Feeler: ez760 - Compressor/Limiter/Expander/Gate

Gustav · Jun 20, 2014

salomonander said:
just got it working!
guess i got really unlucky and had a faulty pcb. one trace simply didn't conduct. bridging it solved the issue. thanks god - i went nuts after 12 hours of error searching

Maybe some stress on the actual solder point? Try scraping it a bit, test for continuity again. The boards should be tested.

And hey - pics or it didn't happen!

Gustav

salomonander · Jun 20, 2014

hey Gustav

pics coming up as soon as both channels are actually calibrated

i still have one problem.
i can't match q13 and q14. whenever i touch the base the voltage drops. looks like there is some at first but it dissapears. any idea what im doing wrong? im measuring ac with respect to aground. when touching the base the limit led lights up. although i calibrated the threshold. taking the probe away turns it off....

i do get a reading when connecting the other probe to xlr out hot pin.....

salomonander · Jun 21, 2014

...and more problems. the comps go through calibration just fine now. i cant say the same for the expander cards.
depending on how i pre-trim my trimpots i get different results. i get through calibration. but at the end my range control never works. i can diminish the reduction to a point. after that the pot seems to go "reverse" giving more reduction again.
the entire calibration is really tuff without any ballpark pretrims honestly. calibration #114 for instance will only with certain pre-trimmed settings. i have no clue where to start. but i guess i approached a project just a little over my head

can anyone who has a working unit maybe measure the resistance of the trim pots (in working postion)? maybe this will give me a ballpark to start at.

Gustav · Jun 21, 2014

salomonander said:
...and more problems. the comps go through calibration just fine now. i cant say the same for the expander cards.
depending on how i pre-trim my trimpots i get different results. i get through calibration. but at the end my range control never works. i can diminish the reduction to a point. after that the pot seems to go "reverse" giving more reduction again.
the entire calibration is really tuff without any ballpark pretrims honestly. calibration #114 for instance will only with certain pre-trimmed settings. i have no clue where to start.
this project is soooooo frustrating - and my last diy adventure for shure. i should have just bought a used compex....

can anyone who has a working unit maybe measure the resistance of the trim pots (in working postion)? maybe this will give me a ballpark to start at.

First of all, I once categorized all the projects into difficulty on my site - this is the only one I marked as "hard", so please done let it break your DIY balls. The calibration is unusually "hard", and if you can take this to completion, I bet you can build 99% of projects on the group in an afternoon.

What meter are you using? I am almost ashamed to admit it, but I put a VU-scale meter in mine and dialed it to zero to start off my first, second and third round of calibration

I did not see a problem until I reached the gate/expander calibration part of the guide, where the internal meter is used. Weird part was, that I was getting the correct readings at the output of the unit, but at the meter, I was getting the "forward/reverse" behavior you mention. When I put a scope on it, I saw the current move across the reference voltage point when the meter changed direction, even if I was getting expected increase or decrease measuring the output on the XLR. It took me a whole days work to stop investigating the circuit, checking if the transistors around the meter circuit were doing weird things and actually just checking the specs for the meter required (DC, 1ma)

I only mention it because your symptoms seem to match - I would've kept it a secret otherwise

Gustav

Edit:And PS, I did catch this on my first pass, but my trimmers were all opposite of Colin's directions. Although most of them say "go CCW or CW until you reach value X", you may not notice if you went opposite to get there. "move trimmer fully CCW" types of steps with no target value will mess you up, if your trimmers are like mine.

salomonander · Jun 21, 2014

Hey Gustav

thanks a lot for your reply!
yes, this is indeed a tough project. but on the other hand i just plugged in some xlrs and ran a few drumgrooves through this thing. wow.
the limiter sounds great - regardless of the voltage drop i got duting measuring.

i use the hairball meter. and honestly i never really checked if they are ok for this circuit. as you know - i dont know much

i sounds as if i have the same problem as you had. how did you actually solve it? by replacing the meter?

Gustav · Jun 22, 2014

salomonander said:
i use the hairball meter.

