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Location: Tampa, FL | Never paid much attention since this did not seem to be a huge issue with my Adamas, or I did not recoginze it as such. But now a question for the EE's out there or anyone that has some detail surrounding phantom power and it's implication in the Ovation world.
I've been through the archives and read the various postings about P-Pwr, yet I still seem to have an unanswered question or five. This weekend I tried to used my 2005 with the church PA and could not get things to work (naturally I left this detail to the last and so ran out of time before I could get things working). Fortunately, I recently changed my 2005 to medium strings. I was directed by our choir director to ease off on my volume even as a straight acoustic so the PA would have been a little excessive. But should I need it for fingerstyle it'd be nice to have it work. So here're the questions.
How's the Phantom Power work? What voltages and what polarities are present on the pins (is it DC or AC)? What is the purpose of the pin 1 (neutral?) to ground? Doesn't this contribute to noise pick up in the line? Perhaps not if the audio freqs involved do not have the transients necessary to exploit some of the potential ground loop problems introduced in this kind of design. Any help or guidance here would be appreciated.
Thanks,
R. |
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Posts: 4413
| The last time this came up it turned out that 48v phantom power worked fine with no cooking smells coming from the preamp. I think Waskel, Noah and AFG all tried it out - but get one of them to confirm before you try. |
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Location: Tampa, FL | I know it is supposed to work and in one of my church gigs it works without a hitch. I get the little yellow light and everything. This church was set up by an acoustic professional and they tend towards doing things 'pricey but right'. My other gig is a little lower budget and a little more 'stuck together' but it is also my main venue. It is in this environment that I am courious about the detailed workings of phantom power. Even if someone could point me towards reference documents I'd be glad to work it out on my own. Problem is, I've only seen anecdotal information to date. Think I'll go fishing out on google and sees what's out there...
Although, often google can be worse that anecdotal :rolleyes: |
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Posts: 604
Location: Tampa, FL | AFter the breifest search my questions appear to be answered.
+48VDC appears to be applied (through limiting resistors) to pins 2 and 3 as a common mode voltage. This +48VDC is referenced to earth ground, which may or may not be the same as pin 1. It would appear that there is no problem connecting pin 1 and shield as they should be roughly identical versions of the same thing anyway. Not sure why the OP-Pro needs an explicit connection in the connector. Anybody got thoughts on that one? It could just be a case of "you gotta make decisions sometimes and this is what the mothership decided." |
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Posts: 1300
Location: Madison, Wisconsin | ChatMan,
You can do without the "special" cable by just inserting a 1/4" plug into the 1/4" jack whild using a XLR cable. It activates the preamp. I keep a right angle plug in my case, with no wires attached, jus for that purpose. |
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Posts: 604
Location: Tampa, FL | It is now an addition to my guitarsenal as well. But does this mean I am running off battery or phantom? I am pretty sure there is phantom power available, but may not be used if the proper reference points are not connected (e.g. pin 1 to shield). |
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Location: Warren,Pa. | When you use a regular XLR cord, the preamp doesn't receive phantom power. When you plug in a 1/4" plug, it connects the battery to the preamp. The tuner (if you have one) works only off battery power. Interestingly, if you're using a regular XLR cord AND push the tuner button the battery will power the preamp for the 60 seconds that the tuner stays on. I have had the nerveracking experience of having to play like this for a few minutes till things got figured out |
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Location: closely held secret | Ok. One more time. :rolleyes:
If you use 1/4" you are on battery.
If you use XLR with a 1/4" jack plugged in as well, you are on battery.
If you use XLR only, AND there is phantom power provided (usually from the mixer) AND you are using a "pin 1 to shell" XLR cable, you are NOT on battery, unless the tuner is on.
The easiest way to tell if you have a correct XLR cable is to plug it in, then turn on the phantom power. If the light on the preamp comes on and your guitar is amplified, all is well.
