The sound of 30 Volts.

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The sound of 30 Volts.

Postby Thirteen » Tue Apr 08, 2008 11:24 pm

Lately I have been replacing transformers in several synthesizers, it's actually getting quite difficult now to find mains transformers to run analog synths, I guess there is less and less gear running -15...0...+15 volts, all the new digital stuff is going low power. I used to be able to go to dick smith or Jaycar and find 36V centre tapped transformers, but not any more. I don't like using 15...0...15 AC transformers, I like to have a couple of extra volts to keep the regulators happy.

It occurred to me tonight that it is quite likely that some of the reason that analog synths usually sound so good is probably much like old preamps and compressors, because there is such huge headroom internally, the power rails have 30 Volts to generate all the internal doings, rather than just 5 Volts. Then again maybe I am imagining things and should get off the computer and go to bed.
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Postby NYMo » Wed Apr 09, 2008 1:18 am

Hi there,

Too early for bed !!

Cheers
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Re: The sound of 30 Volts.

Postby rachelp » Wed Apr 09, 2008 11:50 am

Thirteen wrote:Lately I have been replacing transformers in several synthesizers, it's actually getting quite difficult now to find mains transformers to run analog synths, I guess there is less and less gear running -15...0...+15 volts, all the new digital stuff is going low power. I used to be able to go to dick smith or Jaycar and find 36V centre tapped transformers, but not any more. I don't like using 15...0...15 AC transformers, I like to have a couple of extra volts to keep the regulators happy.

It occurred to me tonight that it is quite likely that some of the reason that analog synths usually sound so good is probably much like old preamps and compressors, because there is such huge headroom internally, the power rails have 30 Volts to generate all the internal doings, rather than just 5 Volts. Then again maybe I am imagining things and should get off the computer and go to bed.



I think you're right - if the buss bar of a mixer determines the quality of the sound, headroom and so on, then surely a heavier duty power rail and and more stable current draw must add to the overall
sound of a synth, the waveforms generated in mains being evened out or more precise or something.

I recently did a course on disk storage technology and learnt that the length and quality of your SCSI cables does a lot for the efficiency of data storage and movement.
SCSI is such a finely tuned protocol that having a cable that is the wrong length or poorly insulated can lead to many problems including data loss, and in fact
if you bend a cable into a 30 degrees loop it can actually cause the passage of current to fail and cause "reflections" ie the waveform generated by the current going down the cable
is such that it mismatches the bend in the loop and serious amounts of energy are lost - using a cable of exactly the right length improves the waveform just like any standing wave
in a room or on a beach and so it goes with electricity too.

So I think you're probably right - even though my electronics knowledge is minimal. But the physics will add up. I am sure there is a way to calculate all this
stuff. I still don't go along with all the guff about "magic power cords" because once it hits the transformer, everything changes, but I do think that speaker
cables cut to a certain length and setup a certain way probably does do something to the sound.

I think there is something going on at a quantum level that none of us quite understand yet and the choices made by designers in the past has been
based on what's worked and what doesn't - all these low power digital devices are quite new and not fully realised, unlike 100 years of electronics
that has gone on before! Now am I the one who needs their brain examined?!


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Postby Thirteen » Wed Apr 09, 2008 11:57 am

Yes, I heard an interview in the ABC yesterday where an Intel scientist has developed a sensor to detect cosmic ray collisions inside CPU's by the sound that the impact generates, he was saying that even this can be a significant source of errors in complex computer systems. When it hears a collision it tells the processor to go back and re-do the calculation it was up to at the time. Yikes.
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Postby rachelp » Wed Apr 09, 2008 12:11 pm

Thirteen wrote:Yes, I heard an interview in the ABC yesterday where an Intel scientist has developed a sensor to detect cosmic ray collisions inside CPU's by the sound that the impact generates, he was saying that even this can be a significant source of errors in complex computer systems. When it hears a collision it tells the processor to go back and re-do the calculation it was up to at the time. Yikes.


Heh - too right! In fact we sometimes blame system panics and crashes (UNIX) on cosmic rays and sunspots, when no other analysis can find a cause!
They actually mentioned this at another course I was on (fault analysis) but it wasn't actually proven. So now I guess they have proof!


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Postby wez » Wed Apr 09, 2008 2:00 pm

rachelp wrote:we sometimes blame system panics and crashes (UNIX) on cosmic rays and sunspots


brilliant!

client... "why does this sound so shit?"

engineer..."cosmic rays, dude."

client... "oh, ok".


i'll never need another excuse ever.
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Postby TimS » Wed Apr 09, 2008 2:08 pm

wez wrote:
rachelp wrote:we sometimes blame system panics and crashes (UNIX) on cosmic rays and sunspots


brilliant!

client... "why does this sound so shit?"

engineer..."cosmic rays, dude."

client... "oh, ok".


i'll never need another excuse ever.

I can just imagine the look on thier face - priceless!!! :-)
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Postby JulienG » Thu Apr 10, 2008 12:27 am

rachelp wrote:Heh - too right! In fact we sometimes blame system panics and crashes (UNIX) on cosmic rays and sunspots, when no other analysis can find a cause!
They actually mentioned this at another course I was on (fault analysis) but it wasn't actually proven. So now I guess they have proof!


