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TS cable into TRS input (Tascam DP-24 SD)

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TS cable into TRS input (Tascam DP-24 SD)

Postby garrettendi » Thu Jul 13, 2017 2:37 pm

Hi,

I'm really confused by the instructions that come with the Tascam DP24 SD). The input jacks are XLR/TRS jacks, yet the manual diagrams show TS cables coming from a keyboard, going into the combination jacks (and not the HI-Z input either which is listed as TS).

My bassist will be going into the Hi-Z input, and I planned to use a normal TS instrument cable from my Line 6 Pocket Pod into one of the TRS inputs.

Will this work? As even though the manual states XLR/TRS, the diagram clearly shows a TS cable going into the jack. On top of that I've seen a tutorial video on the DP-24 SD showing a stereo 3.5mm to 2 x TS 1/4" cable for stereo recording.

So I'm very confused. And I'd rather not have to shell out for a DI-box when I'm already getting the DP-24 SD. I've emailed Tascam direct but I haven't had a reply in over a week.

Cheers for any help!
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Re: TS cable into TRS input (Tascam DP-24 SD)

Postby Dave B » Thu Jul 13, 2017 2:41 pm

Should work fine. TS is an 'unbalanced' signal and TSR is 'balanced'. Rule of thumb : you can stick an unbalanced lead into a balanced input and it will be fine (a slight loss of possible signal but nothing to worry about), but not the other way round.
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Re: TS cable into TRS input (Tascam DP-24 SD)

Postby garrettendi » Thu Jul 13, 2017 2:49 pm

Thanks Dave. Just out of curiousity what would happen if I plugged a TRS into a TS input?

Also am I right in terminology: TRS is a "stereo" jack, and TS is "mono"?
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Re: TS cable into TRS input (Tascam DP-24 SD)

Postby Hugh Robjohns » Thu Jul 13, 2017 3:00 pm

Dave B wrote:Should work fine.

Agreed

Rule of thumb : you can stick an unbalanced lead into a balanced input and it will be fine (a slight loss of possible signal but nothing to worry about), but not the other way round.

There shouldn't be any loss of level when plugging an unbalanced source into a balanced input. In this case the unbalanced signal will be applied across the tip and ring connections of the balanced input, thanks to the extended sleeve of the unbalanced TS plug, and the full signal will be received.

The reduced level issue you refer to can occur when connecting an active symmetrical balanced output to an unbalanced input. In that case, only half the balanced signal is received, so the level is 6dB lower than it should be.

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Re: TS cable into TRS input (Tascam DP-24 SD)

Postby Hugh Robjohns » Thu Jul 13, 2017 3:08 pm

garrettendi wrote:Just out of curiousity what would happen if I plugged a TRS into a TS input?

It depends on exactly what is wired to to TRS plug!

If we are talking about an unbalanced stereo source, you will end up with only the left channel.

If its an active symmetrical balanced source you will have a signal that is 6dB lower than expected.

If its an impedance-balanced output you will have the full signal level.

And if it's a transformer balanced output you will either have the full output, or nothing at all, depending on whether the TS socket has a grounded ring contact or not.

Also am I right in terminology: TRS is a "stereo" jack, and TS is "mono"?

Those plugs can be used for those purposes, or for balanced and unbalanced signals.

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Re: TS cable into TRS input (Tascam DP-24 SD)

Postby Mike Stranks » Thu Jul 13, 2017 3:50 pm

Yup! This TRS: is it stereo or balanced mono causes all sorts of confusion.... especially if you (not unreasonably) think that a plug is a plug and it fits in that socket so...

Just a coupla days ago I was called-in to an install I've recently started 'caretaking'. They have a pre-me-installed facility to connect a 'phone/tablet for playback... could I "come over as it's not working properly."

Connecting lead was 3.5mm TRS to 6mm (quarter-inch) TRS. Amp end was an adapter to convert 3.5mm TRS to the larger size...

That was all I needed to see as I already knew the amp input was balanced mono. Thus the left channel was going to the tip of the larger TRS (the balanced 'plus'), the right channel was going to the ring (the balanced 'minus'). Thus all sorts of electrical and aural funnies result... (Feel free to explain, Hugh! :) )

Solution was to replace the amp-end arrangement with a new 6mm TS plug... tip and ring from 3.5 mm stereo connected to tip and sleeve to sleeve. Problem solved...
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Re: TS cable into TRS input (Tascam DP-24 SD)

Postby Hugh Robjohns » Thu Jul 13, 2017 4:06 pm

Ah yes, the classic case of an 'unbalanced stereo' output feeding a balanced mono input!

The key to understanding the problem here is to remember that:

1. a 'balanced input' always employs a differential receiver (whether constructed from a passive transformer or active op-amps).

2. a differential receiver is only interested in the difference in signal voltages between its two input terminals (hot and cold, or plus and minus).

