Mic Upgrade Versus Preamplifier

[Gweeble]

Unfortunately, I tried 33-100uf caps to block the PIP voltage but it didn't remove the fizz and line hum from the Denecke PS-2 unit for example. My best guess is the noise is from the switching power supply and the Art and Rolls use higher switching frequencies. The amount of noise may also be affected by the current load from the mic-- another reason we need to run tests on more condenser mics. Understandng what is happening, though, might help in making arguments to Sony/others for a better/more compatible future mic input design. Rob D.

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Indeed! An Off switch!

Gweeb

[AllanH]

This is all very interesting.I've tried a Denecke PS-2 phantom unit with my Pearl MS8CL tonight, and I haveen't found any problems with buzzing or hum.

I'll try my Rode NT4 tomorrow and see if I get the problems with than combo.

Its possible that the interference is coming from electronics in the phantom supply that are producing 48V from the 9v battery that is usually used/

[AllanH]

Hi all.

More info on condenser mics and phantom power supplies with NH-900.

I have a Denecke PS-2 phantom unit. This can be powered either by a single 9v battery internal to the unit. It can also be powered externally at up to 24V. I usually use it with an external 12v supply (8 x 1.5 batteries in a holder) as this gives a longer running time.

Test results as follows:

PS-2. Internal 9V battery. Pearl MS8CL mic. Result: very noisy (hiss) with some popping/cracking noises.

PS-2. Internal 9V batterry. Rode NT-4. Result: very noisy (hiss) with some popping/crackling noises.

PS-2. External 12v supply. Pearl MS8CL. Result: almost no hiss. No popping/crackling noises.

PS-2. External 12v supply. Rode NT-4. Result: almost no hiss. No popping/crackling noises.

So - there appears to be significant effect of supply voltage on the results with a PS-2 phantom unit and an NH-900.

Interestingly, the ART Phantom II uses an 18V supply (2x 9v). Maybe this has something to do with its superior perrformance.

Since it takes the two batteries internally, which is more convenient than using a PS-2 with external power, my ART is on order!

[clyborne]

Thanks Allan--

Some interesting clues from your tests. They are pretty consistent with what I found. The PS-2 would work much better using a hi current 9.6volt "RC" battery pack but would hiss and sputter on the standard 9 volt batery. Seems like you're getting even better performance on 12 volts because I could NOT get a fully clean signal out of 9.6 volts on the PS-2. I understand using a battery sled, the PS-2 I tested did draw-down a 9volt bat within 45 minutes.

The Art and Rolls (no fizz etc) will run on the 2-9 volt bats or wth 12vdc inout plug option too. I Maybe the switching transformer puts out more noise with less supply current to work with? Its possible that you could find that an ART or Rolls could put out less noise,.. You can hear from my test that the NH-900 isn't contributing much noise at all (if any). Rob D.

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Hi all.

More info on condenser mics and phantom power supplies with NH-900.

I have a Denecke PS-2 phantom unit. This can be powered either by a single 9v battery internal to the unit. It can also be powered externally at up to 24V. I usually use it with an external 12v supply (8 x 1.5 batteries in a holder) as this gives a longer running time.

Test results as follows:

PS-2. Internal 9V battery. Pearl MS8CL mic. Result: very noisy (hiss) with some popping/cracking noises.

PS-2. Internal 9V batterry. Rode NT-4. Result: very noisy (hiss) with some popping/crackling noises.

PS-2. External 12v supply. Pearl MS8CL. Result: almost no hiss. No popping/crackling noises.

PS-2. External 12v supply. Rode NT-4. Result: almost no hiss. No popping/crackling noises.

So - there appears to be significant effect of supply voltage on the results with a PS-2 phantom unit and an NH-900.

Interestingly, the ART Phantom II uses an 18V supply (2x 9v). Maybe this has something to do with its superior perrformance.

Since it takes the two batteries internally, which is more convenient than using a PS-2 with external power, my ART is on order!

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[AllanH]

Hi Rob

So the next logical step is to up the volts on the PS-2 to 18v or 24v using combinations of battery holders. I'll try to find time in the next few days.

