Using McCormack DNA-0.5 Deluxe as Mono Amps

You can use them to bi-smp, but not as monoblocks, unless you send them to SMcAudio (Steve McCormack, designer/owner of McCormack prior to its sale to Conrad Johson) for modification. The Smc mods are outstanding and you will not find nicer and more generous (with their time and technical knowledge)people that Steve and Chris at SmC. Steve posts here regularly as Stevemcx.

Hi Morgandogge -

There are a variety of ways to use a matched pair of stereo amplifiers to run your main speakers. There is no “Mono” switch on the DNA amps, but you can simply use one channel per amp (leaving the other channel unused), or you can use one amp per speaker in what is called a “passive vertical bi-amp” arrangement (passive horizontal bi-amping is also an option, but I do not recommend it).

Passive vertical bi-amping works very well and is easy to do if you have a matching pair of stereo amps, but does require that your speakers have bi-wire inputs with the jumpers removed. You simply assign one DNA-0.5 amp per speaker, use a Y-connector (typically) to run the same signal to both inputs, and connect one channel output to the speaker's high-pass input, and the other output channel to the low-pass input (which obviously requires a total of 4 independent speaker wires). The power each amplifier produces does not change, but now each speaker has its own amp so the net system power and dynamic headroom is increased.

Because you have a TLC-1, you have an additional option: you can use the passive output to connect to the high-pass channel on each amp, and use the buffered output to connect to the low-pass side. This requires a total of 4 independent interconnect cables which should all be the same for best results (along with the speaker cable). The potential advantage of this is the slightly superior bass performance of the buffered output. Connect the side of each amp being fed from the buffered output to the low-pass input on your speakers. If you don’t have 2 matched pairs of interconnect cable, skip this idea and just use a good quality Y-connector to bridge the signal across each amp’s inputs.

I often see people trying to use this technique while playing “mix-and-match” with the speaker cables and/or interconnects. Please do not allow yourself to fall into this trap. It may seem like a good idea, but it usually is not. The way this idea works best is when all of the connections are matched as closely as possible.

Finally, there is the option of having your DNA-0.5 amps converted to true monoblock operation. This is one of the upgrade options from SMc Audio. It provides balanced / unbalanced operation, and the power goes up to 400W @ 8 Ohms per amp. I like this option a lot and feel that it gives the best overall performance, but it requires sending the amps in for upgrade work. You can try the passive vertical bi-amp for free (or fairly low cost) and see what you think.

Have fun!

Steve McCormack
SMc Audio

I've been running the passive vertical biamp arrangement Steve describes for a couple of years now and have had great results (I'm using Electron Kinetics Eagle 4 amps, not DNA 0.5). I considered converting them to monoblock but after asking the speaker designer which to use, I was advised biamping with 125 w/c would be better than a 400w monoblock, so I saved my money. FYI my speakers are Von Schweikert VR4genIIIs, and I think your results are very speaker dependent as I received the opposite advice when asking the same question about my Totem Mani-2's.

Could they be parallelled with jumpers? Maybe using a small resistor (<1 ohm) between the outputs to reduce circulating current?

There would be an advantage driving low impedance speakers this way. Less voltage but more current than bridging.

Steve: Greetings! Would you be willing to comment on why you do not recommend "passive horizontal bi-amping"? Thanks, Din