TRS or TS Jacks - MOD Dwarf

Using MOD devices Device Details
#21

This is something the Dwarf already handles internally :wink:

That’s clever!
Thanks - useful to know.

1 Like
#22

This isn’t a reply to your original question re TRS but is a description on how I achieve the dynamic stereo effects you desire with my mod duo. I use 2 instruments harmonica input 1 Guitar input 2. Each has its own FX chain and each splitting to stereo via stereo plugins then both stereo fx chains go to output 1 stereo left and output 2 stereo right This does mean that both instruments will go to the same two channels of my mixer (panned hard left & right) but are tonally and volume balanced within the mod so that the mixer channels are left flat i.e. the mixer only has control of overall volume of both instruments all other control is done within the Mod.

2 Likes
#23

This is something the Dwarf already handles internally

Oh - I just tried plugging my dwarf into an amp with what I presume is a mono jack input using a stereo cable and it doesn’t work (or at least it’s extremely low level) unless I partially remove the plug from the amp.

So the Dwarf doesn’t appear to be auto detecting and switching from balanced to unbalanced output?
:confused:
Wishing I’d brought a mono jack cable but that stereo one was just the right length…

1 Like
#24

I might be completely wrong on this, but I think it’s the insertion of a TRS plug that the Dwarf detects. It is then sending a balanced signal out. If you plug in a TS cable, the Dwarf will send an unbalanced signal.

#25

Thanks @malfunction54. What you’ve described sounds like standard behaviour when you have a balanced out on a TRS socket:

  • If you connect a TRS jack cable you’ll get a get the signal on Tip and Ring and ground on sleeve.
  • If you connect a mono TS cable the longer sleeve connects one leg of the balanced signal via the ring to the ground on the sleeve and so you automatically get an unbalanced output (which is what you’d want if you’re using a mono cable).

@Jan seemed to be describing some other kind of behaviour, where maybe it detects that the ring is open circuit (when, like in my instance today you use a TRS cable to connect the dwarf’s TRS outputs to a the TS input on an amp) and so switches to unbalanced mode with all the signal on the tip and nothing on the ring, but maybe I’ve misunderstood…

1 Like
#26

and… now I’m out of my depth :slight_smile:

1 Like
#27

Considering

and

Either the amp plug is not TS (which is rare for instrument amps) or your cable has the “hot” (positive) is running on the ring in at least one side, which is unusual. If I were to bet on something, I’d say your amp plug is not TS, because it responded to your pulling the plug halfway out.

(Power amps – the likes of Crown, QSC etc – would most likely take balanced signal in. Musical instrument amps, specifically those for guitar and bass, have in their vast majority unbalanced inputs. Keyboard amps vary, but most these days are also balanced input-only.)

And if that’s happening, the hot is getting shorted with the ground. You’d get little or no sound if that happened, other than a lot of noise.

So I’m wondering if the TRS cable you’re using has a connection that is mixed between the 2 sides? That would actually confuse the Dwarf or any device that auto adjusts for balanced and unbalanced signal. Do you have a multimeter to test the cable or another cable to try?

(Of course, it can always be a fault with the Dwarf itself.)

You’re not. If a system detects the isolation between negative and ground – which happens with a balanced connection, it is precisely the insertion of a cable that does not mix one with the other that would enable the balanced signal. Upon inserting a TS cable, it should detect that negative (ring) is mixed with ground (sleeve). That is precisely @ianr’s description here:

Now, I gotta say some dedicated amp circuits (special ICs or microchips) these days may have other ways of doing that, so I’m not sure how the Dwarf handles it.

2 Likes
#28

Balanced cable TRS for input and output only makes sense if the external device also has such an input/output.
A guitar has normally a unbalanced output.
Therefore it makes little sense to use a TRS to the input of the Dwarf.
With Dwarf output, a TRS cable can be useful if e.g… the mixer has a corresponding input.
The manual of the respective device probably provides information here.
The Dwarf can tolerate both types of cords.

1 Like
#29

I think @ianr was mentioning the Dwarf output into the amp, if I’m not mistaken:

Yes, it makes no sense to use a TRS cable out of a guitar at all. And yes again, TRS into a mono and unbalanced input does no good at all.

Now, as per the Dwarf Wiki page, it has TRS plug inputs, but the input itself is unbalanced. And the outputs are TRS balanced:

image

2 Likes
#30

If the amp doesn’t have a balanced input, a TRS cable at Dwarf output doesn’t make sense either.

1 Like
#31

Thanks for the replies. Just to give a bit more detail:

  • When I’m playing out and about I always take a mono jack if I’m plugging straight into an amp or the jack input on a desk, and/or I take a TRS (A.K.A stereo/Balanced) jack to XLR cable to plug into a stage box balanced. This always works fine.

