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PROBLEM SOLVED - new thin cable DPA 4063 has RF problems


RadoStefanov

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Block 21 for me. I have two of the suspect DPAs and having not really used them when this problem surfaced (other than routine checking that they worked) I have not experienced the problem. As for Billy's recount of the history of the rfi problems (Schoeps, Sanken, etc.) and Zaxcom wireless, this was the whole reason I went with DPA lavs in true first place. Never had ANY rfi problems up until this current event reported first by Rado. This is why it is so troubling that NEW DPAs are having a problem.

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have used block 33 and then 608-638 with no problems with my 6 old spec 4063s.

ordered 4 more to accompany some new transmitters, but had held off wiring them as this came to light before they arrived. at the request of the dealer i bought them from, i wired one and it had the same rf issue. it would change depending on where i had the cable and where i held it, but still present and unusable.

so i have returned the new microphones in anticipation that DPA will solve and rectify the problem. though am not foolish enough to hold my breath hoping that it will be a quick fix.

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I'm guessing it will be a pretty simple fix.  Since DPA's had always been immune to AM RFI (Digital radios, video transmission, and interference from neon lights are all forms of AM) they must have made a change in the latest batch.  Once the figure out what is different that should solve the problem.

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So if Schoeps, Sanken, DPA (and others?) all have a problem with rfi but only with Zaxcom transmitters, shouldn't it be Zaxcom who have to fix it?

The design changes implemented to accommodate digital transmitters vastly improved the RFI rejection for all of the above mentioned microphones. Schoeps mics had much more susceptibility to rfi before the re-design, as did Sanken. I believe, as well, that the current problem with DPA did occur with Lectro transmitters, so it is not exclusive to Zaxcom digital transmitters (again, reading Billy's post, AM modulation produces the problem more easily). It is not a Zaxcom problem because the original DPA lavs worked flawlessly with Zaxcom transmitters for years and it was only after DPA changed (something) that the problem surfaced.

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So if Schoeps, Sanken, DPA (and others?) all have a problem with rfi but only with Zaxcom transmitters, shouldn't it be Zaxcom who have to fix it?

 

No. If a microphone can pickup RF and convert it to audio it is the sole responsibility of the microphone manufacturer to fix their microphone so it only responds to audio frequency not Radio frequency.

 

Glenn

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[snip]

I believe, as well, that the current problem with DPA did occur with Lectro transmitters, so it is not exclusive to Zaxcom digital transmitters (again, reading Billy's post, AM modulation produces the problem more easily).[

snip]

 

Hi Jeff,

I'm not aware of DPA-Lectro interaction. In any case, I agree that it is a DPA problem. As a pro company,  I'm sure DPA will solve it.

Best Regards,

Larry Fisher

Lectrosonics

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Larry, I could very well be wrong about the Lectro report --- somewhere in the middle of these reports I thought I heard that a Lectro user was getting cell phone-type interference while using one of the new DPAs. I'm sure that the problem relates much more significantly to digital wireless and I'm also sure that DPA will sort it out.

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Larry, I could very well be wrong about the Lectro report --- somewhere in the middle of these reports I thought I heard that a Lectro user was getting cell phone-type interference while using one of the new DPAs. I'm sure that the problem relates much more significantly to digital wireless and I'm also sure that DPA will sort it out.

Hi Jeff,

That certainly is possible and probable. Since the AM signal from the cellphone would be demodulated in the mic head itself, the innocent transmitter has no choice but to transmit it.

Best,

Larry F

Lectro

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Please, let's stop trying to figure out whose problem it is. DPAs have performed beautifully and flawlessly with Zaxcom transmitters for many years --- I started using DPA lavs because the others had too many intermittent and unpredictable problems with digital wireless transmitters. Recently, something changed with DPA and problems showed up, rfi problems for the very first time. I'm sure this will be sorted out and I think there shouldn't be any more energy expended trying to figure out who is to blame or who should fix it.

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Please, let's stop trying to figure out whose problem it is. DPAs have performed beautifully and flawlessly with Zaxcom transmitters for many years --- I started using DPA lavs because the others had too many intermittent and unpredictable problems with digital wireless transmitters. Recently, something changed with DPA and problems showed up, rfi problems for the very first time. I'm sure this will be sorted out and I think there shouldn't be any more energy expended trying to figure out who is to blame or who should fix it.

I too think that DPA will probably sort it out. And I'm sorry that I forgot that the two words "Zaxcom" and "trouble" in one sentence will invariably lead to trouble. ... For the poster.

Anyway, I shouldn't've said Zaxcom anyway (perhaps) but digital transmitter.

This is not about a blame game at all. It's not about DPA, either (for me). I was interested in the technical aspect, why mics, any mic (that's why I mentioned my Schoeps) would at times be more susceptible to RFI than at other times. Sure, this particular model of DPA has more pronounced problems, but I am mostly curious about the apparent fact (this is only my own experience and from what I've read) that RFI occurs more easily when the mic is connected to a digital (or digital hybrid) tx.

Hence my question about using the DPA mic without a tx

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but I am mostly curious about the apparent fact (this is only my own experience and from what I've read) that RFI occurs more easily when the mic is connected to a digital (or digital hybrid) tx.

Hence my question about using the DPA mic without a tx

I think Billy Sarokin, Glenn Sanders and Larry Fisher have already explained the nature of RFI, AM modulation, FM modulation, digital transmission and so forth.

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"but I was asking about those which are causing problems "

many are using them without knowing that they may, in your mind, be "troubled"...

 

" I was interested in the technical aspect, "

it is typically very technical,

while in this case, it may be the thinner cable not shielding adequately,

would you feel better if I told you that the transverse bypass FET drain capacitance value was a couple of picoFarads too high for the cables shield impedance  ??

the bottom line is: because CRAP happens...

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I think Billy Sarokin, Glenn Sanders and Larry Fisher have already explained the nature of RFI, AM modulation, FM modulation, digital transmission and so forth.
Jeff, I don't know why you don't want me ask this question? Maybe you don't like my ignorance, but that's fine, you don't have to. But I do feel as though my question is valid one, which as yet does not appear to have been answered: Why are microhones more susceptible to rfi when used with a plug-on tx, but less so when cabled? That's all, nothing devious, no manufacturer bashing, nothing. Just curiosity. You mentioned the cellphone's rfi, Jeff. This will occur only when the mic is on a zx. This same phone will not cause rfi when the same mic is on a cable. Is that not a curios fact, worth inquiring about?
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" I don't know why you don't want me ask this question? "

you are incorrect in that conclusion, I suspect JW is saying about what I say: it has been discussed thoroughly already.

 

" Why are microhones more susceptible to rfi when used with a plug-on tx, but less so when cabled? "

that can be difficult to say, as there could be numerous and various reasons, -but one is certainly: proximity-

as well as the fact that your "more susceptible" observation may be flawed.

There is plenty of Physics out there for all sorts of issues!

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