I think they have a gazillion different meters to choose from, so which one?

salomonander said:
how did you actually solve it? by replacing the meter?

Yep, simple as that.

You can check by seeing if the output you're measuring from the unit follows the meter direction, even as it reverses - and of course, if your meter zero calibration was done to a 0 VU scale on the meter.

Gustav

tonycamp · Jun 22, 2014

Gustav said:
salomonander said:

i use the hairball meter.

Click to expand...

I think they have a gazillion different meters to choose from, so which one?

salomonander said:

how did you actually solve it? by replacing the meter?

Click to expand...

Yep, simple as that.

You can check by seeing if the output you're measuring from the unit follows the meter direction, even as it reverses - and of course, if your meter zero calibration was done to a 0 VU scale on the meter.

Gustav

come on bro... what meter did you replace it with? lol

Gustav · Jun 22, 2014

tonycamp said:
Gustav said:

salomonander said:

i use the hairball meter.

Click to expand...

I think they have a gazillion different meters to choose from, so which one?

salomonander said:

how did you actually solve it? by replacing the meter?

Click to expand...

Yep, simple as that.

You can check by seeing if the output you're measuring from the unit follows the meter direction, even as it reverses - and of course, if your meter zero calibration was done to a 0 VU scale on the meter.

Gustav

Click to expand...

come on bro... what meter did you replace it with? lol

Sorry, I already wrote that two posts back

- 1 ma DC meter! I just wanted to know which one he was using, since he didn't seem to know what the specs were, and it might be good to check before throwing money at a different meter to solve the calibration problem

If you wanna know exactly which, this is it, but it wouldnøt be a good choice for designing a front for this unit due to its size. Just get the Sifam mentioned in Colin's BOM.

https://pcbgrinder.com/index.php?route=product/product&path=94_95&product_id=105

Gustav

salomonander · Jun 22, 2014

hey Gustav

its this one (8027-b):
http://www.hairballaudio.com/shop/product_info.php?cPath=25&products_id=61
i have it connected to the two outer pins on the molex. i use a 1k 3W resistor for the LEDs.

thanks again!

i do get through calibration every time now (on the expander). but i always end up with the range pot doing too little and having its lowest point at about 3 o clock. it goes reverse after that. during the expander calibration i aslo permanently have the feeling of working against the meter. it seems as if there is some force pulling the needle to either side.
in the end my vu meter seems to agree with my ntps though (roughly at lease. but 20db of expander reduction is shown on the ntp). but the "reverse" behaviour is audible and shown on the ntps as well......
disconnecting the hairball meter doesnt fix it.
measuring dc on the range pots wiper i see the same happening. voltage goes up as expected but gets dragged down after 3 o clock.
when turning the threshold knob down (no red) my range pot seems to go up as expected. turning threshold up again i get the weired behavior.

am i correct that the expanders range pot should be fully counter clockwise when starting the expander calibration?

salomonander · Jun 22, 2014

salomonander said:
hey Gustav

its this one (8027-b):
http://www.hairballaudio.com/shop/product_info.php?cPath=25&products_id=61
i have it connected to the two outer pins on the molex. i use a 1k 3W resistor for the LEDs.

thanks again!

i do get through calibration every time now (on the expander). but i always end up with the range pot doing too little and having its lowest point at about 3 o clock. it goes reverse after that. during the expander calibration i aslo permanently have the feeling of working against the meter. it seems as if there is some force pulling the needle to either side.
in the end my vu meter seems to agree with my ntps though (roughly at lease. but 20db of expander reduction is shown on the ntp). but the "reverse" behaviour is audible and shown on the ntps as well......
disconnecting the hairball meter doesnt fix it.
measuring dc on the range pots wiper i see the same happening. voltage goes up as expected but gets dragged down after 3 o clock.
when turning the threshold knob down (no reducton) the voltage on my range pot seems to go up as expected. turning threshold up again (engaging the expander) i get the weired behavior.

am i correct that the expanders range pot should be fully counter clockwise when starting the expander calibration?

