Can I add a TRS Balanced Input to my SS Amp? Or make a custom TRS to TS Cable?

[RedJamaX]

I have a PreSonus AudioBox iOne that I use with Guitar Rig, but currently I do not have any monitors. If your answer is going to be "save up for some monitors", please don't bother... I already know that is the "best" solution, and I like to think outside the box. The AudioBox iOne has two Balanced Outputs (left and right channels), and currently I am just connecting them to my computer speakers input, and sometime the input on my Amp (Matrix MA100SC). Of course, these do not have Balanced Inputs, so there is quite a bit of Line Noise with any of the settings that use a lot of Gain.

 

Based on the explanation on Balanced vs Unbalanced connections I found (link below) It seems like this should be do-able...

http://www.presonus.com/learn/techni...ced-unbalanced

 

But admittedly, I'm not even a novice when it comes to wiring electronics, and I like to tinker. Also, the Amp is not great, nor expensive, so if I broke it, I wouldn't really care.

 

Based on what I'm seeing here... I should be able to:

1. Mount a TRS Jack to the Amp (like this one)

http://www.ebay.com/itm/Switchcraft-...IAAMXQBg5RsQY6

2. Add a resistor between the Hot and Cold line on the new connector tip (Tip & Ring) - if so, what resistance would be needed?

3. Solder a connection from the T&R leads over to my TS Input Jack SIGNAL line

4. Solder a connection from the Sleeve to my TS Input Jack GROUND

 

Or... is there something I am missing in regards to how that balanced line-in would effect the Amp Input??

 

Another possibility I have seen (and seemingly much easier) is to simply make my own custom cable by modifying a TRS cable by replacing the tip wit a TS Cable tip in one of the following configurations: See attached pictures...

1. Wire TIP & RING from TRS to the TIP on the TS Male

2. Wire in two 5K resistors in parallel on the TIP & Ring, connected to the TIP on the TS Male

3. Wire in a single 10K resistor between the TIP & RING, connected to the TIP on the TS Male

 

Are any of these options feasible to reduce the line noise going out from my AudioBox iOne and into my Amp?

[RedJamaX]

Some more searching turned up this page... with the solution in the attached picture:

http://www.rane.com/note110.html

 

Thoughts?

[r0bo01]

Some more searching turned up this page... with the solution in the attached picture:

http://www.rane.com/note110.html

 

Thoughts?

 

this should work (theoretically ). low impedance (51 ohm in your case) -> the (probable) higher impedance of your amp input won't "load" the signal. be sure that you do not connect the trs shield to the ts sleeve...

won't cost you much to try. good luck!

[RedJamaX]

be sure that you do not connect the trs shield to the ts sleeve...

 

Ok. I've made the cable per the wiring shown on that last diagram. It is certainly quieter... but not "quiet". My guess is that it simply won't ever be, since the out put is supposed to go to a balanced input.

 

 

Two more questions...

I'm really curious, you stressed that I should not connect the Shield to the Sleeve... but previous to making this cable, by way of adapters, that's pretty much what I was doing. It was louder, but nothing appeared to get damaged. Can you explain (simply) what the problem is? According to the first site I listed, it looks like they are both Ground connections...

 

Second, is it possible that a Ground Loop Isolator would help at all in this situation?

 

[RedJamaX]

Ok...

 

I've got a solution! So I combined a few idea by using the cable diagram from my second post and wiring in a Ground Loop Isolator. This has made a pretty nice solution for a very quiet TRS to TS Cable for those who are on a budget and just cannot afford Monitors.

 

See below for my quick diagrams... I should have a video posted on YouTube soon to show the difference that the Ground Loop Isolator makes.

[WRGKMC]

First, I'd have to say, you aren't being clear on what your problem is and what you're wanting to do.

The best I can make out is you're wanting to use a mono guitar amp as a monitor for the Audio Box.

 

Second the TRS outs on the Audio box can be used balanced or unbalanced. What happens when you connect the unbalanced TS cord is one side of the balanced signal gets grounded with the shielded cable.

 

Noise wise, if you're working with a cable under 25' it isn't going to matter whether you are using a balanced of unbalanced cable. The only thing that happens is with longer unbalanced cables is the capacitance and resistance is higher and it begins to attenuate high frequencies.

 

If you're using a guitar amp as I suspect, cord length isn't going to matter anyway. Guitar amps use midrange speakers and aren't anywhere close to being high fidelity. You're lucky if you can get 6Khz out of them and cable attenuation begins up in the 20K range.

