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Another Accent Problem (Volume)
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Another Accent Problem (Volume)

by midiquestions on Thu Sep 15, 2016 9:37 am

I bought a used x0x off of eBay a few months ago, and it's in really good shape, unlike the last one, which was falling apart, so that's exciting. The only problem is that the Accent isn't working as it's supposed to do. If I turn the Accent knob past 2-3 o'clock, it's making the accented notes spike way high in volume, like 12-15 dB if I had to guess off the top of my head. It doesn't sound like it's clipping though. Any ideas as to what's wrong? I am not that good with electronics but can solder.

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Re: Another Accent Problem (Volume)

by antto on Thu Sep 15, 2016 11:49 am

did it ever work properly?
it might help if you record an audio clip demonstrating the problem

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Re: Another Accent Problem (Volume)

by midiquestions on Thu Sep 15, 2016 6:45 pm

I'll see if I can record some audio later tonight. I don't know if it ever worked properly; I bought it this way. I decided it was still worth keeping and sorting out later.

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Re: Another Accent Problem (Volume)

by midiquestions on Sat Sep 17, 2016 9:12 pm

http://www.filedropper.com/x0xb0xaccentproblem

Wave is saw; tune, cutoff, res, env, and decay are at 12 o'clock. There are five variations of the same pattern:

1: accent at min
2: accent at 9 o'clock (no effect)
3: accent at 12 o'clock (no effect)
4: accent at 3 o'clock (some effect)
5: accent at max (12 dB spike on accented note)

I should stress (or "accent") that the effect of the accent on this unit, even on the lower, 9 o'clock setting, jumps way out of the pattern like a "pop."

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Re: Another Accent Problem (Volume)

by antto on Sun Sep 18, 2016 3:05 am

you had the resonance knob somewhere in the middle, and the cutoff/envmod knobs low
at those settings the accent has not only a sharp VCA modulation (as always) but also a sharp cutoff modulation

on normal notes, the cutoff is almost closed, so their volume appears quieter, then suddenly an accent comes and it's not just louder but it causes the filter to get opened up with a sharp envelope
the 303 has quite some dynamics ;]

in other words, i don't see anything too strange there, there's clipping you probably had the volume knob at max and it may also have clipped in your audio input afterwards

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Re: Another Accent Problem (Volume)

by antto on Sun Sep 18, 2016 5:58 am

okay, i didn't see that you've written the knob settings in your post, so they were in the middle
check the values of R119 and R46, both of them should be 47K, i suspect yours might be 4.7K by mistake
check their colors or even measure them in-circuit with a multimeter (but with the x0xb0x powered off)

if they are the right value then it might be something else - record another audio clip with cutoff/reso/decay/accent set at max, and envmod at zero

also, is this a modified x0xb0x? does it have some extra knobs or trimmers? then it's very likely that R46 has been replaced with a lower value for the "more accent" mod, see if it looks like it has been desoldered

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Re: Another Accent Problem (Volume)

by midiquestions on Sun Sep 18, 2016 5:18 pm

Thanks. The only mod it has (that I know of) is a power switch. I've also run it with all kinds of cutoff/res settings, and it more or less does the same thing -- unusually high volume spiking on accented notes. Also, when it run it in "all Accent" mode (playing a sequence with the Accent button turned on), the knob only has an effect in that uppermost, 3 o'clock-to-max range; it's pretty much inaudible for the other 80% of the knob range. And it cranks the volume up.

I won't have any free time to open it up for several days, but I'll try your suggestions.

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Re: Another Accent Problem (Volume)

by midiquestions on Thu Sep 29, 2016 8:26 pm

I finally was able to open it tonight, and I think I made an interesting discovery which confirmed what my ears heard. I have very little electronics knowledge, but it appears to me that there are no actual resistors at R119 and R46, just little pieces of wire, so effectively Accent is at the maximum possible. Correct?

r46.jpg
r46.jpg (844.86 KiB) Viewed 472 times


r119.jpg
r119.jpg (102.13 KiB) Viewed 472 times

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Re: Another Accent Problem (Volume)

by antto on Thu Sep 29, 2016 11:41 pm

yup, there's the problem... the resistors have been replaced by wires (zero ohms)

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Re: Another Accent Problem (Volume)

by midiquestions on Thu Sep 29, 2016 11:54 pm

Great, I will order some 47K resistors, install, and post an "after" clip with the same settings.

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Re: Another Accent Problem (Volume)

by antto on Fri Sep 30, 2016 12:28 pm

on the photo i see also R61 replaced with a short, that smells like the "envmod extend to zero" mod
R61 should be 10K
this x0x might have other mods too

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Re: Another Accent Problem (Volume)

by midiquestions on Fri Sep 30, 2016 7:14 pm

Good catch! Thanks. I will replace that one too. The Env control wasn't giving me any noticeable problems or aesthetic concerns, but I think I'd prefer a standard x0x to start with.

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Re: Another Accent Problem (Volume)

by midiquestions on Tue Oct 04, 2016 9:45 pm

So I put in 47K resistors at R46 and R119 to undo the Accent mod and a 10K at R61 to undo the envelope to zero mod.

While I had it open, I also noticed some resistors attached to the flipside of the board. Looked like some had attached an additional resistor at R47 for the increased filter cutoff low range. I just snipped it off for now. There was also one on the backside of each of the TM4 and TM5 controls, but I didn't know what those were, so I left them.

I don't have an audio clip ATM, but the Accent is now behaving much closer to what I was expecting originally. Truth be told, it wasn't a terrible mod, and I might even go back at some point. Actually, realizing how easy these mods are to do and to undo has made me really interested in trying out more of them.

Thanks!

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Please be positive and constructive with your questions and comments.