skilsaw Posted October 24, 2014 Posted October 24, 2014 Is that enough questions? I"m new here, and this seems to be the best place for my questions. My son got a traynor acoustic amp for guitar and vocals that puts out a low level of phantom power. I understand phantom power is needed to run a condenser mic, so that is what we purchased to go with the amp. Now we are looking at an amp for electric guitar that doesn't state "Phantom power". Do we need a dynamic mic for it, or will the condenser mic work? Do dynamic and condensor mics both use the same 3 prong jacks? Can a mic be plugged in to an amp through a 1/4 inch jack? Please help me with these totally rookie questions. I'm new at this and am trying to learn fast.
Versatile Posted October 24, 2014 Posted October 24, 2014 Good questions skilsaw... Many folks hereon know, understand and use all types of mic... Many folks hereon use all types of mic without understanding their intricacies... IMX the majority of dynamic mics are 3 pin 'XLR' for direct connection to mixer/amp/PA Similar with powered condenser mics...although some are 2 pin jack... There are however, XLR into 1/4" conversion cables which can input into 'mic' or 'line' level 1/4" jack inputs which some amps have... Any guitar and vocal amp (loosely termed PA) will have a specification defining it's inputs etc V
capmaster Posted October 24, 2014 Posted October 24, 2014 The most common balanced signal connector format is the XLR 3-31 standard. Since it also is the most common of all the XLR connectors, I will call it simply XLR in the following. It is widely used for audio applications, analog as well as digital. The following is narrowed to analog only. Common rules are the following: - XLR mic inputs with switchable phantom power will accept dynamic and condenser mics as well. - When connecting or disconnecting, the phantom power source unit or the phantom power itself should be turned OFF. The volume control of the related channel must be turned down to zero or more precisely minus infinity. - Mics calling for phantom power can be operated only using inputs providing appropriate phantom power level. - Next to all amps for electric guitars won't provide phantom power capability. Moreover, mics won't sound nice through them. Their overall frequency response is rather uneven and the treble range fairly limited. - Most acoustic guitar amps will make nice vocal amplifiers, too, and are often used for guitar and vocals the same time. They will also accept electric guitar signals and transduce a "HiFi tone" from magnetic pickups. (Personal comment: This is my favoured way of practicing with all of my electric guitars.) Here are some details for your reference which I think are worth knowing. Female XLR connectors are used as signal inputs and phantom power outputs if provided. Male XLR connectors will put out a signal and accept phantom power if applicable. XLR plugs (male connectors) and sockets (female connectors) each have three contacts. 1 is shield or ground, 2 is "hot" or "up-phase" signal, 3 is "cold" or "down-phase" signal. The terms in quotation marks are common but sloppy; in fact both signals have same phase but reversed polarity. This is often assumed to characterize a signal called balanced. Again, in fact the balanced impedances (plural, for either legs) are what counts, not the voltage which is not referenced on principal. A balanced signal is not required, the balanced line is what rejects interference and improves signal to noise ratio. Withstand voltage can be a reason for referencing the signals to ground but it's not required for dynamic microphones. Things will change when using microphones or other active components like DI boxes calling for "Phantom Power". Pin 1 is used for DC current flow, and thus the signal will be referenced to ground as well. (This is the reason for the infamous pin 1 problem soluble with input transformers only, but I won't discuss it further here.) There are three different analog phantom power sources defined. They provide +12V, +24V or +48V idling voltage at a defined source resistance. The most important one is +48V and two 6.8kOhms resistors, one for each signal leg. Therefore the voltage drop during operation is 6.8V per mA leg current, respectively 3,4V per mA total load current (either legs). Both the signal legs get positive voltage, negative is connected to shield/ground and defined as 0V. Due to both signal lines being at the same potential, there is no voltage between them, hence the term "phantom". A dynamic mic won't "see" the phantom power since the coil is not connected to ground. In contrary, most ribbon mics will be destroyed in an instant when connected to phantom power. Their transformers often have a tap to ground, causing an inductive peak during connecting or switching on. This will burn the ribbon diaphragm. However, there also are ribbon mics using preamps instead of or combined with a transformer which expressively call for phantom power. Always refer to their manuals. Basically it is correct that condenser mics need a voltage for operation since the condenser has to be charged for creating a signal. However, there also is an impedance convertor which will need a power supply as well and not just for a moment of charging up. This kind of preamp is needed within electret condenser mics, too. They have a "frozen" static voltage, usually within the condenser backplate. This gave them their name "back electret microphone": The backplate material behaves as an "electret", i. e. acts as a "trap" for static electricity. Anyway, their preamp calls for phantom power although some allow for using batteries as an option. This is uncommon with "real" condenser mics. Mics or other devices using phantom power forcibly call for balanced line operation. In case they shall be connected to an unbalanced input, a transformer or - rarely used - isolating amplifier is required. Hope this helps. Feel free to ask any further questions.
capmaster Posted October 24, 2014 Posted October 24, 2014 You, Cap, are a gem. rct Thank you very much, Rct. When this topic came up, I simply thought I'd share these points here. I have to deal with it all due to running my recording gear with lots of balanced sources, XLR and TRS, connected via transformers and XLR - TS adaptors to unbalanced guitar, bass and vocal amps: http://forum.gibson.com/index.php?/topic/116109-recording-gear-pictured/
rct Posted October 24, 2014 Posted October 24, 2014 It's so hard to explain, and it's hard to say "google it". I don't have near the amount of stuff you do, but I don't need that much! Drum machine, so no mics there. Amp, cab, bass amp, and the keys are direct. So I have too many mics from when I had a crapload of cabs to mic up. On a related note, some of my 8 year old or so Behringer stuff has begun crapping out on me. rct
capmaster Posted October 24, 2014 Posted October 24, 2014 It's so hard to explain, and it's hard to say "google it". ... On a related note, some of my 8 year old or so Behringer stuff has begun crapping out on me. rct Browsing the web for infos about connectivity of particular audio gear would be hell for a newbie. One may read hours and hours even in fine documents and end up in total confusion. Then there are all the blurbs of snake oil sellers... When about Behringer, they release very few information on possible backup batteries for SRAMs contained in their units. One has to find out oneself before all the painstakingly created memory content is lost. I guess they even wouldn't specify publicly by serial number when a certain unit was redesigned for EEPROMs (flash memories). <_< I think EEPROM use is cheaper for manufacturers since some years when compared to SRAM, battery holder and battery.
rct Posted October 24, 2014 Posted October 24, 2014 Well, I haven't even looked at fixing them. A 4 channel compressor and two 15 band EQs were just humming along nicely and BAM! One side of the compressor just stopped working, same for one of the Eqs, and the other EQ started buzzing on the out side. So I lived with it for a bit, took them out, gave them to a local computer guy to see if he could salvage anything out of them, maybe even fix them I don't know. I'll find something soon, I gotta some stuff to do, need that compressor as a limiter for the keys and drum machine. rct
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