spud wrote:

Lost this thread. Any success with the in-line pre amp booster
project?

Yes. I built one for my Bang & Olufsen microphone from some SIL Hitachi
chips that are/were aimed for use as lo-output mc preamps and similar.
No extensive testing done, do not read me as claiming it to be "very
good", I only say that it can be done with some, as yet unspecified
result. An inline transformer may be better suited than electronics.

{leaving the context in]

I need a bit more gain in between a pair of MXL603's and the
Tascam US224. I power the 603's with 4, 9v batteries in series and the
US224 runs off a laptop but there's not enough signal. If someone has
an easy circuit for a battery powered, quiet, compact amplifier stage
that will bump the signal up a bit that I could try that would be
great. Thanks as always, s.


Kind regards

Peter Larsen

--
************************************************** ***********
* My site is at: http://www.muyiovatki.dk *
************************************************** ***********

"spud" wrote in message
...
Lost this thread. Any success with the in-line pre amp booster
project? I need a bit more gain in between a pair of MXL603's and the
Tascam US224. I power the 603's with 4, 9v batteries in series and the
US224 runs off a laptop but there's not enough signal. If someone has
an easy circuit for a battery powered, quiet, compact amplifier stage
that will bump the signal up a bit that I could try that would be
great. Thanks as always, s.

What are you doing with those 603s? IME they have a pretty robust output.

Just would like to post an observation here which would be relevant if
someone is designing a "pre-preamp" for ribbon microphones: The actual
output impedance of the microphones should be checked carefully.

I recently arranged for careful measurements to be performed on two of
my microphones, and found out that the Royer SF-1 ribbon has a somewhat
challenging output impedance curve. It is 300 Ohms as specified only in
the midrange and above. At lower frequencies, however, the impedance
climbs continually, going past 1000 Ohms (!) at the bottom end.

I don't have the corresponding information for any other types of ribbon
microphone, but if other ribbons have their highest impedance at their
resonant frequency (where this seems to be), then that would need to be
taken into account in any pre-preamp's design. And this certainly helps
to explain why different preamps make ribbon microphones sound different.

In article group writes:

Lost this thread. Any success with the in-line pre amp booster
project? I need a bit more gain in between a pair of MXL603's and the
Tascam US224.

I saw exactly what you're looking for at the AES show, the Sanken
HAD-48. It provides 20 or 40 dB of gain, and runs off 48V phantom
power. It's really intended to use with ribbom and other typically low
output mics, so it doesn't pass the phantom power through. If you got
one, you'd need two phantom power supplies, one between the US224 and
the HAD-48, and another between the HAD-48 and the mic. That probalby
doesn't help very much.

I think that the best solution for you would be simply to get a mic
preamp that has sufficient gain for your application, one that
provides phantom power (to reduce the number of pieces and connections
in your system) and then just connect the preamp output to a line
input of your US224.

What is it that you're recording that you need more gain? I thought
the MXL603 was a pretty "normal sensitivity" mic, unless its
sensitivity is limited by the lower phantom voltage. You might try
putting another 9V battery in series with your present power source,
even temporarily, to see if that helps.

Also, understand that you don't HAVE to hit full scale with the
quietest whisper.


--
I'm really Mike Rivers - )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

On 26 Nov 2003 06:27:09 -0800, (David Satz) wrote:

Just would like to post an observation here which would be relevant if
someone is designing a "pre-preamp" for ribbon microphones: The actual
output impedance of the microphones should be checked carefully.

Hi David,
Thanks for this very interesting note. Real data is rare on
ribbon mic's.

And I haven't forgotten the DIY mic pre-preamp project promised.
I'll spare you the excuses, but ..... prototypes soon.

Chris Hornbeck
"That is my Theory, and what it is too."
Anne Elk

the mm-1 from sound devices will give ability to drive long lines ,excellent
pre with low cut and work on 1.5 v bat

--
Oleg Kaizerman (gebe) Hollyland
"Mike Rivers" wrote in message
news:znr1069852061k@trad...

