OMP modules from BK Electronics.

[Andy Westcott 0]

Anyone make up their own amps from modules?

 

I have always used the modules as sold by BK Electronics - the OMP range:

http://www.bkelec.com/Modules/Amplifiers.htm

Good power outputs for small to medium rigs, and cheap as only the bare minimum is supplied.

 

I work them heavy, 2 of them into minimum impedances (4 ohms), and have never had a failure.

 

Before I put them into 'proper' service I soak tested each of the modules by feeding a sine wave of high enough level to slightly clip the amp, and fed the output into a 5 ohm resistive load. 12 hours later all four of the amps were fine: The heatsinks were hot as would be expected, as were to transformers, but not overhot.

 

My opinion is that apart from silly loading and short circuits, they are bullet-proof. I did actually short the output of one of the 200W models by mistake, and apart from a large spark and 2 blown internal fuses, things were OK and I still use the module to this day. (With the fuses replaced of course....)

 

One important point:

If you do use them, be sure to fit cooling fans to blow a good flow of air through the heatsinks as the lower power models don't have fans, and I think for reliability they should have.

 

I'd be interested to hear if anyone else has used these amps, and your experiences.

[chrismk 0]

So would they be ideal for driving subs

[Andy Westcott 0]

Yep.

Good for anything really. For a long time I ran two 200s as a stereo pair into 4 ohms full range.

 

I use a pair of 450s driving a single 18" 8 ohm bass driver on each side. This actually produces just a shade over 300 watts to each driver, but as the figures quoted are for very low distortion figures, they will output rather more than this before audible clipping occurs.

 

You will need an active crossover, and there is no option for balanced input to the amps, but this isn't really a problem. Don't try bridging though, as unless you can electronically invert the phase of one of the inputs to one of the amps by 180 degrees, you may run into trouble with earth shorts an so-on.

 

If you go for the biggie, this will output a reliable 725 watts per side into a 4 ohm load (two bass drivers.)

 

You will have to build a cabinet for these amps, and ensure the necessary forced air ducting. With the 200s I simply screwed them to a base panel, back to back so the heatsinks made a 'tunnel' and fitted a fan to blow air through there. I found the fins ran nicely warm at best, even at the loudest parties.

[chrismk 0]

At least it ran warm and not hot, warm is good when it comes to MOSFET amps, I believe this is when they operate at thier best

[RobbieD 0]

Interesting.....

 

A couple would be idea to build in to my next console. Then for smaller gigs (ie no subs) I could leave the amp rack in the car. At other larger gigs I could use these built in amps to drive some monitors whilst the amp rack drives the main PA.

[superstardeejay 0]

The OMP modules are a similar design (but not identical) to the guts fitted in BK's OMP and DNA series amplifiers, originally they used Hitachi dual-chip mosfets and the last ones I saw had the ubiquitous Semelab (SML) transistors. Most people will have heard an OMP/DNA amp at sometime as they are all over the place and have been for years. They're pretty reliable beasts, mostly due to their simplicity and over-engineering, no fancy circuitry, relying on the mosfets with their intrinsic safe operating area.

 

Most of them only fail after many, many years of hard use, (or abuse), they usually blow their LCR bus capacitors or supply resistor, but if its sound quality you want, maybe something more expensive would fit the bill as I think I remember the damping factor is a little low for very bassy response.

 

A very good DIY module, see also Terralec's Lyonforge modules which are v.similar.

 

 

 

 

 

 

 

 

[HeadlineDJ 0]

The two mono amps I have listed in the classifieds section are built using two of the MF1000 modules.

 

BK sent me the circuit diagram also, so the input sensitivity can be changed whenever you wish.

 

I built custom cases around each module and have 2 mains fans on a push pull arrangement.

 

As said above these are bullet proof amps, I just need more power than these module provide now, so am selling them as my new amps and processing are on their way :)

 

The point about over engineering on these is an understatement, if only everything was built to this level of robustness.

 

 

[superstardeejay 0]

Over here, the nightclub with the largest dancefloor in Stoke-on-Trent uses BK DNA600 amps, I know for a fact they're run into hard clipping most nights, I was called to repair them a couple of years ago as they were tripping when hot, to alleviate the problem the DJ had pulled them from the rack and spaced them apart with spent 9V radiomic batteries as spacers!! Luckily it was just worn-out fan thermostats.