Topic: PMD661 for ambient recording

[Tronette]

I recently purchased a Marantz PMD661 from B&H, with which I have been recording with a Rode NT4 mic.  Musical performances have come out very well.

I have also been recording soundscapes and very low level sounds and am finding the 661 preamp noise unacceptable.  Would anybody be able to offer some opinion, or ranking on the following possible solutions:

1.  Sell my current PMD661 and buy one that has been pimped by Mr. Oade
2.  Purchase a SD mixpre to use on the front of my un-modded PMD661
3.  Splash out on a SD 702

Thanks!

[refrain]

3. Splash out on a SD 702, and your troubles are over... and never think about a recorder for years to come... if you have the budget... that's what I should had done with my Fostex FR2LE...

[Tronette]

Thanks for the feedback.
mshilarious, I am no expert, but have been led to believe that the nt4 has very low self noise compared with similarly priced mics and that it is a good ambient mic.  Are there any other stereo mics in the same price range with a much lower self noise that you could recommend?
I have read a lot comments saying that a stock PMD661 does have excessively loud pre's for high gain ambient recording

[tedyun]

I don't think you have to sell your current one to have it SuperMod'd. I think you can send it in and have Doug Mod it for $150. Certainly the cheapest option of the three.

I recently purchased a Marantz PMD661 from B&H, with which I have been recording with a Rode NT4 mic.  Musical performances have come out very well.

I have also been recording soundscapes and very low level sounds and am finding the 661 preamp noise unacceptable.  Would anybody be able to offer some opinion, or ranking on the following possible solutions:

1.  Sell my current PMD661 and buy one that has been pimped by Mr. Oade
2.  Purchase a SD mixpre to use on the front of my un-modded PMD661
3.  Splash out on a SD 702

Thanks!

[moooose]

Hi Tronette

most of my recordings are soundscapes and nature sounds.  Often I use a Rode Nt4, especially if I'm walking around and can't use a bulkier mic array. Imho it is quiet enough to get nice recordings even in silent, natural environments. Obviously, it is not as quiet as my AT 3032s (8 dB self noise), but on the other hand a single point stereo mic is sometimes a huge advantage.
Previously I had a SD MixPre and a Sony D50 - together with the Nt4 the combo was great - the MixPre is really quiet. Now I have a SD 702 and the results are better. But in both cases the Nt4 has always performed well. Of course, it is just my 0.02.

[DigiGal]

One final possible issue is a bad interaction between the mic and recorder's phantom power supply.  This can unfortunately happen with some portable recorders--the Tascam is bad about that, but I am not aware of any adverse reports with the PMD661.  I can't rule that out however without testing the combo.  Such noise will usually manifest itself as an unusual noise spectrum or even oscillation within the audio band.  If there is such an issue, then switching recorders may help.

Tronette,

The phantom supply on PMD661 is spec'd for 48V @10mA max, effectively 5mA per channel max.  Some mics require more current like a Nevaton MC49 for instance that draws 10mA each.

Do you know how much current your Rode NT4 is drawing?  If not then a query to Rode Support should help answer.  Another thing to try is powering the NT4 with its own internal battery although this generally adversely affects a mics performance too.  Additionally, performance may take a hit if using weak batteries.

[Tronette]

Thanks,
I have tried the same mic with two PMD661 units and recordings sound the same, so I doubt they both have in identical fault.
I will try my NT1a and see if the noise is drastically lower.

DigiGal, thanks, I have tried with and without the mic battery and can't hear any difference.

Otherwise I am a little confused..  moooose and refrain both seem to think I'll get very much quieter and clearer recordings by splashing out on a SD702, plus I like the fact that it has a huge dynamic range and a good limiter, both lacking on the marantz.

[mepaca]

Get a Sound Devices Usbpre 2 and go coax into your 661. It will then sound just like a Sound Devices recorder (dead quiet). It also has 80db of gain. I love mine.

[refrain]

For instances, the preamps on the Fostex FR2 LE are quieter than the 661, if you go naturesrecording list, you'll see that there's a lot of people using it, even with the rode stereo mic... that's my reason for buying it (also looked at the 661 at the time) but that's if you're on tight budget, otherwise nothing beats the SD stuff, only the upper cost recorders: Cantar, Deva, Sonosax or Nagra...

