Dedicated pre amp vs duet 3

[rec71]

Hi all,

I’m want to test out a few microphones (telefunken u47, u87ai and a few others that I’ll bring up on another thread to keep things more orderly on the forum), I currently have a duet 3.

In order to get a fair representation of the mics, should the mic run into a pre amp before going into the duet 3? I’ve read about people going straight into an Apollo twin for example. I’ve also seen online that a c800g for example needs a certain level of power(?) from a pre in order to get the true sound.

Is this correct? Or am I able to test out these mics and get an accurate picture of what works in my recording set up by just going into a duet 3?

[Matt Houghton]

I reckon you're best testing one variable at once, so stick with the Apogee's preamps. There should be ample clean gain and it won't unduly colour the sound. If you want to look into preamps later, for whatever reason (colouration, facilities, more gain etc), please do... but I'd definitely do that separately.

[rec71]

Thanks, Matt. That makes a lot of sense.

[James Perrett]

You'll be able to hear the differences in those mics through even the cheapest of preamps (assuming we are talking about a real U47 and U87). Apogee have a good reputation so stick with what you know.

[Hugh Robjohns]

In order to get a fair representation of the mics, should the mic run into a pre amp before going into the duet 3?

If you have a particular preamp you always use then use it if not, the duet preamps are high quality and will reveal the mic differences perfectly well.

I’ve also seen online that a c800g for example needs a certain level of power(?) from a pre in order to get the true sound.

The C800G is a valve mic with a dedicated power supply — it doesn't rely on phantom from the preamp.

[ef37a]

Regarding phantom power?
It might be good to monitor the phantom voltage at each microphone,
1) to ensure the source is delivering the correct voltage although I am sure that will not be a problem for the Duet.
2) That will give us all a reasonably precise 'real world' figure for the current consumption of particular microphone models. Something that can often be hard or impossible to discover.

Dave.

[Hugh Robjohns]

This is completely irrelevant to the OP, so please ignore...

It might be good to monitor the phantom voltage at each microphone,
1) to ensure the source is delivering the correct voltage...

Measuring the voltage at the mic tells you nothing about the phantom supply voltage. You can only measure that at the Interface/preamp/mixer with no mic connected (and it should be between 44 and 52V).

2) That will give us all a reasonably precise 'real world' figure for the current consumption of particular microphone models. Something that can often be hard or impossible to discover.

All reputable mic manufacturers specify their mics' current requirements. But if not you can work it out if you know the actual source (off-load) phantom voltage and the voltage at the mic when connected*... but it really won't tell you anything useful at all.

* mic current (in mA) = 2x ( (phantom volts - mic volts) / 6.8)

[Arpangel]

Measuring the voltage at the mic tells you nothing about the phantom supply voltage. You can only measure that at the Interface/preamp/mixer with no mic connected (and it should be between 44 and 52V).

This can produce a few surprises!
I’ve measured PP on a few mixers I’ve owned, and it’s been anything from 38v to 50v sometimes around 48v
The cheaper mixers tend to be on the low side, sometimes, it’s definitely not a consistent voltage.
I think a Tapco I owned once was 38v, I haven’t measured my A&H but I'm guessing it’ll be pretty much spot on.

[ef37a]

This is completely irrelevant to the OP, so please ignore...

It might be good to monitor the phantom voltage at each microphone,
1) to ensure the source is delivering the correct voltage...

Measuring the voltage at the mic tells you nothing about the phantom supply voltage. You can only measure that at the Interface/preamp/mixer with no mic connected (and it should be between 44 and 52V).

2) That will give us all a reasonably precise 'real world' figure for the current consumption of particular microphone models. Something that can often be hard or impossible to discover.

All reputable mic manufacturers specify their mics' current requirements. But if not you can work it out if you know the actual source (off-load) phantom voltage and the voltage at the mic when connected*... but it really won't tell you anything useful at all.

* mic current (in mA) = 2x ( (phantom volts - mic volts) / 6.8)

Well ignore me if you like but (and you are going to be even more upset with me soon!) since the OP was running tests on several mics I thought this might be a good 'diagnostic'? Of COURSE, measure the off load voltage. He could also make up a load to check that the supply was up to spec.
Should the mic load I be different from expected it might shed light on some performance shortcoming.

