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

[supiarmando]

Are there still some PCBs available? I would like to build a stereo version!

[sedit1]

Hi, I need some help 

I have some gain problems in my unit, I cheked the previous posts concerning about gainloss but didn't help.

So when the unit is bypassed the gain is normal but when I put the eq on the gain drops about 10db's, it's the same with both channels and it doesnt matter if i use balanced or unbalanced jumpers.

I have a stepped version using harpos xls values and the only thing different is that I'm using green pre psu with +-15v rails.

I just have cheked all my caps, they are the right value no errors there, also cheked solder bridges, all fine.
And measured all the ic pins and +-15v were on the right spots, I'm using JRC 5532d/5534d's


Do you have any pointers that I should check?

Edit...I also checked all the resistors with colour charts, all fine there and measured the ic:s hey were fine also.

So I'm litlebit confused and I was thinking that did I made some mistake using the rotary switches? I used Harpos xls v1 to calculate the pot values(no parallel resistor), I used 11 step lorlins and the center is normal 56k2 the rest of the build is done exactly by the bom. Did I made somekind of mistake, do I need to change some other parts to make the switched version to work normally?

Thanks!

[leafcutter]

Quick sanity check:

Do you think that this: http://uk.farnell.com/multicomp/mcta060-18/transformer-60va-2-x-18v/dp/9530444

would be ok to power 4 channels of Nite Eq via Green PSU board?

also anyone know if any of those Audio Maintenance switches are the right pin spacing for the Nite Eq board?

Cheers,

John.

[peterc]

John

That transformer will work, but is a lot bigger than you actually need. A 30VA 2 x 15v transformer will work just as well and be a tad cheaper.

This one would be good: MCTA030/15

http://www.farnell.com/datasheets/79607.pdf

Peter

[leafcutter]

Thanks Peter,

Is the Green PSU shown here set up for +/- 15 or +/- 18. Am I right in thinking that to get +/- 18 I'd need a 2 x 18v transformer?

Cheers,

John.

[peterc]

With a 2 x 18v trasnformer, the rectified voltage will be +-((18 x 1.414) - 1.4v) = +-24v.

With a 2 x 15v trasnformer, the rectified voltage will be +-((15 x 1.414) - 1.4v) = +-19.8v

Regulators need 3v to work properly, so the 2 x 18v transformer is good for +-18v.

Having done these calcs, I dont like running projects at +-18v. The gain is dynamic range  is in the region of 2dB, and most times I have used 17.5v  on the projects, something has gone up in smoke..... This is using max +-18v opamps like the TL074

[sedit1]

Nobody? 

Could it be the Ic's? They all measured 40/50k between pins 4-8/7.

First I doubted cap values but they are correct. What could possibly cause the gainloss? Just cheked the gainloss is 14db's. Otherwise everything works great and the sound is good.

Hi, I need some help 

I have some gain problems in my unit, I cheked the previous posts concerning about gainloss but didn't help.

So when the unit is bypassed the gain is normal but when I put the eq on the gain drops about 10db's, it's the same with both channels and it doesnt matter if i use balanced or unbalanced jumpers.

I have a stepped version using harpos xls values and the only thing different is that I'm using green pre psu with +-15v rails.

I just have cheked all my caps, they are the right value no errors there, also cheked solder bridges, all fine.
And measured all the ic pins and +-15v were on the right spots, I'm using JRC 5532d/5534d's


Do you have any pointers that I should check?

Edit...I also checked all the resistors with colour charts, all fine there and measured the ic:s hey were fine also.

So I'm litlebit confused and I was thinking that did I made some mistake using the rotary switches? I used Harpos xls v1 to calculate the pot values(no parallel resistor), I used 11 step lorlins and the center is normal 56k2 the rest of the build is done exactly by the bom. Did I made somekind of mistake, do I need to change some other parts to make the switched version to work normally?

Thanks!

[Hank Dussen]

Hi, I need some help 

I have some gain problems in my unit, I cheked the previous posts concerning about gainloss but didn't help.

So when the unit is bypassed the gain is normal but when I put the eq on the gain drops about 10db's, it's the same with both channels and it doesnt matter if i use balanced or unbalanced jumpers.

I have a stepped version using harpos xls values and the only thing different is that I'm using green pre psu with +-15v rails.

I just have cheked all my caps, they are the right value no errors there, also cheked solder bridges, all fine.
And measured all the ic pins and +-15v were on the right spots, I'm using JRC 5532d/5534d's


Do you have any pointers that I should check?

Edit...I also checked all the resistors with colour charts, all fine there and measured the ic:s hey were fine also.

So I'm litlebit confused and I was thinking that did I made some mistake using the rotary switches? I used Harpos xls v1 to calculate the pot values(no parallel resistor), I used 11 step lorlins and the center is normal 56k2 the rest of the build is done exactly by the bom. Did I made somekind of mistake, do I need to change some other parts to make the switched version to work normally?

Thanks!

If everything is working fine and it's just a 14dB gain loss it's more likely there's a wrong resistor somewhere. Double check the resitors around U4 and U5.
Sometimes reading color-codes can be really tricky. White looking like grey etc...
The color-code, for example, of a 10K reistor looks really alike 100K...
Try measuring the resistors. Though it might not always read the correct value when there's another resistor or cap in parallel but it could give you a clue...

