for audio inside your unit, connect the shield at one side only, else you most likely build a ground loop. You might have an unbalanced signal connected between XLR-pins1/2 and pin3 left floating.
The 1kHz at 0dBanana (is it dBu, dBV, dBFS, ...?) doesn't say what level you are sending. You could check the level at the output of the line receiver for half the level you sent in by measuring the AC voltage, so you know the unbalancing is working properly.

 

[whomper]

Hi,

Trying to apply the EQ to some mastering applications that I have, the Cut/Boost potential is way too big for my use. Is there a way to cut by half the Cut/Boost range with a simple mod?

Also, can others post sample freq curve of their EQ builds? Trying to see how mine (posted earlier) compare to see whether I should play some more with resistor values of the 650 (or 640Hz) band or what others get is inherently similar to mine.

Thanks.

 

[positrons]

I don't have scope,how can I check (the input/de-balancing stage)???

Feed the input XLR with a balanced or unbalanced signal at a frequency your multimeter can handle (maybe 300Hz sine). Amplitude doesn't matter much, as long as its peak value is below the supply rail voltages and more than zero V (maybe 100mV ... 1V). Take your multimeter, set for measuring AC voltage and measure between XLR-pins2/3. Confirm same value ariving at J1-pins2/3. Write down this measured voltage. Now measure AC voltage between U4-pin1 and 0V reference voltage. This measured voltage will be half the value of previously noted voltage (this stage has voltage gain of 0.5=-6dB).

I don't change the pots yet and they are 500K liner with 100k resistor soldering between 2 pins,are they problematic parts or not???

If the pots are connected as shown in your previously shown pic (without the black wires), you don't have a 100k resistor between 2 pins, as the leftmost CCW pin and wiper connection are joined on schematic and pcb, so your 100k resistor is shorted out as well. The pot, wired as rheostat, varies resistance between wiper connection and rightmost CW pin (between the red wires from your pic), setting the amount of gain of the inverting summer for the frequency band it controls (rheostats highest resistance value gives lowest gain and vice versa). With your linear taper pots you'd have to dial them in for ~90% of rotation for the otherwise +/-0dB center position of pots with rev.log taper.

From 3. of Peters reply, DON'T apply a signal to U5-pin2 directly (will most likely kill the opamp, missing a current limiting/gain setting input resistor). Apply this at the junction R5/R25/R48/C1 and switch the unit to bypass, so R48 is in circuit as this required resistor. Otherwise as Peter posted.

Thank you harpo for your helps. my problem is solved. the problem was those two 22u caps!!!!!I remove them and put jumper instead of them and now I have sound.I didn't understand the reason of that. ???
I don't change the pots yet and they are linear and they don't work properly.I will change them.
one quastion when I connect output of EQ to input of my speakers with TS cables,I hear a little bit of distortion!!but when I connect the output to a headphone,there is no distortion.what is the reason for that?should I use TRS cable only??

 

[positrons]

1.Is it possible to explain the AIR,VARY and SUB band of this EQ??when I change the VARY I can't understand exactly what happened.VARY and AIR are related to each other??I mean the frequency of AIR band choose by the VARY selector??or vary is a shelve??

2.and the sub band is a band under 40HZ??

3.It seems that the Q of this EQ is very wide, isn't it??

thanks