In article group writes:

Lost this thread. Any success with the in-line pre amp booster
project? I need a bit more gain in between a pair of MXL603's and the
Tascam US224.

I saw exactly what you're looking for at the AES show, the Sanken
HAD-48. It provides 20 or 40 dB of gain, and runs off 48V phantom
power. It's really intended to use with ribbom and other typically low
output mics, so it doesn't pass the phantom power through. If you got
one, you'd need two phantom power supplies, one between the US224 and
the HAD-48, and another between the HAD-48 and the mic. That probalby
doesn't help very much.

I think that the best solution for you would be simply to get a mic
preamp that has sufficient gain for your application, one that
provides phantom power (to reduce the number of pieces and connections
in your system) and then just connect the preamp output to a line
input of your US224.

What is it that you're recording that you need more gain? I thought
the MXL603 was a pretty "normal sensitivity" mic, unless its
sensitivity is limited by the lower phantom voltage. You might try
putting another 9V battery in series with your present power source,
even temporarily, to see if that helps.

Also, understand that you don't HAVE to hit full scale with the
quietest whisper.


--
I'm really Mike Rivers - )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

I've run impedance curves on various RCA, B&O & Beyer ribbon mics, and have never seen such a
wild curve. All mics from the brands mentioned were virtually spot-on their rated Z until
either nearing there resonance range(12-20Hz for RCA's & RCA-ribboned B&O's) or the low F
limits of the transformers in the case of RCA-ribboned Beyers(30-40Hz)(Stock ribboned Beyers
resonance is typically 100-200Hz), but no Z observed exceeded about 30 percent over rating. In
the RCA mics, the resonance peak is typically barely discernible in Z rise, being at most 5
percent up, even on the "cheap" 74B.

--
Stephen Sank, Owner & Ribbon Mic Restorer
Talking Dog Transducer Company
http://stephensank.com
5517 Carmelita Drive N.E.
Albuquerque, New Mexico [87111]
505-332-0336
Auth. Nakamichi & McIntosh servicer
Payments preferred through Paypal.com
"David Satz" wrote in message
m...
Just would like to post an observation here which would be relevant if
someone is designing a "pre-preamp" for ribbon microphones: The actual
output impedance of the microphones should be checked carefully.

I recently arranged for careful measurements to be performed on two of
my microphones, and found out that the Royer SF-1 ribbon has a somewhat
challenging output impedance curve. It is 300 Ohms as specified only in
the midrange and above. At lower frequencies, however, the impedance
climbs continually, going past 1000 Ohms (!) at the bottom end.

I don't have the corresponding information for any other types of ribbon
microphone, but if other ribbons have their highest impedance at their
resonant frequency (where this seems to be), then that would need to be
taken into account in any pre-preamp's design. And this certainly helps
to explain why different preamps make ribbon microphones sound different.

Mike Rivers wrote:

I saw exactly what you're looking for at the AES show, the Sanken
HAD-48.

That unit is not due for release until this coming March. I have a
pair on order and will let the group know how they are when they arrive.

The preliminary specifications are a bit confusing in certain respects,
e.g. the required load impedance is rather high for most preamps. But
this is said to have been a translation problem--there was an engineer
from Sanken (Japan) at the AES show, who said that it would work with
a more typical input impedance such as 1 kOhm.

Also, the published frequency response curves are a down a little at
both the top and bottom ends of the audio spectrum--1 or 2 dB.

The best results I've gotten so far with ribbon mics and preamps has been
with preamps that use stepup transformers; specifically the Amkek/Neve 9098
and the Jensen dual 990.

