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

[druu]

Just to update, I've resolved the issue by removing the parallel R as above and altering the R24 value to compensate for the loss in voltage gain.

I'd suggest to anyone looking to build to avoid using a parallel R across a _series string_ rotary. My circuit has no audible max cut between between step positions as suggested in Harpo's V2 worksheet and I am using 23 step shorting type rotaries.

Thanks for the advice Harpo, appreciate it as always, learnt a lot about this circuit by simulating it (and of course your shared analysis of the circuit in your excel document!).

 

[imloggedin]

I just finished my Nite EQ and everything works but the middle of each pot is not flat - which I can deal with by adjusting the knobs, but the right channel is also 0.5-1 DB lower than the left. I wanted to use it as a stereo eq and I am not sure if swapping the opamps might help even out the levels. Any suggestions?

Thanks

 

[Whoops]

I just finished my Nite EQ and everything works but the middle of each pot is not flat - which I can deal with by adjusting the knobs,

Hi, did you read this thread?

All the problems you're having are described in this thread and the solutions given

For the all the center points of each pot to be 0dbs you need to adjust resistor value on each pot.
there's an excel doc made by harpo that does the calculation, the doc it's in this thread

 

[imloggedin]

Hi, did you read this thread?

All the problems you're having are described in this thread and the solutions given

For the all the center points of each pot to be 0dbs you need to adjust resistor value on each pot.
there's an excel doc made by harpo that does the calculation, the doc it's in this thread

I ended up reading almost all of the pages after I posted and realized that. Sorry for the premature post. I am looking to do stepped switches instead of pots after reading all of the pot issues. Now if I can find the page that spreadsheet was on!

Thanks

 

[imloggedin]

Harpo's Stepped Pot spreadsheet is very helpful but it seems I would need a 21 step rotary switch to get from -5 to +5 in 0.5 db increments. Those don't seem to be very available or cheap so I guess I'll be sticking to pots until I find some.

 

[bruno2000]

Harpo's Stepped Pot spreadsheet is very helpful but it seems I would need a 21 step rotary switch to get from -5 to +5 in 0.5 db increments. Those don't seem to be very available or cheap so I guess I'll be sticking to pots until I find some.

https://www.ebay.com/itm/2Pole-23-Step-Rotary-Switch-Attenuator-Volume-Control-Pot-Potentiometer-DIY-New-/251286602182?_trksid=p5731.m3795

https://www.ebay.com/itm/1x-4Pole-23step-24Step-Rotary-Switch-DIY-Attenuator-Volume-Control-Shaft-6-0mm/292028066313?hash=item43fe3aaa09:g:FDIAAOSw5cNYfKtg

Best,
Bruno2000

 

[Whoops]

I ended up reading almost all of the pages after I posted and realized that. Sorry for the premature post. I am looking to do stepped switches instead of pots after reading all of the pot issues. Now if I can find the page that spreadsheet was on!

Thanks

You don't need switches, pots work fine. I did a lot f builds already always with pots and the center position was spot on after  replacing the resistors using the spreadsheet.

If you didn't find the spreadsheet in this thread it's because you still didn't all, lol

 

[mrdarwin]

Hi!
I feel confused with balanced or unbalanced...
Started to wire the unit with balanced jumper, as I'd like to use the unit  with analog inserts with pro tools and an orion 32 (in/out +4dB balanced) but I have -6dB loss... I've read some posts about tweaking some resistors but what about other users?
When I removed the jumpers, here is a little loss... but unit is unbalanced...

I know the difference between balanced  and unbalanced, with wires with 2 or 3 connectors (xlr)...

Can I have some help please? or a link?
thx

 

[Whoops]

Hi!
I feel confused with balanced or unbalanced...
Started to wire the unit with balanced jumper, as I'd like to use the unit  with analog inserts with pro tools and an orion 32 (in/out +4dB balanced) but I have -6dB loss... I've read some posts about tweaking some resistors but what about other users?
When I removed the jumpers, here is a little loss... but unit is unbalanced...

I know the difference between balanced  and unbalanced, with wires with 2 or 3 connectors (xlr)...

Can I have some help please? or a link?
thx

I don't know if I completely understand your questions

 

[mrdarwin]

Unit finished, balanced jumper, true bypass relays boards, -6dB loss with pots in middle position

 

[mrdarwin]

How work the jumpers? Do they affect the gain?

 

[Whoops]

How work the jumpers? Do they affect the gain?

What pots did you use?

Did you adjust the middle position gain of the Pots?

 

[mrdarwin]

I use 470k rev log pots with center detent from AML.
Even if the unit is in bypass (not hardbypassed), I dont have unity gain... is it normal?

 

[Whoops]

I use 470k rev log pots with center detent from AML.
Even if the unit is in bypass (not hardbypassed), I dont have unity gain... is it normal?

I don't think so.

you should check all the resister values you used.

Could be possible that you might got some value wrong.

 

[Harpo]

...When I removed the jumpers, ...

You need both jumpers on board. For balanced connection the center pin and right pin gets shorted on both jumper blocks, for unbalanced connection the center pin and left pin gets shorted on both jumper blocks. One jumper sets the connection of XLR-pin3, the other changes a feedback resistor value by paralleling another resistor. Difference is 6dB.

 

[mrdarwin]

With no jumper signal is present with more gain than with balanced jumpers...

 

[Whoops]

With no jumper signal is present with more gain than with balanced jumpers...

Check all the components and connections in the output circuit

Schematic attached

 

[mrdarwin]

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?

 

[Whoops]

I use 470uF 25v... could this be the problem?

Depends on where did you use that, if you used it in C13 then might not be that nice.

As far as I can see 470uF 25v are for:
C1
C14
C15
C29
C30
C40
C41

 

[mrdarwin]

I use a 22pf cog for c13.
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.

Anyway the unit seems to work now, it has a different behavior with Smaart Analyser and audio in from PTools...