calrec PQ1549 help thread

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pedroplanet said:
that's the sontec case, not calrec
Ahh thanks! Didn't notice the name difference..
Is it much different in design and sound from the Calrec?
 
Lucin Niega said:
Does anyone have the pcbs for this project that they would be willing to part with? I want to build a single channel.
http://www.groupdiy.com/index.php?topic=10776.0
 
Hi guys. I'm new to the thread and somewhat to DIY. I recently built the calrec 1549 project, but put it in a API-500 series format. (yes, I dished out some $ here, but what the hell, why not go for it) Everything works fine but it is noisier than expected. I used the schematic but didn't look over the PCB close enough and noticed there's some components I didn't include, i.e.

1) the diodes (I'm concerned now. I can't logically figure out why there there but don't want to dismiss them)
2) all the 100n and 22u caps grounded to the power rails

3)In addition to that I added an op amp just for ease of layout.

I realize the pwr voltage is slightly lower, but didn't think it would attribute to noise like this. Am I wrong? Other than problems attributed to trace layout, any ideas as to helping with the noise problems? All the above?

Thanks in advance for any help.


Take it easy and if it's easy take it twice.

 
2) all the 100n and 22u caps grounded to the power rails

You will need these - this circuit likes to oscillate if local supply power is not kept calm

Maybe try hanging them on the underside of the PCB from each of the IC's power supply pins to ground?

Jakob E.
 
gyraf said:
2) all the 100n and 22u caps grounded to the power rails

You will need these - this circuit likes to oscillate if local supply power is not kept calm

Maybe try hanging them on the underside of the PCB from each of the IC's power supply pins to ground?
Second that.  It's likely your "noise" is hash from oscillation & marginal stability.
 
hey folks,

i have a quick question - i'm building a single channel unit, using toggles instead of pushbutton switches for both q and bypass/shelving switches. mostly for aesthetics :)

i've figured how to wire them and all (off board), just wanted to verify that the pots/switches are not in the audio path in this sort of design - i.e. that the quality of the pots/switches, and the wire connections to the board i'll be making won't affect the sound. i should be able to use no-frills unshielded ribbon cable for these connections without any issues, correct?

i'm assuming that since it's ic based, the pots are simply adjusting the control voltage to the chips...however i'm not at the point where i can really study the schemo/pcb layout and fully comprehend what's going on, but i'm getting there (i think)...

any insight would be greatly appreciated!

thanks
 
ncoak said:
.. just wanted to verify that the pots/switches are not in the audio path in this sort of design ..
Except your mains power switch every pot and switch in this design is in the audio path.

i'm assuming that since it's ic based, the pots are simply adjusting the control voltage to the chips
Your audio signal is the voltage that this state-variable-filter design responds to. This is not a VCF or switched cap design. The ICs used in this design are opamps (a bunch of transistors, diodes, caps and resistors built by a piece of silicone chip).
 
ah, i see - that was the impression i was getting by following the signal path, but i figured i must have been mistaken. guess i wasn't!

thanks very much for clearing that up.
 
hey folks,

just wrapping up my calrec, everything seems to be working as planned - dead quiet and boosting/cutting as expected. only issue is the frequency distribution; i used (what i believe to be) 100k revlog pots as specified, the ranges are spot on for each band (30-470Hz, 180-2.3kHz, etc.)...but i get much more resolution in frequency selection at the ccw end of the pot turn - at the cw end there is virtually none. for example, in the high mid band, 7.5kHz is about a half millimeter turn away from 5kHz...slightly problematic!

it seems all the frequency pots display this behavior - is it possible there is something i've slipped up on circuitwise, or more likely i was sold some phony revlogs?

outside of that it works/sounds great, really looking forward to putting it to use.

thanks for any tips!

 
here are a few pics:

SANY0453B.jpg


as you can see opting for toggles and off board pots complicated things a bit  ;)

SANY0455B.jpg


mounted the pcb upside down to facilitate a left-to-right/low-to-high layout - this introduced an interesting wiring dilemma - i opted to flip the back panel of the case as well, running the power switch lines under the xlrs but keeping the in/out audio cables shorter. if i were to do it again i'd likely go with the original layout.

the psu was my first attempt at a self-fabricated circuit, mounted it upside for easy access just in case...works like a charm.

SANY0458B.jpg

 
thanks jakob! using it in my vocal chain, sounds great. fun and easy build and learned a lot along the way...really appreciate the work you've done making these projects available.

assuming everything else on the board is up to spec, is it safe to assume i have some mislabeled c100k pots? can't think of any other explanation with regards to the freq distribution issue, unless i'm missing something. guess i'll pick some up from another source and plug them in...glad i used the screw terminals  ;)
 
ncoak said:
.. is it safe to assume i have some mislabeled c100k pots?
Unsolder the pots and measure the resistance from each end with the pot set to 50%.  Compare this to a good volume control pot which should be Log.
Antilog pots will have the high & low resistance the other way round compared to a Log pot.
 
Does anybody have a front panel layout that could share with me?
I searched the forum and all the links are broken  :-\
 
Hello Guys... I have a big problem whit my 1549 EQ...
I'll Check Thousands times the PCB and shematic... for  I don't see it the problem...
Hi and Lo section is not working...
LO section Work Like minimoog or something....
Hi section no change absolut anything... I will reed all forums...

Please...
Can you tell me Rev. 4 does it work...

Thank you!!!
 
Rev. 4 works.

oscillation is a common problem - reported several times in this thread. My guess is wrong component, bad solder, or broken copper track...

Jakob E.
 
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