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my x0x is too silent... [solved! faulty ba6110, mcu and q32]
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my x0x is too silent... [solved! faulty ba6110, mcu and q32]

by LoopStar on Tue Sep 04, 2007 5:33 pm

Hello fellas!

Today I completed my second (self-sourced) x0x. Everything seems to be fine, except the fact that the output on both the mix out as well as the headphone jack is _very_ low. When I turn up the volume of the x0x, the input gain on my soundcard and the volume on my hifi-rack to the max, I can hear the x0x making the sound I expect of it... only it nearly gets lost in the noise of my computer... As I said, the sounds are just as they should be... but they're hardly to hear. Any suggestion what the problem could be? I already checked all the jumper wires. They're all okay and connected correctly.
Last edited by LoopStar on Fri Sep 21, 2007 1:43 pm, edited 1 time in total.
website: http://www.myownmusic.de/artistpage_info.php?artist_id=141458
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by guest on Tue Sep 04, 2007 9:55 pm

recheck the signal pathway
make sure the vco is outputting a strong singal
make sure the vcf is outputting a strong signal
and if they are working
its probably not enough current going into the vca
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by LoopStar on Wed Sep 05, 2007 11:56 am

thanks for your reply! I've just started to do some measuring, starting with the powersupply.... and I'm getting strange readings. When I built it, everything was fine and all the values were as they should be. now my multimeter tells me, that I have 25V when I check middle to left pad at j4, middle pad to right pad gives me 11V.

What place would be good to check the vco and the vca?

edit:

checked the vco (did the headphone test with the x0x in random mode): sounds normal to me. saw and square wav sound as expected. don't know, how loud they should be, though. they were audible, but not loud

checked the vca (headphone test again, x0x still in random mode): ... and heard nothing but a hum... buggers! What could this be? Also, I'm a bit confused because the faint output I'm getting seems to tell me that the sound generation works without a problem. All the knobs work as they should. As I said, my impression is, everythings allright basically, because I _do_ get the sound I want out of the box. But to me it seems like the sound doesn't get amplified at the end.
website: http://www.myownmusic.de/artistpage_info.php?artist_id=141458
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by LoopStar on Thu Sep 06, 2007 5:03 pm

Is it possible that this problem is the result of substituting the 2sc536f trannies with 2sc945p transistors?
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by LoopStar on Fri Sep 07, 2007 6:34 pm

Okay... I did a side by side comparison of my two x0x's and found out, that the vco of my second x0x really seems to have a very weak output. Tomorrow I'll check the vco for misplaced parts. What other reasons could be there, as the powersupply was working perfectly when I built it?
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by guest on Sat Sep 08, 2007 6:23 am

are both the square and saw weak
how did you test them

the different transistors might have an effect
if it sounds good to you though
you might be able to boost the volume a bit
by reducing r131
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by LoopStar on Sat Sep 08, 2007 4:14 pm

guest wrote:are both the square and saw weak
how did you test them

I plugged in the x0x, connected my cheap headphones to the 7805 and touched the waveform-switch with the tip of the headphone-plug. On my first x0x, the signal was a much louder than on my second x0x.

edit: ... to answer your question: yes, both the saw and the square a lot weaker. I think I didn't point this out clearly enough

guest wrote:the different transistors might have an effect
if it sounds good to you though
you might be able to boost the volume a bit
by reducing r131


Okay, I'll give it a try tomorrow and report the result. Thank you very much for you reply!

UPDATE: I've tried decreasing r131 with various resistor values. the signal does get a bit louder, but if the value is too low, the x0x stars sound very strange. right now, there's a 100k resistor in, but this also distorts the sound a bit.

I've also checked if the resistor values in the vco are correct, just to see if I have mixed up any parts, which gladly is _not_ the case.
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by LoopStar on Sun Sep 09, 2007 8:08 am

UPDATE: Today, I've tried decreasing r131 with various resistor values. the signal does get a bit louder, but it's still far away from line-level. also, if the value is too low, the x0x stars sound very strange. right now, there's a 100k resistor in which boosts the signal enough to be clearly audible, but this also distorts the sound a bit.

I've also checked if the resistor values in the vco are correct, just to see if I have mixed up any parts, which gladly is _not_ the case. The other parts also are the right ones just in the place where they belong.
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by guest on Sun Sep 09, 2007 8:53 am

if you had to go to 100k
then the signal is way too low
and locating the issue might be best

the amplitude of the vco
is determined by q24 q25 q27 d25 and r101
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by LoopStar on Sun Sep 09, 2007 10:06 am

guest wrote:if you had to go to 100k
then the signal is way too low
and locating the issue might be best

the amplitude of the vco
is determined by q24 q25 q27 d25 and r101


thanks for the reply! I've reduced r101 to 1k just to see what would happen. Gladly, the headphone-test now showed a much louder signal on the waveform switch, which was equally loud as the signal on my other x0x! But the output through the line-out and headphone-out didn't get louder.

here's a sample of what I'm getting through the line-out. http://www.sendspace.com/file/dbgj33
I haven't amplified or normalized the file to give you a proper impression of how things are right now.

maybe decreasing some resistors in other places could also help?
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by guest on Sun Sep 09, 2007 11:55 am

i couldnt hear anything on that recording

it is so low that im guessing there is something broken
rather than it being a slight difference in transistors
or some other minor variation

can you do the headphone test on the resonance knob
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by LoopStar on Sun Sep 09, 2007 12:05 pm

I did the headphone test at the resonance pot and I could hear a good signal. The volume of it was really good. I did the test again routing the singal into my computer: http://www.sendspace.com/file/p1rhjd

edit: http://www.sendspace.com/file/r4gj3j this file contains the output of the resonace pot (rightmost pin), the pure square and the pure saw, both picked up at the wave-selector

the crackling noise & the dropouts were made when the tip of the plug lost touch with the pin
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by guest on Sun Sep 09, 2007 2:24 pm

if the level is the same for both of your x0xen
then the problem isnt in the vco
and is probably after the vca someplace
which makes sense as you were describing distortion
from driving more signal into the vca
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by LoopStar on Sun Sep 09, 2007 5:26 pm

thanks for replying! After reading your post, I did the headphone test of the vca and my x0x fails here. I've recorded a sample of the noise that I find at the rightmost pin of vr8: http://www.sendspace.com/file/ovlwau

But maybe this has to do with the envelope generator. Using the method described in the manual, I wasn't able to get the proper result here.
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by guest on Mon Sep 10, 2007 7:32 am

the envelope is the easiest part of the vca to test
so check that first
and make sure its going from 0v to 12v
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Please be positive and constructive with your questions and comments.