Rookie question about replacing 500 series PS

[knadles]

I apologize in advance if this is too on the basic side, but I haven't found an answer to my question anywhere else. Please bear with me.

I have a Radial Six Pack rack that seems to have an issue with at least one preamp/mic combo; specifically my Telefunken TF11 and a brand new Avedis MA5. This specific combination outputs a rather loud oscillating thump that makes it absolutely unusable. Placing the MA5 in my CAPI rack (with floor box PS) eliminates the issue. For the record, I don't have this problem with any other pre or any other microphone, so I don't know exactly where the problem lies. However, since the Avedis seems above reproach and the mic works fine, my *guess* is that the line lump power supply on the Radial is somehow not keeping up with the Joneses.

I'm pretty married to db25 connectors to the patchbay at this point, so rather than replacing the whole Radial rack, I wonder if I can just replace the power supply. Obviously, I can simply order a new Radial supply, but if this is a design issue, it won't solve my problem, and it would cost a hundred bucks to find that out.

So I'm looking for other options. I realize that whatever I get, I would need to rewire the connector because Radial uses a non-standard XLR pinout, but that's not particularly intimidating. I built my CAPI racks and PS myself, so I can muddle through a simple soldering operation. (I can't get another CAPI floor box because these days they seem to be in stock for about five minutes every six months.)

My question: Given that, does it make sense to buy something like the BAE Bi-Polar PS and wire it to work with the Radial? Or am I asking for some kind of trouble I haven't anticipated? The BAE has a four-pin XLR and the Radial a five, but I assume I can just tie the grounds and make sure the pins are correct and all should be well, right?

Or alternatively, does someone else make an after-market 500 series PS that could easily be made to work with the Radial? It looks like I could construct a supply myself using several JLM kits, but that's a little more DIY than my experience level allows. In any event, I'm working on a project and would like to get things up and running sooner rather than later.

Any thoughts? Thank you,
Peter

 

[sodderboy]

Does it work normally with the mic if it is the only module in the Six Pack?
If so, re-load modules (power-cycling off-on of course) one at a time until the issue happens, indicating that indeed there is not enough current capability.
Also make sure it is not interacting with a specific module next to it when in the Six Pack, or in a specific position. You want to rule-out any interaction issues. And if it works in a different rack, maybe leave it there.
If it is a current issue, then a higher current power supply is in order. Any differences in connector pinout wiring have to be absolutely determined first before installing something new, and then the rack tested with no modules in it to make sure the PS is connected properly.
Mike

 

[knadles]

Good thoughts. Thank you. I didn't think to try them one at a time.

I did hear from Avedis, who had some opinions on his experience with the Radial rack, and also from someone at Telefunken, who said that a weak 48V supply could cause an oscillation issue with the mic, so I'm continuing with my "blame" on the Radial. I took a look and they may have improved their power supply...at least they now use the same unit CAPI sells for those who don't want to build their own, so it seems I'm honing in on the issue.

Thanks!

 

[ccaudle]

a weak 48V supply could cause an oscillation issue

Shouldn't that be easy enough to check with a DMM? Phantom power loads are usually relatively constant, I would not expect something like transients causing short drops to be much of a problem.

 

[RoadrunnerOZ]

Some mics are drawing more from phantom these days - had an issue with a mic popping and dropping in and out - turns out the inbuilt Pattern Status LED in conjunction with the inbuilt preamp was dropping the phantom voltage at the XLR to 16V. Solved the problem by dropping the value of the phantom feed resistors. Check the phantom voltage at the mic - just take the shell of one of the mic lead XLR’s to access the pins.