EQN build thread

[briomusic]

RV4/5 -what is the alignment procedure for these trimmers? is it similar to the 'symmectrical clipping' process on the 1290 preamp?
Exactly.

Ok, i looked at the 1290 thread.  I still am a little un clear on how to do this. 

1. Do we need to adjust just RV5 or both RV4 and RV5?

RV5 is the clip adjust. RV4 is to adjust level difference of 'eq in' vs 'eq out'. adjust RV4 with all the frequencies set to "off" to get the same level at both positions of the 'eq in' switch.

2. I don't have a scope but maybe able to go to a friend who has one.  Do I want it to hard clip or just clip?  Not sure what to look for.

"Just clip" is best. you are basically trying to find out if the top or bottom half of the sine waves clips first. if you hard clip it will look like they both clip all the time. it just needs a bit of tinkering with the amount of level you send into the eq and the setting of RV5. when the onset of clipping is happening at both the top and bottom half of the sine wave you have the correct bias.

3. Is there anyway to do this without a scope? 

yes, you can do it with the waveform display of your DAW but it takes a little longer (make adjustment/record audio/zoom in to waveform/make another adjustment/record again/etc)

 

[dandeurloo]

The wiring for the input transformer is on the previous page. Also take 6 (screens) to SCR.
For the output, we'll have to wait for colour confirmation from Ed.

I've got a number of minor issues with my EQ's.  I tried biasing the eq's and found this so far.

1. I have a much lower output then going into the eq.  Could it be that I don't have anything hooked up to the SCR pad on the input transformer?  I saw the earlier hook up diagram and just saw this.  Does pin 6 go to SCR?

2. My gain pots are wired backwards.  Easy Fix.

3.  So far I noticed that my LF switch is a little wierd.  "Off" is in the second position and I have sound coming out of the 1st position?  Is that something to do with the stopper pins in the grayhill or something else.

 

[dandeurloo]

I wired pin 6 of the input tranny to SCR. 

I fixed the backwards wired gain pots. 

But now I have random scratchy sounds out of both eq's and at least -20db signal lose. 

I am also pretty sure my stop pins are all in wrong positions of the grayhill's because it doesn't seem to be working properly.

Any ideas on how to trouble shot this. 

 

[haima]

you can remove the switch pins from the front using a strong magnet i imagine...

i've got photos of where the switch pins need to go - i'll post them asap in case you need help.

 

[dandeurloo]

Thank you! That would help a ton.

I'm going through part by part now to check again for errors as well.  

would it matter if I have R1 and R2 installed even though I'm using it with 51x?  I did it before I saw they aren't needed and I checked the Schemo and didn't see them on it.  So I figured it would be completely by passed so it wouldn't hurt to leave them in.  Am I correct in my thinking?

 

[dandeurloo]

I just cross checked all the resistors and the COG's and tant's and electrolytic.  All good!

It must be the switch pins in the wrong spot or some how I messed up the WIMA's?  

I don't have anything in J1.  Does that need anything?

I'm using 750R in R29 as well.

 

[loopermc5]

I just cross checked all the resistors and the COG's and tant's and electrolytic.  All good!

It must be the switch pins in the wrong spot or some how I messed up the WIMA's? 

I don't have anything in J1.  Does that need anything?

I'm using 750R in R29 as well.

i think your right to check your pins I bet it solves it. MY first one worked perfect then somehow the second one got all messed up must have been up to late anyways it did all sorts of foolishness till i fixed it.My pins were right but the switch shaft was turned to the wrong side when I place them.

 

[dandeurloo]

I think that will fix it.  I just need to figure out the proper place for the pins.  I have been doing this stuff late at night so I'm sure it was my fault.

 

[crisotop]

Anyone found suitable pots with center click in europe? I was browsing Farnell and RS (and the smaller shops ones like Banzai and Musikding) but found nothing that would fit (nor the recommended Vishays)? Any links would be very handy..

Thanks!
Christoph

 

[peter purpose]

Punch prv6 into Farnell

 

[crisotop]

thanks peter, already looked at them - but as far as I've understood they have no center click?

cheers again,
Christoph

 

[peter purpose]

What do you need a click for....... is this a brail eq?

 

[dandeurloo]

Hey peter can you give me some help figuring out the stop pins on the grayhills?  I think they are all messed up.

Also, I used Clarostat 308 pots.  That portion works great.

 

[peter purpose]

Page 6

 

[briomusic]

What do you need a click for....... is this a brail eq?

I agree with this, given the common pot tolerances you're more likely not to be at +-0dB on your centre click anyway. better and easier to switch the band off with the frequency selector if it is unused.

 

[dandeurloo]

Peter, is this right for the switches?

I stuck resistor leads in to show the placements.

This is for the top 2 switches.

And this for the bottom 2 switches.

 

[peter purpose]

Peter, is this right for the switches?

No.

 

[dandeurloo]

Ok, it makes sense because it doesn't work.  Haha.  At least I can narrow it down to the switches hopefully then.

I love your answers.  hahaha

Any help?

 

[peter purpose]

Dan, read the instructions that come with the switches... Then go to page 6.

 

[dandeurloo]

Sorry the instruction got thrown out in a frantic house cleaning by the wife.  I looked on grayhill's site but couldn't find a digital print of them.  Anyone have a link?

I have read page 6 a number of times, still trying to sort it out.

thanks