Regards,

Ty Ford

**Until the worm goes away, I have put "not" in front of my email address.
Please remove it if you want to email me directly.
For Ty Ford V/O demos, audio services and equipment reviews,
click on http://www.jagunet.com/~tford

Mike Rivers wrote:

I saw exactly what you're looking for at the AES show, the Sanken
HAD-48. It provides 20 or 40 dB of gain, and runs off 48V phantom
power. It's really intended to use with ribbom and other typically low
output mics, so it doesn't pass the phantom power through.

http://www.sanken-mic.com/english/acce/pdf/had-48.pdf

Anyone know what sort of topology it uses?

Kurt Albershardt wrote:

Anyone know what sort of topology it uses?

I'm not sure that this product exists yet beyond the prototype stage.
They were supposed to be in production two months ago already, but have
been delayed ~6 months in Japan.

As I said, I have a pair on order already; in the process, I've been
on the phone and e-mail a fair amount with Sanken's U.S. distributors,
and also saw them at the AES show. There were no prototypes at the
booth as far as I could find out, but a Japanese engineer was there
who could answer certain questions. I have the sense that while just
about everybody acknowledges the great usefulness of this type of item
and wonders why it isn't already available everywhere, it is not so
easy to meet everyone's particular expectations. What we get eventually
may vary in some significant ways from the preliminary spec sheets--I
for one am hoping for slightly lower noise and flatter frequency response
than originally proposed. However, it may be difficult to offer that
level of performance for the price.

The amount of current needed for phantom powering could be an issue
as well. I'm sure everyone here has seen my rants here about preamps
(and even some dedicated phantom supplies) from well-known manufacturers
which fall out of spec if a microphone tries to draw more than about
1 mA. The HAD-48 is supposed to draw "less than 3 mA" which may mean
that a fair amount of portable preamps, mixers and recorders with
built-in phantom power will not drive it properly.

In article writes:

I've been
on the phone and e-mail a fair amount with Sanken's U.S. distributors,
and also saw them at the AES show. There were no prototypes at the
booth as far as I could find out, but a Japanese engineer was there
who could answer certain questions.

I fondled one at the booth, or maybe it was just a dummy. Not much to
it but a tube with an XLR at each end and a gain switch. I wanted to
ask about it but whenever I walked by there was never anyone at the
booth who knew what it was beyond the obvious.

I have the sense that while just
about everybody acknowledges the great usefulness of this type of item
and wonders why it isn't already available everywhere, it is not so
easy to meet everyone's particular expectations.

When I read that someone isn't getting enough level out of a mic, I'm
always suspicous that either they simply don't have a preamp with
enough gain or their expectations of hitting full scale digital are
not being fulfilled. A microphone preamp has to deal with a very wide
range of even nominal signal level. A loud vocal will barely need
20 dB of gain to reach the maximum output level of the preamp (which,
depending on the calibration of the A/D converter, may still not get
to full scale digital level). A nature recording may need more than
75 dB of gain to move the meter. 55 to 60 dB seems to be the typical
maximum gain for a modern preamp. I don't need my toes to count the
number of models that I can think of (out of maybe 500 different
outboard preamps on the market) that have more than 65 dB of gain.

So an extra 20 dB might come in handy, though I'm not sure what you'd
use the 40 dB setting for. It would have to be mighty darn quiet for
that to be of any use.

The HAD-48 is supposed to draw "less than 3 mA" which may mean
that a fair amount of portable preamps, mixers and recorders with
built-in phantom power will not drive it properly.

I didn't realize that there were units out there that were that
feeble. A lot of mics draw more current than that. And since it
doesn't pass the phantom power through, it means that in order to use
it with a condenser mic, you'd need an outboard power supply. With all
that extra stuff in line, it makes me thing that you (the user "you")
is starting off with the wrong equipment. I can't ever remember not
having enough gain with a Nagra, but they don't make 'em like they
uster.



--
I'm really Mike Rivers - )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

This is a dumb question from somebody who's never built anything (but
wants to start messing around some). You get the most efficient
coupling of one stage to another stage when the impedance you're
driving is totally resistive. At least I think I remember learning
that in a basic circuits course in my college days. A lot of the
coloration from a mic and a preamp comes from the various reactive
components in those devices. That's where your frequency response and
phase distortion get introduced. Am I remembering this more or less
correctly?

