...A useful scheme for software based transmit audio processing for the Kenwood TS-870S.
Why do it?
As noted elsewhere on this website, digital audio processing an handling in newer transceivers such as the Kenwood TS-590 is relatively easy to implement due to the presence of a digital audio path between the transceiver and a PC. Accomplishing these techniques with older transceivers such as the Kenwood TS-870S, although doable, is somewhat more problematic. Nonetheless, the advantages justify doing so. This article was created to share setup information and lessons learned and in intended for other hams who are considering this approach as an effective alternative to hardware based external transmit audio processing.
Audio flow chart:
- Digital audio from the Rode microphone is routed to a Windows 10 PC via a type AB USB cable.
- Digital audio is thence processed internally in the Windows 10 PC by a software based processing system called "Breakaway Live".
- Processed digital audio is converted to analog and routed from the software back to the microphone via the USB cable.
- Processed analog audio is routed from the microphone via 3.5mm cable to the front panel of the Kenwood 870's microphone connector.
- Processed analog audio is thence transmitted by the 870, amplified by the AL-80B and routed to the balanced line tuner thence onward to the antenna.
- Received analog audio is routed from the 870 directly to a pair of Behringer MS40 near field studio monitor speakers.
Note: Hams who prefer not to invest in a USB microphone may want to consider using their favorite conventional microphone together with a external USB audio interface such as the Focusrite Scarlett Solo. This device inputs your mic output audio into the front panel XLR connector, thence routed as digital audio to your software based processing system via a USB cable. Processed audio is then routed from the PC back to the interface via the same USB cable, thence converted back to analog audio before being outputted to the rear panel left and right channel rca jacks which are connectedt to the microphone input connector on the front of the 870 via a splitter patch Y Cable - 1 XLR Male to 2 RCA Male such as the one described HERE.
Microphone audio routing scheme
The NT-USB is ideally suited for recording musical performances in addition to spoken word applications such as podcasting, voice-overs and amateur radio
The microphone is fully compatible with all mainstream recording applications on both Windows and Mac OS based computers, as well as the Apple iPad using RODE Rec, GarageBand, or any other recording app that accepts an external microphone.
For zero-latency, there is a 3.5mm jack on the front of the microphone where you can attach heaphones to monitor the output of the microphone or the output of your software based processing system. More importantly, and for purposes of this article, connect a 3.5mm cable to this jack with a male TRS plug on one end and a male XLR plug on the other end such as the cable described at https://www.bhphotovideo.com/c/product/691059-REG/Hosa_Technology_XVM_101M_XVM_101M_Angled_3_5mm_to.html.
Two adjustable control knobs are located on the front of the microphone. One knob selects either unprocessed audio direct from the microphone. The other knob adjusts the level of processed audio coming from the output of the software based processing system. This control, together with windows sound manager level adjustment and the processing software's adjustments must be fined tuned in unison in order to provide the faithful and clean audio input to the 870. Additional setup information and tips are provided below.
- Kenwood TS-870S HF transceiver.
- PC running Window’s 8.1 and internal Realtek sound card.
- Necessary interconnection cabling as described above.
- Rode NT-USB microphone as described at https://www.amazon.com/Rode-NT-USB-USB-Condenser-Microphone/dp/B00KQPGRRE/ref=sr_1_1?ie=UTF8&qid=1483446440&sr=8-1&keywords=rode+nt-usb+microphone .
Transmit audio processing software:
K4QKY often uses a software based audio processing system called "Breakaway Live” audio processor which features:
- Professional grade audio processing appropriate for live commercial and amateur radio transmitting purposes.
- Low latency resulting in imperceptible delay.
- Efficient computer CPU usage to permit multitasking without interruption.
- Multiple audio preset configurations depending on purpose, e.g. DX or Rag Chewing.
(1) Download Universal ASIO driver for Windows audio "ASIO4ALL" from http://www.asio4all.com/.
(2) Download and install the demo version of Breakaway Live from http://www.claessonedwards.com/index.php?option=com_content&view=article&id=95.
Kenwood 870 initial settings:
VOX is set to on as described in the operator’s manual. Microphone gain initially set at about 8:30 knob position. The speech processor and TX EQ are both off as the audio processing software system incorporates superior EQ and compression. Menu 29 is set to 3000 and menu 30 to 100.
Windows sound manager initial settings:
> Speakers Realtek High Definition Audio Device set as default device. Properties set at level 90, no enhancements, 16 bit, 48000Hz and no exclusive mode.
> Speakers Rode NT-USB set as the default communications device. Properties set at level 56, no enhancements, 16 bit, 48000Hz and no exclusive mode.
Note: This important device controls the level of processed audio going to the 870 for transmission. To reiterate, there are two adjustable control knobs are located on the front of the microphone. One knob selects either unprocessed audio direct from the microphone. The other knob adjusts the level of processed audio coming from the output of the software based processing system. This control, together with windows sound manager Speakers Rode NT-USB level adjustment and the processing software's adjustments must be fined tuned in unison in order to provide the faithful and clean audio input to the 870.
> Microphone Rode NT-USB is set as Default Device. Properties set at level 24, 16 bit, 48000Hz and no exclusive mode. Close talk (about 2 inches) the microphone in order to alleviate pickup of shack noise.
Breakaway Live Audio Processor Software setup:
When Breakaway Live is first started, configuration settings will need to be established including those shown on the below Signal Settings window:
Once the above settings are made, click the “I/O Configuration" button which will bring up a I/O configuration window like the one shown below.
Select the ASIO device as shown at the top of this window. Be certain to activate the "Enable ASIO' button. Then click the "ASIO config" which will bring up a pop-up window like the one shown below.
Configure the settings as shown in the above screen shot. Then exit the window which will take you back to the I/O configuration window where you can now enter the correct settings as shown in the screen shot. Then, exit out of this window which will take you back to the previous I/O configuration window where you should select 48000 HZ sampling . Next, select Rode NT-USB 1 as the InputL1 device and then scroll down to select Rode NT-USB 1 as the OutputL1 device. Finally, click the “Finish” button. Lastly, restart Breakaway Live. Provided all your settings are compatible, you should now be viewing the main screen similar to the one shown in the below screen shot:
Click BreakawayLive Settings to print and learn more about each of the settings on the above graphical user interface. As noted, there are several presets to choose from. It is suggested that you start out by selecting the "Reference Jazz" preset. It works well for rag chew purposes. Initially adjust the various green sliders (see pop up tool tips for each) to conform with those in the above screen shot. Now, for the all Important final step! Set the level control button of the front of the NT-USB microphone to the 4 oclock position and the 870's microphone gain control to the 8 oclock position and leave them both at these settings. Also, make sure that the the audio level of the Rode NT-USB Speakers device in the Windows sound manager playback tab is set at 56 and the “Microphone” audio level in the recording tab are set to 24 and avoid changing either setting. Lastly, while speaking into the microphone and listening with head phone to the 870's monitor, adjust the “Peak Reference level slider” on the above window as necessary to achieve just a slight deflection of the ALC meter on voice peaks This is your “Sweet spot”. Avoid excessive ALC as you will invite non-linearity.