A friend of mine once did the stats and worked out that on average one bit of memory will flip per week due to cosmic rays. (Of course there were so many rough numbers in that calculatio, but it's kinda neat)
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Postby no-fi » Fri Apr 11, 2008 5:04 pm

I dion't think its a case of centre tapped 30V being less commonly needed. I think it's an issue of DSE and jaycar getting out of electronic component supply, and just concentrating on selling shitty plastic novelty gizmos made in china.

my last few attempots to get ANYTHING from jaycar or DSE have been pretty fruitless.
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Postby Howard Jones » Fri Apr 11, 2008 5:20 pm

I don't think its a case of centre tapped 30V being less commonly needed.


Correct. Any circuit using op amps needs such a transformer, or something with a very similar secondary output voltage. They're not going away anytime soon.

Any circuit using active regulation e.g. 3-terminal voltage regulators will only provide the voltage rails and current supply that the designer intended. The input voltage to the regulators (i.e. the output from the transformer secondaries) needs to be a few volts above the output voltage or else the regulator risks going into dropout.

If you supply an input voltage to the regulator that is well above the output voltage from the regulator, that is a total waste as the excess is not usable at the output and is dumped as heat through the heatsink and current through the third leg if the regulator is an adjustable type.

An example of this is where our American friends supply us with equipment with mains transformers wound for 220 volts and we obviously connect them to our 240 volt mains supply. The result is that the secondary output voltage from the mains transformer is proportionally higher and this higher voltage is fed to the positive and negative regulators in the power supply. These then have a much higher thermal load than they are designed for as they have to dissipate the extra input voltage as heat.

The result? Blown regulators and cooked circuit boards (Hello Kris, hello lunchbox).
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Postby Thirteen » Fri Apr 11, 2008 5:21 pm

no-fi wrote:I dion't think its a case of centre tapped 30V being less commonly needed. I think it's an issue of DSE and jaycar getting out of electronic component supply, and just concentrating on selling shitty plastic novelty gizmos made in china.

my last few attempots to get ANYTHING from jaycar or DSE have been pretty fruitless.


Yes, Jaycar seems to sell a lot of land fill now. I was there this afternoon and didn't get most of what I wanted because every box/drawer that I pulled out was either empty or had the wrong parts in it. I tend to order stuff from Wagner/WES at Ashfield now, they have good prices, and whatever I can't get there I get from Farnell or RS. Luckily I do have pretty good stocks of specific synth chips like Curtis and SSM, and other out-of-manufacture stuff like CA3280's, ua726's and lots of 2SC/A and Japanes transistors.
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Postby Thirteen » Fri Apr 11, 2008 5:30 pm

Howard Jones wrote:
I don't think its a case of centre tapped 30V being less commonly needed.


Correct. Any circuit using op amps needs such a transformer, or something with a very similar secondary output voltage. They're not going away anytime soon.

Any circuit using active regulation e.g. 3-terminal voltage regulators will only provide the voltage rails and current supply that the designer intended. The input voltage to the regulators (i.e. the output from the transformer secondaries) needs to be a few volts above the output voltage or else the regulator risks going into dropout.

If you supply an input voltage to the regulator that is well above the output voltage from the regulator, that is a total waste as the excess is not usable at the output and is dumped as heat through the heatsink and current through the third leg if the regulator is an adjustable type.

An example of this is where our American friends supply us with equipment with mains transformers wound for 220 volts and we obviously connect them to our 240 volt mains supply. The result is that the secondary output voltage from the mains transformer is proportionally higher and this higher voltage is fed to the positive and negative regulators in the power supply. These then have a much higher thermal load than they are designed for as they have to dissipate the extra input voltage as heat.

The result? Blown regulators and cooked circuit boards (Hello Kris, hello lunchbox).


I know what you mean, I get a lot of stuff through with failure due to the 220-240 issue. I heard that the government is contemplating dropping us to 220V to bring us into line with the rest of the world, but I think it's a myth as I can't see that the generators that we have installed in Australia could be varied in voltage output and still run at 50Hz.

As for the 30V centre tapped tranny's, I do agree that every extra volt over the regulators necessary input is just more heat to dissipate, I have noticed though that all the old Japanese synths that come through the shop with regulator IC's tend to have 18 to 20V secondaries on their mains transformers. I wonder if they were intended for 240V and have the extra output so that if it is run at 220V that they don't drop out of regulation?
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Postby smash » Thu Apr 17, 2008 8:01 pm

I know what you mean, I get a lot of stuff through with failure due to the 220-240 issue. I heard that the government is contemplating dropping us to 220V to bring us into line with the rest of the world, but I think it's a myth as I can't see that the generators that we have installed in Australia could be varied in voltage output and still run at 50Hz.


I wish I was getting 240V through my wall sockets.

I live right on the border of Fairlight, and Manly, on the Northern Beaches of Sydney, and I'm getting a constant 257 V on the input of my UPS !!

Been through 3 Cinema Displays so far - now have a big chunky UPS for the Computers, and a Big Chunky Power Regulator for the Desk.
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