So has anybody ever tried to cancel out the reactance in a mic with
the preamp? IE, say your mic has a transformer output stage, that
introduces some inductance to its output impedance. Could you then
try to tune the amount of capacitance in the input stage of the preamp
to cancel out the inductance in the mic and get a net reactance of 0?
Is there any to do that without screwing up the freq response in the
audio realm? I've heard of mic pre designs that you let you vary the
input impedance to try to get the best sound from a particular mic,
but they all use resistors. I've never heard of a variably reactive
design to try to get the most efficient transfer of energy and reduce
coloration.

I'm assuming that if I've never heard of it, and a lot of people
smarter than me have built mic pres, that there's probably a very good
reason or two why it's either not possible or not beneficial. But,
you know, I figure if I ask I might learn something.

rossi


(David Satz) wrote in message om...
Just would like to post an observation here which would be relevant if
someone is designing a "pre-preamp" for ribbon microphones: The actual
output impedance of the microphones should be checked carefully.

I recently arranged for careful measurements to be performed on two of
my microphones, and found out that the Royer SF-1 ribbon has a somewhat
challenging output impedance curve. It is 300 Ohms as specified only in
the midrange and above. At lower frequencies, however, the impedance
climbs continually, going past 1000 Ohms (!) at the bottom end.

I don't have the corresponding information for any other types of ribbon
microphone, but if other ribbons have their highest impedance at their
resonant frequency (where this seems to be), then that would need to be
taken into account in any pre-preamp's design. And this certainly helps
to explain why different preamps make ribbon microphones sound different.

Chris Rossi wrote:
This is a dumb question from somebody who's never built anything (but
wants to start messing around some). You get the most efficient
coupling of one stage to another stage when the impedance you're
driving is totally resistive. At least I think I remember learning
that in a basic circuits course in my college days. A lot of the
coloration from a mic and a preamp comes from the various reactive
components in those devices. That's where your frequency response and
phase distortion get introduced. Am I remembering this more or less
correctly?

So has anybody ever tried to cancel out the reactance in a mic with
the preamp? IE, say your mic has a transformer output stage, that
introduces some inductance to its output impedance. Could you then
try to tune the amount of capacitance in the input stage of the preamp
to cancel out the inductance in the mic and get a net reactance of 0?
Is there any to do that without screwing up the freq response in the
audio realm? I've heard of mic pre designs that you let you vary the
input impedance to try to get the best sound from a particular mic,
but they all use resistors. I've never heard of a variably reactive
design to try to get the most efficient transfer of energy and reduce
coloration.

I'm assuming that if I've never heard of it, and a lot of people
smarter than me have built mic pres, that there's probably a very good
reason or two why it's either not possible or not beneficial. But,
you know, I figure if I ask I might learn something.

Good idea, here's a market opportunity complete with room to add all the
additional hype you can come up with!

Phono cartridges are (at least they used to be) specified to work into a
specific capacitance, like 100 mmF (now known as pF). And some high-end
preamp manufacturers added a switch to the phono input so you could add
a little extra capacitance if the cabling wasn't enough.

In article writes:

So has anybody ever tried to cancel out the reactance in a mic with
the preamp? IE, say your mic has a transformer output stage, that
introduces some inductance to its output impedance. Could you then
try to tune the amount of capacitance in the input stage of the preamp
to cancel out the inductance in the mic and get a net reactance of 0?

Did you have a particular frequency in mind? I don't know that you
could successfully do this over the full audio bandwidth.


--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

Chris,
I think you need to consider that the microphone designer has already
considered these reactive elements when designing the microphone as a
complete system that includes its output transformer, and that whole
system is tuned to provide a specific frequency response wehn fed into
a "standard" preamp (whatever that is). So if you were to nullify the
reactive elements of the output transformer, you might find the
designer's equation becomes "unbalanced", leaving some other factor of
the ribbon or the grille or something unaccounted for.