[sedit1]

If everything is working fine and it's just a 14dB gain loss it's more likely there's a wrong resistor somewhere. Double check the resitors around U4 and U5.
Sometimes reading color-codes can be really tricky. White looking like grey etc...
The color-code, for example, of a 10K reistor looks really alike 100K...
Try measuring the resistors. Though it might not always read the correct value when there's another resistor or cap in parallel but it could give you a clue...
[/quote]

Thanks good advice!
I triple cheked the resistors but nothing. Everything correct. Here's two pictures if you can see something that I don't.

[sedit1]

Second. The pcb shot.

[sedit1]

Thanks good advice!
I triple cheked the resistors but nothing. Everything correct. Here's two pictures if you can see something that I don't.

Any more pointers?
Getting really confused, because I have checked all the resistor/cap values many times and I don't think it's soldering error because the two channels are identical and behaving the same. Can a broken opamp cause something like this?

Or can it be something to do with the rotary switches? The switch values are about 660k/switch. And when I measures the bypass resistor, when unit bypassed it showed about 15k resistance and when eq on it was 56k2.

Please help me 

Thanks!

[peterc]

Sedit1

Did you actually measure the resistors suggested above? I know I have a batch of 1% resistors where the 100k looks exactly like a 10k, i.e. the red stripe looks like an orange stripe and vice versa......

Peter

[sedit1]

Sedit1

Did you actually measure the resistors suggested above? I know I have a batch of 1% resistors where the 100k looks exactly like a 10k, i.e. the red stripe looks like an orange stripe and vice versa......

Peter

Thanks Peter, yes I measured them twice and were hoping that that would have been the solution because thats the most obvious, but no.

[Whoops]

Sedit1

Did you actually measure the resistors suggested above? I know I have a batch of 1% resistors where the 100k looks exactly like a 10k, i.e. the red stripe looks like an orange stripe and vice versa......

Peter

Thanks Peter, yes I measured them twice and were hoping that that would have been the solution because thats the most obvious, but no.

Hard to understand, its strange that its the same in both channels.

You should do a signal tracer cable, and follow the schematic, tracing the circuit and figure out at which point does the sound drop. 
I would also guess its a wrong resistor value on the same place in both channels

[sedit1]

Sedit1

Did you actually measure the resistors suggested above? I know I have a batch of 1% resistors where the 100k looks exactly like a 10k, i.e. the red stripe looks like an orange stripe and vice versa......

Peter

Thanks Peter, yes I measured them twice and were hoping that that would have been the solution because thats the most obvious, but no.

Hard to understand, its strange that its the same in both channels.

You should do a signal tracer cable, and follow the schematic, tracing the circuit and figure out at which point does the sound drop. 
I would also guess its a wrong resistor value on the same place in both channels

Thanks! So it seems like it's the only possibility to have fault like this? I checked the boards again yesterday and eaven for some resistors that I wasn't sure measuring from the board I took one leg off and did the mesurment, also compared the bom to my mouser order confirmation(of course they make mistakes too).

Can it be something in the caps? Still there are just few different cap values and I have cheked them several times. Also tested with new opamps.

[Harpo]

What could possibly cause the gainloss? Just cheked the gainloss is 14db's. Otherwise everything works great and the sound is good.

If it sounds good (read linear response) and no gain loss when bypassed, this will not be in the input stage or band stages.
Double check/measure the voltage divider R23 / R24 and double check the wiring and parts values of the summing resistors at your stepped gain switches.

[sedit1]

What could possibly cause the gainloss? Just cheked the gainloss is 14db's. Otherwise everything works great and the sound is good.

If it sounds good (read linear response) and no gain loss when bypassed, this will not be in the input stage or band stages.
Double check/measure the voltage divider R23 / R24 and double check the wiring and parts values of the summing resistors at your stepped gain switches.

Measured r23/r24, all ok and also cheked wiring+summing resistors from the stepped switches all ok there. 36k5 going to sum and 100k/wiper going to opamps (using 11 steps +-5db configuration). This is starting to sound very odd, never had so much troubleshooting and not finding any problems 

[Harpo]

cheked wiring+summing resistors from the stepped switches all ok there. 36k5 going to sum and 100k/wiper going to opamps (using 11 steps +-5db configuration).

Just to make sure, resistance between opamp-out in the freq.band stages (U1,U2,U3 pins 1 and 7) and summing node (U5 pin 2) is varying between 31K6 and 100K with R30 being 56K2 ?

[leafcutter]

Quick Grounding question, I'm finishing up 4 nite eq's in a 2u case. I've grounded the AC earth to the case but I can't remember if the 0v/ground from the DC side of the green PSU should go to the case also?

Does my sketch look non-lethal?

Cheers John.

[sedit1]

cheked wiring+summing resistors from the stepped switches all ok there. 36k5 going to sum and 100k/wiper going to opamps (using 11 steps +-5db configuration).

Just to make sure, resistance between opamp-out in the freq.band stages (U1,U2,U3 pins 1 and 7) and summing node (U5 pin 2) is varying between 31K6 and 100K with R30 being 56K2 ?

Thanks Harpo!

Sorry I meant 31k6 not "36k5" going to sum and thats the step 11 on lorlin and the first step is 100k like in your xls.

I measured the resistance( U5 pin 2) to  (U1,U2,U3 pins 1 and 7)  and The smallest value was 31k6 and the biggest was ~660k witch is the total value of the pot, Is this wrong?