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McCormack monoblocks using DNA-HT1 / DNA-0.5

Greetings all! Still thinking about the best McCormack path to take for my main amp.

So I had a crazy idea the other day while sitting in an airport (which I end up doing a lot). I wonder if anyone has ever modified a DNA-HT1 to make it into a dual monoblock stereo amplifier, taking it from a three channel amp where the center gets the bridged output of to two channels and left and right only get one channel each to a stereo amp where left and right get two channels each?

Since the innards of the DNA-HT1 is essentially two DNA-0.5’s (correct?) I would assume it would theoretically be possible to rewire it into what would basically be a set of DNA-0.5 monoblocks set in one chassis. Is this possible? Has anyone ever heard of doing something like this before? Would this leave enough space inside for upgrades to the circuits? Would this then be a true-balanced design?

When I saw SMc's old upgrade literature on the HT1 where he said that the DNA-HT1 "utilizes exactly the same circuitry and parts as the other DNA amps” and “although it is configured as a 3-channel amp on the outside, it is actually a 4-channel amp internally” the old wheels got a-spinning about the possibility of what those four channels could be used for in a stereo set-up. Guess that’s my old engineering degree coming to the surface!

I’ve seen examples of Klaus doing this at Odyssey Audio with his Stratos and Khartago amps, and figured if he can do it then SMc could. This also appears to be a way to build a set of DNA-0.5 monoblocks with a lot less upfront investment, especially given that I can get a used DNA HT1 for only about $150 more than a single used DNA-0.5. Potentially could even wait for a DNA-HT1 DLX.

The main potential downside I can think of is the amount of power the HT1 might be able to draw. If the HT1 only has one power supply, it would likely have a hard time keeping up with the power needs of the two monoblocks in the one chassis. When Klaus does this mod at Odyssey (Stratos Dual Mono) I believe he puts in two power supplies to feed the two monoblocks.

If this upgrade/modification is possible, would using the HT1 with only the left and right channels (leaving the center disconnected) then be the same thing as having a stock DNA-0.5? This would allow me to use the DNA-HT1 for a few months in my 2-channel set-up as I saved up money (and spousal approval, which is harder to find!) for the “operation”. This also would then beg the question of how much this type of modification would cost from SMc? I believe his normal monoblock conversion is $475 or so, but assume this would be more involved.

Final thought is that this might just be too much of a bother and that I could just wait for a pair of used DNA-0.5's or DNA-1's that had already been made into monoblocks so I didn't have to pay full price for the modifications.

Thanks for any and all input/ideas/critiques/etc.
mscott58
ig316b
104 posts
 
Mscott58
If what you suggest is possible then you would have essentially a fully balanced two channel amp in a single chassis. This sounds like a lot of work on Steve and Kris's part. But if you do some reading on Agon you will find that Steve is a fan of monoblocks (read through the answers he's provided here under Stevemcx, lots of good information). He will more than likely recommend you try going in that direction with a pair of amps unless your setup requires a single chassis setup. I noticed you have been looking in the McCormack direction for amplification. Have you heard your Chario Academy 1's driven by the McCormack's. If not and you live within about two hours of Philadelphia we could make an arrangement for you to hear them on a pair of original DNA-1 monoblocks. I happen to have a pair that I'm not using at the moment and would be willing to work something out with you to give you a better idea of what you are looking/listening for. I originally had these driving my Vandy 3A Sig's but after switching to bi-amping with a pair of DNA-1 Dlx Gold's these have been sitting on the side line.
luigi_secchi00
11 posts
 
it wouldn't be much of work I suspect.. Steve would just put two little input transformer each in front of a pair of channel, and he would do a minor rewiring of the inputs and the outputs...

I believe the advantages of the balanced operation would be: i) common mode rejection of ripple/noise from the power supply ii) zero current draw from the power supply iii) cancellation of even order distortion (a questionable advantage, actually) at the output iv) better control of the speakers (some say).

But the bottom line is that you really need to ask Steve/Kris

Mscott58, are you saying that the chario are better than the vandersteen? In that case I must have underestimated those little things :)
mscott58 OP
5 posts
 
Greetings everyone! I heard back from the man himself (Steve McCormack) on my crazy idea regarding modifying the DNA-HT1 into a dual mono. There's good news and bad news.

First the bad news per Steve: "To answer your first question - no, I have never converted an HT-1 (or HT-3) into a pair of bridged channels. There is no reason why this couldn't be done - I have just never done it. As you know, the center channel output is a already a bridged pair, and you certainly could add a bridging circuit to the other pair of channels to form another bridged pair. What you probably don't realize is that the center-channel pair has only 2 output devices per side, while the other (main) output channels have 4 (2 x NPN & 2 x PNP). This gives the main channels greater current delivery capability, although the circuit topology is otherwise the same for all. As you can see, this would mean that the bridges channels would not be truly matched, at least in terms of current delivery."

Now the good news regarding the HT1, again from Steve: "On the other hand, using just the main L-R channels (while leaving the center channel unused) works very well. In fact it has a distinct advantage over a regular DNA-0.5 in that the power transformer is a high-quality toroid, and much larger than the standard 0.5 transformer. I know of several people doing this, and they are very pleased with the result. You would have to add the Plitron transformer to the DNA-0.5 (one of the upgrade options) to equal or exceed this advantage."

Oh, and one last point that would killed the HT1 dual-mono idea out of the gates: "Please note that I do not offer upgrade work on the HT-1 or HT-3 - they have proven to be too fussy and time-consuming to be done economically."

Looking at my system and thinking about the various options I will likely go with some SMc mod'd monoblocks from the get-go.

Just wanted to post this information in case it was helpful/useful to anyone else out there in the Agon universe.
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