Also, those mic preamps you see that have veriable input impedance for
the msot part DON'T do it with resistors. They use multi-tapped input
transformers. Which is essentially what you're suggesting anyway. It
is conceivable that you could provide a capacitive load to alter the
performance of the microphone as well, but the results would vary with
the microphone and the preamp in question and would not be universally
predictable at all. So unless you incorporated this approach into a
preamp that's specifically intended for one particular microphone, it
wouldn't be practically useful. On the other hand, I do think that
designing a preamp for use with a specific microphone is a good idea.

ulysses

Chris Rossi wrote:

This is a dumb question from somebody who's never built anything (but
wants to start messing around some). You get the most efficient
coupling of one stage to another stage when the impedance you're
driving is totally resistive. At least I think I remember learning
that in a basic circuits course in my college days. A lot of the
coloration from a mic and a preamp comes from the various reactive
components in those devices. That's where your frequency response and
phase distortion get introduced. Am I remembering this more or less
correctly?

So has anybody ever tried to cancel out the reactance in a mic with
the preamp? IE, say your mic has a transformer output stage, that
introduces some inductance to its output impedance. Could you then
try to tune the amount of capacitance in the input stage of the preamp
to cancel out the inductance in the mic and get a net reactance of 0?
Is there any to do that without screwing up the freq response in the
audio realm? I've heard of mic pre designs that you let you vary the
input impedance to try to get the best sound from a particular mic,
but they all use resistors. I've never heard of a variably reactive
design to try to get the most efficient transfer of energy and reduce
coloration.

I'm assuming that if I've never heard of it, and a lot of people
smarter than me have built mic pres, that there's probably a very good
reason or two why it's either not possible or not beneficial. But,
you know, I figure if I ask I might learn something.

rossi


(David Satz) wrote in message
om...
Just would like to post an observation here which would be relevant if
someone is designing a "pre-preamp" for ribbon microphones: The actual
output impedance of the microphones should be checked carefully.

I recently arranged for careful measurements to be performed on two of
my microphones, and found out that the Royer SF-1 ribbon has a somewhat
challenging output impedance curve. It is 300 Ohms as specified only in
the midrange and above. At lower frequencies, however, the impedance
climbs continually, going past 1000 Ohms (!) at the bottom end.

I don't have the corresponding information for any other types of ribbon
microphone, but if other ribbons have their highest impedance at their
resonant frequency (where this seems to be), then that would need to be
taken into account in any pre-preamp's design. And this certainly helps
to explain why different preamps make ribbon microphones sound different.

On 29 Nov 2003 09:41:35 -0800, (Chris
Rossi) wrote:

So has anybody ever tried to cancel out the reactance in a mic with
the preamp? IE, say your mic has a transformer output stage, that
introduces some inductance to its output impedance. Could you then
try to tune the amount of capacitance in the input stage of the preamp
to cancel out the inductance in the mic and get a net reactance of 0?

Capacitance is not negative inductance. Net reactance of 0
only occurs at a point (a single frequency).

Chris Hornbeck
"That is my Theory, and what it is too."
Anne Elk

Stephen Sank wrote:

I've run impedance curves on various RCA, B&O & Beyer ribbon mics,
and have never seen such a wild curve.

I will send you a photocopy of the measurement results; you should have
it by mid-week. The output impedance goes literally off the chart, where
the limit of the scale was 1000 Ohms.

Oleg Kaizerman wrote:

the mm-1 from sound devices will give ability to drive long lines,
excellent pre with low cut and work on 1.5 v bat

This could be a nice choice with its 2000 Ohm input--low-frequency losses
should be audibly lower than those which would occur with the more common
input impedance of ~1 kOhm. However, mechanical mounting immediately next
to a microphone might be awkward. A bracket to hold this preamp onto a
mike stand would be a welcome accessory.