3. anything that presents the same voltage to the two terminals (the so-called common-mode condition) will be ignored, which is where the 'interference rejection' property comes from.

So, in this case, you end up presenting the left channel to the differential receiver's hot terminal, and the right channel to its cold terminal. The output will be the difference between the two, and anything that is the same on both will be ignored (and removed).

Consequently, anything panned centrally -- kick drum, bass, vocals etc -- all disappear, and all you're left with is any instruments panned widely, and the stereo reverb! Or, if the source was 'dual mono' -- such as a talking book where the narrator us panned centrally -- very little at all!

There are two solutions. Mike mentioned using a special adapter that mixes the left and right channels together into a mono unbalanced signal and presents that mixed signal to the hot terminal, while the ground reference of the unbalanced source is wired to the cold terminal.

The other solution is a Y-split cable that presents the left channel to one mono unbalanced TS plug, and the right channel to a second unbalanced TS plug -- these would then be plugged into two separate mono channels, or the left and right inputs of a stereo channel, depending on what was available.

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Re: TS cable into TRS input (Tascam DP-24 SD)

Postby garrettendi » Thu Jul 13, 2017 4:08 pm

Hugh Robjohns wrote:In this case the unbalanced signal will be applied across the tip and ring connections of the balanced input, thanks to the extended sleeve of the unbalanced TS plug, and the full signal will be received.

Here's where I'm confused... I thought the tip of a TS is the same size as the tip of a TRS? So wouldn't that mean the grounded sleeve of the TS would go into the ring of the TRS (is that called the "cold" signal?)... Explanation would be appreciated!
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Re: TS cable into TRS input (Tascam DP-24 SD)

Postby The Elf » Thu Jul 13, 2017 5:20 pm

Stereo vs balanced is the teacake of audio technical problems. The number of times I've seen headphone outputs plugged into balanced inputs (or been asked for a jack/XLR adapter to enable such a connection), is countless!

It doesn't help that folk often talk about 'balance' in terms of left/right offsets, which seems to lead some people into believing that 'stereo' and 'balanced' are actually the same thing. Once this kind of belief has dried in it is damned difficult to shift it!
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Re: TS cable into TRS input (Tascam DP-24 SD)

Postby Hugh Robjohns » Thu Jul 13, 2017 5:22 pm

garrettendi wrote:Here's where I'm confused... I thought the tip of a TS is the same size as the tip of a TRS?

It is.

So wouldn't that mean the grounded sleeve of the TS would go into the ring of the TRS (is that called the "cold" signal?)... Explanation would be appreciated!

Yes.

Any circuit path needs at least two connections. In the case of an unbalanced audio signal, one connection -- the sleeve on a TS plug -- provides a reference voltage (usually ground or 0V). The other connection -- the tip of the TS plug -- provides the varying audio voltage (measured with respect to that reference).

In this case you're plugging the unbalanced source into a balanced input, so the TS plug's tip meets with the TRS socket's tip contact, and the TS plug's sleeve meets with both the TRS socket's ring and sleeve contacts.

The differential receiver's hot and cold connections come from the tip and ring contacts, respectively, so you have the varying unbalanced signal voltage being applied to the hot terminal and the ground reference being applied to the cold terminal. And as a result, the differential receiver can 'see' the whole wanted audio signal.

However, there is one potential fly in the ointment here, which is that this arrangement inherently connects the receiving equipment's ground to the source equipment's ground, via the TS plug's sleeve... So if both devices are designed with their ground references being connected to the mains safety earth (ie Class 1 devices) that could result in the creation of a ground loop, with all the nasty hums and buzzes we associate with that problem.

Fortunately, if this proves to be a problem -- it doesn't always -- there are easy ways around it using an approach referred to as a pseudo-balanced connection. This employs a specially wired cable that omits the direct ground connection.

(See SOS shop for ready-made cables -- http://www.soundonsound.com/shop/sos-special-cable )
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Re: TS cable into TRS input (Tascam DP-24 SD)

Postby garrettendi » Fri Jul 14, 2017 9:11 am

Thanks Hugh, an excellent explanation! I'll look into those cables or a cheaper DI box with a ground switch if I get an intolerable hum/buzz
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Re: TS cable into TRS input (Tascam DP-24 SD)

Postby garrettendi » Fri Aug 18, 2017 3:41 pm

Hi Hugh (and everyone else)!

Quick question to resurrect this topic.

My e-drum kit has L(mono) and R audio output sockets. The manual says to use TRS cables for these, but when I asked Alesis Customer Support, they said I should use TS cables.

