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McCormack DNA 500 vs DNA 225 upgraded

I am looking for some feedback on comparing the stock DNA500 to a DNA225 upgraded by Steve McCormack. There were a few posts that only touched that subject. I am thinking about adding one of those amps to my system and relegating the HT5 to the surrrounds and center.

The DNA500 has amazing reviews, as the DNA225 upgraded also does. Is there a benefit to either one? I notice at this point there are no upgrades available on the SMC site for the 500. I imagine the cost for either is similar.

Thanks again for any help. This forum has been outstanding for me to learn from.
still_learning
stevemcx
166 posts
 
Hi Stefan,

Like the DNA-500, the DNA-750 monoblocks are fully balanced with differential outputs. The input is transformer-coupled using the same circuit as the DNA-500. Input impedance is 10K.

Best regards,

Steve McCormack
SMc Audio
lanx0003
1,192 posts
 

@stevemcx  What are the rated RMS and peak currents? I’m by no means an expert, but I wonder why your amp was designed with a low input impedance (10k ohms), which tends to create an impedance mismatch issue. Since it is transformer-coupled, could the input stage be adjusted to increase its impedance?  Thanks.

mitch2
4,325 posts
 

I believe Steve is partially/mostly (trying to be) retired, like others of us, so you may not hear from him.  He has not had anything to do with the DNA 500 or 225 for many years as Conrad Johnson acquired McCormack Audio and took over those designs.  Steve’s company SMc Audio performed upgrades to both but maybe not the DNA 500 any more.

I will not try and answer your questions but as a former owner of the DNA 500 I can say it is effortlessly driven by virtually any solid state preamp, and that I have successfully used it with tubed preamps with output impedance as high as 600 ohms.  The old rule was a minimum of 1 to 10, output impedance of the source to input impedance of the load.  My personal goal was to keep that ratio at 1:20 or better.

Here are some specs for the DNA 500, FYI:

 

  • Output Power:
    • 500 watts per channel RMS into 8 ohms
    • 900 watts per channel into 4 ohms
  • Output Current: 50 Amps peak per channel
  • Input Impedance: 100k ohms
  • Input Sensitivity: 1.2V
  • Frequency Response -3dB at 0.5Hz and 250kHz
  • Rise Time: ±2µs
  • Slew Rate: 50V/µs
  • S/N Ratio: 88dB, "A" weighted
  • Damping Factor: >100 (1kHz, 8 ohm load)
lanx0003
1,192 posts
 

Thank you for the response, @mitch2.  Very kind of you. 

It is strange that the input imp. vary across the different model same series - 100k for DNA 225, 10k for DNA 500 and 13k for the mono DNA 750.  The measurements by Stereophile on the 225 show 91k ohm for its input impedance and ideally low 0.07 ohm for the output.  Don't quite comprehend the inconsistency.

mitch2
4,325 posts
 

Different designs. The DNA 500 and 750 are bridged designs while I believe the 225 is a stereo amp. 

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