[tim_k]

Perhaps another thing to look into, my 661 was made very noisy by heat (within, but near the top of the operation range as quoted by Marantz). I have the SuperMod by Oade, and originally he thought it was something in the mod, but it turned out to be a problem on the main board. He worked with Marantz and they discovered a solution, Doug made the repair and now my unit is great. I mention this because even though I have a mod unit, the flaw was not part of the mod so perhaps your unit is experiencing the same thing.

[Tronette]

Get a Sound Devices Usbpre 2 and go coax into your 661. It will then sound just like a Sound Devices recorder (dead quiet). It also has 80db of gain. I love mine.

Looks good but, I understand the USB pre2 is dependant on USB power - not much good in the field...

[rastasean]

Get a Sound Devices Usbpre 2 and go coax into your 661. It will then sound just like a Sound Devices recorder (dead quiet). It also has 80db of gain. I love mine.

Looks good but, I understand the USB pre2 is dependant on USB power - not much good in the field...

its dependent on 5 volt power, not necessary to have connected to a computer.

[Tronette]

Get a Sound Devices Usbpre 2 and go coax into your 661. It will then sound just like a Sound Devices recorder (dead quiet). It also has 80db of gain. I love mine.

Looks good but, I understand the USB pre2 is dependant on USB power - not much good in the field...

its dependent on 5 volt power, not necessary to have connected to a computer.

So some kind of rechargeable USB battery would be required?

[mepaca]

This http://www.tekkeon.com/downloads/dtasht_MP3450i.pdf powers my usbpre2 and my r-44 for over 9 hours. It would probably power your 661 for even longer. It has 2 outputs. One is usb power. The other is variable between 5 and 19 volts.

[spzkt]

Tronette,

Before you run out and buy a new pre/recorder I'd suggest taking a look at the cable that came with your NT4.

The stock Rode Y cable has a 12dB pad built in which seriously compromises the performance of the NT4. You can either mod the cable or replace it. If you want to mod there are instructions on Rob Danielson's web site:

https://pantherfile.uwm.edu/type/www/audio-reports/Rode_NT-4_Cable_Mod/NT-4_CableMod-index.htm

I did this mod on the cable of an NT4 I was using a few years ago and the improvement was significant.

You won't get much benefit from the SD in terms of reducing noise with the NT4...

The self-noise of the NT4 creates an output noise of -114dB at the mic connector -- this is the output you'd get from the mic in a dead quiet room.  This is calculated from the self-noise and sensitivity of the mic.  The output noise of the mic can be compared directly to the EIN figures given on the Avisoft website.  The rule of thumb is that the preamp EIN needs to be 8dB lower than the mic's output noise to ensure that the preamp does not degrade the output of the mic.  This means that if you have a preamp with -122dBu or lower EIN, the NT4 is going to be the limiting factor when it comes to noise. Going from the 661 to a SD preamp with the NT4 will bring you small improvements in the overall system (mic + preamp) noise floor - in the range of 0.25dB.  The PMD661 preamps + NT4 will have a combined noise 0.34dB higher than the mic alone, while SD7series + NT4 will have a combined noise 0.11dB higher than the mic alone.

Anyway I'd start by fixing the cable issue if you haven't done so already.

cheers
Paul

http://soundcloud.com/offtracksound

[dream]

Before you run out and buy a new pre/recorder I'd suggest taking a look at the cable that came with your NT4.

The stock Rode Y cable has a 12dB pad built in which seriously compromises the performance of the NT4. You can either mod the cable or replace it.

That's only true for the 7 pin XLR to stereo mini jack cable. The Y-cable with two XLRs doesn't have this. Although I use a higher quality Y-cable with my NT4 than the
original Rode one, I just opened the connector of the Rode XLR Y-cable to double check this.

[spzkt]

I stand corrected.  I was using a minidisc recorder at the time, so using the y to stereo mini cable.

Even so, unless the PMD661 has faulty preamps the overall self-noise improvement from upgrading to a SD preamp is going to be marginal. The Avisoft self-noise tests include a link to a page titled http://www.avisoft.com/tutorial_mic_recorder.htm, which discusses what I was trying to show with the calcs above. The illustration in particular shows the relationship mic self-noise and sensitivity vs recorder EIN.

Where the recorder EIN really becomes important for ambient recording is when the mics have low output noise. The AT3032 and it's replacement the AT4022 are pretty popular mic for nature recording, and the AT3032 was independently tested as having a self-noise of around 8dB(A) and a sensitivity of 20mv/Pa. This gives an output noise of -117.8dBu(A) which makes it a fairly demanding mic in terms of preamp self-noise, and these mics require a recorder with an EIN -126dBu(A) or better.

cheers
Paul