XLR to 1/4 inch jack..
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. |
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...1538159&sr=8-5 |
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 |
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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! |
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Louis |
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Louis |
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! |
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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. Quote:
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/a...%20Chapter.pdf Quote:
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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. |
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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/ItemI...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. |
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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. |
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