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Quieting an old Casio?
Old 3rd September 2013
  #1
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Quieting an old Casio?

I have a Casiotone CT-6000 which is fun but very noisy for my liking; Hissy and occasionally 'ticky' (if you know what I mean), both through the speakers and 1/4" outs. It's not the most amazing vintage-cool piece but I think it'd very usable if I could only get that damn noise down.

My question is: Is there a simple rule for replacing parts to lessen internal noise? I was hoping to be able to open her up and replace components that might help. Is there anything that can be a presumed culprit in hiss creation inside a Casio of this era? Basic bits, not chips I think.

While I was at it I was thinking to maybe swap the power supply transformer (go external?) and put in shielded audio cables. Anyone know if this is a reasonable plan? Or am I barking up the wrong tree? Please pardon my ignorance, searching hasn't yet been very helpful. A little point in the right direction would be amazing. Also, if it's not worth it or possible I'll need to change my outlook.

Thanks!
Old 4th September 2013
  #2
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Richard Crowley's Avatar
A great deal depends on exactly what kind of "noise" you are talking about. The most common types are HISS and HUM.

If HUM is the problem, then yes doing things like removing the power transformer are possible (but not necesarily likely) remedies.

However if the noise you are complaining about is HISS, that is a very different matter, and not as easily reversed.

So, start by doing a thorough analysis of what noise you are talking about here. Exactly what is the nature of the noise? Is there more than one kind? If you don't know what the different kinds of noise are called, do some research on the internet to see what the definitions are and what they sound like. Or make a sample recording of all the different noises you can get from your gadget and post the recording (with a description) somewhere we can hear it.

Does the noise change with any user controls? levels? modes? Good analysis that the noise comes from both the internal speakers and from the output connectors.
Old 4th September 2013
  #3
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Thanks, Richard, for your speedy and insightful (to me) reply. To get the unequivocal "Replase tha CAPS dude!!1" kind of answer I was hoping for I would have been better off going to Yahoo Answers...

Listened very closely on good headphones to cut the speakers/amp out of the picture. I found that when I switched between instruments (this unit has those soft-press contact button thingies) there was a brief moment of clean signal before noise kicked back in. Moreover each patch had it's own distinct noise quality. My supposition is that it has something to do with the way the PD synth makes the waveforms (or whatever, I dunno nuthin') because it definitely sounds waveformy. Too deep for me I'm afraid.

Thanks again!
Old 4th September 2013
  #4
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Richard Crowley's Avatar
Quote:
Originally Posted by drips View Post
Thanks, Richard, for your speedy and insightful (to me) reply. To get the unequivocal "Replase tha CAPS dude!!1" kind of answer I was hoping for I would have been better off going to Yahoo Answers...
The "replace all the caps" shotgun approach is often unproductive busy-work and a placebo IMHO.

Quote:

Listened very closely on good headphones to cut the speakers/amp out of the picture. I found that when I switched between instruments (this unit has those soft-press contact button thingies) there was a brief moment of clean signal before noise kicked back in. Moreover each patch had it's own distinct noise quality. My supposition is that it has something to do with the way the PD synth makes the waveforms (or whatever, I dunno nuthin') because it definitely sounds waveformy. Too deep for me I'm afraid.
Those are quite excellent observations and would give provide significant clues to the source (and remedy) of the noise. But you would likely need a schematic diagram and an oscilloscope to nail down these kinds of things.
Old 4th September 2013
  #5
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Hi
As Richard says, replacing caps for the sake of it, indiscriminately is pointless (misquote!).
Recording the 'noise' onto a DAW of some description (as a poor alternative to a decent oscilloscope) at as high a sample rate as possible MIGHT reveal various high frequency 'tones' that are present continually. The 'break' in noise may simply be the internal D/A or equivalent stage 'muting' or having no signal during the switching operation which while interesting may not be much help although it would indicate that the subsequent audio stages are at least reasonable.
You say headphones is 'OK' during switching, is the speaker out also quiet during this (admittedly useless) phase or are the speakers noisy throughout?
Large quantities of 'HF' signal can appear as noise and my initial guess would be there is a significant amount of this going on which is managing to appear at the 'output' of the D/A conversion.
Finding then remedying this sort of problem seems a good game, Best of luck!
Matt S
Old 4th September 2013
  #6
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Richard Crowley's Avatar
Another possible source of noise is digital signals leaking into the analog audio path. Assuming it is not a congenital design flaw, replacing or adding power filtering/bypass capacitors could be a remedy.
Old 5th September 2013
  #7
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Hmmm... This is all very interesting. Thanks gents for your replies.

