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Aston Stealth not working

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Re: Aston Stealth not working

Postby Sam Spoons » Mon Feb 22, 2021 4:01 pm

Phantom power specs have not changed ion the recent past (last 30 years at least) it should measure a voltage between 1&2 and 1&3 and 0VDC between 2&3.
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Re: Aston Stealth not working

Postby Hugh Robjohns » Mon Feb 22, 2021 4:37 pm

alansalty wrote:i'm on my third Aston Stealth now and still haven't got it working. I think we can be pretty sure now that it isn't the mic.

That would seem increasingly likely... :lol:

I have a 12 year old focusrite saffire audio interface which successfully supplies phantom power to my condenser mic.

Some mics are much more tolerant of low phantom volts than others...

I have read in a highly respected music magazine that the input on the power supply should be reading 46 - 52v across pins 1/3 and 2/3.

Close... The off-load voltage (with no mic plugged in) should be 44-52VDC measured between pins 2-1 and 3-1 (negative on pin 1, positive on pins 2/3).

Mine is reading a bit less, about 30v according to my rather old analogue meter, and only between pins 1/3 - not 2/3.

There should be no voltage measured at all between pins 2-3.

30V between 3-1 (and presumably 2-1) -- if measured off-load (with no mic connected) -- implies a broken phantom supply within the preamp.

However, if you measured it with the mic attached it is probably fine as the voltage on the cable to the mic will always show a reduced voltage once current is flowing. So we need to be clear on exactly what your measurement conditions were.

Is it possible that phantom power standards have changed, so that my old interface is out of date?

No. The phantom standard has been unchanged since the mic 1970s. And Focusrite have always made gear that complies to the standard (AFAIK) -- some lesser manufacturers have offered sub-standard phantom supplies (15V is not uncommon on some cheap budget gear). So your interface isn't out of date... but it could possibly be failing.

Subject to confirmation of your measurement conditions, it looks likely that your interface phantom supply is poorly.

If that is the case, you could:
(a) have the interface repaired
(b) buy a new interface
(c) keep the poorly interface and buy a separate phantom power unit

If (c), you can buy stand-alone phantom power units that are either mains or battery powered and simply plug in between the mic and the preamp input. You'll see plenty on a google search. They typically range from £20 up to £150... I'd avoid the very cheapest! You can get single and dual channel units too. ART seem to make good quality reliable products...

If you buy from Amazon you could try it to see if that cures your Stealth problem and return if not!
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Re: Aston Stealth not working

Postby James Perrett » Mon Feb 22, 2021 11:52 pm

alansalty wrote: I have read in a highly respected music magazine that the input on the power supply should be reading 46 - 52v across pins 1/3 and 2/3. Mine is reading a bit less, about 30v according to my rather old analogue meter,

It may be worth saying that analogue meters will load the circuit under test more than digital meters so, with the cheapest analogue meter you could buy with an input specification of 1k ohms per volt you would expect a reading on the 50V range of 42V for a 48V phantom power voltage thanks to the series resistor on the input. A better meter will show a higher voltage - something like an Avo model 8 with an input spec of 20k ohms per volt would have an input impedance of 2M ohm on the 100V range which would read 47.8V on a 48V phantom power supply.
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Re: Aston Stealth not working

Postby CS70 » Tue Feb 23, 2021 10:02 am

alansalty wrote:i'm on my third Aston Stealth now and still haven't got it working. I think we can be pretty sure now that it isn't the mic.

Yeah, already two broken ones in a row was very unlikely.

It’s a dynamic with an added preamp, so it should work without phantom power (with less output).

So it should be as simple as plug it in, turn up the gain of your interface until you see signal.

If that doesn’t happen, there’s something in your cable, routing on the interface or routing on the DAW which you aren’t aware of and it’s tricking you.

Note that the sensitivity in passive mode is 1mVolt/Pascal average (vs 150 mV/Pa in active mode). That is less than a sm7B, so you will need to crank the gain a lot in passive mode, probably all the way to the top (and you probably won’t get a pristine signal with the interface preamps, but it’s just to see that the signal passes thru).

Also sing loud and very near the mic - like in a few millimetres.

Once you see that it works in passive mode and you know the routing is correct, bring the gain to zero, turn on the active mode (I.e. phantom power) and try.

If that doesn’t work there’s either something off with the phantom power, or your cable doesn’t pass it right. Can be simple things as pins in the XLR male plug on the cable not up to spec, and not making good contact with a specific microphone female socket (while working with another).
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Re: Aston Stealth not working

Postby alansalty » Thu Feb 25, 2021 5:16 am

Problem solved. Thanks to PMT. I have been powering the audio interface from the computer for so many years that I had forgotten there was a mains adapter I could plug in. Mic is getting enough phantom power now.
Thanks to everyone for their help.
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Re: Aston Stealth not working

Postby Hugh Robjohns » Thu Feb 25, 2021 11:12 am

:thumbup: its always the simplest things we overlook. :-)
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