Good Low Cost Audio to USB Interfaces For Digital Modes

[Jim Brown-10]

in the last few days I've been evaluating a couple of low cost audio to
USB interfaces for use primarily with digital modes -- RTTY, PSK, JT65,
FSK441. My primary objective is to improve decode performance at low
signal levels. I studied the catalogs and chose two low cost units that
looked like they would do the job and would not have RF problems.

Here's a link to a little Numark adapter that I bought for $33.  t's as
cute and easy as it looks.  Power from the computer, a couple of RCA to
1/8-in cables for gozinata and gozouta.

http://www.bhphotovideo.com/c/product/639303-REG/Numark_STEREO|IO_Stereo_iO_USB.html


The other one I bought is this Tascam unit.  A bit larger, more
mechanically robust, mostly metal enclosure, more flexible with respect
to levels.  The 1/4-in jacks for guitar and mic have more gain, so will
work with lower signal levels.  $70

http://www.bhphotovideo.com/c/product/648495-REG/Tascam_US_100_US_100_USB_2_0_Computer.html 


To evaluate them I hooked them to different Thinkpads running JT65-HF
and fed both of them from the line of a K3, then compared their decode
performance, and also compared them with the Thinkpads' internal sound
card.  The two new adapters performed equally well, and often produced
almost twice as many decodes on a given pass as the the internal cards.
Next I transmitted through them and looked at their spectrum on a P3
hooked up to a second K3. Distortion products look minimal on both units.

I also pulled them apart and studied their construction.  Both use
proper construction that avoids the Pin One Problems that cause RFI
issues. Now that I'm sure that they work well, I'm rewiring my station
to use them in place of the sound cards built into my Thinkpads for SO2R
contesting and everyday digital operation on both HF and VHF.

Both of these units are a real bargain from well known audio vendors.
Their interface to the K3 (and other rigs) is really simple. They don't
do any control functions, so you still need a serial or USB to serial
for that. I use VOX to key the K3.

Both are available from other vendors, but B&H had the best prices I
found, and shipping by UPS Ground was free.

73, Jim K9YC
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[Igor Sokolov-2]

Jim,
Thank you for the research.
Do you think these two cards will be good candidates for mating with KX3 and
netbook to be used for panadapter and SDR?  Are they 96khz or only 48?

73, Igor UA9CDC


----- Original Message -----
From: "Jim Brown" <[hidden email]>
To: "Reflector Elecraft" <[hidden email]>
Sent: Friday, March 09, 2012 7:59 AM
Subject: [Elecraft] Good Low Cost Audio to USB Interfaces For Digital Modes

> in the last few days I've been evaluating a couple of low cost audio to
> USB interfaces for use primarily with digital modes -- RTTY, PSK, JT65,
> FSK441. My primary objective is to improve decode performance at low
> signal levels. I studied the catalogs and chose two low cost units that
> looked like they would do the job and would not have RF problems.
>
> Here's a link to a little Numark adapter that I bought for $33.  t's as
> cute and easy as it looks.  Power from the computer, a couple of RCA to
> 1/8-in cables for gozinata and gozouta.
>
> http://www.bhphotovideo.com/c/product/639303-REG/Numark_STEREO|IO_Stereo_iO_USB.html
>
>
> The other one I bought is this Tascam unit.  A bit larger, more
> mechanically robust, mostly metal enclosure, more flexible with respect
> to levels.  The 1/4-in jacks for guitar and mic have more gain, so will
> work with lower signal levels.  $70
>
> http://www.bhphotovideo.com/c/product/648495-REG/Tascam_US_100_US_100_USB_2_0_Computer.html
>
>
> To evaluate them I hooked them to different Thinkpads running JT65-HF
> and fed both of them from the line of a K3, then compared their decode
> performance, and also compared them with the Thinkpads' internal sound
> card.  The two new adapters performed equally well, and often produced
> almost twice as many decodes on a given pass as the the internal cards.
> Next I transmitted through them and looked at their spectrum on a P3
> hooked up to a second K3. Distortion products look minimal on both units.
>
> I also pulled them apart and studied their construction.  Both use
> proper construction that avoids the Pin One Problems that cause RFI
> issues. Now that I'm sure that they work well, I'm rewiring my station
> to use them in place of the sound cards built into my Thinkpads for SO2R
> contesting and everyday digital operation on both HF and VHF.
>
> Both of these units are a real bargain from well known audio vendors.
> Their interface to the K3 (and other rigs) is really simple. They don't
> do any control functions, so you still need a serial or USB to serial
> for that. I use VOX to key the K3.
>
> Both are available from other vendors, but B&H had the best prices I
> found, and shipping by UPS Ground was free.
>
> 73, Jim K9YC
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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> Please help support this email list: http://www.qsl.net/donate.html 

