Volume Prob

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guest
 
Posts: 3155
Joined: Fri Feb 17, 2006 5:35 am

Re: Volume Prob

Post by guest »

so the problem is in the vca it seems

have you double checked your sound interface
just to make sure that it reads 0db on a good signal

what is the volume level like on the resonance pot
it should be +6db or so

cuxoni
 
Posts: 29
Joined: Wed Jan 11, 2012 6:06 pm

Re: Volume Prob

Post by cuxoni »

The sound card is difficult to test because this is the only piece of outboard gear I have. I took a master out back into my sound card where the out was showing 0db in my DAW and I set the master vol on the sound card output to full, it looked low to me when it came back in so maybe it is the sound card which is cutting it somehow. Or maybe the actual output was less then 0db. I have no way of knowing, there's too many variables in the mix. I guess the only way I can tell is to try it in another sound card somehow or to send another output into the card where I know for sure what the db output of it is. How I can do that I don't know.....

guest
 
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Re: Volume Prob

Post by guest »

do you have another synth
or a cd player or radio or something
most audio electronics output close to 0db

cuxoni
 
Posts: 29
Joined: Wed Jan 11, 2012 6:06 pm

Re: Volume Prob

Post by cuxoni »

The most suitable test I can think of was to put my iPod into one of the inputs, turn the iPod on full, and turn the gain up on the sound card input until it was 0db in my DAW. Then I unplugged the iPod and stuck the xoxbox in, again turned up full, without adjusting the gain and that shows as -24db. So unless the iPod on full is meant to be way more loud than the xoxbox on full then I guess the issue does lie in the x0xbox.

I'll recheck everything in the VCA if that sounds like the problem, but I didn't find an issue last time using the voltage map. Unless I was doing something wrong? I just plugged it in and checked it with a multimeter with no pattern being played.

cuxoni
 
Posts: 29
Joined: Wed Jan 11, 2012 6:06 pm

Re: Volume Prob

Post by cuxoni »

Also, this might sound a bit stupid cos I'm not sure what kind of response I should be getting from it but I'll just say this in case it helps. I put in a pattern playing just the note a1, which actually shows in my spectrum analyser as a0, but I don't think it matters for this.... Then I put all knobs down to 0 except cutoff, which I put to half way. Now in the spectrum analyser the peak at 54hz is about -27db. If I push up the cutoff to full its about -17db. I would have though that at half way the cutoff would be letting though everything at 54hz. Could this be related to the issue or am I just wrong!!?? There's a definite audible boost in volume on that cutoff too even for that low note.

While I was typing this I thought maybe it was cos the speakers don't go low enough, but I pushed it up an octave and the same happens. But then I guess the higher the note the more likely it is the filter is holding it back.

Maybe I'm just talking rubbish!!

cuxoni
 
Posts: 29
Joined: Wed Jan 11, 2012 6:06 pm

Re: Volume Prob

Post by cuxoni »

... In fact no matter what octave you put it at there's a definite boost off the filter which doesn't seem relative to the pitch being played.

guest
 
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Joined: Fri Feb 17, 2006 5:35 am

Re: Volume Prob

Post by guest »

check the volume level off the resonance pot

cuxoni
 
Posts: 29
Joined: Wed Jan 11, 2012 6:06 pm

Re: Volume Prob

Post by cuxoni »

Sorry, I'd checked that earlier and forgot to post it. Just checked again with the gain set as it was for the iPod test and it's -28db.

guest
 
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Re: Volume Prob

Post by guest »

thats not right at all
can you check with a multimeter on ac setting
and check the waveform switch as well
they should both read around 1.5vrms

cuxoni
 
Posts: 29
Joined: Wed Jan 11, 2012 6:06 pm

Re: Volume Prob

Post by cuxoni »

The outside pins on the res pot range from 0.1 to 0.6 depending on what position it is in. The waveform switch is about 1.5 as expected, and is really loud in volume.

guest
 
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Joined: Fri Feb 17, 2006 5:35 am

Re: Volume Prob

Post by guest »

finally were getting somewhere

measure the resistance of
r62 220k
r70 2.2k
r111 22k
r110 22k
r113 100k
r108 2.2k

the gain is off in the vcf
if all of those resistors seem ok
then compare all the voltages in the vcf section
to those listed in the voltage map in the making x0x forum

cuxoni
 
Posts: 29
Joined: Wed Jan 11, 2012 6:06 pm

Re: Volume Prob

Post by cuxoni »

OK, thanks. I'm checking now, the resistors seem ok so I'm just checking the chart now. Just so I know, what's an acceptable level of error? Some of my voltages seem spot on, some are out but .1 or .2 of a volt, is that a problem or am I looking for something way off the mark?

Thanks again for your help.

cuxoni
 
Posts: 29
Joined: Wed Jan 11, 2012 6:06 pm

Re: Volume Prob

Post by cuxoni »

As an example one of the most out I've found so far is the inside pin on Q13, the chart says 9.63V and I'm reading 9.81V

cuxoni
 
Posts: 29
Joined: Wed Jan 11, 2012 6:06 pm

Re: Volume Prob

Post by cuxoni »

OK, so I checked all the resistors in the VCF. The build manual says the tolerance on the 10k resistors should be 5%. They're gold banded, but the values on some of them (47,61,64,65,109, 112 & 116) are closer to 7K. Do you think that would cause an problem like this?

guest
 
Posts: 3155
Joined: Fri Feb 17, 2006 5:35 am

Re: Volume Prob

Post by guest »

resistors usually measure a bit smaller
when you measure them in the circuit
because the rest of the circuit is in parallel with them

small changes in voltage shouldnt be a problem

ill give it some thought and get back to you
in the meantime
it might be helpful to just rehit
every solder joint in the vcf section

do you have access to an oscilliscope

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