  • Normally when practicing at home I take the Dwarf balanced output into the mono input of a PJB Suitcase bass amp via a TRS jack cable. I didn’t expect this to work but tried it because the cable was a nice (short) length and I liked the fetching shade of red. When @Jan said “this is something the Dwarf handles internally” I thought “ah it must be somehow detecting that it’s connecting to an unbalanced input and so is switching the Dwarf output to unbalanced”.

  • This weekend I’ve gone away on a short trip and was travelling light, so brought the dwarf and little Samson Expedition Express portable speaker to use for practicing. As the red TRS cable worked OK at home with the PJB amp I brought that too, but as I mentioned earlier it doesn’t work with the Samson.

My suspicion is that:

  • The Dwarf isn’t doing anything clever, but the PJB amp is doing the same trick as Mod do on the Dwarf inputs: install as TRS socket but connect the ring to the sleeve so that if idiots like me plug in a balanced cable it just gets mono’d and all is well.

  • The Samson is using a standard mono jack that only has a contact at the tip, and uses the shank of the socket to pickup the sleeve signal but there’s no contact for the ring, so it’s just left floating - hence getting extremely low signal level. However if I pull the plug out a bit, the ring gets shorted to the sleeve (but the tip is still just about connected) so it sort of works.

I’ll do some more experimentation with a 'scope when I get home and possibly get proved completely wrong (again)!

I think this is worth double checking because I think in other posts people were claiming that the output from the Dwarf was very low level - if it was just that they were mistakenly using a TRS cable into a mono input it would be an easy fix to swap in a mono cable.

2 Likes
#32

I can’t fathom the meaning of what you’re doing.
TRS cables are designed to eliminate incoming interference.
This only works if both connected devices also have the appropriate input/output circuitry.
If one is missing in the two devices, there is no interference compensation, only signal transmission.
These are always mono signals. (compensated or not) .
It has nothing to do with stereo.

Half unplugging the signaling device can cause a short circuit that is not perfect.
It is possible that the receiving participant still receives a signal with a significantly reduced volume.

I use a so-called silent plug for the guitar, which is plugged into the guitar side. T
This creates a complete short and I can plug and unplug the cable without the amp complaining with a loud cracking noise. You see it’s a TS Jack

#33

I’m sorry I might have not worded things very clearly.

The Dwarf doesn’t detect or switch anything. The ring output carries the balanced signal, but also allows to be shorted to ground or to be left floating. So this should cover most configuration with mono inputs. With stereo inputs, phase issues will of course occur.

2 Likes
#34

It has nothing to do with stereo.

Sorry @Sharry - I didn’t mean to imply that I was trying to send a stereo signal - I was just trying meaning that this is what people often call a TRS cable over here, just as the IEC mains cables that people use to power their amps are often called “Kettle leads” even though they’re not at that moment being used to power a kettle.

To get a signal from a balanced device into an unbalanced one, you do normally need to “short”, or at least connect, the ring connection to the sleeve connection to make sure that there will be a circuit from the tip signal back via the sleeve. This is very different to a silent plug that shorts the tip to the sleeve on a TS jack to make sure that there’s no signal getting through until it’s fully plugged-in.

2 Likes
#35

Thanks @Jan, that’s helpful.

So I think you’re saying that whereas usually the two signal connections are floating relative to earth (typically in devices that have a balancing output transformer), in the Dwarf, the tip and ring signals are both referenced to ground/sleeve (but in anti-phase to each other of course), so even if the ring’s connected to nothing there should still be a circuit from the tip back to ground - is that right?

That makes logical sense to me even though it doesn’t correlate to what I’m experiencing (and some purists might take issue with it :wink: ) - maybe it’s something weird with my Samson amp - will investigate more when I get home.

Thanks again.

1 Like
#36

To conclude the topic (at least for me).
Dwarf input: TRS cables to the dwarf input make sense if the signal generator also delivers a balanced signal.
This could be keyboards and other audio sources.Guitars or basses without active electronics normal deliever an unbalanced signal.
Since I’m a guitarist, I use TS cables (with silent plugs on the guitar side.)

Dwarf output: TRS cable from Dwarf Output only makes sense if the amp, mixer etc. is also equipped for it. Otherwise, a TS cable is sufficient. TRS cable is unnecessarily more expensive.
At home, for example, I use studio monitors with a ballanced input → hence the TRS cable.

For connect the Dwaf live to my mixer, I use TRS cable, since the mixer is also equipped with balanced jack inputs.
If I were using a guitar amp, I would use a TS cable.

Since the Dwarf provides balanced outputs, I don’t think a DI box is necessary.
For multicore cable boxes with XLR I would use the “XLR Male Plug 3-Pin to 6.3 mm Stereo Jack / Balanced Signal / Audio / Patch Cable”.
@ianr Good luck to find your issue with samson.

XLR Male Plug 3-Pin to 6.3 mm Stereo Jack / Balanced Signal / Audio / Patch Cable, yellow : Amazon.de: Musical Instruments & DJ

2 Likes
#37

yes this is correct!

