PDA

View Full Version : XLR to 1/4 inch jack..


steveyam
11-17-2011, 03:46 AM
Ok, I'm connecting my Boss GT-10 output to an RCF powered speaker. The output of the Boss is 1/4 inch jack, and the input to the RCF is XLR (male or female choice). Presently, I am using an inline 'line transformer' (switchable 'low' or 'high') to connect them because it has a jack one end and an XLR the other, and in that respect, it 'does the job'. It seems to work ok, and it works best when set to 'low'. Nonetheless, IF IT IS JUST A MECHANICAL CONNECTION ISSUE (ie jack vs XLR) I would prefer to do away with the inline transformer and use a simple inline Jack to XLR converter plug (or similar lead) that just makes the connections to suit.

But! does anyone know for a fact, is it just a simple matter of mechanical connections that is best sorted by the simple jack to XLR converter plug (or XLR to 1/4 jack lead), OR, is there an impedance issue going on that is best addressed using the transformer - as I am presently. My point being, I don't want a transformer in the signal path if it is not needed to be there for want of simple mechanical converter plug or lead. I am an electronics engineer myself, but wanted the view/opinion of a knowledgable person in this field please.

mchalebk
11-17-2011, 07:58 AM
I am an electrical engineer. Won't claim to be an expert on this, but have some knowledge. I'm not sure exactly what you're using for this. I have an XLT to 1/4" TS adapter that has a transformer in it. It converts from unbalanced to balanced and solves the impedance issues. this works much better than some of the simple XLR to 1/4" adapters that don't actually do any impedance matching and don't convert the unbalanced signal to balanced.

Here's an example of what I'm talking about:

http://www.amazon.com/Audio-Technica-Audio-Technica-In-Line-Transformer/dp/B003HZQQGW/ref=sr_1_5?ie=UTF8&qid=1321538159&sr=8-5

lschwart
11-17-2011, 09:21 AM
I'm no expert, but if the output of the unit is line-level, then you shouldn't need anything but a 1/4" to XLR cable to plug into the speaker as long as the switch on the speaker is set to receive a line-level signal and not a mic-level signal.

There might be an advantage to converting the signal from unbalanced line-level to balanced line-level, so if that's what your transformer is doing, it should be fine. If it converts it to balanced mic-level, then make sure the switch on the RCF is set to "mic."

FWIW, I use a balanced 1/4" TRS to XLR cable to connect the balanced, line-level signal from the monitor out on my powered mixer to an RCF 312a and that works just fine with the speaker set to "line."

Louis

steveyam
11-17-2011, 09:39 AM
I'm no expert, but if the output of the unit is line-level, then you shouldn't need anything but a 1/4" to XLR cable to plug into the speaker as long as the switch on the speaker is set to receive a line-level signal and not a mic-level signal.

There might be an advantage to converting the signal from unbalanced line-level to balanced line-level, so if that's what your transformer is doing, it should be fine. If it converts it to balanced mic-level, then make sure the switch on the RCF is set to "mic."

FWIW, I use a balanced 1/4" TRS to XLR cable to connect the balanced, line-level signal from the monitor out on my powered mixer to an RCF 312a and that works just fine with the speaker set to "line."

Louis

Thanks Louis. Yep my RCF 310a is set to line. Thinking about it, the inline transformer is actually working back to front since it is designed to feed a balanced mic into a 1/4 jack socket. But there's no 'power' involved, so I guess it's just as happy to work the other way round ie how I'm using it now.

BTW, I have found the RCF to be incredibly accurate with great bass and very clear, hi-fi like reproduction quality. It accepts the speaker sims patches from the GT-10 and it sounds I'm playing a Marshall through a real 4x12!

lschwart
11-17-2011, 09:51 AM
Thanks Louis. Yep my RCF 310a is set to line. Thinking about it, the inline transformer is actually working back to front since it is designed to feed a balanced mic into a 1/4 jack socket. But there's no 'power' involved, so I guess it's just as happy to work the other way round ie how I'm using it now.

BTW, I have found the RCF to be incredibly accurate with great bass and very clear, hi-fi like reproduction quality. It accepts the speaker sims patches from the GT-10 and it sounds I'm playing a Marshall through a real 4x12!

You're welcome Glad that was helpful. I love my 312a. I'm still amazed to have that level of quality for the price I paid.