If you happen to be thinking about this when it is not 2 minutes before worship, performance, etc., You can check a cable with an ohmmeter. If you put one probe in the pin 1 hole, or on pin 1, and touch the other probe to the shell (the outer casing of the XLR) you should get continuity (0 resistance). If you do not, this cable will not work for you. If you do, check it against the shells at both ends. If you get continuity at both ends and between both shells, it's your lucky day.
You can also go buy one. Or you can take one that doesn't work (if it has a metal shell) and solder a jumper between pin 1 and the ground inside the shell.
Have fun. Anymore questions, I'll be in tomorrow... |
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Location: Tampa, FL | Well Waskel,
A little condescending but no matter, reminds me of my early Unix days. Goes into the mindless factual side of things well enough. Clarifies the combined use of 1/4 inch and XLR. But does not address at all the question of why do you have to do this in the first place? Is there a circumstance where pin 1 SHOULD NOT be connected to ground? Presumably there is, otherwise why not just make the connection internally in the preamp and be done with it? |
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Posts: 5750
Location: Scotland | Originally posted by ChatMan:
Doesn't this contribute to noise pick up in the line? Perhaps not if the audio freqs involved do not have the transients necessary to exploit some of the potential ground loop problems introduced in this kind of design. Any help or guidance here would be appreciated.
Thanks,
R. The whole point of a 3 conductor cable such as an XLR or TRS jack is to enable a balanced signal. I explained the concept of balanced signals some time ago (check the archive) but in a nutshell it is designed to cancel noise by using phase inversion, which it does very effectively. It also provides a signal which is around 6dB hotter than unbalanced line level. Occasionaly ground loops occur. This is why direct boxes have a ground lift function, which disconnects pin 1. The idea of an onboard XLR output is to eliminate the need for a direct box. I have yet to encounter ground-loop problems with XLR-equipped Ovations, but in that event I would simply switch to the unbalanced output through a DI box & hit the ground lift. |
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Posts: 1300
Location: Madison, Wisconsin | Quote from the Optima Owners Manual
Phantom Power
Here's another unique Ovation feature: If your mixer or acoustic guitar amp has phantom power available (a voltage source that is superimposed inaudibly on the same wires as the signal), using the XLR connector on the guitar (with any balanced XLR cable) will direct this voltage to your preamp. This will dramatically extend battery life, as only the tuner will require battery current. Even without a battery, using the phantom powering option will ensure that you're getting the ultimate response and output from your preamp. Please note however, that the tuner will not function without a serviceable battery installed in the guitar.
According to this, you don't need the 1/4" plug or the "special" XLR if you have phantom power. |
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Location: Tampa, FL | Willard,
The issue is that there is no universal standard for what constitutes 'Phantom Power.' Just some more or less widely accepted conventions. Because of this lack of a Standard, there are multiple ways in common use for providing phantom power and not all of them are mutually compatible. Ovation's description of using the Optima preamp may be fine in most environments, but due to the lack of a Standard, there may be some configuration out there that won't work.
My Adamas works fine in all the venues I play in. In all casea I use the house cabling. My 2005 ES works in one and not the other, which was the motivation for this thread.
To summarize, my third post in this thread along with Paul's post covers all the technical bullet points I originally asked. The other posts tend to describe various effects resulting from these design condsiderations. Waskel succintly describes the interaction of XLR and 1/4 inch modes of supplying power.
Thanksto all that contributed.
R. |
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Location: closely held secret | To Chatman and all, my apologies. After reading my post from yesterday afternoon, yes, it was very condescending. I can only say it was at the end of a busy, stressful, frustrating day and beg your forgiveness.
Master T is right about ground loop problems. He's a smart man, listen to him. He explains the whys and hows better than I ever can.
Being able to use the XLR is important to me, important enough to drill a hole in my guitar and wheedle a wiring harness out of the Mothership. The difference between 100' of high imp. compared to low is audible even on our church's decaying sound system. The ability to use phantom power is not as important, but extending battery life is a nice plus. I own a good DI box (which also runs on phantom power!) but it always seems to be needed elsewhere.