 

If you want to change from low impedance to high, it needs to be done properly. You either need a transformer or an active circuit to change impedance. As you noted the Audio box has an impedance of 51 ohms and a guitar amp likely has an impedance of 10K or so.

 

More importantly, a guitar amp is instrument level and Audio box is line level. You need to reduce the signal gain so it doesn't overdrive the guitar amp. Guitar pickups generate a weak signal. You need to weaken the line level output of the audio box to match the signal; strength.

 

By far the easiest way to do this is with a DI box. A passive DI box contains a transformer like this.

 

 

 

 

This transformer will work in either direction. The input and outputs can be swapped. The key is it matches the impedance of the two devices. As you can see here, left side uses a single signal wire and a grounded shield. (like a guitar cord) The right side uses two signal wires and a grounded shield (Like a Mic Cable). You can use XLR or TRS, it doesn't matter but you need this transformer to change impedance and drop the signal from Mic Level to Instrument level.

 

 

 

Unless there's some dire need to mount this in the amp, the simplest solution is to simply buy a passive Direct box. They only cost $12 http://www.ebay.com/itm/Pyle-Pro-PDC...cAAOSwmtJXajnq

 

These boxes have two other important items. They have a attenuator switch which can drop the signal level either -10dB or -20dB. These are for matching the signal strength to various levels like connecting it to a guitar amp which has a hot preamp.

 

You also mention noise and hum. The reason you have this is because the guitar amps preamp is way too hot and its bringing the noise floor up too high. The DI box will attenuate the signal so the noise isn't noticeable. The DI also has a ground lift switch in case your computer and guitar amps are plugged into two different outlets. The best solution of course is to plug them into the same outlet so you aren't passing AC voltage between chassis grounds.

 

The next problem you have is the Audio box has a stereo output and a guitar amp is mono.

 

First I'd say it isn't going to matter if you combine the stereo output to mono before/in the DAW program or after the Audio box using a mixer. You aren't going to hear a stereo signal anyway and its less expensive to simply use a stereo to mono plugin in the DAW to make everything mono then use a single output from the Audio box to the amp.

 

If you wanted to combine the Audio box outputs then you first need to use a Dual DI like this. https://www.ebay.com/p/?iid=391598580157&&&dispItem=1&chn=ps These have two transformer, two attenuator switches and two ground lifts. They work exceptionally well by the way, I have one I use to feed a stereo line level drum machine into to mic level inputs. It has no noticeable tone sucking.

 

That dual DI will get both outputs to the proper signal level. It doesn't stop there however. You still have to combine them to Mono. You cant simply Y jack them together. There is nothing stopping the output from one side from feeding back into the output of the other. The DI transformers should prevent damage to the interface but you shouldn't combine signals from stereo to mono without buffering or at least a resistive bridge.

 

You can do it with an actual mixer that buffers its inputs from one another,

 

or resistive summing circuit like this.

 

 

Or you can use a sum box like this to combine a stereo signal to mono.

http://www.bswusa.com/Matching-Amplifiers-Accessories-Galaxy-Audio-JIBR-P2361.aspx

 

Again, combining the outputs using a dual DI and summing circuit is unnecessary. All you need is to run a stereo to mono plugin within the DAW and combine it there and use a single output to an amp in mono. It will likely sound allot better there too because you wont have all the phase and impedance imbalances trying to combine to line levels to a single instrument level.

 

As I said, your posts weren't very clear on what you were wanting to do, but If I read the bits and pieces, what I've posted here is by far the cheapest alternative to do what you want.

 

Of course, getting something/anything to run as monitors, even if its only an old Hi Fi with a pair of bookshelf speakers will be a hundred times better then using a guitar amp as a monitor. You'll be able to hear the tracks but the key to mixing is to have a perfectly linear sound so any adjustments you make are actually adjustments the mix needs.

 

Even a set of computer monitors are cheap as hell. Something like this is only $12 https://www.cdw.com/shop/products/Cyber-Acoustics-CA-2016WB-2.0-Channel-Speaker-System/3323711.aspx?cm_cat=GoogleBase&cm_ite=3323711&cm_pla=NA-NA-ACU_HE&cm_ven=acquirgy&ef_id=V@dFiwAAASRai1uQ:20170529132555:s&gclid=CKrI2YOaldQCFQwPaQod8kgCgQ&s_kwcid=AL!4223!3!197433481916!!!g!303390842050!

 

You just need to get a 1/8" stereo to two 1/4" adaptors and you can plug them right into the interface. They wont be highly linear but you can supplement them using headphones up to a point.

