Cheap & Not So Nasty Sub Amp

[Gary Cook]

My DIY sub pre amp and 300 watt power amp combo finally gave up after 25+ years of service. It has been powering the sub woofer in my home office, supplementing the Airmotive 4's, for the last couple of years, but last week it started to sound "off"  (that's a technical term) and lost its grunt (also a technical term). The sub woofer is a 12" Soundstream driver in a dual ported DIY cabinet that sits under the long desk, so it doesn't need a lot of watts to power it. I opened up the old rack mount case and had a quick pock around, it has 6 output devices and it looks like 4 of them have left the building (I'm being very technical today). That amp board is no longer available and it had particular requirements in input and power voltage plus impedance. Despite a few days of internet exploration I couldn't find anything that was a straight substitute, which meant changing the pre amp and the power supply board. Leaving just the case and the toroidal transformer as being reusable, maybe not worth the effort.

While I was internet browsing for a replacement amp board I came across Nobsound Class D subwoofer amps www.doukaudio.com/nobsound-100w-subwoofer-power-amplifier-mono-channel-audio-mini-amp-p0041.html


For $A40 + $A25 for the power supply on Amazon.com.au (free delivery) I thought I might give one a try, nothing to lose.  The specs aren't world class but it uses TI op amp and amp chips so should be OK;

Audio input: 3.5mm AUX
Audio output: banana speaker jack
Op amp: NE5532
Amp chip: TPA3116D2
Max. output power: 100W
Dimensions(W*H*D): 68.5×33×90mm / 2.70*1.30*3.54in
Net weight: 200g / 0.44lb
Package weight: 320g / 0.71lb
Working voltage: DC 12V-24V
Built-in low pass filter, 20 Hz - 120Hz 0.04% THD, 18db/octave

I wasn't expecting much, just something to fill in until I decide what to do with the DIY pre/power amp. But I have to say I was surprised, it has more than enough power for what I need and it sounds pretty good.  Just by the ears it blends in OK with the Airmotive 4's, but I'll try an REW test at some stage.  Next weekend I'm going to also give it a run with a not as efficient subwoofer, a 12" Sony driver in a sealed enclosure, to see how it handles that. 

It is plugged into the speaker output of the BigEgo via a spare Emotiva (mono) trigger cable (why not). Whereas the Airmotive 4's are plugged into the headphones output so as to utilise the resister ladder volume control. I control the volume of the sub woofer via the volume knob which also doubles as the turn on switch. Not a problem for a home office system.

If anyone is looking for sub pre amp/amp to compliment a small system it would be well worth a try.


Cheers
Gary

[Boomzilla]

Hi Gary -

You want CONTROL? Buy an old Crown DC-300a. Available used only, but IRON GRIP control in the bass!