Synth outputs... balanced or unbalanced?

Discussions on sound production outside the synthesizer such as mixing, processing, recording, editing and mastering.

Re: Synth outputs... balanced or unbalanced?

Postby Solderman » Thu Mar 16, 2017 8:16 pm

Didn't see a mention of the ARP Odyssey mk III and Korg remake, which has XLR balanced for its high level output. I find this output is preferred unless I want a guitar pedal inserted.
I am no longer in pursuit of vintage synths. The generally absurd inflation from demand versus practical use and maintenance costs is no longer viable. The internet has suffocated and vanquished yet another wonderful hobby. Too bad.
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Re: Synth outputs... balanced or unbalanced?

Postby Matlad » Sun Oct 14, 2018 9:00 pm

I'm upping this topic because I would like to add one more question.
I would like to go direct from a synth to line inputs of my soundcard. The impedance is 10kΩ on both sides.
From what I understand it's better to maintain a 1:10 ratio between output and input impedances.

How can I lower the output impedance of the synth while maintaining line level? (i.e without dropping to mic level and getting back to line level through a preamp/clean boost)
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Re: Synth outputs... balanced or unbalanced?

Postby Mooger5 » Mon Oct 15, 2018 1:49 pm

Are you saying your synth´s output impedance is 10K? That´s way too high. What synth is it BTW?
Synths output line level signals. You should have no problems connecting your synth to the line input of your soundcard...
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Re: Synth outputs... balanced or unbalanced?

Postby Matlad » Mon Oct 15, 2018 8:52 pm

Yes it seems strange to me too, but I heard that there could be some exceptions and idiosyncrasies with older synths.
It's a Yamaha TG-77 and I found the info here: https://www.manualslib.com/manual/10132 ... 203#manual

Level-wise all seems good indeed, but I was worrying a bit about this 1:1 impedance ratio. Coming from the guitar world I am used to considering this with care, as impedance ratio variations between output and input have a quite drastic impact on sound.
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Re: Synth outputs... balanced or unbalanced?

Postby Mooger5 » Mon Oct 15, 2018 10:28 pm

Hey I´ve got a TG77 too. Really, upon reading the specifications there´s reason to be alarmed. But let´s fear not! Please read the second last reply in the following thread:

https://www.diyaudio.com/forums/instrum ... -mods.html

1K output impedance for all practical purposes. And there´s the 1:10 ratio!

Cheers.
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Re: Synth outputs... balanced or unbalanced?

Postby Matlad » Tue Oct 16, 2018 8:18 pm

Thank you very much Mooger!
For once it feels good not having to buy another piece of gear! :D
I think it's time for me to learn how to read a schematic though, because these guys' conversation flies way above my head, and I need to answer the same question for a Roland D-550 for which there is no published spec AFAIK.

Cheers, and I hope you enjoy your TG as much as I do :)
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Re: Synth outputs... balanced or unbalanced?

Postby Mooger5 » Tue Oct 16, 2018 11:02 pm

I love the TG77!
Yeah, I think that poster complicated it a bit by including the blocking caps and the muting transistors. He used the Thevenin theorem to calculate the output resistance which is roughly the same as the impedance. Hence why he said "for all practical purposes". The 10K imp mentioned in the TG´s specifications has got to be a typo. Coincidently, that same poster himself commited an identical typo at the end of the sentence :D

Basically what he did was: take the guessed output impedance of the opamp (100 Ohms in series) and parallel it to the 10K grounding resistor, since according to Thevenin the voltage source should be considered as a closed circuit. The resulting value, less than 100R is now added to the 1K series resistor and that´s it, 1100R resistance roughly equates to 1K impedance!
The SY77 and the SY99 have a grounding resistor of 47K instead of 10K. Still negligible once paralleled with the out imp of the opamp. What matters most is the resistance in series after the opamp, so next time just a quick look at that section of the schematic will tell you enough for a rough estimate of the output impedance.

BTW I have a D550 too and love it. The output impedance is around 3K. Still nothing to worry about :)

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Re: Synth outputs... balanced or unbalanced?

Postby Matlad » Thu Oct 18, 2018 8:40 pm

I still think I need a boost in electronics knowledge, but you dissipated a lot of confusion in me. Thank you very much for taking the time to explain all of this!

I am very fond of the D-550 too! But you are saying 3K!? We don't have the 1:10 ratio there! My OCD is hyperventilating. Won't we lose a bit of high end?
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Re: Synth outputs... balanced or unbalanced?

Postby Mooger5 » Thu Oct 18, 2018 9:59 pm

Only if you use long and capacitive cables. But the D´s output seems stronger than the TG´s, or so I recall. Truth be told, I too read that poster´s reply and drew my own conclusions. There is a blog from another D50/550 owner where it´s said the output impedance is 1K, not 3K. So I could be wrong. Having a second look at it, the muting transistors seem arranged in a peculiar way, taking a portion of the signal at the input of the last opamp as well as the output. Curious stuff. Need to spend more time dissecting it. But anyway there´s nothing to worry about, whatever is the output impedance, it is what it is and it has served musicians quite well over the years. It sounds crystal clear without having to resort to DI boxes or whatever :)

Audio electronics are very rewarding (when they work). You could start by building a few fuzz pedal clones and join diystompboxes forum and freestompboxes forum. Good helping people with knowledge from whom you can learn a lot.
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Re: Synth outputs... balanced or unbalanced?

Postby Mooger5 » Fri Oct 19, 2018 7:12 pm

And here is the output impedance of that industry standard that is the Minimoog :mrgreen:

Audio Output Levels
High Level Output
Typical Voltage: 0.5 volts
Maximum Voltage: 4.2 volts (peak-to-peak)
Nominal Output Impedance: 3K Ohms :)
Low Level Output (30 dB below High level)
Typical Voltage: 15 millivolts
Nominal Output Impedance: 1K Ohms

Cheers and put that OCD to rest!
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