LAB­O­RA­TORY TEST RE­PORT

Australian HIFI - - ON TEST -

Newport Test Labs mea­sured the fre­quency re­sponse of the Lun­dahl Mov­ing-Coil Step-Up trans­former us­ing the 24dB gain set­ting and found it ex­tended from 9Hz to 110kHz –1dB, ex­ceed­ing Lun­dahl’s own spec­i­fi­ca­tion. Part of this ex­tended re­sponse is shown in Graph 1, where you can see the re­sponse is just 2.5dB down at 5Hz and 0.2dB down at 20kHz. From 50Hz up to 20kHz it’s ab­so­lutely ruler-flat along the 0dB ref­er­ence grid be­fore it starts to roll-off slowly at 35kHz to be 0.1dB down at 40kHz, which is the ex­tent of the graph­ing limit. Sep­a­ra­tion be­tween the two chan­nels was mea­sured as be­ing 84dB, which was main­tained across the au­dio spec­trum.

THD+N is shown in Graph 2, for a 1kHz test sig­nal. You can see there’s a sec­ond har­monic dis­tor­tion com­po­nent at –90dB (0.0031% THD) and that’s about it.

It ap­pears there is a 6th-or­der com­po­nent, but it’s down at –95dB (0.0017% THD), which means it’s es­sen­tially buried in the noise floor at –100dB. There is some low-fre­quency noise, as you can see from the left end of the graph, which is mostly in­duced hum, since the trans­former was be­ing tested in a lab­o­ra­tory en­vi­ron­ment, which is elec­tri­cally very noisy, but even in this noisy en­vi­ron­ment, over­all sig­nal-to-noise was mea­sured as 72dB A-weighted, al­most all of which was low-fre­quency. Above 200Hz, noise was more than 80dB down and above 1kHz, es­sen­tially 100dB down.

In­ter­mod­u­la­tion dis­tor­tion (CCIF IMD) was al­most non-ex­is­tent, as you can see from Graph 3, as mea­sured by Newport Test Labs. The two test sig­nals at 19kHz and 20kHz dom­i­nate the graph, of course, but there’s only a sin­gle high-fre­quency side­band, at 18kHz, that’s 91dB down (0.0028%).

There is a re­gen­er­ated sig­nal at 1kHz, but it’s around 90dB down (0.0031%). Newport Test Labs mea­sured the gain of the LL1931 trans­form­ers as 17.76dB in the 18dB gain set­ting, and at 23.36dB in the 24dB gain set­ting, with both chan­nels be­ing iden­ti­cal, which is sig­nif­i­cant sign of trans­former qual­ity. Wind­ing trans­form­ers to this level of gain ac­cu­racy is a stun­ning achieve­ment. The dif­fer­ence in level be­tween Lun­dahl’s stated gain and Newport Test Labs’ mea­sure­ments, on the other hand, are not at all sig­nif­i­cant be­cause they would be due to the lab us­ing a dif­fer­ent in­put and out­put loads to those used by Lun­dahl when test­ing.

Over­all, su­perb mea­sured per­for­mance from this Lun­dahl step-up trans­former.

Steve Hold­ing

Over­all, su­perb mea­sured per­for­mance from this Lun­dahl mov­ing-coil step-up trans­former

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