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[Jim Brown-10]

Hi Igor,

I don't know enough about the KX3 to have a good guess. They are 48 kHz
units, which is plenty for ham radio use.

73, Jim K9YC

  On 3/9/2012 12:35 AM, Igor Sokolov wrote:
> Jim,
> Thank you for the research.
> Do you think these two cards will be good candidates for mating with
> KX3 and netbook to be used for panadapter and SDR?  Are they 96khz or
> only 48?

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[Mike Reublin]

Interesting, especially the decode number. Have you an opinion on the iMic?

73, Mike NF4L

On 3/8/2012 8:59 PM, Jim Brown wrote:

> in the last few days I've been evaluating a couple of low cost audio to
> USB interfaces for use primarily with digital modes -- RTTY, PSK, JT65,
> FSK441. My primary objective is to improve decode performance at low
> signal levels. I studied the catalogs and chose two low cost units that
> looked like they would do the job and would not have RF problems.
>
> Here's a link to a little Numark adapter that I bought for $33.  t's as
> cute and easy as it looks.  Power from the computer, a couple of RCA to
> 1/8-in cables for gozinata and gozouta.
>
> http://www.bhphotovideo.com/c/product/639303-REG/Numark_STEREO|IO_Stereo_iO_USB.html
>
>
> The other one I bought is this Tascam unit.  A bit larger, more
> mechanically robust, mostly metal enclosure, more flexible with respect
> to levels.  The 1/4-in jacks for guitar and mic have more gain, so will
> work with lower signal levels.  $70
>
> http://www.bhphotovideo.com/c/product/648495-REG/Tascam_US_100_US_100_USB_2_0_Computer.html
>
>
> To evaluate them I hooked them to different Thinkpads running JT65-HF
> and fed both of them from the line of a K3, then compared their decode
> performance, and also compared them with the Thinkpads' internal sound
> card.  The two new adapters performed equally well, and often produced
> almost twice as many decodes on a given pass as the the internal cards.
> Next I transmitted through them and looked at their spectrum on a P3
> hooked up to a second K3. Distortion products look minimal on both units.
>
> I also pulled them apart and studied their construction.  Both use
> proper construction that avoids the Pin One Problems that cause RFI
> issues. Now that I'm sure that they work well, I'm rewiring my station
> to use them in place of the sound cards built into my Thinkpads for SO2R
> contesting and everyday digital operation on both HF and VHF.
>
> Both of these units are a real bargain from well known audio vendors.
> Their interface to the K3 (and other rigs) is really simple. They don't
> do any control functions, so you still need a serial or USB to serial
> for that. I use VOX to key the K3.
>
> Both are available from other vendors, but B&H had the best prices I
> found, and shipping by UPS Ground was free.
>
> 73, Jim K9YC
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

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[Jim Brown-10]

On 3/9/2012 7:59 AM, Mike wrote:
> Have you an opinion on the iMic?

Know nothing about it -- I live in the PC world.

73, Jim K9YC
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[Mike Reublin]

Well dang! Thanks, Jim.

73, Mike NF4L

On 3/9/2012 5:52 PM, Jim Brown wrote:

> On 3/9/2012 7:59 AM, Mike wrote:
>> Have you an opinion on the iMic?
> Know nothing about it -- I live in the PC world.
>
> 73, Jim K9YC
> ______________________________________________________________
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[Tom Azlin N4ZPT-2]

Works for both Jim. Windows has the drivers. Is very nice.