Also, this model contains a headphone amplifier which would not be so
useful in this application. The same company's model MP-1 costs about
15% less, and appears to have the same specifications as the MM-1.

I have an MP-1 here, which I have been meaning to test and measure; will
report back when I've done so.

--best regards

Chris Hornbeck wrote in message . ..
On 29 Nov 2003 09:41:35 -0800, (Chris
Rossi) wrote:

So has anybody ever tried to cancel out the reactance in a mic with
the preamp? IE, say your mic has a transformer output stage, that
introduces some inductance to its output impedance. Could you then
try to tune the amount of capacitance in the input stage of the preamp
to cancel out the inductance in the mic and get a net reactance of 0?

Capacitance is not negative inductance. Net reactance of 0
only occurs at a point (a single frequency).

D'oh. I knew there was a good reason. Maybe I'll get a chance to
reread my old circuits text in a bit.

thanks,
rossi
--
http://spacelabstudio.com

"David Satz" wrote in message
om

Stephen Sank wrote:

(David Satz) wrote in Message-ID:


I recently arranged for careful measurements to be performed on two of
my microphones, and found out that the Royer SF-1 ribbon has a somewhat
challenging output impedance curve. It is 300 Ohms as specified only in
the midrange and above. At lower frequencies, however, the impedance
climbs continually, going past 1000 Ohms (!) at the bottom end.

I've run impedance curves on various RCA, B&O & Beyer ribbon mics,
and have never seen such a wild curve.

I will send you a photocopy of the measurement results; you should
have it by mid-week. The output impedance goes literally off the
chart, where the limit of the scale was 1000 Ohms.

Since this impedance rise is at low frequencies, any chance there's a
blocking capacitor?

In article ,
Arny Krueger wrote:
"David Satz" wrote in message
. com

Stephen Sank wrote:

(David Satz) wrote in Message-ID:


I recently arranged for careful measurements to be performed on two of
my microphones, and found out that the Royer SF-1 ribbon has a somewhat
challenging output impedance curve. It is 300 Ohms as specified only in
the midrange and above. At lower frequencies, however, the impedance
climbs continually, going past 1000 Ohms (!) at the bottom end.

I've run impedance curves on various RCA, B&O & Beyer ribbon mics,
and have never seen such a wild curve.

I will send you a photocopy of the measurement results; you should
have it by mid-week. The output impedance goes literally off the
chart, where the limit of the scale was 1000 Ohms.

Since this impedance rise is at low frequencies, any chance there's a
blocking capacitor?

Nope, it's the transformer inductance that is doing it.

It's a wonder ribbon mike transformers work at all. The fact that they
provide sort of a weird source isn't all that surprising in the face
of the fact that they produce any output at all.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Justin Ulysses Morse wrote in message om...

On the other hand, I do think that
designing a preamp for use with a specific microphone is a good idea.

ulysses
************************************************** *********************

This has been briefly mentioned several times over the years, but
never really discussed. To some extent, it has been done by mic
manufacturers like DPA who offer a single preamp model intended for
use with their mic products. Can anyone think of any other preamps
designed specifically for use with a certain mic? It seems like such
an obvious idea, and with the very large numbers of certain mics in
use, there would probably be a decent market for a preamp that was
"guaranteed to be optimally designed for use with your U87ai." (or
any of another dozen microphones that are in widespread use.) I'm
sure that some of you can come up with mics and preamps from a single
manufacutrer that were advertised and sold together as a "system", but
has any company ever produced a preamp specifically for use with an
existing microphone (from another manufacturer)? Other than a
decidedly limited potential market, are there any other reasons why
this wouldn't be a good idea?

I wrote:

The output impedance goes literally off the chart, where the limit
of the scale was 1000 Ohms.

Strangely, Google's interface to this newsgroup isn't allowing me to
reply to Arny Krueger or Scott Dorsey's messages a little further down
along this thread. And a message that I'm sure I posted here this
morning has yet to show it's face, so this one may or may not make it,
either; I guess we'll see.

