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Author Topic: Upgrade / Replacement for the Nady CBM-40 phantom power adapters?  (Read 2034 times)

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Offline Sunday Driver

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So since mid 2008, I've been running ATU853 > Nady adapters > PS-2 > R-09HR, and for the most part have been very pleased with the results. However, one thing I've noticed on some of my tapes is a very slight amount of distortion in higher volume parts. You have to listen pretty closely to hear it, but it's there. I really think this is caused by the Nady adapters, which is the lowest quality piece of my gear at the moment. So my question is, are there any higher quality alternatives to these things? All they're doing is taking the 48 volts of phantom power and converting it to about 10 volts of supply voltage. I'm thinking for something so simple, there has to be something out there of that does a better job of this than the Nady adapters. Thanks for any reply.

Offline Sunday Driver

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Re: Upgrade / Replacement for the Nady CBM-40 phantom power adapters?
« Reply #1 on: May 22, 2011, 08:48:16 PM »
Thank you as always, mshilarious, for your response. I'm very much aware of the inefficiency, and would LOVE to get rid of the adapters and PS-2 but I never found anything comparable. Last year I purchased  a LittleBox from you  to replace them, but for some reason the Audio Technica U853s that I use ran too hot for your box and overloaded the input on the Edirol. In fact, you and I had an email discussion exactly a year ago about this, and never really came to a conclusion on what happened. That particular LittleBox is now in the good hands of another taper that has put it to better use than I could.

I see you now have a "Tinybox". That box can have a "0db" setting to add power and NO gain at all, correct? If so, that may be a solution to my problem.

Offline Sunday Driver

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Re: Upgrade / Replacement for the Nady CBM-40 phantom power adapters?
« Reply #2 on: May 22, 2011, 10:58:30 PM »
Yea, I remember you saying Littlebox emits 12db of gain automatically just by plugging the mics in. In hindsight, I really wish I knew about that before I bought the box, because when you run mics that run fairly hot on their own, +12db can make a big difference.

Offline Todd R

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Re: Upgrade / Replacement for the Nady CBM-40 phantom power adapters?
« Reply #3 on: May 23, 2011, 11:33:28 AM »
From a quick search on guysonic's website, from his testing the R-09 can take a +16dbV signal and the r-09HR can take a whopping +28dbu (not bad for a little handheld!).

On that basis, it's hard to see that the distortion is coming from the littlebox>R-09HR part of the chain.  Are you sure that the sound you're hearing isn't just how the U853's sound, or that the U853 pair you have isn't "broken" or out of spec? ???

I've used much hotter mics with my littlebox (e.g., my Beyer mc950's with a sensitivity of -28dbV), coupled to a Sony D50 that has a lower max input than the R-09HR.  Even at loud shows, I've never had any distortion from the LB>D50 chain, and that was with 20-25db of gain on the LB, not the minimum of 6db.
Mics: Microtech Gefell m20/m21 (nbob/pfa actives), Line Audio CM3, Church CA-11 cards
Preamp:  none <sniff>
Recorders:  Sound Devices MixPre-6, Sony PCM-M10, Zoom H4nPro

Offline Sunday Driver

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Re: Upgrade / Replacement for the Nady CBM-40 phantom power adapters?
« Reply #4 on: May 23, 2011, 11:43:17 PM »
I don't want anyone that stumbles on this thread to get confused, so I'm going to explain the back story here. When I first received the Littlebox, I tested it out at home with my mics (AT U853) and main recorder (Edirol R-09HR). Everything functioned normally, so I proceeded to tape a show shortly after with it. I was maybe 10-15ft back from the stacks for this first recording, and again just like at home, everything functioned normally even considering the loud ear drum crushing environment. I had the Edirol's gain at about 40 if I remember correctly, and had even added some gain from the Littlebox. There were no issues with distortion at all.

So, thinking everything was OK, I attempted to tape a second show with the same gear. I used just about the same settings as the first recording. (Edirol at 40 with some gain from the Littlebox to get levels of about -6 to -3db on the recorder's meter.) Keeping in mind that I changed no settings during the show, the first half of this recording sounds perfect, while the entire second half is almost entirely distorted. What baffled me the most is that I never managed to get the preamp to work properly again after this show. I tried new batteries....I tried the XLR inputs with the power adapters...I tried swapping the Edirol out for my iriver H120 and Sony RH1....I also tried my other mics (Sennheiser MKE40). Every time, I would simply talk into the mics, and the Littlebox would only output bursts of static/distortion. My Littlebox had a separate 1/8th audio out so it wasn't even necessary to plug it into a recorder to hear the sound it output. This was the reason why I was somewhat convinced this issue had nothing to do with the recorder.

So long story short, I sent the box back to mshilarious, who kindly took a look at it and gave it a 100% clean bill of health. He also generously sent it back to me with mic attenuators to try, but they didn't fix the problem so I gave up, and reluctantly passed the box on to another taper on the board who is still using it to this day without issue.

And lastly but most importantly....
I don't want to discredit mshilarious's preamps in the slightest. When you see of these units up close, you instantly recognize the vast amount of time and personal dedication that went into building it. And the sound quality speaks for itself. I would highly recommend his line of preamps to anyone. Whatever happened in my case was an isolated incident that was most likely my fault in one way or another.

OK, I hope that clears things up.

Offline Sunday Driver

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Re: Upgrade / Replacement for the Nady CBM-40 phantom power adapters?
« Reply #5 on: May 24, 2011, 11:03:34 PM »
Do you know...I actually built my own three wire battery box before I purchased the PS-2. It was a mess of solder and hot melt glue, and didn't even make it through one show before one of the channels started shorting out.  :) The sound quality was pretty good, but the PS-2 sounded much better.

Anyway, the next thing to try is the "resistor mod". Lots of info around here about it. The goal will be to run mics > recorder.

Offline Sunday Driver

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Re: Upgrade / Replacement for the Nady CBM-40 phantom power adapters?
« Reply #6 on: May 26, 2011, 11:02:36 PM »
I think we're talking about two different things here. I built my battery box based on the schematic that is attached to this post. What that does is give 9 volts for the FET drain and 4.5 volts for the FET source, which is actual the same thing the PS-2/adapters are doing albeit in a much less efficient way. I more or less assumed your preamps were providing power in the same way as shown below, but maybe I'm wrong!

The resistor mod that I was talking about is just something that could go in a cable- the resistor sits between the audio cable and shield before the cables terminate at the miniplug. The value of the resistor depends on the amount of power being fed to the mics. From what I can tell, it looks like Chris Church discovered this.

If I misread your post, then I apologize. But I'm not sure how the resistor hack / battery box that I described go hand in hand.

 

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