Will a passive mixer do it?

[Tobiah]

I have a dual boot computer, and each OS must use a different
audio interface (Can't get Linux to see my Studio 18/10).
I'd like to just combine the stereo outs from each to go
into the amplifier.

I tried an old mechanical A/B switch from Radio Shack, but
for some reason it picked up just enough noise to be unusable.
It was also more annoying than you might think to reach over
and flip the switch!

So I was wondering how a passive mixer might work. I saw
this online:

INPUT 1 -------\/\/\/\---+
---+ R1 10K +------------ OUTPUT
| | +----
INPUT 2 -------\/\/\/\---+ |
---+ R2 10K |
| (shields) |
+---------------------+

Will that do it? I have plenty of volume to spare, but
I was curious about how much attenuation I'd experience.
Is there a product that essentially does the same thing?
I don't even really need volume controls.


Thanks

[Tobiah]

Also, I noticed that on the back of my Denon power amp, each channel has two
RCS inputs, one labeled 'CD', and the other 'Normal'. I assume that it would
be a bad idea to try to utilize both at the same time, but I'm not completely
sure.

[John Williamson]

Check the circuit. The CD input will probably be designed to accept the
usual digital 1 Volt input, while the normal *should* be 0.775 V at 600
ohm impedance (0dB Reference voltage for pro gear), but for domestic
gear, this will be a lower voltage.

This could be either active or passive attenuation. Either way, you
won't do any physical damage

--
Tciao for Now!

John.

[John Williamson]

The attenuation will depend on the load and source impedances.

[palli...@gmail.com]

John Williamson wrote:
====================

> Check the circuit. The CD input will probably be designed to accept the
> usual digital 1 Volt input,

** CD & DVD players output up to 2V rms.

> while the normal *should* be 0.775 V at 600
> ohm impedance (0dB Reference voltage for pro gear), but for domestic
> gear, this will be a lower voltage.

** 250mV is about normal sensitivity for tuners and cassette players.


...... Phil

[Scott Dorsey]

In article <sned0j$2c8$1...@gioia.aioe.org>, Tobiah <to...@tobiah.org> wrote:
>I tried an old mechanical A/B switch from Radio Shack, but
>for some reason it picked up just enough noise to be unusable.
>It was also more annoying than you might think to reach over
>and flip the switch!

This is likely because when you connected the two devices to the same
ground, you created a ground loop.

A passive mixer will create the same ground loop. So figure out your
grounding first.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Ty Ford]

Holy Crap! A thread that reads like the good old r.a.p. newsgroup!

Yay!

Regards,

Ty Ford

[Markus Ermert]

Ty Ford <tyre3...@gmail.com> wrote:
> Holy Crap! A thread that reads like the good old r.a.p. newsgroup!
>
> Yay!
>

Usenet is alive.

[Albert A]

I'm in the process of doing a DIY windscreen for an old Zoom H2 recorder
I have. I followed some instructions I found online, which uses felt,
foam, and then a final layer of faux fur. I was able to make everything
from materials I had on hand except the faux, which I had to order.
Quick tests with just the original foam-felt-extended foam still allow
wind noise. Will the faux around all of this curtail the wind once and
for all? Why would it work better than the foam? Thanks.

[Scott Dorsey]

People think that it works better than foam because it slows airflow. It's
still turbulent flow, but it's slower. Juerg Wuetke at Schoeps did some
research in the nineties and you might find a paper from Rycote on the
physics in the AES database.

Personally I find that an open-cell foam ball of six inches or so diameter
like the Olsen windscreens works almost as well as the dead cat screen,
with slightly less effect at high frequencies. Mike Rivers and I did a
test on the Olsen windscreens compared with the baby ball gags and one of
the dead cat screens (a cheap Rycote knockoff that a friend got somewhere) at
Washington Folk Festival one year and the differences between them were
clearly audible but they were all effective and which one you preferred
depended on how much wind reduction you thought necessary and how much top
end loss you could tolerate.

But... as always... the mike pattern has more to do with wind sensitivity
than anything else!

[geoff]

On 28/11/2021 11:46 am, Scott Dorsey wrote:
> In article <snuaqu$udk$1...@dont-email.me>, Albert A <albe...@aol.com> wrote:
>> I'm in the process of doing a DIY windscreen for an old Zoom H2 recorder
>> I have. I followed some instructions I found online, which uses felt,
>> foam, and then a final layer of faux fur. I was able to make everything
>>from materials I had on hand except the faux, which I had to order.
>> Quick tests with just the original foam-felt-extended foam still allow
>> wind noise. Will the faux around all of this curtail the wind once and
>> for all? Why would it work better than the foam? Thanks.
>
> People think that it works better than foam because it slows airflow. It's
> still turbulent flow, but it's slower. Juerg Wuetke at Schoeps did some
> research in the nineties and you might find a paper from Rycote on the
> physics in the AES database.

More random, and 'softer'. Foam itself is fairly rigid in comparison,
and wind 'resonates' on the surface. A different effect to
plosive-filtering for which foam-ball filters are intended for.

geoff

[geoff]

AKA 'dead cat'.

geoff

[Liz Tuddenham]

The theory is that the long hair of the fur produces a wind speed
gradient between the free air and the surface of the material. This
results in less turbulence than a sudden change in speed if the wind
hits something more solid such as short hair fur, silk bonded to gauze
or foam rubber.

The base of the fur material is dense enough to only allow the air to
move through it slowly, but a large air space is necessary between the
underside of the fur and the microphone capsule to allow the internal
air currents to circulate gently without causing a pressure difference
across the capsule. Open cell foam usually performs this task and
supports the underside of the fur. It does not need to be as dense as
the foam used for 'pop shields', although similar foam is often used.

As others have said, the type of microphone also makes a big difference.
A pressure capsule (omnidirectional) is least susceptible to wind noise,
a pressure-gradient capsule (bidirectional 'ribbon') is most
susceptible. Cardioids and hypercardioids are intermediate, the more
directional they are, the more susceptible they are.


--
~ Liz Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

[Albert A]

Thanks for the response and my apologies as I just found out that I
unfortunately posted this in error on an existing thread. Was tempted
to start a separate thread, but since there have been responses here, I
guess I'll continue.

My Zoom H2 is being used to capture nature sounds outdoors. I did a
twelve hour audio capture overnight with the dual foam cover in place as
the faux won't arrive for a few days. The results were good, but I
noted a drop in the high end. Not much, but I did a comparison this
morning using a white noise source I use to help me sleep both with and
without the filters. It wasn't much of a drop and I tried to best
adjust EQ of the white noise to compensate as best as I could. I mainly
used the spectrum display over the speakers as my speakers are not pro
and have a lot of coloration in the low end. However, this is what I
was able to come up with:

https://i.imgur.com/7evLt5q.jpg

It's fairly gentle and I don't think much is needed for compensation
anyway. Would this resemble an approximate compensation curve for this
sort of set up? I welcome suggestions for better refinement. I have
Audacity, but am currently evaluating a demo version of Audition and
that's what was used to create the curve shown. Thanks.

[Liz Tuddenham]

Albert A <albe...@aol.com> wrote:

> ... I did a

> twelve hour audio capture overnight with the dual foam cover in place as
> the faux won't arrive for a few days.

The most suitable type of fur has mixed-length fibres, including quite
long soft ones, so that it produces a gradient effect. Short, bristly
fur, with all the fibres about the same length, won't be as effective.