[H. Khalil]

Hello,

I have a recording application for which I don't get enough gain from
the mic preamp, and am contemplating a naive solution that might work
but, on the other hand, might damage the gear. So I would be grateful
for any advise from the pros.

As I am using a single mic and a 2-channel preamp, I thought I could
connect the output of one channel to the input of the second, then take
the output of the second to the converter. The preamp has for each
channel a balanced mic input and a balanced high-impedance input. Also,
possibly making things worse, it can only turn on/off phantom power for
the mic inputs of both channels simultaneously, and the mic I use does
need phantom power.

Now, is the daisy-chain solution at all feasible under these
conditions? If yes, should I connect the output of the first channel
with the mic input or the high-impedance input of the second channel,
knowing that phantom power must be on? Finally, would it help to
permantly cut the phantom power for the second channel from inside the
box (I don't know exactly how to do it but I dare trying it)?

In case it is relevant, I am using a Shoeps CMC-641 mic (thanks Ty for
the recommendation) and an M-Audio DMP3 preamp (and am quite happy with
the sound I get, except for needing more gain).. From the preamp specs:

Maximum Input: +10 dBv
Maximum Output - Balanced: +22 dBv
Input Impedance (1 kHz) - Mic In: 3 kOhms
Input Impedance (1 kHz) - Instr. In: 100 kOhms
Output Impedance: 500 Ohms.


Thanks!

[Eeyore]

"H. Khalil" wrote:

Hello,

I have a recording application for which I don't get enough gain from
the mic preamp, and am contemplating a naive solution that might work
but, on the other hand, might damage the gear. So I would be grateful
for any advise from the pros.

Yes it's fine. Set the fist mic amp to max gain ( that'll typically help
the noise figure a bit ) and use the second one to boost the level as
required.

Graham

[Eeyore]

"H. Khalil" wrote:

Also,
possibly making things worse, it can only turn on/off phantom power for
the mic inputs of both channels simultaneously, and the mic I use does
need phantom power.

Ah !

Not *quite* so simple. Is there an attenuated 'line level' input too ? That
won't have the phantom on it.

Graham

[Scott Dorsey]

H. Khalil wrote:

Now, is the daisy-chain solution at all feasible under these
conditions? If yes, should I connect the output of the first channel
with the mic input or the high-impedance input of the second channel,
knowing that phantom power must be on? Finally, would it help to
permantly cut the phantom power for the second channel from inside the
box (I don't know exactly how to do it but I dare trying it)?

You won't hurt anything by chaining the output of the first channel into
the high-Z input of the second channel. Try it. I think it will probably
sound pretty awful and it'll probably be noisy too. But try it.

In case it is relevant, I am using a Shoeps CMC-641 mic (thanks Ty for
the recommendation) and an M-Audio DMP3 preamp (and am quite happy with
the sound I get, except for needing more gain).. From the preamp specs:

That's a mike with a pretty high output level. What are you recording
that you need more gain?

Maximum Input: +10 dBv
Maximum Output - Balanced: +22 dBv
Input Impedance (1 kHz) - Mic In: 3 kOhms
Input Impedance (1 kHz) - Instr. In: 100 kOhms
Output Impedance: 500 Ohms.

These aren't really what you need to know. What is the maximum preamp
gain?
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Arny Krueger]

"Eeyore" wrote in message
...


"H. Khalil" wrote:

Also,
possibly making things worse, it can only turn on/off phantom power for
the mic inputs of both channels simultaneously, and the mic I use does
need phantom power.

Ah !

Not *quite* so simple. Is there an attenuated 'line level' input too ?
That
won't have the phantom on it.

This is in fact one of those ways to damage equipment - hook an input with
phantom power capabilities to a line output. There can be things going on
with charged capacitors, etc.

[H. Khalil]

That's a mike with a pretty high output level. What are you recording
that you need more gain?

I am recording classical guitar with the CMC-641. Up close there's no
problem, but I prefer a distance of about 1 m, and here's where the 66
dB gain of the DMP3 turn out insufficient (I turn up the gain only
until noise becomes apparent, which is about 80% of max gain).

As far as I remember, the MK 41 is the Schoeps capsule with least
sensitivity..

[H. Khalil]

This is in fact one of those ways to damage equipment - hook an input with
phantom power capabilities to a line output. There can be things going on
with charged capacitors, etc.

That's what I was afraid of! Is it technically possible (and simple
enough) to internally modify the preamp so as to convert the mic input
or the Hi-Z input of the second channel into a low-impedance line input
with gain?

[Mike Rivers]

H. Khalil wrote:

I am recording classical guitar with the CMC-641. Up close there's no
problem, but I prefer a distance of about 1 m, and here's where the 66
dB gain of the DMP3 turn out insufficient (I turn up the gain only
until noise becomes apparent, which is about 80% of max gain).

In that case, you don't need more gain after the preamp, you need a
better preamp that can provide 65 dB of gain without the noise being
objectionable. That's the "last 5%" that you get when you pay 500% more
for a Millenia or Great River or Hardy or .... than you pay for an
M-Audio.

You can measure the gain at that setting and see how much you're
actually using. That might help you in choosing your next preamp.

[Arny Krueger]

"H. Khalil" wrote in message
oups.com...
This is in fact one of those ways to damage equipment - hook an input
with
phantom power capabilities to a line output. There can be things going on
with charged capacitors, etc.

That's what I was afraid of! Is it technically possible (and simple
enough) to internally modify the preamp so as to convert the mic input
or the Hi-Z input of the second channel into a low-impedance line input
with gain?

Yes, in many cases.

