EQN build thread

[peter purpose]

Did someone say something?

 

[canidoit]

if I try to boost the gain as suggested on the other thread it ceases to look anything like a symmetrical sine wave.

Hi mate, the dreaded callibration process 

What shape does it exactly do when you boost the signal?

Can you post up a pic.

Your signal could be already distorted when it goes into the EQN, so it giving you a funny shape when boosting into the EQN. From my understanding, you need to have a clean but high gain signal into the EQN and the distortion is meant to come from the EQN's inner working, and you adjust it so that the clipping is even at top and bottom as shown in the oscilloscope.

What devices are you using in doing your calibration. eg. laptop, what preamp, etc.

Also dont be afraid to play around with combinations of turning the RV4 and RV5 trim pot and boosting the signal to try to attain that top and bottom, even clipping, cause that's how I finally ended up with the final result and my unit sounds great with the limited time I have had to use it. I hope to assign more time to it in the future : ))))

 

[BrodieSound]

Thanks for the reply.
I found I'd made a stupid mistake with terminating the input transformer but that is now sorted so my earlier post is probably best ignored for now.
I am a bit confused about J1 though, the scant references I have found to it are a bit confusing to me. I have now shorted across the three pins and have something which sounds much more like full range audio, is this the right thing to do?
Assuming J1 is now correct I seem to have a surprising drop in level when putting signal through the EQN. Is this just a question of calibrating RV4 & 5 correctly? Do both of these affect level as only RV4 seems to make any difference at the moment?

Cheers

 

[zayance]

Thanks for the reply.
I found I'd made a stupid mistake with terminating the input transformer but that is now sorted so my earlier post is probably best ignored for now.
I am a bit confused about J1 though, the scant references I have found to it are a bit confusing to me. I have now shorted across the three pins and have something which sounds much more like full range audio, is this the right thing to do?
Assuming J1 is now correct I seem to have a surprising drop in level when putting signal through the EQN. Is this just a question of calibrating RV4 & 5 correctly? Do both of these affect level as only RV4 seems to make any difference at the moment?

Cheers

Go thru the build thread, you'll find your answers, beside maybe some assembly mistake?

 

[peter purpose]

J1.... top pin connects to nothing.
Middle and bottom jumped together puts R37 across the transformer secondaries.

Check your input transformer connections are correct wrt level loss.

 

[BrodieSound]

OK, still in calibration hell so here's hoping someone can help me narrow down the problem...
My set up:
I've got an EQN in slot 1 of 51X Rack
I'm feeding a sine wave from Logic to output 8 of a Metric Halo interface. The sine wave is into the red in Logic as per the 'journey' thread description.
Output goes to the EQN input and the EQN output comes back into the interface on input 1 and I am then using the oscilloscope in Audiofile Engineering's 'Spectre' software.
RV4 turns the level up and down as expected and the level between the EQ being 'in' and 'bypassed' is very consistent. The level however is a bit lower than the signal I am sending. So if I send tone at -12, say, I can't get Spectre to meter as high as -12 even if the I turn RV4 full up.(?) I've checked, and checked and re checked the transformer wiring and I don't think it's that!
Despite this I can turn RV4 up to make the sine wave clip (at the top) and turning RV4 down produces a nice symmetrical sine wave.
I can't make RV5 effect the shape of the wave at all though.
I have tried inserting a preamp to boost the level of the signal and this produces some very distorted shapes on the oscilloscope, but whilst RV4 can turn them up and down, and bring the sine wave back into symmetry, I've yet to find a level where RV5 will do anything.

Any input would be very welcome.

Many thanks,

S.

 

[peter purpose]

Stick in a 1k6 signal and boost it with the eq.... should get you plenty of level.

 

[canidoit]

ShandonSound, I think you still need a preamp after the halo to boost it high enough into the EQN. Try Pete's suggestion cause apparently people were able to get enough levels by boosting it with an EQ. Not sure if they did it in the software though, because I would think that through the software would just clip the signal on the laptop outputs.

Do you have access to a preamp?

 

[BrodieSound]

Do you have access to a preamp?

Thanks for your replies!
Yes I have preamps, I've tried patching in a Sound Skulptor MP73 to boost the level. I have uploaded some screen grabs here:
https://www.dropbox.com/gallery/937959/1/Laz%20EQN?h=e2241f
Which shows the test osc going out of Logic (in the red) and into Spectre on input one (via the EQN). In the first image I have a sine wave which looks something like yours on your journey thread, but then in the second I have upped the level from the preamp and I lose any recognisable sine wave shape.
Do the relative levels going out of Logic and into Spectre look right or is something very wrong? I still can't get RV5 to have any effect on the shape of the wave?

 

[BrodieSound]

Also, when I plug a mic in to the preamp>EQN it sounds very thin. Suspect there is more to this than lack of calibration. I've checked transformer wiring, and cap polarity, any suggestions where I should look next?

Thanks!

 

[peter purpose]

any suggestions where I should look next?

Thanks!

Nope.... I told you I was a rubbish trouble shooter.
What you could do is inject signal into the neg leg of c48 to rule out the output section.
Try the same (in to out) with each upright amp.