2 Likes
#38

Thanks Jan,
I’m now home and have had more of a chance to have a look. It does seem to be a particular issue with that socket on the Samson amp. It works fine with a TS cable and it’s supposed to be a mono input so not sure why it would behave in that way.
Anyway, thanks for your patient replies!
Ian

4 Likes
#39

Hi everybody, sorry to revive an old topic, but I felt the urge to clarify some details and give some useful advice.

The analog inputs on the MOD Dwarf might as well be implemented by physical TRS (Tip Ring Sleeve) connectors but indeed the R (Ring) pin is shorted to the ground (S) as anybody with a multimeter can confirm by inserting an unsoldered TRS male jack inside the input plug and cross-testing the connections without powering up the MOD (read below).

Balanced or simmetrical connections do transfer the signal by mirroring the polarities of the waveform in respect to the ground (Sleeve): so one wire is the + (hot) and the other is - (cold). If it were an oscilloscope tapping both Tip and Ring (with the Sleeve as common ground) one would see the same waveform shape but horizontally mirrored as in … a mirror :slight_smile: while on side goes up, the other goes down by the same amount.

But still we are talking about a mono signal: to transfer a stereo signal with balanced cable you need four wires plus grounds.

This tecnique allows to cancel spurious and unwanted interferences which usually happens to inject inside the wire while being in PHASE and is being used since the telegraph.
In Phase means having the same polarity at any given time of the signal. The level might be different, so the polarity is important.

Let’s suppose a balanced shielded cable unfortunately becomes entangled and coiled right above a Power supply (PSU). The hum noise and/or all the spurious high-frequencies switching harmonics and sub-harmonics (if it were a switching PSU) radiating by the magnetic field generated by the PSU will surely affect the metal wires inside the cable, right?

This kind of unwanted interference, by all means, would reach both conductors IN PHASE because the radiating source generates its magnetic field that moves in the same direction. This translates that you would see the noise as having the same polarity on both Tip (hot) and Ring (cold) signal wires: a spike would go up the same way in the same instant on both wires, a 50 Hz sinewave hum would have the same phase or polarity as well on both wires.

Since the balanced link uses a DIFFERENTIAL input stage, everything that comes in being IN PHASE gets CANCELLED, while everything that is 180° out of phase is correctly transferred to the next stage as it was supposed to be from the beginning.

To be precise only if the level of the noise is the SAME on both wires, it gets completely cancelled, otherwise a little leftover will still be present on the output of the differential stage.

Simple math: +5 - (+)5 = 0; +3 - (+)5 = -2; +5 - (+2) = +3;
please note the plus sign in brackets which identifies the in-phase status of the noise level, while the minus (-) is performed by… the differential stage.
So balanced cables are NOT the panacea of noiseless audio!

Now, back to the MOD Dwarf input stage: if the source is a guitar then no worries as the signal is already unbalanced and a normal TS guitar cable can be used.

If using a mixer bench instead, to be able to feed the Dwarf any audio bus on the desk, and the mixer has a balanced AUX send then the correct way to wire it to the Dwarf is to use a TRS jack on the mixer side and a TS jack on the Dwarf side - no need to use a balanced cable, just a normal “guitar” cable just leaving the Ring not connected. So the connection is TRS → TS simply ignoring the Ring output (leave it floating on the TRS jack side).
This goes for input 1 - the same must be done for input 2 in order to feed the Dwarf both channels from a stereo Aux send - one cable each.

The trick is NOT to short the mixer’s Ring output to the ground to avoid having its output stage to be overloaded (if buffered) or the output level attenuated by -6dB (but this might depend on the implementation though).

Rule of thumb is: if going from a balanced source to an unbalanced input, just make sure the cold signal from the output is left floating.

ATTENTION: This is particularly true if using a DC COUPLED output feeding an UNBALANCED INPUT as it would destroy the op-amps on the output buffer.

If I want to connect my MOTU audio interface using its DC coupled outputs to the Dwarf’s inputs, I make sure I use only TRS → TS cables leaving the Ring floating on the interface side!!!

A DC coupled output is pretty much like a variable voltage battery: there is a constant Direct Current voltage and everybody knows what happens when shorting its terminals. This voltage comes directly from the device’s power supply lines.
AC only transfers energy by capacitive means, without physical connection with the device’s power supply. That’s safer somehow…

When in doubt, just power off everything and stick an open TRS jack on each end of the link you are connecting and check with a multimeter if there is continuity between Ring and Sleeve.

There can be capacitors so a zero might appear briefly and then you should see infinity (open connection). If the zero (or less than few ohms) is stuck there on the multimeter display you are surely dealing with an UNBALANCED connector.

Set the multimeter to the lowest scale (200 Ohms) as you don’t need to see the high resistance of the input which is a completely different thing than impedance :stuck_out_tongue:

Hope this helps to shed some light on the topic. Cheers!

1 Like