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

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weiss

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Whoops said:
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

thank you!
 

jrasia

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I'm using a DIY Racked PCB of this EQ, and have a particular question about 60hz hum I'm getting.

Ch1 is very quiet. 
Ch2 is fine so long as I have the 'Air' switch on.  When its in 'Off' position, I'm getting the 60hz noise. 

I have Mumetal around the transformer, tried rotating it with no change.  Audio cabling is all shielded.  All wiring is nicely twisted and moved away as far as possible from the psu.

Any ideas?

 

Harpo

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jrasia said:
I'm using a DIY Racked PCB of this EQ
assume your schematic and pcb to differ from this topics schematic and pcb.

Ch2 is fine so long as I have the 'Air' switch on.  When its in 'Off' position, I'm getting the 60hz noise.
So this seems pre psu related. (Post psu would be dominant 120Hz from rectification).
Double check traceside of pcb. There might be a wire not clipped off that now connects to your case ground.
Other possibility might be a device inducing mains frequency into your eq with lid open. (halogen spot, ...)
Good luck
 

jrasia

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Thanks guys!  I'll have to measure what frequency I'm getting,  but it may indeed be 120hz. 
 

manulaudic

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Hi, i wanted to build thi project from Diy racked but i can see he stole the project somehow? could i purchase the pcb from the right owner? or could i etch my own?

I'd greatly appreciate it, this would be a super nice project :)

Manu
 

Whoops

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manulaudic said:
Hi, i wanted to build thi project from Diy racked but i can see he stole the project somehow? could i purchase the pcb from the right owner? or could i etch my own?

I'd greatly appreciate it, this would be a super nice project :)

Manu

I still have some pare boards for this project that I will never use, I can sell them.
PM me
 

Whoops

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3nity said:
Hey guys.
Can anyone help adjust the level difference when eq in and bypass?

Hi 3nity,
there's a document for it, it was posted on this thread and I re-posted it again some pages back.

what pots did you use?
 

3nity

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Hi whoops.
I used the 500k from small bear.
I switched r48 from 52.2k to 8.2k and levels are almost identical.
However i lost some low end here.

Ill look for your post.
Thanks
 

Whoops

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3nity said:
Hi whoops.
I used the 500k from small bear.
I switched r48 from 52.2k to 8.2k and levels are almost identical.
However i lost some low end here.

Ill look for your post.
Thanks

I don't think you will ever be able to get the same level with EQ in and in bypass with pots without a center ident/detent.
You need to know the center value of the pot and use the excel document to adjust the resistors for each individual pot.

With those pots without center detent the center position will never be same, so the center value will never be same.

You should get the Pots with center detent from Audiomaintenance
 

shot

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What would be the best solution to adding output level potentiomenter only for EQed signal? I'm not looking for adding gain with that pot but just some attenuation before signal leaves the unit in order to enter next unit in chain with the aprox. same level as was the flat/bypassed signal.

I guess I could put a potentiometer instead of R30 to vary the NFB on U5 opamp but that would affect the bypassed signal also. And I want to have bypass signal intact.
Would a simple voltage divider be enough in the entry of EQ SUM signal to the switch SW7? Or would I need to do it with variable gain opamp at that spot? Or maybe my thinking is wrong and I should do it elsewhere?

:)

Luka
 

Harpo

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shot said:
I guess I could put a potentiometer instead of R30 to vary the NFB on U5 opamp
Yupp. For a FI +/-6dB varying level adjust you need a resistor varying from roundabout 28K up to 112K, so lift one side of R30 in order to build a series string of the required fixed and variable part values, place a 2nd 56k in parallel to the already existing R30, giving 28K for the -6dB min.gain setting, lifted side of this now 28K paralleled resistor connects the ccw end of a 100K pot with 560K in parallel between ccw end and wiper, giving 84K85, pot wiper joined with pots cw end connects to the lifted end of R30 on pcb.
Would a simple voltage divider be enough in the entry of EQ SUM signal to the switch SW7?
No. This spot is a current node (virtual ground), not a voltage node.
Or would I need to do it with variable gain opamp at that spot?
Is one possible solution (built like U5 with same Rfb value as R48, probably 56K, switch now selecting between now variable U5 out or the bypass substitute fixed gain opamp output, switch pole further leading to R27 and C15).
Another (maybe prefered) option could be a hardwire bypass between device input and output.
good luck
 

shot

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Harpo said:
Yupp. For a FI +/-6dB varying level adjust you need a resistor varying from roundabout 28K up to 112K, so lift one side of R30 in order to build a series string of the required fixed and variable part values, place a 2nd 56k in parallel to the already existing R30, giving 28K for the -6dB min.gain setting, lifted side of this now 28K paralleled resistor connects the ccw end of a 100K pot with 560K in parallel between ccw end and wiper, giving 84K85, pot wiper joined with pots cw end connects to the lifted end of R30 on pcb.

Harpo you are fantastic! Super precise answer. No additional questions needed.
Thank you for your effort!

Another (maybe prefered) option could be a hardwire bypass between device input and output.

Yes, I also started thinking in that direction. I would just abandon internal bypass solution and add relay for true bypass.

:)

Luka
 

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