73, tom

On 3/9/2012 5:52 PM, Jim Brown wrote:
> On 3/9/2012 7:59 AM, Mike wrote:
>> Have you an opinion on the iMic?
>
> Know nothing about it -- I live in the PC world.
>
> 73, Jim K9YC

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[Jim Brown-10]

On 3/8/2012 10:26 PM, [hidden email] wrote:
> Hi Jim - I've been using a Griffin iMic for years. Reliable.
> Inexpensive. FYI.

Just looked at it.  Looks good, and it might be the same as this one,
which W0YK swears by.  He takes them to P40X for his record-breaking
RTTY contest efforts. $29.  I just learned about it when I posted the
same notes to the NCCC reflector and he responded.

http://www.byterunner.com/byterunner/product_name=UA580/user-id=/password=/exchange=/exact_match=exact

Here's Ed response on the NCCC reflector yesterday, including Iain's
question to me.

=   =   =   =   =   =   =   =

I've been using a no-name USB soundcard with my traveling contest PCs for a
couple years now with good results.  I discovered recently that it is also
marketed by ByteRunner as their model number is UA580.  It does allow full
duplex and has stereo Line Input so it works well for SO2V RTTY too.
Available from several online vendors besides ByteRunner, and under $30.

Ed - W0YK



Iain, N6ML, wrote:

> I'm curious if either of these support "duplex" operation ...
> i.e. can you connect a mic to the input, connect the output
> to the line-in on the K3, and use them for "live audio" as
> well as recorded messages for software DVK? Some (all?) of
> the cheap USB audio interfaces I've tried didn't seem to be
> able to do that - they could record, and playback, but not
> loop-through...

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[Joe Subich, W4TV-4]

Griffin iMIC is a standard "USB Audio Class" device.  Most modern
operating systems support USB Audio Class devices with standard
drivers.  The iMic is reasonably well built for a commodity device.
Nothing special positive or negative ...

73,

    ... Joe, W4TV


On 3/9/2012 6:13 PM, Tom Azlin N4ZPT wrote:

> Works for both Jim. Windows has the drivers. Is very nice.
>
> 73, tom
>
> On 3/9/2012 5:52 PM, Jim Brown wrote:
>> On 3/9/2012 7:59 AM, Mike wrote:
>>> Have you an opinion on the iMic?
>>
>> Know nothing about it -- I live in the PC world.
>>
>> 73, Jim K9YC
>
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[Ed Muns, W0YK]

I also have some iMic units which work well on RTTY and while they have
stereo Line In, but they do not have duplex audio that Iain is looking for.


Ed - W0YK
 

> On 3/8/2012 10:26 PM, [hidden email] wrote:
> > Hi Jim - I've been using a Griffin iMic for years. Reliable.
> > Inexpensive. FYI.

Jim, K9YC, wrote:

> Just looked at it.  Looks good, and it might be the same as
> this one, which W0YK swears by.  He takes them to P40X for
> his record-breaking RTTY contest efforts. $29.  I just
> learned about it when I posted the same notes to the NCCC
> reflector and he responded.
>
> http://www.byterunner.com/byterunner/product_name=UA580/user-i
> d=/password=/exchange=/exact_match=exact
>
> Here's Ed response on the NCCC reflector yesterday, including
> Iain's question to me.
>
> =   =   =   =   =   =   =   =
>
> I've been using a no-name USB soundcard with my traveling
> contest PCs for a couple years now with good results.  I
> discovered recently that it is also marketed by ByteRunner as
> their model number is UA580.  It does allow full duplex and
> has stereo Line Input so it works well for SO2V RTTY too.
> Available from several online vendors besides ByteRunner, and
> under $30.
>
> Ed - W0YK
>
>
>
> Iain, N6ML, wrote:
>
> > I'm curious if either of these support "duplex" operation ...
> > i.e. can you connect a mic to the input, connect the output to the
> > line-in on the K3, and use them for "live audio" as well as
> recorded
> > messages for software DVK? Some (all?) of the cheap USB audio
> > interfaces I've tried didn't seem to be able to do that -
> they could
> > record, and playback, but not loop-through...
>
> ______________________________________________________________
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[Joe Subich, W4TV-4]