Would using TS cables as they say make any real difference? I know connecting a TS cable into a TRS input is ok, but what about connecting a TS cable to a TRS output? I only have TS cables going spare!
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Re: TS cable into TRS input (Tascam DP-24 SD)

Postby The Elf » Fri Aug 18, 2017 3:53 pm

By the sound of it, assuming the manual is accurate, the edrum has balanced outputs. Unbalanced cables will work fine, as Alesis have said, but if you have the chance to use a balanced connection, then use it! The price of a pair of balanced jack cables is relatively insignificant at the side of the kit you're using, and it will result in the edrum giving of its best. This is assuming that you're going to be plugging into something with balanced inputs - if not then it doesn't really matter which you use.
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Re: TS cable into TRS input (Tascam DP-24 SD)

Postby Guest271017 » Fri Aug 18, 2017 3:55 pm

What does the manual list the outputs as, balanced or unbalanced? Balanced should be TRS, unbalanced TS. As to whether they can/should be interchanged, it depends.

* The Sprite beat me to it.
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Re: TS cable into TRS input (Tascam DP-24 SD)

Postby garrettendi » Fri Aug 18, 2017 4:10 pm

mashedmitten wrote:What does the manual list the outputs as, balanced or unbalanced? Balanced should be TRS, unbalanced TS. As to whether they can/should be interchanged, it depends.

The manual makes no mention of un/balanced, it just says in the specs:

"(2) 1/4" (6.35 mm) TRS main outputs."

I'll get a TRS cable in the future, but am I ok to use TS for now?
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Re: TS cable into TRS input (Tascam DP-24 SD)

Postby Guest271017 » Fri Aug 18, 2017 4:18 pm

garrettendi wrote:
mashedmitten wrote:What does the manual list the outputs as, balanced or unbalanced? Balanced should be TRS, unbalanced TS. As to whether they can/should be interchanged, it depends.

The manual makes no mention of un/balanced, it just says in the specs:

"(2) 1/4" (6.35 mm) TRS main outputs."

I'll get a TRS cable in the future, but am I ok to use TS for now?

Main Outs suggests some kind of amp/ preamp being applied. What do you plan to connect it to? Whatever it is, start with all volume settings down on everything in the chain.

Do you have a link to the manual?
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Re: TS cable into TRS input (Tascam DP-24 SD)

Postby Hugh Robjohns » Fri Aug 18, 2017 4:26 pm

garrettendi wrote:My e-drum kit has an L(mono) and R audio output sockets. The manual says to use TRS cables for these, but when I asked Alesis Customer Support, they said I should use TS cables.

If the manual suggests TRS connectors, that implies the outputs are balanced (either active-symmetrical or impedance-balanced). It would be worthwhile confirming that, as it makes life a lot easier in many situations.

I note the manual for the Alesis E-drums talks about TS connectors for pad inputs and TRS connectors for the main outputs... so there's a good change they really do mean it has balanced outputs on TRS sockets! :-)

Would using TS cables as they say make any real difference?

It depends on the type of balanced output. In short, the outputs will always work feeding a signal to an unbalanced destination via TS cables, but the signal level might end up 6dB lower than expected.

Clearly, inserting a TS plug into a TRS socket shorts the ring and sleeve contacts together, effectively tying the 'cold' output directly to ground. Whether this matters or not, and what effect it has, varies with the type of balanced output.

If it's a transformer-balanced output, this will unbalance the output transformer, but the full signal level is passed normally. (But your e-drums won't have output transformers!)

If it's a simple active-symmetrical output design, the 'cold' output driver will be shorted to ground, leaving only the 'hot' output driver to provide the signal. However, since this is a symmetrical output and you're now sending only half the signal, the output level will be 6dB lower than intended.

In some (now very rare) cases, the shorted cold output driver might become unhappy, potentially introducing distortion. And years ago, with really simple output drivers, it was possible that some may even overheat and die under this condition... but I've not seen that happen in decades! :-)

If it's a cross-linked active-symmetrical output -- as many of the better designs are -- then shorting the cold side to ground will change the feedback arrangements between the two output drivers effectively forcing the hot side to double its output level, thus passing the full signal level to the destination.

If it's an impedance-balanced output, the full signal is always present on the hot output anyway, and the TS plug simply shorts out the impedance-matching resistor in the cold feed to ground... which won't make any difference to anyone.

So by all means use unbalanced TS cables if you must.. but if they really are balanced output it would be a shame not to use them if you're connecting to an interface or mixer with balanced inputs.

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Re: TS cable into TRS input (Tascam DP-24 SD)

Postby garrettendi » Fri Aug 18, 2017 4:36 pm

Wow. That sounds bad. I'll buy a TRS cable asap.

I don't have a link to hand and I'm sending this from my mobile but the manual is on the Alesis website. It's the Forge drum kit.
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Re: TS cable into TRS input (Tascam DP-24 SD)

Postby Hugh Robjohns » Fri Aug 18, 2017 4:49 pm

garrettendi wrote:Wow. That sounds bad.

Not bad, normally, just the possibility of slightly reduced output level in some specific circumstances. In your case I doubt you'll notice a difference.... but using TRS cables would be better in the long run.

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