I think finding a possible solution may be beyond my expertise level but I'm intrigued by the "game" as Matt put it. I don't have any bench gear beyond a soldering iron and I'm guessing finding the schematic online will be an exercise in futility. But I've long been impressed by people who open up boxes and draw their own schematics. If nothing else that might prove to be an interesting way to spend a rainy afternoon.

For now I'll just live with it as it is. Running monitors from the line outs is definitely quieter than through the built-in speakers (hiss-wise) so that helps, as does turning off the effects such as 'Celeste' and being mindful of all the volume sliders.

I can't thank you guys enough for your input as it tore me out of my naivety and got me thinking about what's really under the hood (aka bonnet and what it would take to figure it out. Well, at least if it ever breaks down it'll be time for some serious tinkering I think!
Old 8th February 2020
  #8
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Somebodyperson's Avatar
 

Quote:
Originally Posted by drips View Post
Hmmm... This is all very interesting. Thanks gents for your replies.

I think finding a possible solution may be beyond my expertise level but I'm intrigued by the "game" as Matt put it. I don't have any bench gear beyond a soldering iron and I'm guessing finding the schematic online will be an exercise in futility. But I've long been impressed by people who open up boxes and draw their own schematics. If nothing else that might prove to be an interesting way to spend a rainy afternoon.

For now I'll just live with it as it is. Running monitors from the line outs is definitely quieter than through the built-in speakers (hiss-wise) so that helps, as does turning off the effects such as 'Celeste' and being mindful of all the volume sliders.

I can't thank you guys enough for your input as it tore me out of my naivety and got me thinking about what's really under the hood (aka bonnet and what it would take to figure it out. Well, at least if it ever breaks down it'll be time for some serious tinkering I think!

I know this is late but....


https://www.manualscenter.com/manual...l#.Xj6CAlNOk0M

http://www.manual-download-station.c...&id=39652#ecms
Old 8th February 2020
  #9
I used to record many noisy keyboards back in the 1980's. Stacks of midi connected keys built up the hiss. This is how I fixed that:

Take the keys or multed keys stack and run it into a dbx single ended noise reduction module. It's one of their 900 series modules. Dial it in until the hiss goes away. Then, patch it into an Aphex Type III aural exciter. That will re-generate the lost high frequency harmonics sans noise.
Old 8th February 2020
  #10
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Jim Williams' advice might be the best. This is a 1980s-era synth, generating its tones at 8 bits (or less). There will be noise, particularly compared with modern gear. And probably nothing you can do inside the synth will help.

A dBx decoder-only will hide the noise in realtime. It's a broadband solution, so you might be aware of HF noises on bass sounds.
If the noise is -only- HF, a Dolby B or C might be more transparent.

If you want an even better realtime solution, look for an Orban 290. I kept one in my rack until about six years ago... it could clean up phone interviews, old slow-speed tapes, virtually anything with electronic noise, using both expansion and sliding filters. And it included the harmonic restoration that an Aphex would provide.

Another excellent possibility is a Burwen DNF. These were sliding-filters only, unbalanced and intended for the hifi market, but so useful that I put one into every pro studio I built in the 1980s.

If you don't need realtime, there are plenty of multiband expander noise reducer (the kind that take a noise-only sample to setup) plugins.
Old 12th February 2020
  #11
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acreil's Avatar
 

Quote:
Originally Posted by Jay Rose View Post
Jim Williams' advice might be the best. This is a 1980s-era synth, generating its tones at 8 bits (or less). There will be noise, particularly compared with modern gear. And probably nothing you can do inside the synth will help.
The tone generators themselves aren't inherently noisy; Casio just weren't great at analog design, and this was the most elaborate and complex model they sold at the time. I find it helps to turn down the volume of the parts that you're not using (drums and accompaniment, or whatever).
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