Cutoff and resonance cut the sound !

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exagonal
 
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Cutoff and resonance cut the sound !

Post by exagonal »

I have a problem with the filter section...when turn down the cutoff knob, the output sound goes down...the filter seems to affect the sound in correct way, but the filter affect the volume too !! Any suggestions ??

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rv0
 
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Re: Cutoff and resonance cut the sound !

Post by rv0 »

sounds like the normal behavior

you can use a compressor if you want to level it.

exagonal
 
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Re: Cutoff and resonance cut the sound !

Post by exagonal »

First, thanks Darffader for the reply!
I have already built several x0xb0x and I know the final sound enough, but this time it seems to me, however, slightly lower ... known significant background noise (at least in the headphones) as white noise, high-volume output ... could be normal ?

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antto
 
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Re: Cutoff and resonance cut the sound !

Post by antto »

i'm having a nightmare issue here, maybe it's not related, but to check my theory - can you measure the voltage at R46 when the accent knob is at zero

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antto
 
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Re: Cutoff and resonance cut the sound !

Post by antto »

oh, duh.. only now i see that you're the same guy in the two threads

i blame the weird forum colors/theme for this

exagonal
 
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Re: Cutoff and resonance cut the sound !

Post by exagonal »

ok ok...don't worry Antto...from now we can use only this...now i record a little sample and post it.
And, of course, i measure the voltage in R46...aspetta in linea! stay tuned!

exagonal
 
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Re: Cutoff and resonance cut the sound !

Post by exagonal »

Ok this is the audio sample on RANDOM MODE like you ask me... hope this can explain something! The voltage on R46 in about 2.83 Volt in pattern mode but not playing...
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x0x_sample.rar
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x0x_sample.rar
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antto
 
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Re: Cutoff and resonance cut the sound !

Post by antto »

okay.. the cutoff is rather low
try to figure out at what position TM3 is roughly - above the middle, or below the middle...
TM3 is like another "Cutoff" control, it offsets the whole cutoff frequency
you can raise the cutoff range up by turning TM3 clockwise

in your audio material, the cutoff freq of the filter peaks at ~1.2kHz when you turn the cutoff knob to max... which is rather low
and if TM3 was also set high - then that would be weird surely (tho there can be a bunch of other things that affect it, so don't panic)
if TM3 was set low - then just turn it up (adjust to taste)

however, if you notice the cutoff frequency to be going up or down by itself - shout
also, if you have the feeling that the cutoff has went down compared to last time you noticed it - do measure again at R46 and see if you get a different value
the value there should be around ~3V and definately not below 2.5V
(this is the issue i'm fighting with)

exagonal
 
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Re: Cutoff and resonance cut the sound !

Post by exagonal »

okey ... thanks for the answer, but it seems to me a little bit more complicated than expected!
I noticed that the sound fades slightly after a while you play, until they disappear completely with the cutoff completely closed.
The recording posted previously was performed with a more or less central adjustment of TM3, here enclose with the adjustment to a maximum.
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exagonal
 
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Re: Cutoff and resonance cut the sound !

Post by exagonal »

Then, after several tests I came to the conclusion that the problem occurs after a few minutes that the x0xb0x is turned on. At first everything seems to be back to normal, then the sound fades so much to really become almost imperceptible. It almost seems like some kind of problem related to the charge of some capacitor... off after a few minutes ... in fact, everything starts to normal ... for a while, as you can see by analyzing the new file that I captured with cutoff=min, reso=max, env mod=min, dacay=max.
I also have a problem with the digital section, but I think it's another story ... I can not edit a new pattern, although during assembly are able to program one ... oh well, one thing at a time!
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antto
 
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Re: Cutoff and resonance cut the sound !

Post by antto »

oh, ouch

in the 2nd recording the square wave looked kinda wrong..
and in the 3rd recording, you can see it happen
in the beginning - the square is normal, and then it slowly changes into something.. not normal

measure the "12V" and "5.333V" lines on J4 (on the mainboard) when this issue is in effect

those voltages are used by the whole synth section, and if they do something weird - more or less everything will go weird
altho, in your case, the pitch didn't detune too.. strange

exagonal
 
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Re: Cutoff and resonance cut the sound !

Post by exagonal »

Perfect! Antto, thank you very much, but I've built 5 or 6 other x0xb0x, and you can talk with me even more technical, they are also electronic expert! ;)
The first thing I did of course was to verify that the rails of the power supply are constant throughout the circuit, and so they are.
It looks more like some other defect due to some faulty capacitor or transistor ...

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antto
 
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Re: Cutoff and resonance cut the sound !

Post by antto »

if you have another x0x which works properly - put them side to side and measure voltages and compare
look around the VCO and VCF

exagonal
 
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Re: Cutoff and resonance cut the sound !

Post by exagonal »

Sorry, but I do not have any of these! However, following the pattern that I found here, with the voltage of the analog section, I'm trying to do the checks, I just wanted to try to understand what it could be with the help of another expert!
The signal, both saw that square is stable and good around the VCO. VCF and ENVELOPE should be inspected...

exagonal
 
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Re: Cutoff and resonance cut the sound !

Post by exagonal »

Ok, I think I understand from what depended on the volume down .. helping me with the map of the voltages of the analog section found here in the forum, I noticed strange values ​​in the second and in the fourth leg of Q21, and therefore also in the two capacitors C25 and C27 connected to this.
Initially I used a multilayer monolithic ceramic capacitors type , which evidently, for some reason which I am not yet clear, they do not have to work well ... I replaced it with the classic polyester capacitor and behold, everything is back to normal! Thank you all!
Now the problem is in the digital part ... very strange! In fact, initially, during assembly, I expected to be able to program a simple pattern to calibrate the pitch of the machine and everything going ok with recording the pattern.
Now it seems that is not working properly the PATTERN EDIT mode, even the RUN key seems it don't want to start !! I do not know if reprogram atmega ... what do you think?

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