I understand that these are duplex cards:
   http://www.newegg.com/Product/Product.aspx?Item=N82E16829128010
   http://www.newegg.com/Product/Product.aspx?Item=N82E16829270009
   http://www.newegg.com/Product/Product.aspx?Item=N82E16829180006

as is this one:
   http://www.newegg.com/Product/Product.aspx?Item=N82E16829126101
   http://www.byterunner.com/byterunner/product_name=UA580

Two different designs ... packaged by several vendors.   I know several
users of each card; both have been used with the original microKEYER
as well as MK2R (the version without built-in soundcard) at well known
stations.

This is a new product - again apparently the same device with different
vendors - that claims full duplex playback and recording capability:
   http://www.newegg.com/Product/Product.aspx?Item=N82E16829131001
   http://www.newegg.com/Product/Product.aspx?Item=N82E16829111005

One needs do only a little research ...

73,

    ... Joe, W4TV


On 3/10/2012 11:32 AM, Ed Muns wrote:

> I also have some iMic units which work well on RTTY and while they have
> stereo Line In, but they do not have duplex audio that Iain is looking for.
>
>
> Ed - W0YK
>
>
>> On 3/8/2012 10:26 PM, [hidden email] wrote:
>>> Hi Jim - I've been using a Griffin iMic for years. Reliable.
>>> Inexpensive. FYI.
>
> Jim, K9YC, wrote:
>> Just looked at it.  Looks good, and it might be the same as
>> this one, which W0YK swears by.  He takes them to P40X for
>> his record-breaking RTTY contest efforts. $29.  I just
>> learned about it when I posted the same notes to the NCCC
>> reflector and he responded.
>>
>> http://www.byterunner.com/byterunner/product_name=UA580/user-i
>> d=/password=/exchange=/exact_match=exact
>>
>> Here's Ed response on the NCCC reflector yesterday, including
>> Iain's question to me.
>>
>> =   =   =   =   =   =   =   =
>>
>> I've been using a no-name USB soundcard with my traveling
>> contest PCs for a couple years now with good results.  I
>> discovered recently that it is also marketed by ByteRunner as
>> their model number is UA580.  It does allow full duplex and
>> has stereo Line Input so it works well for SO2V RTTY too.
>> Available from several online vendors besides ByteRunner, and
>> under $30.
>>
>> Ed - W0YK
>>
>>
>>
>> Iain, N6ML, wrote:
>>
>>> I'm curious if either of these support "duplex" operation ...
>>> i.e. can you connect a mic to the input, connect the output to the
>>> line-in on the K3, and use them for "live audio" as well as
>> recorded
>>> messages for software DVK? Some (all?) of the cheap USB audio
>>> interfaces I've tried didn't seem to be able to do that -
>> they could
>>> record, and playback, but not loop-through...
>>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>> Post: mailto:[hidden email]
>>
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>> Please help support this email list: http://www.qsl.net/donate.html
>>
>
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[Pierfrancesco Caci]

>>>>> "Jim" == Jim Brown <[hidden email]> writes:


    Jim> Here's a link to a little Numark adapter that I bought for $33.  t's as
    Jim> cute and easy as it looks.  Power from the computer, a couple of RCA to
    Jim> 1/8-in cables for gozinata and gozouta.