[WRGKMC]

None of that's going to work.

[RedJamaX]

Thanks for all of the information!!

 

So, before I continue, let me say that I have made the different cables I listed above and they all work for exactly what I was looking for. There is still a little bit of line noise, but nothing like it was.

 

 

First, I'd have to say, you aren't being clear on what your problem is and what you're wanting to do.

The best I can make out is you're wanting to use a mono guitar amp as a monitor for the Audio Box.

 

Yeah, I didn't really make that perfectly clear. Just going from one to the other can be achieved with a number of cheap adapters. What I was specifically looking for was a relatively inexpensive cable or device that would provide a connection between the two without a lot of noise. I realize that the "proper" thing to do is to buy Studio Monitors (with dedicated internal amplifiers and TRS inputs), but those are not cheap... especially if you still want "big" sound.

 

 

Second the TRS outs on the Audio box can be used balanced or unbalanced. What happens when you connect the unbalanced TS cord is one side of the balanced signal gets grounded with the shielded cable.

 

Noise wise, if you're working with a cable under 25' it isn't going to matter whether you are using a balanced of unbalanced cable. The only thing that happens is with longer unbalanced cables is the capacitance and resistance is higher and it begins to attenuate high frequencies.

 

What I had (before making the cables) was a Tip/Ring splitter plugged into the L and R OUTPUT channels from the Audio Box, then connected to the input for my Desktop Computer speakers. Desktop Speakers are comprised of an Altec Lansing Sub (with all the various inputs and controls) and Sony Bookshelf Speakers for the front speakers (replaced the original Altecs because these sound better).

 

That setup worked well, but with many of the amp settings, or on High volume, there was a LOT of line noise. I only had the idea of using the guitar amp because I wanted a bigger sound, using equipment that I already own. Routing to the guitar amp created even more line noise.

 

 

If you're using a guitar amp as I suspect' date=' cord length isn't going to matter anyway. Guitar amps use midrange speakers and aren't anywhere close to being high fidelity. You're lucky if you can get 6Khz out of them and cable attenuation begins up in the 20K range.[/quote']

 

The good news here is... I'm using it only to play guitar. And while I am sure that Studio Monitors will still produce a more "accurate" sound from the AudioBox... Playing guitar through this setup out to my guitar amp sounds good.

 

In the interest of keeping it short... For the other points on your post..

 

1. Direct In Box ... THANK YOU!!! - WHY is there no other post that I can find anywhere that says simply... "If you want to send the Balanced Outputs of your DAW Audio Device into your Computer Desktop Speakers, use a Direct IN Box. This will connect the signal between the two device properly and reduce the line noise"

Seriously... it has to be one of the following:

a) Most people just have the money to afford monitors (or credit card debt)

b) They don't KNOW that the use of a Direct In Box can be explained as simply in those terms, for this application (most likely)

c) They just don't care about the extra line noise

 

Stereo vs Mono

I actually do want the stereo capability for when I am connected to my desktop speakers. Guitar Rig has the ability to create different amp configurations on the Left and Right channels. I do realize that I lose this functionality when plugging into my guitar amp.

 

For the rest... Thank You!! Seems like a DI box will be my next purchase. Seriously, I've seen the DI Boxes before, but I have never seen any post or explanation that clarifies that they can be used for exactly the solution I am looking for, ... Or my Google is broken...

 

Thanks again for that wealth of information!

[RedJamaX]

If you wanted to combine the Audio box outputs then you first need to use a Dual DI like this. https://www.ebay.com/p/?iid=391598580157&&&dispItem=1&chn=ps These have two transformer, two attenuator switches and two ground lifts. They work exceptionally well by the way, I have one I use to feed a stereo line level drum machine into to mic level inputs. It has no noticeable tone sucking.

 

That dual DI will get both outputs to the proper signal level. It doesn't stop there however. You still have to combine them to Mono. You cant simply Y jack them together. There is nothing stopping the output from one side from feeding back into the output of the other. The DI transformers should prevent damage to the interface but you shouldn't combine signals from stereo to mono without buffering or at least a resistive bridge.

 

I like the Dual DI Box option the best... But I want make sure I understand how it needs to be connected to various devices... and make sure that these are viable applications for using a DI Box. Can you tell me if this is correct?

[WRGKMC]

Thanks for all of the information!!

