Barry Porter "Net EQ"

[detonator]

@detonator: thanks! je bent altijd welkom om een keer te komen checken als je in de buurt bent hoor.

Zodra je hem kompleet af hebt, maak ik een gaatje.

 

[dagoose]

@detonator: thanks! je bent altijd welkom om een keer te komen checken als je in de buurt bent hoor.

Zodra je hem kompleet af hebt, maak ik een gaatje.

doe maar wel voorzichtig dan, zitten al genoeg gaten in het paneel.  ;D
But cool, you are always welcome to come on over!

 

[dagoose]

all done!
Now i'm in the middle of calibrating it but i was wondering about the input common mode adjust.

The input common mode rejection is set in the following manner:
Apply a 100Hz signal to the input, and monitor the output of the stage at the top of
R11 using either an oscilloscope or AC meter capable of reading down to –80dBu.
Set the input signal level so that it is at +20dBu (7.75V) at the top of R11. Now join
the two inputs together and apply the same signal to the junction. Adjust P1 for
minimum signal at the top of R11. Change the input signal frequency to 10kHz and
adjust C36 for minimum output. Repeat these steps two or three times to reduce
interaction between the two controls. With careful adjustment, a common mode
rejection ratio of 60 or 70dB should be attainable.

About the joining together; i think they mean that on both the + and - on the input there is a + (or -) signal so that it nulls/cancels? Am i correct?

 

[Harpo]

yepp.

Ok.. strange.. i had some bc182L's in there and a couple of BC182B and the L version didn't work and the B version is working. 
In some kind of way the collector of the L had 7v and didn't go to 0 while the B had 12v and went to 0.

BC182L differ in pinout, compared to BC182B.

 

[dagoose]

Thanks! So my first idea was right. 8)

Pics and things... later on!
I have it racked up in the studio right now and it sounds great! No noise and really nice warm low-end.

 

[dagoose]

OK.. time to show off!  8)

http://www.groupdiy.com/index.php?topic=48829.0

 

[dagoose]

anyone else doing this EQ right now? Just curious.  8)

 

[kpearsall]

I'm slowly getting my parts together... I've been distracted by microphones. Not having enough mics is a more pressing concern unfortunately. But I got my old job back so I wouldn't think it's too far off in the future

 

[Assistant]

i ordered almost all parts, still waiting for some to get here and hopefully can start building next week or so  8)

 

[Harpo]

Just another hop for the missing stepped highpass filter and shelfing bands ...

 

[kpearsall]

haha... Harpo, you are awesome

 

[Assistant]

@harpo: i hope i don´t ask to much, but is it possible to modify the hi pass to only 6 steps with 15,20,25,30,35 and 40hz?

this would be much more usable in mastering.

 

[Harpo]

@harpo: i hope i don´t ask to much, but is it possible to modify the hi pass to only 6 steps with 15,20,25,30,35 and 40hz?

this would be much more usable in mastering.

...there are 3 type of.., those who can count and those who ... ;D
sure about your 5 frequency steps for 6 positions ? You want a linear increase in frequency, not logarythmic 15, 18.25, 22.2, 27, 32.9, 40Hz ?
Keeping C86-C89, values for the P3a and P3b series string resistors would be
3k32, 2k74, 2k21, 1k87, 1k50, 6k98 for prementioned logarythmic increase
or
4k64, 2k80,1k87, 1k33, 1k00, 6k98 for your linear increase.

 

[Assistant]

sure about your 5 frequency steps for 6 positions ?

hmm i still count 6 frequencies?

1) 15
2) 20
3) 25
4) 30
5) 35
6) 40

but thank you very much much for all the infos, that´s exactly what i was looking for! 
didn´t really thought about linear or logarithmic before, not yet sure which one is better in use and what i´ll go with.

 

[Harpo]

> ...to only 6 steps with 15,20,25,30,35 and 40hz?
< sure about your 5 frequency steps for 6 positions ?

hmm i still count 6 frequencies?

...and the 5 steps are from
1) 15 to 20
2) 20 to 25
3) 25 to 30
4) 30 to 35
5) 35 to 40

 

[Assistant]

ok got you now 

 

[prescott]

Hello!

I'm also building the Eq, almost done...

I make 2 channels with stepped switches.

In the excell sheet there is a lot a description about changing resistors/sorting out if using stepped switches.
Is it possible that my unit is doing crazy thinks just because a have the rotary switches with the original resistor values on the pcbs?

I've seen Dagoose's unit (pics), and he also have those resistors in their place...

So is it before the change, or this is the right way?

Should I change the values/sorting out as written in the excell sheet?

And where can I find the description about the calibrating?

Help me please :-\

Thanks!

 

[Harpo]

In the excell sheet there is a lot a description about changing resistors/sorting out if using stepped switches.
Is it possible that my unit is doing crazy thinks just because a have the rotary switches with the original resistor values on the pcbs?

Depends on your definition of 'the rotary switches' for frequency, Q or boost/cut, which original resistors you are refering to and how your switched pots substitutes connect to pcb.

I've seen Dagoose's unit (pics), and he also have those resistors in their place...

Jeffrey will know better, but FI the law bending 1K5 resistors (R114,115,111,112,...) at the CCW end of the frequency pots will then be one side connected, doing nothing, when the pots get substituted with the switched string of series resistors. The calc sheet is based on listed values in the calc sheet, so if you FI keep the series resistors (R87,61,83,58,..., these are in parallel to prementioned law benders, connecting to virtual ground and 0V reference voltage, and already part of the series string at the switches), the filters center frequency will be different (FI the previous 2kHz-20kHz range would respond for a 1.528kHz-4.896kHz range instead when you keep the 3K6 resistors R61 and R87 instead of using 0Rs/shorts).

Should I change the values/sorting out as written in the excell sheet?

Do whatever matches your plan best. This is DIY. There is no hidden formula in the calc sheet, so feel free to come up with different parts values.

And where can I find the description about the calibrating?

read the 'readme.pdf', partly quoted by dagoose some posts above.

 

[prescott]

Ok, first of all thank you for your help!

I think we are on different levels of DIY


I've built my unit using the ring resistor list from the sheet, and with the original cap and res values marked on the pcb.
Now it doesnt work fine.

If i change the values on the pcb to values in the sheet will resolve my problem?
example: I have all the ring resistor values from the sheet but i have 2n2 for c84,c61 instead of 6n8...

Is it a problem?


Thanks, and sorry for my beginner questions... :-\

 

[Harpo]

I've built my unit using the ring resistor list from the sheet, and with the original cap and res values marked on the pcb.
Now it doesnt work fine.

At least different.

If i change the values on the pcb to values in the sheet will resolve my problem?
example: I have all the ring resistor values from the sheet but i have 2n2 for c84,c61 instead of 6n8...

probably 2n2 for c85,c63 instead of 6n8 and series resistors 3k6 for R87,R61 fitted as well, switched resistor strings connecting to the center and right hole of the pot outline, left side hole of pot outline unconnected, resulting in a frequency range of 4.725kHz...15.135kHz. A little different from 2kHz...20kHz, but should work.
(You could overwrite the '0.0068' caps value with '0.0022' and replace the '0' with 3600 in the R87,61 cell for the resulting series string of resistor values needed, but as you already have your switches built, an exchange of caps and shorting out these series resistors might be the smaller evil.)
Your problem more likely will be in a different spot.