Gustav · Jun 22, 2014

salomonander said:
hey Gustav

its this one (8027-b):
http://www.hairballaudio.com/shop/product_info.php?cPath=25&products_id=61
i have it connected to the two outer pins on the molex. i use a 1k 3W resistor for the LEDs.

thanks again!

i do get through calibration every time now (on the expander). but i always end up with the range pot doing too little and having its lowest point at about 3 o clock. it goes reverse after that. during the expander calibration i aslo permanently have the feeling of working against the meter. it seems as if there is some force pulling the needle to either side.
in the end my vu meter seems to agree with my ntps though (roughly at lease. but 20db of expander reduction is shown on the ntp). but the "reverse" behaviour is audible and shown on the ntps as well......
disconnecting the hairball meter doesnt fix it.
measuring dc on the range pots wiper i see the same happening. voltage goes up as expected but gets dragged down after 3 o clock.
when turning the threshold knob down (no red) my range pot seems to go up as expected. turning threshold up again i get the weired behavior.

am i correct that the expanders range pot should be fully counter clockwise when starting the expander calibration?

Whats the "ntps"? I am not sure whats going on. Same problem on both channels?

Gustav

salomonander · Jun 22, 2014

hey Gustav

the ntps are simply my external meters (broadcast style plasma meters).
i think i just made some progress. simply disconnecting the expander led solved the reverse problem. very akward. obviously i need the led. but maybe this makes sense to someone who understands this better? wrong led? or is this pointing to some bigger issue? i have a green mini led in there. but changing it to red does the same

anyways - the range control seems to work now.
only thing when going from 20 to 0dbu on the pot slowly i do get a bit of a jump at around 2 o clock (it seems to fall there a little too fast - not shure could be the log pot i guess). going back from 0dbu to 20 is smooth as can be.

well, maybe someone smarter than me can make something out of this info

some more testing. the range control works as long as no led is engaged. disconnecting the expander led fixes things only until the limiter led flashes. it then goes back to the akward behavior. so either im using the wrong leds or my led circuit is messed up somewhere. also my limiter led only works with the expander card inserted. i have an amber led for my limiter....

when measuring the range pots wiper i get 23v with no led connected. everything works fine then. when connecting the led i get a 3v drop. this has to be causing the trouble. interestingly when no led was connected and im at 0dbu with the pot (still measuring 23v) i can insert the led without it causing drops. only when turning the pot again it goes back to reverse. maybe a capacitor problem?

salomonander · Jun 24, 2014

does anyone maybe have an idea? as i said, it looks as if my leds somehow effect my entire unit.
when they start lighting up the entire control output line of limiter, comp and expander are effected (there is a voltage drop).
im just wondering where it would make sense searching.

as said in my post before, removing the expander light (and not having the limiter engaged) makes the range control work as it should. inserting the light gives me the reverse character of the pot. interestingly when bypassing the expander, setting the range to where it normally goes back up again and switching the expander back in puts the expander range in the right position. as soon as i turn the range pot it goes back to reverse.
looks to me as if there is a capacitor that should react to the range pot that is bad maybe?
should the led circuit be completely detached from the rest of the control circuit?
are "frontpanel v positive" and "frontpanel v positive 4" supposed to be connected?

sorry for all the questions

i dont expect a solution. just an idea would really help.

salomonander · Jun 24, 2014

Nevermind. i had a faulty resistor in R191. which prevented the cap after it from working. all good now. think i was cursed on this project

but i guess there is no more room for more errors at this point. knock on wood! thanks to everybody trying to help!

ps: anyone being scared of this project because of my posts please relax. i was just kind of unlucky with my parts. would i have checked all resistors before putting them in, the project would have been a smooth build. so check every part before you put it in. the circuit is so complex that tracking down an error is really no fun at all. thanks again to colin and gustav!

Gustav · Jul 1, 2014

salomonander said:
Nevermind. i had a faulty resistor in R191. which prevented the cap after it from working. all good now. think i was cursed on this project but i guess there is no more room for more errors at this point. knock on wood! thanks to everybody trying to help!

ps: anyone being scared of this project because of my posts please relax. i was just kind of unlucky with my parts. would i have checked all resistors before putting them in, the project would have been a smooth build. so check every part before you put it in. the circuit is so complex that tracking down an error is really no fun at all. thanks again to colin and gustav!

