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Mono or stereo cables?
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ShoNuff
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Joined: 27 Oct 2014
Posts: 174

PostPosted: Thu Apr 11, 2019 6:09 am    Post subject: Reply with quote

this is why i liked my idea of an RCA box: it's a bit fiddly and needs MORE cables but at least you get the jack size and impedance you need at the outputs, and can introduce interesting stuff in-line.
(edit: i really like my little adapter box idea Smile the more i think of it)
(this also sheds some light on why they did the volca mix with a mid-side arrangement: because they could)

i don't want to buy MORE cables lmao i already have boxes full of all-sorts,
'in case' ... stuff i mainly never use. DIY seems good for this, and the little
stereo mini to 2x RCA are well-made, cheap and widely available AND dual-purpose in this case.

this sort of thing (if you can access this link)
https://www.overstock.ca/Electronics/Unique-Bargains-PCB-Mount-6-RCA-Female-Jack-Connector-AV-Concentric-Socket-2-Pcs/18263613/product.html

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TheDoctor
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Joined: 28 Mar 2019
Posts: 86

PostPosted: Thu Apr 11, 2019 9:10 am    Post subject: Reply with quote

ShoNuff wrote:
jeftones wrote:
There is a Hosa cable that is "1/8 TRS to 1/4 TS". I utilized this cable for by volca keys and volca beat. For the other two volcas i have, the sample and the fm, i use those insert style cable.

some individuals are worried about there being no resistor on the TRS to TS cable \, which is a valid concern, but i have experienced no issues and have been utilizing that specific style of cable for the volcas for 3ish years.


i'm not sure what the principle is here, but a passive mixer is not just signal wires joined together with a common ground. i was wondering if it was something more complex than just a resistor.

i don't want to use TRS to 2 mono ('insert cable') because i only want to use 1 mono channel.

edit: OP was talking about the sync cable btw. we're onto audio output now.

Yeah I just noticed hahaha you should use 1/8 stereo for sync volca as you can use for modular, they will only get the tip but strangely volcas wants stereo for sync.


So my confusion here is: I understand I can also use a stereo cable with modular or other synth because it will only use the tip of the jack buy Volcas want stereo cable, so basically the input is splitter?

I would like to know why they work if on the other side there's a gear synced which it which of course output mono signal
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ShoNuff
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Joined: 27 Oct 2014
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PostPosted: Thu Apr 11, 2019 4:17 pm    Post subject: Reply with quote

i think it could be worth recording the sync signal and having a look (via some attenuation perhaps) at what's going on. obviously not a regular clock pulse.

TS sync signals like clock will just ignore the ring, i suppose: nothing to send, nothing receiving at the other end.
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jeftones
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Joined: 03 May 2017
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PostPosted: Thu Apr 11, 2019 9:44 pm    Post subject: Reply with quote

ShoNuff wrote:
jeftones wrote:
also another good article about stereo to mono summing

http://silentsky.net/wordpress/archives/624


this is really good, nice one Cool

some disparity with that 1st vid (that i saw before posting).
i have a feeling your TRS to TS cables may just be sending one side (?).
how else could it be? unless there are some resistors in the monojack, which i somehow doubt.

i would definitely go along with the impedance rules on this. was getting mixed up between signal level and impedance maybe (or is it the same thing?) - so: low impedance must go to high impedance. fairly easy to remember. i'd already heard that Y cables used the wrong way round were a bad idea. worth bearing in mind that volcas are pretty robust: i accidentally ran my Keys on the wrong power adapter one day for an hour or so and nothing happened to it : - /


for those hosa cables the tip and ring signal are shorted together without a resistor. they are marketed to be mono to stereo not the other way around.

an idea and a little speculation about about the sync signal:

on the volca the sync input needs to receive a relatively loud signal for the clock pulse to be properly detected. it may be that the use of trs to trs for sync on the volcas actually function similar to the headphone jack. a split signal where both sides are needed to output the proper volume needed for the sync pulse.

another thing to consider, the pocket operators also utilize a trs cable to send sync signal. but the pocket operators have a few options for how the signal is sent/received. one of those options will send the sync signal on one side of the trs cable and audio through the other side.

i think it ultimately comes down to how the device receives the sync signal which dictates what cables are needed to get the signal to work properly.
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LM
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Joined: 09 Oct 2017
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PostPosted: Thu Apr 11, 2019 10:54 pm    Post subject: Reply with quote

Looking at the schematics for the Volca Bass (should be similar to the others):

Sync In and Out only use T and S. The R terminal is left disconnected.

On the Head Phone Out (Stereo), T and R are each fed by a separate amplifier. Both amplifiers share a mono input (Volca Bass is mono).

What I have observed is that if you use a 1/8" TRS to 1/4" TRS cable and plug it into a balanced 1/4" TRS input, then you will get a very faint signal, due to the fact that the difference between the 2 identical phases is 0.

What I do is use common 1/8" TRS to stereo RCA cables (I have a bag full of them), with a RCA to 1/4" adapter at one of the RCA ends, leaving the other one disconnected. If you plug a TS connector into the balanced TRS jack, basically what you get is the difference between signal and ground, which is the original signal anyway. And if your Volca is stereo, just use the other RCA end with another mixer channel.

I hope that makes sense.
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ShoNuff
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PostPosted: Fri Apr 12, 2019 2:59 am    Post subject: Reply with quote

^^^ bag of RCA-Jack adapters as well Wink

the issue really came up swapping over from a mixer with unbalanced inputs
to one with both balanced and unbalanced. (i'm supposing the 1st is unbalanced) i can insert the 1/4" TRS adapter in all the way, no problem;
but if i do this with the 2nd mixer, i get no signal (i have to check this again)
and have to use it half pulled out/inserted to first click.