What I'd like to point out is that the output impedance curve for the
SF-1 is not monotonically rising at the low end; rather, it peaks at
some frequency between 30 and 70 Hz, then descends again so that at
20 Hz, it's a mere 700 Ohms (!). There's no indication of any output
coupling capacitors there [NB: Arny].

This was an SF-1 that was re-ribboned by Royer to match my other SF-1,
and somewhere here I do have their resonance frequency written down,
but unfortunately I can't find it at the moment. I believe it is right
in the region of the microphone's highest output impedance, however.

--best regards

"David Satz" wrote in message
om
I wrote:

The output impedance goes literally off the chart, where the limit
of the scale was 1000 Ohms.

Strangely, Google's interface to this newsgroup isn't allowing me to
reply to Arny Krueger or Scott Dorsey's messages a little further down
along this thread. And a message that I'm sure I posted here this
morning has yet to show it's face, so this one may or may not make it,
either; I guess we'll see.

What I'd like to point out is that the output impedance curve for the
SF-1 is not monotonically rising at the low end; rather, it peaks at
some frequency between 30 and 70 Hz, then descends again so that at
20 Hz, it's a mere 700 Ohms (!). There's no indication of any output
coupling capacitors there [NB: Arny].

Well that settles that!

This was an SF-1 that was re-ribboned by Royer to match my other SF-1,
and somewhere here I do have their resonance frequency written down,
but unfortunately I can't find it at the moment. I believe it is
right in the region of the microphone's highest output impedance,
however.

Yes this looks more like a bass resonance of a speaker driver. Same basic
physics should relate to both woofer cones and mic diaphragms.

In article writes:

Can anyone think of any other preamps
designed specifically for use with a certain mic?

Two contemporary companies doing that are BLUE (the Blue Ball) and
Royer (the powered series). The preamp is built into the mic and puts
out a fairly hot nominal mic level (so it still needs a traditional
preamp) but what's built in removes much of the effect of the
microphone/preamp interface, which is the major contributor to why
mics sound different with different preamps.



--
I'm really Mike Rivers - )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

I wrote not too long ago:

I was notified by my dealer today that Sanken has decided not to produce
the announced HAD-48 inline "pre-preamp" module in the foreseeable future.
No particular explanation was given.

--The HAD-48 has continued to be listed on Sanken's Web site all along, and
today I received email from my dealer saying that indeed it should become
available some time around the end of this month (March, 2004).

I've renewed my order for a pair of these items, and will let the group know
how they are when I receive them and have a chance to check them out.

I tried out the Sanken HAD-48 "pre-preamps" this afternoon with a pair of
Beyer M 160 and also with a pair of Royer SF-1. Both these types of ribbon
microphone had picked up fairly low-level, but plainly audible, electrical
buzz when I tested them in this same room six or eight months ago.

The HAD-48 seemed to work very well. There were no operational problems
whatsoever, and no particular sonic drawbacks were immediately evident--
though I didn't make a direct A/B comparison (e.g. coincident mikes with
one channel "pre-preamped" and the other one not, with the preamp gain
set to compensate). They do have a few dB of very low-frequency rolloff,
but for vocal recording I don't mind; it's even a slight advantage,
especially with the SF-1 which have strong response to low frequencies.

Also, I've made no noise measurements whatsoever up to this point, so I'm
unable to comment on that very important aspect of the units' performance.

Unfortunately the pre-preamps didn't solve the original problem for which
I had bought them (the electrical buzz at this recording location)--but
that's a topic for another thread, I think. In fact I think I've already
brought it up in another thread, so I'll go find that one and rejoin it.

Unfortunately the pre-preamps didn't solve the original problem for which
I had bought them (the electrical buzz at this recording location)--but
that's a topic for another thread, I think. In fact I think I've already
brought it up in another thread, so I'll go find that one and rejoin it.

Darn! Now you've made me go looking for it. I had posted a reply to
this about that.

--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo