Ribbon mic, build in a preamp or not

[microx]

Just got me of the Thoman/Nady type ribbon mics. I have in the past fried the ribbon in a mic by plugging it into phantom 48v. My desk has a global switch for 48v so murphys law says one day it will happen again.
Ribbons have rather low output so I thought one way round this would be a preamp built in the mic. this would block the DC and raise the output of the mic to be more in line with other types. Any suggestions.
Steve

 

[clintrubber]

This sounds good, looks just like what the active Royer is doing.

 

[clintrubber]

I have in the past fried the ribbon in a mic by plugging it into phantom 48v.

The Thomann/Nady has a TX I understood, but don't know how much this differs in practice w.r.t. protection against phantom.

 

[microx]

+The tranny does not give protection, rather it causes the problem by stepping down the phantom to give a heavy current through the ribbon. To be exact it's the discharge of the blocking caps in the mixer input when the mic is plugged in (IMHO)
Steve

 

[bassmec]

Dear All
I think that ribbons sound best with a dedicated valve pre amp normally using three RCA 1620 valves. It will have a balance line transformer in the output so no problem. I dont think the results will be good enough to put a U87 back in its box. Most IC Pre Amps are an insult
to a good ribbon.
Regards Mark

 

[microx]

Hi Mark and welcome. I am just trying to avoid the previous accident by building something into the mic to isolate it from the phantom supply. While it's true that I.C. preamps can be coloured something simple with bipolars should be pretty nuetral.
Steve

 

[mshilarious]

I've bought the parts for buttachunk's phantom blocker here, but it will be a couple of weeks before I get around to banging it together:

http://www.groupdiy.com/index.php?topic=30103#30103

 

[Rossi]

I accidentally plugged my Thomann Ribbon into my preamp, and when I powered on the pre, phantom power was engaged. It did not fry the ribbon; the mic still works fine.

The tranny should theoretically block DC if everything is wired as it should. The only problem is the powering on and powering off. Without power ramping you might still harm your ribbon. I would also recommend closely matched phantom power resistors. I'm not exactly sure bad matching actually hurts the ribbon, but the extra expense is miniscule. No need to take risks.

The active Royer Ribbon uses a high ratio transformer for voltage gain, the active component is a source follower stage for low impedance output and current gain. Interesting concept. It's described on www.royerlabs.com

 

[microx]

The tranny will of course not pass DC. Problem comes when you plug or un-plug, the pulse caused if one leg makes or breaks contact before the other flows through the tranny and is stepped down in voltage but up in current. The ribbon I fried developed a burn spot near one end and fell to bits when I touched it. It was a re-ribbon I had done so I just did it again.
Steve