(1) Find the resistors that apply the phantom power to that mic input and
lift one end.

(2) Or be very sure of the phantom switch is "off", make sure that any caps
that are associated with the phantom voltage are fully discharged, and then
hook things up.

[Paul Stamler]

"H. Khalil" wrote in message
oups.com...
This is in fact one of those ways to damage equipment - hook an input
with
phantom power capabilities to a line output. There can be things going
on
with charged capacitors, etc.

That's what I was afraid of! Is it technically possible (and simple
enough) to internally modify the preamp so as to convert the mic input
or the Hi-Z input of the second channel into a low-impedance line input
with gain?

The Hi-Z input should already offer additional gain, and it doesn't have
phantom on it. You should be able to go from Ch. 1 out to Ch. 2 Hi-Z in with
no problems.

Peace,
Paul

[Brian Running]

The Hi-Z input should already offer additional gain, and it doesn't have
phantom on it. You should be able to go from Ch. 1 out to Ch. 2 Hi-Z in with
no problems.

I used to do that with a two-channel mic pre I used in my bass rig, in
order to get two XLR outs for DI. I ran the XLR out from a SansAmp into
the XLR in of one pre channel, then jumped a 1/4" cable from channel
one's out to channel two's in. This gave me two XLR outs to use. No
problems with that set-up, just fiddle with the gains to get least
noise/most headroom.

[Steve Scott]

Yes, it can work. But why? Are you trying for 0 dbFS?

I'd rather just record where the analog gear sounds good, even if it
comes in at -20 or so, and get any needed makeup digitally at mixing.

Or if more level is really necessary, maybe just patch a compressor
with no threshold at 1:1.

Steve

[Steve Scott]

Yes, it can work. But why? Are you trying for 0 dbFS?

I'd rather just record where the analog gear sounds good, even if it
comes in at -20 or so, and get any needed makeup digitally at mixing.

Or maybe just patch a compressor with no threshold at 1:1.

Steve

[Eeyore]

"H. Khalil" wrote:

This is in fact one of those ways to damage equipment - hook an input with
phantom power capabilities to a line output. There can be things going on
with charged capacitors, etc.

That's what I was afraid of! Is it technically possible (and simple
enough) to internally modify the preamp so as to convert the mic input
or the Hi-Z input of the second channel into a low-impedance line input
with gain?

It doesn't need to be low impedance. Why did you think it did ?

Graham

[Brian Running]

Yes, it can work. But why?

I think I mentioned not just once, but twice, that it was a way to get
two balanced outputs. You gotta work with the gear that's on hand, you
know?

The point is, it will not destroy the mic pre, as someone had suggested.

[Rob Reedijk]

Steve Scott wrote:
Yes, it can work. But why? Are you trying for 0 dbFS?

I'd rather just record where the analog gear sounds good, even if it
comes in at -20 or so, and get any needed makeup digitally at mixing.

Or maybe just patch a compressor with no threshold at 1:1.

Too bad the 1176 doesn't have a 1:1 setting since it makes for a fine
mic preamp. It works quite well with tube mics as they provide hot
levels due to having real power supplies. But I seem to remember with
an 1176 there is enough make up gain that you can avoid hitting the
threshold so it is workable anyway.

:x

[hank alrich]

H. Khalil wrote:

That's a mike with a pretty high output level. What are you recording
that you need more gain?

I am recording classical guitar with the CMC-641. Up close there's no
problem, but I prefer a distance of about 1 m, and here's where the 66
dB gain of the DMP3 turn out insufficient (I turn up the gain only
until noise becomes apparent, which is about 80% of max gain).

As far as I remember, the MK 41 is the Schoeps capsule with least
sensitivity..

As this point I am questioning the quality of your preamp. Many stunning
tracks of acoustic guitar have been captured with the MK41 without
shoving the mic in the face of the instrument. Try an FMR RNP and see if
that doesn't rock your world a little more satisfactorily.

--
ha

[Steve Scott]

Brian Running wrote:
Yes, it can work. But why?

I think I mentioned not just once, but twice, that it was a way to get
two balanced outputs. You gotta work with the gear that's on hand, you
know?

The point is, it will not destroy the mic pre, as someone had suggested.

I was replying to the OP's question, re needing more gain. I've
chained preamps, of course it is usable.

I just think for what he is doing some of that needed level might be
able to come from the mix gain, rather than all upfront at the preamp.

Steve

[Plush]

Clearly the problem here is the mic amp. 66dB of gain on a Schoeps is a
lot of gain since output is already high from the mic body.
There's no way that you need that much gain with classical guitar. (you
might need that with a lute!)

Use a different mic amp.

We recommend the DAV electronics Broadhurst Gardens No. 1.

[Paul Stamler]

H. Khalil wrote:

That's a mike with a pretty high output level. What are you recording
that you need more gain?

I am recording classical guitar with the CMC-641. Up close there's no
problem, but I prefer a distance of about 1 m, and here's where the 66
dB gain of the DMP3 turn out insufficient (I turn up the gain only
until noise becomes apparent, which is about 80% of max gain).

Okay, I think that may be where you're running into problems. The DMP3, if
it's similar to M-Audio's other preamps, is not all that quiet, particularly
at intermediate gain settings. A good-quality preamp -- say, a Great River
or Millennia Media -- will be plenty quiet with a Schoeps mic, even a few
feet in front of a classical guitar.

On the other hand, is it possible you're turning up the mic until you hear
noise, but it's really room noise -- air handling equipment, etc.? If that's
the case, then no improvement in the preamp will fix it.

Peace,
Paul