Louis

steveyam
11-17-2011, 10:02 AM
You're welcome Glad that was helpful. I love my 312a. I'm still amazed to have that level of quality for the price I paid.

Louis

What/how do you use your for Louis? general PA in mono?

lschwart
11-17-2011, 11:02 AM
What/how do you use your for Louis? general PA in mono?

I use it as a small PA for solo/duo shows (guitar/voice/percussion), hooked up to an A&H ZED10fx, and to amplify background vocals, accordion and clarinet for small shows with my band when the electric guitar, bass and my lead vocals and acoustic go through combo amps. I've only played out solo/duo with it a few times, but I was delighted with how it worked. Works very well with the band, too. At some point I'm probably going to get another one and start using the pair as FOH for our full PA with a larger passive mixer. They sound better than the Yorkville YX15's we now use with a powered mixer. Don't have the cash yet, though.

Louis

Butcher
11-18-2011, 04:02 PM
There is an impedance "matching" issue to always consider when connecting professional audio gear.

In order to have an efficient (and therefore good sounding) transfer of signal, the input must be rated for at least 10 times to 100 times the impedance rating of the source.

For example, a Sure SM58 sends out about 150-300 Ohms. A mix input on a mixer is rated at about 2,000 - 3,000 Ohms. There is the 10x factor.

Your pedal has an input rated at 1,000,000 Ohms (1M), while your guitar puts out probably 2,000 - 5,000 Ohms (2K - 5K). Here is the 100x factor.

The little inline lowZ to highZ transformer you have is designed to plug professional mics into guitar amps. Not sure exactly what it is doing for you in terms of impedance using it backwards.

The best approach is to pick up an inexpensive DI box (ART, Whirlwind etc.) for about $50. Run the 1/4" out of your pedal into the DI box input, then the DI box XLR output into your powered speaker or a mixer etc. That also converts the unbalanced signal into a balanced signal which will be much more interference resistant (use as short a 1/4" cable as possible).

Hope this helps!

mchalebk
11-18-2011, 07:38 PM
The little inline lowZ to highZ transformer you have is designed to plug professional mics into guitar amps. Not sure exactly what it is doing for you in terms of impedance using it backwards.

The best approach is to pick up an inexpensive DI box (ART, Whirlwind etc.) for about $50. Run the 1/4" out of your pedal into the DI box input, then the DI box XLR output into your powered speaker or a mixer etc. That also converts the unbalanced signal into a balanced signal which will be much more interference resistant (use as short a 1/4" cable as possible).


Actually, those 1/4" to XLR transformer coupled adapters work in both directions (not just for connecting a mic to a guitar amp). In fact, they are the simplest form of a DI. They work perfectly for connecting an unbalanced line out to a balanced XLR input.

Dr.Agave
11-19-2011, 12:42 AM
There is an impedance "matching" issue to always consider when connecting professional audio gear.

In order to have an efficient (and therefore good sounding) transfer of signal, the input must be rated for at least 10 times to 100 times the impedance rating of the source.



I can't think of any case where 10:1 ratio of load to source impedance would be insufficient for connecting to line level devices or a microphone to a mixer input. Even a 5:1 ratio presents negligible load to the source.

RCF doesn't quote the input impedance for that speaker, but I wouldn't be surprised if it is in the neighborhood of 10K ohms in the line input mode. The Boss GT-10 has a 2K output impedance. Assuming a 10K input impedance a 5:1 ratio of in to out is perfectly acceptable. There is no need to use a transformer.

The little inline lowZ to highZ transformer you have is designed to plug professional mics into guitar amps. Not sure exactly what it is doing for you in terms of impedance using it backwards.

It is called bi-directional reflection of the impedances. Inserting the 1/4" (high impedance) side of the transformer into the Boss, and sending the XLR side (low) reduces the source impedance seen by the speaker and raises the destination impedance seen by the Boss processor.

There is voltage change, a corollary of the impedance change.
If you want to know the theory behind it, download the Bill Whitlock's chapter on transformers, published in the Audio Cyclopedia.

http://www.jensen-transformers.com/an/Audio%20Transformers%20Chapter.pdf


The best approach is to pick up an inexpensive DI box (ART, Whirlwind etc.) for about $50. Run the 1/4" out of your pedal into the DI box input, then the DI box XLR output into your powered speaker or a mixer etc. That also converts the unbalanced signal into a balanced signal which will be much more interference resistant (use as short a 1/4" cable as possible).