 

[canidoit]

You are getting the same thing I was getting at the first part of my callibration in my journey. When I got the bottom clip on my oscilloscope, I would turn the RV4 until I lost the bottom clipping in the wave and it became a normal sine wave again. Then that is when I boosted my signal more using my preamp and got a top clipping where I was able to use RV5 to get clipping at the top and bottom evenly.

Do you have access to a preamp?

Thanks for your replies!
Yes I have preamps, I've tried patching in a Sound Skulptor MP73 to boost the level. I have uploaded some screen grabs here:
https://www.dropbox.com/gallery/937959/1/Laz%20EQN?h=e2241f
Which shows the test osc going out of Logic (in the red) and into Spectre on input one (via the EQN). In the first image I have a sine wave which looks something like yours on your journey thread, but then in the second I have upped the level from the preamp and I lose any recognisable sine wave shape.
Do the relative levels going out of Logic and into Spectre look right or is something very wrong? I still can't get RV5 to have any effect on the shape of the wave?

 

[BrodieSound]

What you could do is inject signal into the neg leg of c48 to rule out the output section.
Try the same (in to out) with each upright amp.

Peter, I'm afraid I have no idea how I would go about injecting a signal!
Looks like I'm out of my depth, probably have been for some time actually, I've just been lucky and tenacious!
I strongly suspect it's a fault/mistake rather than calibration but I don't want to impose on anyone's good will any longer.
If there is anyone out there that might be able to help me fix this I would be very happy to pay for your time and expertise, or if anyone can suggest someone to help (preferably UK based) I would be glad if you would PM me.
Thanks for all the help you have tried to give, I shall have a crack at my second channel and see if that reveals anything about the first!

 

[peter purpose]

Calibration is unimportant. You'll never drive the thing hard enough to clip it.
Put rv5 in the middle and forget it for now.
RV4 is a fader... match in to out.

Injecting a signal.....  you've been doing it already into the input... you're just putting it somewhere else.

 

[canidoit]

What you could do is inject signal into the neg leg of c48 to rule out the output section.
Try the same (in to out) with each upright amp.

Peter, I'm afraid I have no idea how I would go about injecting a signal!
Looks like I'm out of my depth, probably have been for some time actually, I've just been lucky and tenacious!
I strongly suspect it's a fault/mistake rather than calibration but I don't want to impose on anyone's good will any longer.
If there is anyone out there that might be able to help me fix this I would be very happy to pay for your time and expertise, or if anyone can suggest someone to help (preferably UK based) I would be glad if you would PM me.
Thanks for all the help you have tried to give, I shall have a crack at my second channel and see if that reveals anything about the first!

I am presuming that injecting means the following. On an audio output of a TS output jack, there is the positive, which is the tip. I think it  means hooking that tip up to the leg of whatever? As for the sleeve of the TS output jack, I think you would connect that to where it usually be connect to, like the output sleev socket of the unit.

## before you do this, please wait for a confirmation from someone who knows more. I am just presuming here. 

 

[BrodieSound]

I am presuming that injecting means the following. On an audio output of a TS output jack, there is the positive, which is the tip. I think it  means hooking that tip up to the leg of whatever? As for the sleeve of the TS output jack, I think you would connect that to where it usually be connect to, like the output sleev socket of the unit.

## before you do this, please wait for a confirmation from someone who knows more. I am just presuming here. 

I imagined it would be something along those lines, but like you was unsure. Nice to know I'm not the only one!

Thanks!

 

[peter purpose]

 

[zayance]

Hi Guys,

Lately i've been having some weird things with my EQN,
i had same things some time after building tem, and
recognised i had forgot to put one of the jumpers on the Output
transformer of one module, and had the both EQN's fitted apart in the rack afterwards,
so i tought that was resolved....

Anyway, today i have two EQN next to each other, and i noticed same weird
oscillation noises as before, in the high frequency region, most noticeable on attacks of percussive sounds...
So i said maybe transformer too close to each other since i don't remember having this
when a couple of slots away.
So i tried this again today, one in slot 1 and the other in slot 4 for example, (all other stuff out in there just the EQN's)
Weird oscillation noise reduced, but as soon as one of the modules is out, no more oscillation at all,
well maybe still but can't hear it then....and one out or the other, same same, i tought one would cause the other etc...
Seems it's not the case.
When back close together, the Noises get back....

Kind of weird and i'm a little unsure about the symptoms, the units work as suppose to tough.....
I'll try to flux clean all the board as i only did this on the opamps... (minor trooblshooting) And try again,
but i don't think it will be that easy.
And i'll push the testing a little more when i have some time this week end....

EDIT: And i'll record a sample of what i'm talking about...

But any toughts on why? And what i could check...


Thanks a lot

 

[zayance]

Nah couldn't wait, took them out, fluxed cleaned, reheated some solder joints, reracked next to each other,
and seems it's gone huh, hope for good, time will tell, stupid gremlins....
Maybe some stress on the board taking them In/out  causing a small crackle somewhere or whatever,
i'll put this in the "mistery folder"......
Nevermind.

 

[dmp]

I've had similar gremlins with my pair of EQNs. The noise is more like a quiet sputtering. It is very soft, but noticeable. It increases as the pots are turned up. It exists in all the bands, so it is on the input side of things. I replaced some of the pots and it didn't change it. And when I turn the pots the make noise, like there is DC across the pots.
I'll try cleaning the boards and see if that takes care of my problem as well.