The 1.5V AA (LR6) cells are capable of meeting a higher current than 9V PP3, but the higher volts should have less current demand anyway, and also give any switching circuits in the electronics any easier time.

With my 8x 1.5V battery pack I run a PS-2 and an AD-20 pre-amp/ADC togther and get several days intermittent use before the voltage dies - much better performance than using internal 9v cells. On the basis of the work you have reported, I'm looking to abandon use of the AD-20 and rely on the HiMD pre-amp.

One drawback with this method of building up the volts is the weight and bulk of the cells. May be worth my checking the catalogues to see if there are any suitable high power/voltage camcorder batteries at a sensible price.

[clyborne]

Hi Alan-- Give it a shot and see. 24 volts might not silence it completely. Battery cost ~ new Art Phantom II? The Art and the Rolls seem to pull considerably less juice.

I tried Schoeps MK-8/MK-21 mics->Rolls-> NH-900 mic input today. The owner, who swears by Lunatec V3 outboard preamp, said, "Sounds pretty clean to me." Let us know about the A/B test with your AD 20! Rob D.

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Hi Rob

So the next logical step is to up the volts on the PS-2 to 18v or 24v using combinations of battery holders.  I'll try to find time in the next few days.

The 1.5V AA (LR6) cells are capable of meeting a higher current than 9V PP3, but the higher volts should have less current demand anyway, and also give any switching circuits in the electronics any easier time.

With my 8x 1.5V battery pack I run a PS-2 and an AD-20 pre-amp/ADC togther and get several days intermittent use before the voltage dies - much better performance than using internal 9v cells. On the basis of the work you have reported, I'm looking to abandon use of the AD-20 and rely on the HiMD pre-amp.

One drawback with this method of building up the volts is the weight and bulk of the cells. May be worth my checking the catalogues to see if there are any suitable high power/voltage camcorder batteries at a sensible price.

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[AllanH]

A few more ad-hoc results - subjective only, based on my ears!

Equipment line up: Rode NT4- Denecke PS-2 phantom supply - NH-900 or RH-10

Cables: Starquad between mic and power supply. Unbalanced lead from phantom supply to HiMD, with 10kohm resistor between 'cold' and ground on each channel.

1. 9V battery supply to PS-2. Very hissy with clearly audible crackling/popping (as previously reported). NB Noise present whether the mic was switched on or not. Unusable for practical recording.

2. 12v external supply to PS-2. No significant noise when the mic was on. When off, slight hiss with crackling just audible.

3. 18V (nominal) external suppy to PS-2. No significant noise when the mic was on. With mic off, hiss and noise was slightly louder than with the 12V supply above.

Same results obtained with both NH-900 and RH-10.

It seems that:

i) 12V external supply is optimum for my Denecke PS-2.

ii) the noise is due to combination of the PS-2 AND the cables/circuit to the mic on/off switch.

4 Rode NT4 powered by internal 9V battery in the mic body. (This is not plug-in power from the Hi MD). Little noise once the electronics were given time (30 sec) to stabilise after switching on, as recommended by Rode. Noise had a different spectrum that noise from PS-2 combinations (less top end).

Overall, I'd say that set up (2) and (4) were similar but with different noise spectra. (1) was terrible.

Back again when I get my hands on an ART Phantom II.

Edited August 10, 2005 by AllanH

[clyborne]

Hi Alan--

Good to hear that the RH-10 mic pre is also compatible. You should be able to get the noise down to where the Nt4's self noise is loudest and covers all of the other noise sources. The NT1A mics in the test movie have 11dBA less self noise than the NT4. At that noise bed, it seems all of the contributing components are pretty much on par. Thank again for your pursuits. Rob D.

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A few more ad-hoc results - subjective only, based on my ears!

Equipment line up: Rode NT4- Denecke PS-2 phantom supply - NH-900 or RH-10

Cables: Starquad between mic and power supply. Unbalanced lead from phantom supply to HiMD, with 10kohm resistor between 'cold' and ground on each channel.

1. 9V battery supply to PS-2. Very hissy with clearly audible crackling/popping (as previously reported). NB Noise present whether the mic was switched on or not. Unusable for practical recording.

2. 12v external supply to PS-2. No significant noise when the mic was on. When off, slight hiss with crackling just audible.

