K&K Audio / Lundahl Transformers

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K&K Audio / Lundahl Transformers

LL1664 vs. 1620/1623/1627 vs. 1693

84.202.203.195

oyvinza@gmail.com

Hi!

I am considering building a PPP amp with 4 pairs of tridode strapped EL84 for each channel. I suppose I need about 3kOhms primaries. LL1664 should work. I have seen that LL1623 and LL1627 is a better quality transformer, and 1693 even better. But is that mostly in the bass and that it can give higher power? Or is it also better for high frequencies? The amp will not be used much below 50Hz, so I suppose the bass is not that important. My speakers are by the way Quad ESL (57). They will be used with a pair of subwoofers.

I have also seen that it is possible to parallell a pair of primaries to give lower primary resistance and inductance. This will give worse low frequency response, but will the high frequency response be better? This way I understand the LL1620 can also get about 3kOhm primaries.

The 1664 is cheaper, but 1620 etc. are more flexible, so they may be possible to use if I happen to stack two quads for each channel and thus getting 4Ohm speakers instead...

So, does anyone have any suggestions or information? They will be most welcome.

Regards,
Oyvind Saanum Eithun

Follow Ups:

RE: LL1664 vs. 1620/1623/1627 vs. 1693 - KevinC 16:58:45 12/08/13 (0)
I would argue that the three transformers mentioned are not significantly different in the context of your loudspeakers for low frequency cut-off. I don't have any data to support the generalization, but, all other things being equal, the transformer with the shorter wire path may have the high frequency response advantage, although unless you are using global negative feedback, even that probably isn't consequential either.

I have no experience with paralleling primaries, so you would need to ask Per Lundahl that question.

The LL1620, LL1623, and LL1679 are more flexible. That's a judgement call on your part.

Kevin Carter
K&K Audio
www.kandkaudio.com
RE: LL1664 vs. 1620/1623/1627 vs. 1693 - oyvinza@gmail.com 08:55:25 12/08/13 (1)
I see that there is also a LL1679 with stated "10 Hz � 70 kHz +0/-3 dB" that also can use 2,6kOhm. That seems to be better in the high frequencies than the stated "7 Hz - 25 kHz +/- 0.5 dB" for the 1623, but that may not be the real situation for all I know (one is given for PP, the other for SE for instance).

Regards, Oyvind Saanum Eithun
- RE: LL1664 vs. 1620/1623/1627 vs. 1693 - KevinC 17:04:01 12/08/13 (0)
  Once again, response above 20kHz may only be really relevant to the sound in the case of global feedback and challenge of compensation of the feedback loop for the the stability of the amplifier.
  
  I have used all of these transformers at one time or another, but never compared them in one amp with no changes. My opinion is that there are much more important issues in amplifier design than a few Hz or kHz of response at the limits of the audio band.
  
  Kevin Carter
  K&K Audio
  www.kandkaudio.com

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