Came here just to check on you. Excellent news

Aside from that, is there no drawing with front panel dimensions or an FPD file available for this project? Anything at all?

Gustav

salomonander · Jul 1, 2014

Gustav said:
salomonander said:

Nevermind. i had a faulty resistor in R191. which prevented the cap after it from working. all good now. think i was cursed on this project but i guess there is no more room for more errors at this point. knock on wood! thanks to everybody trying to help!

ps: anyone being scared of this project because of my posts please relax. i was just kind of unlucky with my parts. would i have checked all resistors before putting them in, the project would have been a smooth build. so check every part before you put it in. the circuit is so complex that tracking down an error is really no fun at all. thanks again to colin and gustav!

Click to expand...

Came here just to check on you. Excellent news

Aside from that, is there no drawing with front panel dimensions or an FPD file available for this project? Anything at all?

Gustav

thanks mate!
yes, its all good now. love this thing on drums. really amazing for getting that 70s breakbeat squish

i think you can find a FDP file in post #297. cheers

MountCyanide · Jul 3, 2014

With the front panel standoffs being important to grounding I couldn't stick with my ghetto face plate. Just finished an album so I stepped away for a bunch but now I'm back on the pipe, the solder pipe. Now we've gone suburbs with the panel and finally heading on to calibration (after I hook up the xlr's, CLEARLY). Can't wait to hear this. Salomonander saying breakbeat gets me stoked as that's exactly what I was looking for when I signed up for this, a little dedication to Andy Johns who mastered all of his later stuff here at my studio complex until the day he left us.

Gustav · Jul 4, 2014

Been playing a little more with mine now - It can tighten up things and make them come alive a again with some careful setting.

I do have one ghost in the machine. I can make the light in the expander section come on with no input signal coming through...Not sure what to do about that, or if I am misunderstanding something.

Also haven't tried the stereo link yet. My PSU can't power both channels at once, and I am still waiting for one

Gustav

salomonander · Jul 4, 2014

Gustav said:
Been playing a little more with mine now - It can tighten up things and make them come alive a again with some careful setting.

I do have one ghost in the machine. I can make the light in the expander section come on with no input signal coming through...Not sure what to do about that, or if I am misunderstanding something.

Also haven't tried the stereo link yet. My PSU can't power both channels at once, and I am still waiting for one

Gustav

hey Gustav
you mean your expander light goes on with no signal connected to input? that would be normal as the expander is "working" as soon as the signal goes BELOW the set threshold. so with no input signal the expander is certainly below any threshold.
expanders work just the other way around from comps. a comp works when the signal goes ABOVE the threshold. expanders do so, when the signal is BELOW the threshold.

if you mean that the light is on while you feed it input but you dont get any output play with the range knob.

hope this helps
jakob

Gustav · Jul 4, 2014

salomonander said:
Gustav said:

Been playing a little more with mine now - It can tighten up things and make them come alive a again with some careful setting.

I do have one ghost in the machine. I can make the light in the expander section come on with no input signal coming through...Not sure what to do about that, or if I am misunderstanding something.

Also haven't tried the stereo link yet. My PSU can't power both channels at once, and I am still waiting for one

Gustav

Click to expand...

hey Gustav
you mean your expander light goes on with no signal connected to input? that would be normal as the expander is "working" as soon as the signal goes BELOW the set threshold. so with no input signal the expander is certainly below any threshold.
expanders work just the other way around from comps. a comp works when the signal goes ABOVE the threshold. expanders do so, when the signal is BELOW the threshold.

if you mean that the light is on while you feed it input but you dont get any output play with the range knob.

hope this helps
jakob

I do know the expander function, but I probably expected the light to indicate that the unit was working/expanding. Ill see if it makes sense when I have some time with the unit again early next week

Gustav

Feeler: ez760 - Compressor/Limiter/Expander/Gate

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