    Jim> http://www.bhphotovideo.com/c/product/639303-REG/Numark_STEREO|IO_Stereo_iO_USB.html  

If anyone cares, I got one of these after Jim's suggestion and it is
recognized by linux as follows:

Mar 24 21:11:29 penny kernel: [612304.150052] usb 2-8: new full speed USB device using ohci_hcd and address 9
Mar 24 21:11:29 penny kernel: [612304.378571] usb 2-8: configuration #1 chosen from 1 choice
Mar 24 21:11:29 penny kernel: [612304.532757] input: Burr-Brown from TI               USB Audio CODEC  as /devices/pci0000:00/0000:00:02.0/usb2/2-8/2-8:1.3/input/input8
Mar 24 21:11:29 penny kernel: [612304.533036] generic-usb 0003:08BB:2900.0004: input,hidraw2: USB HID v1.00 Device [Burr-Brown from TI               USB Audio CODEC ] on usb-0000:00:02.0-8/input3

 # lsusb
Bus 002 Device 009: ID 08bb:2900 Texas Instruments Japan PCM2900 Audio Codec

(lsusb -v output available on request)

Volume control only shows a PCM slider, which is a bit weird. I have not
yet tried to hook it up to the radio.

Jim, how do you set the little volume control?

Pf

--
Pierfrancesco Caci, ik5pvx
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[Jim Brown-10]

On 3/24/2012 1:19 PM, Pierfrancesco Caci wrote:
> Jim, how do you set the little volume control?

I've never found a gain control for Record. :)  There are two inputs --
a Line level input that I suspect is designed to work at a few volts,
and a Phono input which is designed to work at the level of a phono
cartridge (the type used to play vinyl records).

The Phono input has RIAA equalization, which boosts low frequencies and
rolls off high frequencies.  I use the Phono input with a simple RC
filter network between the radio and the Numark.  I'm going from memory,
but I believe what I used was 200 ohms across the output of the radio,
200 ohms across the input to the Numark, and 0.22 uF between the radio
and the Numark.  This simple network is designed specifically to match
the K3. The Phono input has a LOT more gain than the Line input, so this
gives the unit the ability to handle any signal level you're likely to
get from a radio.

73, Jim K9YC
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[Pierfrancesco Caci]

>>>>> "Jim" == Jim Brown <[hidden email]> writes:


    Jim> On 3/24/2012 1:19 PM, Pierfrancesco Caci wrote:
    >> Jim, how do you set the little volume control?

    Jim> I've never found a gain control for Record. :)  There are two inputs --


I was talking about the rotary control on the side of the box.

    Jim> a Line level input that I suspect is designed to work at a few volts,
    Jim> and a Phono input which is designed to work at the level of a phono
    Jim> cartridge (the type used to play vinyl records).

    Jim> The Phono input has RIAA equalization, which boosts low
    Jim> frequencies and  
    Jim> rolls off high frequencies.  I use the Phono input with a simple RC
    Jim> filter network between the radio and the Numark.  I'm going
    Jim> from memory,  
    Jim> but I believe what I used was 200 ohms across the output of the radio,
    Jim> 200 ohms across the input to the Numark, and 0.22 uF between the radio
    Jim> and the Numark.  This simple network is designed specifically to match
    Jim> the K3. The Phono input has a LOT more gain than the Line
    Jim> input, so this  
    Jim> gives the unit the ability to handle any signal level you're likely to
    Jim> get from a radio.

Interesting. If it has more gain, isn't it more likely to saturate,
given that the radio has a Line level output? Your suggestion seems
counterintuitive to me, I must be missing something.

Pf

--
Pierfrancesco Caci, ik5pvx
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[Jim Brown-10]

On 3/24/2012 2:48 PM, Pierfrancesco Caci wrote:
> Interesting. If it has more gain, isn't it more likely to saturate,
> given that the radio has a Line level output? Your suggestion seems
> counterintuitive to me, I must be missing something.

The words "Line Level" are pretty elastic. In the consumer audio world,
that means a PEAK value of 1V. In the pro audio world, it means a peak
value of 10-20V. Also, early production K3s (the first couple of years,
which i have) have a design error that caused the output transformers to
create distortion if you ran the Line Out much above about 10. That
means that to keep the distortion low you need to keep the output below
about 100 mV peak, which is sort of marginal to drive the Numark.

The simple network I described introduces both some attenuation and the
desired equalization, and the result is that if you run the K3 Line Out
fairly low nothing gets overloaded.

73, Jim K9YC
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