 

What I had (before making the cables) was a Tip/Ring splitter plugged into the L and R OUTPUT channels from the Audio Box, then connected to the input for my Desktop Computer speakers. Desktop Speakers are comprised of an Altec Lansing Sub (with all the various inputs and controls) and Sony Bookshelf Speakers for the front speakers (replaced the original Altecs because these sound better).

 

Using a 1/8 stereo to dual TS mono is fine here. Your interface is nothing more than an external sound card. The main difference is it has Pro connectors instead of Consumer style connectors. Computer/desktop speakers are line level and will work with any interface with the proper adaptors.

 

1. Direct In Box ... THANK YOU!!! - WHY is there no other post that I can find anywhere that says simply... "If you want to send the Balanced Outputs of your DAW Audio Device into your Computer Desktop Speakers, use a Direct IN Box. This will connect the signal between the two device properly and reduce the line noise" Seriously... it has to be one of the following:

 

The reason you don't find that because it isn't completely true. There is absolutely no noticeable difference in noise between using balanced and unbalanced when you are running short cables. If there is you have bad cables with poor shielding.

 

You should also know, just because a device has a balanced jack, it doesn't mean it is actually balanced. Many pieces of gear use XLR jacks that short the balanced cable to ground and when you connect a mic cord it simply turns it into an unbalanced guitar cable.

 

 

 

 

a) Most people just have the money to afford monitors (or credit card debt):

You're not the only one that's had to work with less then optimal gear. I spent decades using work around's before I could afford monitors. Back when I got into recording you couldn't touch a good set of monitors for under 10K. What I did was buy a good used power head cheap and built my own speakers (several sets) They actually worked pretty good too. One set I still use is a set of 6X9" Triaxial car speakers in boxes. They work well for getting a mix to sound good in a car.

 

I eventually bought a pair of used monitors, then more recently bought a pair of M-Audio BX5's on sale for $200.

 

 

 

b) They don't KNOW that the use of a Direct In Box can be explained as simply in those terms, for this application (most likely)

c) They just don't care about the extra line noise

 

Again, there is absolutely no difference in noise levels. What you're dealing with is an impedance/gain level difference which is giving you higher noise levels, not a balanced/unbalanced level.

 

 

Stereo vs Mono

I actually do want the stereo capability for when I am connected to my desktop speakers. Guitar Rig has the ability to create different amp configurations on the Left and Right channels. I do realize that I lose this functionality when plugging into my guitar amp.

 

For the rest... Thank You!! Seems like a DI box will be my next purchase. Seriously, I've seen the DI Boxes before, but I have never seen any post or explanation that clarifies that they can be used for exactly the solution I am looking for, ... Or my Google is broken... Thanks again for that wealth of information!

 

The reason I mentioned the DI is strictly for use with a guitar amp. You don't need it connecting computer speakers. You need to brush up on the differences between signal levels.

 

The 5 different signal levels most commonly used are: Get to know them like the back of your hand. They are very important.

 

 

1. Mic level = Very weak signal .01V and usually 600 Ohms impedance

 

2.Instrument Level = 700mv and impedance of 10K or more

 

3. Line level = up to 2 to 3 volts. There are two main types of line levels Consumer -10dB and Pro +4dB Impedance can be up to 1K. Outputs have lower impedances then inputs.

 

4. Headphone level = Impedance can be between 8 and 64 ohms. Voltage between 1~3V. Some headphone jacks can double as line level jacks but beware. Never connect a line level device to a headphone jack unless you know for sure is a jack designed for both. You can instantly damage either unit if they aren't designed to work as both a line level and headphone jack.

 

5. Speaker level = Speaker level is for speakers only. You're talking high voltage and high current here and you'll fry any line level devices and likely blow the amp with the wrong load connected. There are some special devices that can drop a speaker level down to line level, but these usually have to be hand built. Most new amps have line outs and effects send jacks that allow connections to other devices.

 

 

The reason I mentioned the DI box has nothing to do with balanced vs unbalanced. It has to do with matching line level voltage/impedance to instrument level voltage/impedance. Unfortunately most DI's don't offer TS ins to TS outs. It could be wired that way but they are multi functional devices so you work with what's readily available.

 

The XLR input takes either line level or mic levels in. If it was a TS jack you could use an unbalanced cable to connect to your interface outs and not hear any difference in noise levels, again if the cable lengths are short and you use quality cables.

 

The most important thing here is the DI has an -10 ~ -20dB attenuator. The line level coming out of your interface can be as high as 2 or 3 Volts and has an impedance of 600 ohms. Your guitar amp wants to see a maximum voltage of 700 millivolts. The DI set for -10 ~-20dB will drop the signal level down to what a guitar pickup will be and the transformer steps up the impedance so the signal matches the amp.

