First XOX Demo - used as a synth

by **REwire** » Sun Jul 02, 2006 2:07 am

I bought my XOXBOX used off of a guy on the Analogue Heaven list after my 303 took a dump and been in repair. I can't compare them side by side but love the fact that this has midi. I went nuts and just played it all over the place, multitracked, no Eq and some delay only on lead lines. only non XOX are drum samples. I tried to fill the track as wide as possible using saws only as low DnB type lines and pulse for everything else. About the Resonance - I cranked the power trimpot to max to get those highs but that kinda ruins the lower sounds and response so it's back and forth on different parts.

http://REwire.12inch.com/Audio/Demos/RE ... OX_ROX.mp3 (mp3 128mbps 3:27)

Thanks for checking it out and hope this shows the range of the XOXBOX.
Dan

P.S. I went to see how my 303 was doing today and heard it for a moment and went ,"Ick - that's what the real thing sounds like, so nasally and weak!"

by **sash** » Sun Jul 02, 2006 2:57 am

very goood sound ! the high resonance just before the half of the sound is like a real 303 ! You said you cranked the power trimpot to max, do you mean the trimpot on the Power Supply board, not the one in the VCF section ? And, by the way, did you made the "resonance boosting mod" proposed by Ladyada changing R97, R108, R109 or R112 ?
I have my x0x327 kit still unbuilt and I plan to decrease R108 to 2k (not 1.8k as proposed) and increase R 112 to 22k, but will use a socket for R108 (if it's too whistling, i'll go back to 2.2k).
I heard also that the 2sc536F transistor at Q11 should be the highest beta (hfe), let's try...

by **sash** » Sun Jul 02, 2006 2:59 am

oooops, I meant "increase R109 to 22k", sorry.

by **REwire** » Sun Jul 02, 2006 9:50 am

Since I bought mine assembled and have only experience soldering cables, it'll take a while to grasp modifying any components. The trimpot I cranked was the 5.3333 one as suggested by Kokoon in the Resonance thread. It sounded OK to get that whistley sound but if I left it there, normal 303 bassy sounds were tinny and thin.

by **evilxsystems** » Sun Jul 02, 2006 2:09 pm

How much did you pay for it?

just curious

by **CoolColJ** » Sun Jul 02, 2006 5:57 pm

put the basss boost mod in and that will sort out the tinny sound

personally I prefer the filter feedback method to boosting resonance

by **REwire** » Mon Jul 03, 2006 12:57 am

evilxsystems wrote:How much did you pay for it?

$500 for it used, last run. I paid $1000 for my broken 303, this was chump change.

I am thoroughly confused about what's the easiest most perfect way to get the resonance right. I keep reading different suggestions, from trimpots, changing transistors, resistors, testing beta values etc.
Someone needs to just spell it out clearly.

by **kokoon** » Mon Jul 03, 2006 4:37 am

i've done the high beta thing, the PSU "warble mod" but haven't done any resonance boost mods - everybody says it doesn't work right.
that thing with the PS trimpot works perfectly for me, i haven't noticed any degradation in lower end... can you explain what you're hearing a bit more?
if it was possible i'd push that trimpot even a bit further but i'm not sure how it'd effect circuits other than the VCF (digital? VCO?)
i haven't got the slightest idea what it does technically but it sounds right. maybe i'll smoke the machine soon because of that... can anyone say anything about this?

by **guest** » Mon Jul 03, 2006 6:09 am

im still trying to figure out why modding the 5.333
would have an effect on the vcf
but here is my current theory

the 12v is a fucntion of the 5.333v via r178 and r179
so as you turn up the 5.33v you are also turning up the 12v
so the gate voltage and subsequent envelope votlages
are all higher
so the vca gets turned on a bit more
and the vcf gets a bit more control voltage
and the gain in the feedback gets turned up a bit
so the frequency response is higher and more resonant

turning up the 5.333 shouldnt have too terrible an effect
the only chip which will care much is the 74ac174
it is run off the 5.333 but only recieves 5v signals
from the microcontroller
since the inputs arent schmitt trigger inputs
there is a chance that the output stage wont turn on fully
and could be sourcing a lot of current internally
this would merely get the 74ac174 really hot until it fried
a pain to replace but not expensive

the other draw back is that the cv is no longer 1v per octave
and that it may not be entirely linear anymore
if the output stages arent working correctly

if r178 was increased or r179 decreased
you could get the same increase in the 12v
without having to change the 5.333v

by **kokoon** » Mon Jul 03, 2006 10:16 am

the "width" VCO trimpot takes care of the changed CV scaling so that's nothing to worry about.

what value would you recommend for R178 or R179 replacement? i don't wanna fry the 74AC174... maybe put a trimpot there?

by **guest** » Mon Jul 03, 2006 12:00 pm

try replacing r178 with a 2.4k
that should give the same 12v increase
with the 5.333v at 5.333v
assuming you cranked your 5.33v to 5.6v

the width pot will keep the x0x in tune
but it wont ouput 1v per octave to slave other synths to
which is probably not a concern for most people

by **kokoon** » Mon Jul 03, 2006 1:58 pm

oh. damn. forgot about the CV out...

how about just raising separate voltages for everything but the CV?

by **mome rath** » Mon Jul 03, 2006 7:58 pm

Well well well... VSE invades x0xb0x is it then?

Good stuff as always, ReWire. And an instrumental at that!

First XOX Demo - used as a synth

First XOX Demo - used as a synth

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