3. 18V (nominal) external suppy to PS-2. No significant noise when the mic was on. With mic off, hiss and noise was slightly louder than with the 12V supply above.

Same results obtained with both NH-900 and RH-10.

It seems that:

i) 12V external supply is optimum for my Denecke PS-2.

ii) the noise is due to combination of the PS-2 AND the cables/circuit to the mic on/off switch.

4 Rode NT4 powered by internal 9V battery in the mic body. (This is not plug-in power from the Hi MD). Little noise once the electronics were given time (30 sec) to stabilise after switching on, as recommended by Rode. Noise had a different spectrum that noise from PS-2 combinations (less top end).

Overall, I'd say that set up (2) and (4) were similar but with different noise spectra. (1) was terrible.

Back again when I get my hands on an ART Phantom II.

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[dalion]

Thanks for the xcellent work guys.

I am curious whether the Art/Rolls provides enough gain for line level input

(Mic->Art->line-in) without an external preamp. Would line-in be quieter?

[clyborne]

The Art and Rolls units are strictly mic level. Yes, previous wisdom said "line level" is better and you can judge the vaildity of this assumption yourself with the quicktime movie test. Practically speaking, no external pre is going to introduce less noise than the pre in the 722. Listen to the diference between the NT1A's going directly to the 722 and then through the Rolls or Art to the NH900 mic input. That's the best possible "improvement" I can think of that one could make instead of using the "lowly" HiMD mic level input. Gain wise, there's plenty with the mic level input too. There are folks who would prefer using another analog-digital converter rather than that built into the NH-900. We'd probably have to be using the exact same monitoring system to get into analyzing these differences. Rob D.

Thanks for the xcellent work guys.

I am curious whether the Art/Rolls provides enough gain for line level input

(Mic->Art->line-in) without an external preamp. Would line-in be quieter?

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[AllanH]

Hi Rob

Yes the NT-1A's look attractive fron a S/N point of view but might be difficult to get in a zeppelin for outdoor recording.

Even so, NT-4 is a bit heavy for outdoor use - I was thinking of a pair of NT-5s, but the capsules sizes are the same so I won't gain anything in terms of S/N.

Got the ART Phanom II today. Only chance for a quick play so far, but results disappointing. No crackles but plenty of hiss. NT4+PS-2(12V) or NT-4 with internal battery still the best for me. Possible that impedences play a part. I'll let you know what else I find direct to your e-mail address.

Thanks for raising the issue - its opened my eyes to the HiMD mic pre-amps: previously I've been biased against them.

[clyborne]

Alan-- I just went over and hooked up NT-4-> Art-> NH900 and its working great (as it did ithe tests). Still showing the 13 dB increase in gain compared to NT4 (9volt)->NH900. Something odd is going on. Maybe take out the 9 volt battery, try other cables and then both recorders? Please do let us know what you discover.

I use the Nt1A's outside (exclusvely) in DIY cut away PVC shock-mounts with big hairy zeps. No, nothing like a compact m-s rig, but workable. Lots of hours. I knifed the capsules where they join the posts in one pair and rotated them 90 degrees so they are front-facing. Then I mounted the bodies horizontally which looks more like a "field" mic, but both my vertical and horizontal sets have similar bulk and handability in the field. There's a litle less handling noise with the horizonatl set for some reason.

As for the NT-5's, maybe look at the Studio Projects C-4's too? These mics are getting some very nice things said about them and they come with cardioid and omni caps-- and weigh only 3.3 ounces each. Rob D.

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Hi Rob

Yes the NT-1A's look attractive fron a S/N point of view but might be difficult to get in a zeppelin for outdoor recording.

Even so, NT-4 is a bit heavy for outdoor use - I was thinking of a pair of NT-5s, but the capsules sizes are the same so I won't gain anything in terms of S/N.

Got the ART Phanom II today. Only chance for a quick play so far, but results disappointing. No crackles but plenty of hiss. NT4+PS-2(12V) or NT-4 with internal battery still the best for me. Possible that impedences play a part. I'll let you know what else I find direct to your e-mail address.

Thanks for raising the issue - its opened my eyes to the HiMD mic pre-amps: previously I've been biased against them.

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