 

The reason the noise is reduced isn't because you went from balanced to unbalanced, its because you dropped the signal line level output down to instrument levels. The Noise floor went down as the signal level was dropped. This all deals with gain staging which is a critical aspect in working with signals.

 

I'll also say the article you posted at the beginning is highly superficial. There's truth in there but it's highly superficial. They don't give you details as to how and why and you cannot jump to assumptions like you have during this thread. Electronics is fairly complex once you go beyond the basics most users deal with. 1+1 doesn't always add up to two. There are other unseen and unknown factors you must know to tie it all together.

 

I do suggest you go here and do some studying. I'm sure what's I've covered here is included there, possibly in an easier to understand format. Its got chapters on the left covering just about everything a beginner needs to know and will save you many years of screwing around reinventing the wheel which has been around long enough where it doesn't need to be improved, just understood how its used. http://tweakheadz.com/

[RedJamaX]

T

The reason I mentioned the DI box has nothing to do with balanced vs unbalanced. It has to do with matching line level voltage/impedance to

I do suggest you go here and do some studying. I'm sure what's I've covered here is included there, possibly in an easier to understand format. Its got chapters on the left covering just about everything a beginner needs to know and will save you many years of screwing around reinventing the wheel which has been around long enough where it doesn't need to be improved, just understood how its used. http://tweakheadz.com/

 

Clearly, I've got some studying to do.

 

I'd like to thank you for taking the time to respond with the level of detail that you've provided here. Your posts were not short and I am sure have taken time out of your life to share that information. It's uncommon to find forum members who are so willing to educate on matters to this degree. I am one who also takes time to expand on topics in which I have knowledge in (obviously not this one ...), and your time and willingness to share that information is greatly appreciated.

 

Thank You!

[r0bo01]

 

Two more questions...

I'm really curious, you stressed that I should not connect the Shield to the Sleeve... but previous to making this cable, by way of adapters, that's pretty much what I was doing. It was louder, but nothing appeared to get damaged. Can you explain (simply) what the problem is? According to the first site I listed, it looks like they are both Ground connections...

 

this is how you make a ground loop. if that's what you want...

[WRGKMC]

I never said that. The shield is always connected to the sleeve unless you are running balanced and then you can use a ground lift to remove the ground from one end of the cable. The shield is still there it simply isn't connected to both chassis of two devices so you have current flow from one AC outlet to the other.

 

It takes two wires to complete a circuit. In an unbalanced circuit the shield carries half the signal. If you disconnect the shield you also loose the signal. In a balanced circuit you have two wires carrying the signal and a separate shield, you can lift the shield at one end and not loose the signal and just one chassis/AC outlet will carry the noise to ground instead of two.

 

The difference in loudness is immaterial. That's coming from an improper impedance match not because you're running balanced vs unbalanced. You should have plenty of gain available and loudness has nothing to do with quality. When your record and mix the standard loudness needed is 83dB which isn't very loud at all. This level is about as loud as you'd watch TV. You can hear everything going on but your ears don't get fatigued.

 

Always remember, Recording is about quality, not quantity. Its not like the DB levels you use playing out live. There was a time when studios would record the big live rigs consisting of Marshall stacks and SVT's. They don't do that any more, except rarely. Look how famous players like Clapton and Townsend first used those big rigs to record. Today they all use small combos in the lower wattage ranges.

 

Big tone doesn't come from big amps either, it comes from an illusion that makes you think they are big amps. The key is, more drive makes the amp sound smaller and less drive makes them sound bigger. the actual loudness recording doesn't matter unless its beyond the sensitivity of the mic which is huge with most recording mics. Too soft and you have a high noise floor, too loud you may distort the mic element, but that's well above the safe listening level of 120dB or more with most mics. That's like having a jet engine from a 747 in your bedroom.

 

You can take a small amp with an 8" speaker mic it clean with a tad of drive and compare it to a full Marshall stack cranked to saturation. The clean amp with the small speaker will sound bigger in a blind listening test because the sound is less compressed and has a greater dynamic range between soft and loud. The driven amp is all one volume and nothing in between. Its the dynamic range/punch that gives the sound emotion and makes for a big sound, not the gain levels. Of course there are tricks of making gained guitars sound big but that mostly comes from the bass and drums sounding big in comparison to the guitar.

[r0bo01]

my reply was directed toward redjamax, who stated that that was what he'd done previously...