That's one way to do it, and a legitimate approach, though I see no real disadvantage to connecting the GT-10 directly to the RCG speaker.

Butcher
11-19-2011, 09:41 AM
Wow, that's good to know. I keep a couple of them in my case for when singers show up to a jam session expecting someone else to amplify them.

I had wondered how he was connecting the xlr cable to the speaker because the end that connects to the transformer is the same end that usually connects to the mixer. I was hoping that we wasn't plugging into the xlr line out on the speaker.

I had never seen/read any literature or use other than mic to instrument level input.

I wish I had saved the references, but on some sound tech forums and preamp building sites I had read about the 10x-100x factor and it has really improved the sound of my setups and explained when I was struggling to get a good sound with various connections.

Thank you for the info reference, I will definitely read it. I love learning something new everyday. These music community forums are such rich sources for information.

steveyam
11-19-2011, 03:36 PM
Actually, those 1/4" to XLR transformer coupled adapters work in both directions (not just for connecting a mic to a guitar amp). In fact, they are the simplest form of a DI. They work perfectly for connecting an unbalanced line out to a balanced XLR input.

To me, as an electronics engineer, that makes sense. And, given that that is what I am currently using, and it works fine, I'm going to carry on that way. I figure it's better to use the inline trannie that takes a mono signal and converts it to an XLR balanced signal, is the best way forwards. Merely 'reconnecting' the output of the Boss (mono !/4 jack) to physically mate with the XLR balanced input of the RCF does not seem right.

steveyam
11-19-2011, 03:39 PM
There is an impedance "matching" issue to always consider when connecting professional audio gear.

In order to have an efficient (and therefore good sounding) transfer of signal, the input must be rated for at least 10 times to 100 times the impedance rating of the source.

For example, a Sure SM58 sends out about 150-300 Ohms. A mix input on a mixer is rated at about 2,000 - 3,000 Ohms. There is the 10x factor.

Your pedal has an input rated at 1,000,000 Ohms (1M), while your guitar puts out probably 2,000 - 5,000 Ohms (2K - 5K). Here is the 100x factor.

The little inline lowZ to highZ transformer you have is designed to plug professional mics into guitar amps. Not sure exactly what it is doing for you in terms of impedance using it backwards.

The best approach is to pick up an inexpensive DI box (ART, Whirlwind etc.) for about $50. Run the 1/4" out of your pedal into the DI box input, then the DI box XLR output into your powered speaker or a mixer etc. That also converts the unbalanced signal into a balanced signal which will be much more interference resistant (use as short a 1/4" cable as possible).

Hope this helps!

Re your last para; that's what the inline trannie that I am using is presently doing. No need to add extra DI units and leads.

Butcher
11-21-2011, 08:59 AM
I'm going to give that a try and a-b it with my DI box setup.

The one question I have is what kind of XLR cable are you using? The xlr end of the inline adapters are usually the female end and the xlr inputs on a mixer or powered speaker are also female. Are you using a male-male xlr cable?

Here are the adapters I have.
http://www.americanmusical.com/ItemImages/Large/p171.jpg

Also, I have often wondered why more instruments don't have built-in transformers so that you can run either XLR directly out of your guitar/bass (I play bass mostly) or 1/4" or both. I know some acoustics do this. If the circuitry is small enough to fit in those inline transformers... I may be modifying some axes pretty soon.

steveyam
11-21-2011, 09:55 AM
I'm going to give that a try and a-b it with my DI box setup.

The one question I have is what kind of XLR cable are you using? The xlr end of the inline adapters are usually the female end and the xlr inputs on a mixer or powered speaker are also female. Are you using a male-male xlr cable?

Here are the adapters I have.
http://www.americanmusical.com/ItemImages/Large/p171.jpg

Also, I have often wondered why more instruments don't have built-in transformers so that you can run either XLR directly out of your guitar/bass (I play bass mostly) or 1/4" or both. I know some acoustics do this. If the circuitry is small enough to fit in those inline transformers... I may be modifying some axes pretty soon.

My XLR cable is the standard mic cable, ie different at each end. The RCF will take either as I said in the first post; they're just parallel connections. The xlr end of my inline trannie is female. Really, the cable's gender is not an issue or a problem, I just arrange/connect it suit the plugs and sockets it needs.

Anyway chaps by all means carry on with the thread, but as far as I am concerned, I have my answers and I'm happy with the way I'm doing things. Many thanks to all.