(thank you Tony!)

Dave.

[Kwackman]

For what it's worth, I think the phantom power thing is a totally unnecessary rabbit hole to the initial query.

[ef37a]

For what it's worth, I think the phantom power thing is a totally unnecessary rabbit hole to the initial query.

You are of course perfectly entitled. I make that fifteen all?

Dave.

[Hugh Robjohns]

...since the OP was running tests on several mics I thought this might be a good 'diagnostic'?

Diagnostic of what, exactly?

All he wants to know is how the mics compare sound wise.

I have zero concern over Apogee's ability to make a phantom supply to spec.

[ef37a]

...since the OP was running tests on several mics I thought this might be a good 'diagnostic'?

Diagnostic of what, exactly?

All he wants to know is how the mics compare sound wise.

I have zero concern over Apogee's ability to make a phantom supply to spec.

Neither have I.

Dave.

[Hugh Robjohns]

I have zero concern over Apogee's ability to make a phantom supply to spec.

Neither have I.

Dave.

Grand.

So we're agreed, then, that any connected mic will be powered as intended and thus perform as intended, and so electrical testing to gain physical knowledge of its current requirement will be utterly irrelevant, completely uninformative, and of no use or interest to the OP?

[ef37a]

I have zero concern over Apogee's ability to make a phantom supply to spec.

Neither have I.

Dave.

Grand.

So we're agreed, then, that any connected mic will be powered as intended and thus perform as intended, and so electrical testing to gain physical knowledge of its current requirement will be utterly irrelevant, completely uninformative, and of no use or interest to the OP?

Not if you don't measure them!

Dave.

[Hugh Robjohns]

Of the mics of interest mentioned by the OP here and in the other related thread, the Telefunken U47, Flea47, Neumann U67, and Sony C800G are all valve mics with their own bespoke PSUs, so phantom current consumption is not applicable.

The AEA A440 is a long-ribbon mic, so phantom current consumption is not applicable.

But the Neumann U87ai is phantom powered and draws 0.8mA according to the manufacturer's spec.

Pray tell what the OP can learn to their advantage from this hard won knowledge?

[ef37a]

Of the mics of interest mentioned by the OP here and in the other related thread, the Telefunken U47, Flea47, Neumann U67, and Sony C800G are all valve mics with their own bespoke PSUs, so phantom current consumption is not applicable.

The AEA A440 is a long-ribbon mic, so phantom current consumption is not applicable.

But the Neumann U87ai is phantom powered and draws 0.8mA according to the manufacturer's spec.

Pray tell what the OP can learn to their advantage from this hard won knowledge?

Confirmation. (800uA seems remarkably low?)

Dave.

[Hugh Robjohns]

Confirmation.

Confirmation of what, exactly?

(800uA seems remarkably low?)

Every day's a school day... Here, do the maths from the schematic if you're so untrusting of Neumann's published specs

http://recordinghacks.com/images/mic_ex ... ematic.gif

But it's a fact that most of Neumann's early transformer-output mics draw very little phantom current. The KM84 needs only 0.4mA, for example, and the stereo SM69Fet needs 0.5mA per capsule.

The modern transformerless TLM models need more (obviously, because of the cable drivers) — so the TLM170 is around 3mA, for example.

But it's not just old Neumanns that don't draw much. The classic AKG C414EB needed less than 1mA, too.

Perhaps your knowledge of phantom power requirements isn't quite as comprehensive as you think ? 0.8mA is not "remarkably low" at all. It's actually pretty typical for that kind of mic.

[ef37a]

That is quite an achievement! All those transistors and under 1mA current draw.
I am more used to mics drawing 3-4mA and reading (SoS of course) of some pulling 8mA and even the maximum ten.

OK, point conceded. Nothing to see here, move along folks!

Dave.

[Hugh Robjohns]

That is quite an achievement! All those transistors and under 1mA current draw.

The benefits of high-impedance circuitry!

I am more used to mics drawing 3-4mA and reading (SoS of course) of some pulling 8mA and even the maximum ten.

A few milliamps is common, especially where transformerless outputs are involved due to the need to drive current down the cable directly. There aren't many that need 8 or 10mA, but obviously important to mention in a review when they do!

OK, point conceded. Nothing to see here, move along folks!