-but isn't a balanced signal one side normal polarity, and the other side inverted? or would that just cancel out? where/how does this balancing occur?

i then had a freaky sync issue with a mono 1/8" to mono 1/4" (TS-TS) for audio output with the Sample, where the sync clocks were being dictated by
the audio emitted Shocked -eventually figured out that it had to be something
to do with Ground, swapped cables back to TRS and resolved it. (unless
something's up with the 2nd hand Sample)
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LM
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PostPosted: Fri Apr 12, 2019 3:46 pm    Post subject: Reply with quote

ShoNuff wrote:

-but isn't a balanced signal one side normal polarity, and the other side inverted? or would that just cancel out? where/how does this balancing occur?



Yes, one side (T) carries the original signal (A) and the other (R) carries an inverted version of it (-A). This inversion is done at the source.

The inverted signal is inverted one more time at the destination and then added to the original one, cancelling any noise (N) picked up by the cable along the way:

Output = (A+N)+(-(-A+N)) = (A+N)+(A-N)
Output = A+A+N-N = 2A ---> Noise is cancelled

When you plug a stereo or dual mono, unbalanced TRS connector into a balanced TRS jack:

Output = (A+N)+(-(A+N)) = (A+N)+(-A-N)
Output = A-A+N-N = Zero

Or close to zero, as there is always some small amount of phase distortion in the circuits, that's why you might still get a very low signal in the end (or the subtle difference between the channels, if it's a stereo signal).

When you plug an unbalanced TS connector into a balanced TRS jack (Ground=Zero):

Output = (A+N)+(-0) = A+N ---> Original signal + any noise picked up
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ShoNuff
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PostPosted: Fri Apr 12, 2019 4:04 pm    Post subject: Reply with quote

LM wrote:

Output = (A+N)+(-(-A+N)) = (A+N)+(A-N)
Output = A+A+N-N = 2A ---> Noise is cancelled

When you plug a stereo or dual mono, unbalanced TRS connector into a balanced TRS jack:

Output = (A+N)+(-(A+N)) = (A+N)+(-A-N)
Output = A-A+N-N = Zero

Or close to zero, as there is always some small amount of phase distortion in the circuits, that's why you might still get a very low signal in the end (or the subtle difference between the channels, if it's a stereo signal).

When you plug an unbalanced TS connector into a balanced TRS jack (Ground=Zero):

Output = (A+N)+(-0) = A+N ---> Original signal + any noise picked up


very nice, thank you.
hahaa: which leaves:
dual mono on TRS to un/balanced (dual mode) mono input ?

?output= A+A+N = 2A+N
arrives as?

How do you feel about the option of having this little adapter box i suggested, using a strip of RCA pairs as inputs, then having the 470 ohm resistors? - and there were a few options on the Rane page higher up on this page - with a switch option for normal stereo thru (and whatever else). apart from a quick bit of DIY seems no more hassle than having loads of RCA-jack adpaters (i do have a decent collection of them but i don't want to just use one channel, or have to use 2 to get optimal signal level.
(this is all theoretical right now: i just bodge along as things stand Wink )
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LM
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PostPosted: Sat Apr 13, 2019 4:53 am    Post subject: Reply with quote

I'm not quite sure I understand the question, but just to make sure, what I described as Output on my previous post is the final result at the destination.

I don't know about the box, don't get me wrong, but in my case it seems that it would be just one more thing in the middle to deal with. I have a fairly compact setup, with enough mixer inputs and a box filled with bags of cables and adapters. Smile

And for "optimal level", that's what the gain/level controls on the mixer are for.
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TheDoctor
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Joined: 28 Mar 2019
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PostPosted: Sun Apr 14, 2019 6:04 pm    Post subject: Reply with quote

LM wrote:
I'm not quite sure I understand the question, but just to make sure, what I described as Output on my previous post is the final result at the destination.

I don't know about the box, don't get me wrong, but in my case it seems that it would be just one more thing in the middle to deal with. I have a fairly compact setup, with enough mixer inputs and a box filled with bags of cables and adapters. Smile

And for "optimal level", that's what the gain/level controls on the mixer are for.

Not really! If your signal is quiet because you didn't use the best cable set up you'll gain more and it will bring also noise level from your mixer or your audio interface. The lower is your gain(not your level, you should consider differently) the cleanest the signal.
You get shocked how much noise you cut with the right gain, I was using a gate before I don't need it anymore.
Also don't match at 0db, try to stay around -18db so you have plenty of room for mix and mastering don't touch the fader till you're in mixing. Everytime you use an effect match the increment of volume how it was it, if the effect has an output control is ideal otherwise you can use the faders.
Gain is the volume when your instruments come inside something so they should match the same level, also if you gain stage properly your fader will be more sensible and you have a long travel till the sound disappear.
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ShoNuff
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PostPosted: Sun Apr 14, 2019 7:24 pm    Post subject: Reply with quote

with you there, Doc'. this is why i want to be able to, on the one hand sum the 2 mono sides when needed, and on the other, provide 1/4" output.

i'm a little bit concerned my RCA box project could pick up RF if not metal. what do you think? or crosstalk or whatever. have in mind a slimline hard drive case - it's roughly the size of a volca - and has thin aluminium sheet on
top and bottom. hoping that might provide enough shielding, if needed.

btw: have now located suitable female minijack sockets that will fit in the
volca case under the pcb - regular ones don't; you can shave the plastic down but it's messy and not very satisfactory.

https://www.ebay.fr/itm/Embase-Jack-femelle-chassis-stereo-3-5mm-lot-de-8/171659925491?hash=item27f7ba97f3:g:PwEAAOSwb-JcXvJw
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