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Re: Non-symmetrical and 1635 vs 1660

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gdahl

(D)

In Reply to: Non-symmetrical and 1635 vs 1660 posted by IslandPink on July 06, 2004 at 01:19:26:

When you look at the 1676 data sheet, the diagram for pin numbering looks a lot like the pin side of the transformer. But the diagram is really the top view of the pin "footprint" on a circuit board, as if you could see through the transformer to the pins underneath.
If you connect the transformer as if the diagram was the underside view, even though it is clear that there are 4 pins on one side and 5 on the other, you will inadvertently use pin 1 for 5, 2 for 4, 6 for 10, and 7 for 9.
As for the second question, we haven't tried the 1660's. The 1635's are optimized for PP:PP operation, and have the most extended bandwidth, according to the data sheets. The 1660 is capable of greater output, but with less frequency extension. Maybe someone who has heard both can comment. Kevin?
Gary Dahl
"So many tubes, so little time..."

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Oops .. - IslandPink 14:34:20 07/06/04 (0)
Thanks Gary,
Better look at that then , I connected it up assuming the pins were seen from underneath . What was the conclusion, is this likely to affect anything ?
Mark
Re: Non-symmetrical and 1635 vs 1660 - KevinC 07:22:33 07/06/04 (2)
I haven't done a side-by-side comparison, but some comments are in order. The LL1635 is most appropriate for PP:PP as Gary rightfully concludes and needs to see a pretty low driving impedance to reach its potential. The ECC99 is probably as high as I would go in that regard. The LL1660 is more forgiving in the Rp department and is usable with a wider range of tubes. There is also a special version of the LL1660 called the LL1660S, which has a Faraday shield incorporated into the winding scheme to provide substantially better high frequency performance in SE:PP applications. While the specs indicate wider bandwidth for the LL1635, this property is dependent on the specific implementation.
I've built excellent sounding amplifiers using both of these transformers.

Kevin Carter
K&K Audio
www.kandkaudio.com
- 1635 vs 1660 - IslandPink 14:32:31 07/06/04 (1)
  Thanks Kevin,
  Using the 1635 with ECC99's driving, would you expect any shortcomings (vs the 1660) to be a slight loss of HF bandwidth, or could there be any loss of very-low-level signals ?
  Mark
  - Re: 1635 vs 1660 - KevinC 15:24:49 07/06/04 (0)
    If anything, you will probably get flatter response up through 50KHz with this arrangement than you would with the LL1660, due to the pretty good impedance match between the LL1635 and ECC99.
    
    Kevin Carter
    K&K Audio
    www.kandkaudio.com

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