| AB6SL |
Rating:  |
2024-12-04 | |
| An affordable 12V audio DSP with volume limiter, EQ and more |
Time Owned: 0 to 3 months. |
At about 1/3rd the price of other devices known to the amateur radio community that offer some functional overlap, I've found the Taramps Pro 2.4D to be a very capable and portable (12VDC) audio DSP. It is designed for use with high-end, automotive car stereo systems, offering a configurable, 4-channel Crossover (four stereo outputs), each meant to supply line-level signals to separate audio amplifiers driving four different sets of transducers (i.e. low bass, mid-bass, mid, and treble, for multi-driver loudspeakers), a configurable 5-band EQ for each of the four Crossover outputs, and a very flexible, easily-configured Volume Limiter (invaluable when working DX pileups) for each of the Crossover outputs - among several other features that hams might find useful.
The Taramps Pro 2.4D audio DSP is adaptable for use with any transceiver or receiver having a mono or stereo output jack - placing the DSP unit in between the radio's audio output jack and a powered external speaker or speakers.
In my primary application, the Pro 2.4D sits between a Yaesu FT-710's external speaker jack and a repurposed pair of old, powered PC speakers that operate on 12VDC, having a built-in stereo audio amplifier, tone control and volume control. (Numerous used PC speakers can be found on eBay for $25 or less.) I'm only using one of the Pro 2.4D's stereo Crossover outputs - to send a line-level stereo signal to my self-powered PC speakers - having converted the mono output of the radio's external speaker jack to dual-mono (stereo) by using an inexpensive, mono-to-stereo 3.5mm plug-to-jack adapter, at the radio.
Note that the Yaesu FT-710 has very effective HCUT Freq, HCUT Slope, LCUT Freq and LCUT Slope parameters within its Radio Settings menu, so the 5-band EQ feature of the Taramps Pro 2.4D is not as valuable with the FT-710 as it is with my VHF mobile radio, which has no built-in mic EQ or output EQ settings. Anyone using any radio that lacks similar built-in audio output EQ settings would appreciate the 5-band EQ feature of the Taramps Pro 2.4D.
For those with similarly equipped Yaesu HF radios, feel free to experiment, of course, but I have adjusted the HCUT Freq to 1000 Hz with the default HCUT Slope value of 6 dB/octave, and the LCUT Freq to 2250 Hz, with the more aggressive LCUT Slope value of 18 dB/octave. Further tuning of EQ values is done with the Taramps Pro 2.4D 5-band EQ - my goal being to greatly attenuate all but the 1000 Hz to 2250 Hz range necessary for voice communications, but leaving some wiggle room at the bass end (with the 6 dB / octave LCUT Slope in the radio settings). In truth, all audio output EQ adjustments could be done within the Taramps PRO 2.4D.
My main purpose in ordering the Taramps Pro 2.4D ($79 at Amazon, at the time of this writing) was to take advantage of its Volume Limiter function. I cannot count the number of times my FT-710 has been blasted by a sudden incoming S9+100 signal - especially when I am attempting to pull out a very weak DX station with my RF gain and/or Audio gain adjusted to be "just right" for most signals I am hearing from competing stations that are heard in a pileup. But then along comes somebody here in the States, running 600W or 1500W into a 3-element quad or whatever. The radio's AGC can't deal with some of the more monstrous signals and I can never reach the RF gain knob fast enough. This very affordable and effective product has put an end to those situations, limiting the sound pressure levels heard from my external speakers.
This is not the same effect as simply using an attenuating patch cord (an inline resistor) between the radio and the external speaker(s) - which would attenuate all voltages equally. This DSP-controlled Volume Limiter allows all signal levels (all voltages) below your specified ceiling to pass unattenuated, while reducing higher voltages to your specified maximum.
