Hello all -
Please note Darrin's reference to the DNA-500. He is correct when he says that it has the same 10K input impedance as the DNA-2 *after* adding the Jensen input transformer. This is also the same input circuit used in any of my SMc Audio monoblock amps (but *not* the same as the original McCormack Audio DNA-1 monoblocks) or any SMc Audio amp upgrade with balanced inputs. I believe there are several members here who have the DNA-500 (or my monoblocks, or my amps with balanced inputs) and their experience should be valuable.
I usually design my amps with a 100K input impedance for maximum compatibility, but using the Jensen (or Lundahl) input transformers forces a shift to 10K (at least for the 1:1 types I prefer). It would be nice if I could offer all of the advantages of the transformer input topology along with high input impedance, but I feel strongly that the strength of this approach more than outweighs this small disadvantage. Using these transformers allows me to simplify my input stage somewhat, and provides a brickwall filter against DC and RFI without the need for blocking capacitors or additional filters. Like many audiophiles, I used to look askance at the use of transformers, but I must say that I have become very fond of them. Used properly, I feel they offer a lot of advantages, and their main drawback is high cost.
I know that many owners of these amps are using tube preamps happily. I havent made a list (apparently I should!) but I have heard quite a few mentioned: C-J, ARC, ART, Sonic Frontiers, VTL, Rogue Audio, just to name those that jump to mind. Most of these have output impedances in the several-hundred-Ohm range, but Im pretty sure that none of them exceed 1KOhm. I have even heard one person say that they tried the DNA-500 with a Hovland HP-100 and liked what they heard, despite the Hovlands high output impedance (over 2KOhm, I believe). While I would not recommend this combination as a good impedance match, it is interesting to hear that at least one person liked it. Of course, solid-state preamps should work fine, as well as buffered passive designs and some transformer-based volume controls (TVCs).
It would be great to hear from owners of these amps about their experience with various preamps. Ill make a point of noting the models people have used successfully ;-)
Best regards,
Steve McCormack
www.SMcAudio.com
Please note Darrin's reference to the DNA-500. He is correct when he says that it has the same 10K input impedance as the DNA-2 *after* adding the Jensen input transformer. This is also the same input circuit used in any of my SMc Audio monoblock amps (but *not* the same as the original McCormack Audio DNA-1 monoblocks) or any SMc Audio amp upgrade with balanced inputs. I believe there are several members here who have the DNA-500 (or my monoblocks, or my amps with balanced inputs) and their experience should be valuable.
I usually design my amps with a 100K input impedance for maximum compatibility, but using the Jensen (or Lundahl) input transformers forces a shift to 10K (at least for the 1:1 types I prefer). It would be nice if I could offer all of the advantages of the transformer input topology along with high input impedance, but I feel strongly that the strength of this approach more than outweighs this small disadvantage. Using these transformers allows me to simplify my input stage somewhat, and provides a brickwall filter against DC and RFI without the need for blocking capacitors or additional filters. Like many audiophiles, I used to look askance at the use of transformers, but I must say that I have become very fond of them. Used properly, I feel they offer a lot of advantages, and their main drawback is high cost.
I know that many owners of these amps are using tube preamps happily. I havent made a list (apparently I should!) but I have heard quite a few mentioned: C-J, ARC, ART, Sonic Frontiers, VTL, Rogue Audio, just to name those that jump to mind. Most of these have output impedances in the several-hundred-Ohm range, but Im pretty sure that none of them exceed 1KOhm. I have even heard one person say that they tried the DNA-500 with a Hovland HP-100 and liked what they heard, despite the Hovlands high output impedance (over 2KOhm, I believe). While I would not recommend this combination as a good impedance match, it is interesting to hear that at least one person liked it. Of course, solid-state preamps should work fine, as well as buffered passive designs and some transformer-based volume controls (TVCs).
It would be great to hear from owners of these amps about their experience with various preamps. Ill make a point of noting the models people have used successfully ;-)
Best regards,
Steve McCormack
www.SMcAudio.com