I don't know why the preamps are wired the way they are. I can only assume they had good reason. I know that condenser mics which require phantom power work with cables that my O does not.
Bill, they put the important stuff in the part above the part you quoted (why? who knows?).
Lo-Z Connection
If you have chosen to connect the guitar to a low impedance mixer or amp, there are a couple of options. If you have a conventional, Lo-Z balanced line XLR (or mic) cable, connect the guitar to the amp/mixer and insert a ¼” “activation plug1” into the phone jack on the guitar. This plug connects
the battery’s current to the preamp circuitry. If you have purchased an Ovation Lo-Z XLR Activation Cable2, simply connect your guitar to your amp or mixer and play! So if you have an Ovation Lo-Z XLR Activation Cable2 you have the right cable. Or you can use one which has pin 1 connected to the shell. Same animal.
Again, please forgive me for my attitude yesterday. I get cranky on Mondays. I usually get over it by Friday afternoon. :rolleyes: |
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Location: NJ | (bitch.) |
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Location: Scotland | Originally posted by ChatMan:
Willard,
The issue is that there is no universal standard for what constitutes 'Phantom Power.' Just some more or less widely accepted conventions.
R. Devices that operate on phantom power can generally tolerate and work happily on anything between 3 to 52 volts DC. The higher the voltage, in the case of condenser mikes usually results in improved sensitivity & headroom. (Some Microtech-Geffel mikes operate at 85V, they use phantom power to drive LEDs, and tiny internal solar cells to convert the light from the LEDs to voltage - very clever) The actual delivery of phantom power is absolutely "standard" throughout every last piece of equipment out there. It has to be.
The exception to this rule may be the current Ovation pre-amps. The need for a cable modification is totally amateurish on a supposedly pro piece of kit. Noone needs to go fishing for a specific cable to make a preamp work, it's a joke and needs to be addressed. I'm guessing here, but I think the ground to shell short is so the Ovation preamp is aware that phantom power is present. This was not neccesary on the Optima. |
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Location: Tampa, FL | I stand corrected. Poor phrasing on my part, but I would suggest that if the delivery is absolutely "standard", then the quirky sensing of same might be interpreted as possibly flawed. |
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Location: Scotland | Nope, it's totally flawed. |
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Location: Tampa, FL | Instead of offering an XLR "enablement" (or whatever term is used) cable, Ovation should offer an XLR 'dongle' similar to what some companies use to license their software. In this scenario, you could have a M-F adapter plug that would be inserted between the XLR cable from the PA (or whatever) and the guitar. It would function as a passthrough for the signal pins but would short the appropriate connections for Phantom operation. This technique was commonplace back in the old RS232 days. Everyone enjoyed it so much then, here is an excellent oppportunity to resurrect that piece of conceptual technology. I made a good living connecting serial equipment back in the day.
Alternatively, the mothership might consider a design upgrade from the OP-Pro to the Optima (backward so we might progress, sounds like a skit for Firesign Theater). |
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Location: Scotland | Originally posted by ChatMan:
Ovation should offer an XLR 'dongle' similar to what some companies use to license their software. Beavis: hehehehehe, he said "Dong"
Butthead: Shutup fartknocker etc etc. |
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Posts: 604
Location: Tampa, FL | Pre-emptive "anti-Cliff' strike.
In the preceding ChatMan post M-F refers to Male-Female interface connections. Although I somehow doubt that this explanation is going to help. |
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| Jesus Help me! I had to copy these threads so I could go over them again when I need them!
Great stuff though.... another thread to help some of us get around the learning curve.
Thanks
RAndy |
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Posts: 1300
Location: Madison, Wisconsin | In the preceding ChatMan post M-F refers to Male-Female interface connections. Although I somehow doubt that this explanation is going to help. They were mother f*cking interface connections as well. |
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Phantom Power - yet again?