To my knowledge, even the most expensive HF transceivers, especially the SDR rigs, lack a built-in, operator-adjustable volume limiter function, but once you start using a volume limiter, you will not want to operate without it. My ears are so much happier now, especially when working weak signals, as I no longer have to worry about somebody hitting my receiver with S9+1000, or whatever. LOL
I could share the settings I've specified in the Taramps Pro 2.4D, but that would be of little use, given the very low probability that a reader of this review would be using the same powered PC speakers that I'm using. I will share, however, that my installation setup is as follows:
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1) A 3.5mm TS Mono Plug to 3.5mm TRS Stereo Jack Adapter is plugged into my radio's external speaker jack (as mentioned above). See: https://www.amazon.com/Monoprice-107128-Stereo-Adaptor-Plated/dp/B002N1XMPO
2) A short, 3.5mm TRS male to 3.5mm TRS male, shielded stereo patch cord is connected to the mono-to-stereo adapter. See: https://www.amazon.com/Syncwire-Auxiliary-Braided-Headphone-Stereos/dp/B091Y9RK1F/
3) A 3.5mm Female to 2 RCA Male Stereo Audio Y Cable connects the stereo patch cord to the stereo RCA jacks labeled "Inputs" on the front of the Taramps Pro 2.4D. See: https://www.amazon.com/gp/product/B06XCR898P
Note that items 2) and 3) could be replaced with a well-shielded 3.5mm TRS male to dual RCA male cable, but finding well-shielded audio cables that will not ingest stray RF is difficult. (My HF antenna is an indoor, elevated ground-plane vertical, located only 6 meters from my bench, so your mileage may vary.)
4) A second 3.5mm Female to 2 RCA Male Stereo Audio Y Cable connects the stereo RCA jacks for only one of the four Crossover channels, labeled "Outputs 3." See: https://www.amazon.com/gp/product/B06XCR898P
5) Lastly, a second, short, 3.5mm TRS male to 3.5mm TRS male, shielded stereo patch cord sends the output of the Taramps Prio 2.4D to the 3.5mm input jack of my self-powered PC speakers. See: https://www.amazon.com/Syncwire-Auxiliary-Braided-Headphone-Stereos/dp/B091Y9RK1F/
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That, above, describes the audio signal path from my radio to the Taramps DSP, to the powered PC speakers. I can use the same adpaters and cables with any radio's external speaker jack.
Note that another set of stereo audio signal inputs are available at the rear of the Taramps unit via a 4-pin connector at the left rear of the unit, but I found everything to work much better for my amplified signal coming from the radio, when (surprisingly), I made use of the RCA inputs that are intended for un-amplified, line-level signals. Feel free to experiment, with your setup.
For 12VDC power, connect your power leads to the outermost two of four screw terminals that are located at the right rear of the Taramps unit.
Important note: Given that this device was designed for installation under a seat or in the trunk of a vehicle, in between the "head unit" of a car stereo, and as many as four external amplifiers driving four sets of speakers (via its four-channel crossover), THERE IS NO POWER SWITCH. It is designed to turn on automatically, whenever an audio signal is detected at one of its two inputs. This feature, is however, very dependent on both the low voltage and high impedance of an incoming line-level signal. The external speaker jack of my radios (and yours) put out a low-impedance, high voltage (already amplified) audio signal. I was unable, therefore, to make use of the automatic turn-on feature.
Here is an undocumented solution for easily attaching an external SPST power switch (instructions I received by email, from the excellent customer support staff at Taramps - located in Brazil - and I mean EXCELLENT - they are awesome.):
Any SPST switch would work, but I used this rocker switch with power leads already attached:
https://www.amazon.com/gp/product/B07G17HWW8
Connect one lead of the SPST switch to the 12VDC "+" screw terminal (sharing that terminal with the conductor coming from the "+" side of your 12V battery or DC power supply) AND connect the other lead of the SPST switch to the terminal that is next to the 12VDC "-" screw terminal.
In other words: Looking at the four screw terminals from above, imagining they are numbered 1 through 4, from left to right, the number 2 screw terminal will not be used. 12VDC power comes in on terminals 1 and 4 (+ and -). Leads from the SPST power switch must be connected to terminals 1 and 3).
I always start by turning on my radio, then turning on the Taramps Pro 2.4D, then turning on the self-powered speakers.
I will leave it at that, to avoid making this review any longer, but if interested, you can download and peruse the very well-written user manual, found here:
https://www.taramps.com.br/wp-content/uploads/2024/02/Manual_R00_Pro-2.4D_ENG.pdf
The Taramps Pro 2.4D seems to have been completely overlooked by the amateur radio community. In summary, I'm nothing short of thrilled with the price, the features and functionality (especially the volume limiter), as well as the customer support that's available for the Taramps Pro 2.4D, a DSP audio accessory offering a 5-band EQ and volume limiting functions, in addition to several other features described in the user manual. Again, these functions are adaptable to any transceiver or receiver that has an external speaker jack, as long as you also have a self-powered speaker.
One last note: The Taramps Pro 2.4D is small and runs on 12VDC, pulling only 1 Amp when in use, unlike some of the large and expensive, rack-mounted volume limiters intended for studio use, that require 120VAC power.
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