Finishing up some iron

that colorado rocky mountain high.
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dave slagle
Posts: 2102
Joined: Sat Jan 22, 2005 3:54 am
Location: NYC

Finishing up some iron

Post by dave slagle »

I'm putting the finishing touches on a bunch of Iron that the guys will be playing with. Included in the shipment will be the following:

3 different bobbins for a plate choke to load the RS-241. These should shed some more light on the turns vs. gap vs. inductance tradeoff for a specific situation.

A pair of outputs for the 75TL that will have slightly fewer primary turns than the samples they have been playing with. The first set I sent to John was replaced with a second set of bobbins with 1/3 less turns which he much preferred. Since steve needs at least another octave on the low end, I am splitting the difference between the two versions they have heard for the first attempt. Then looking at the size of the gap chosen for best sound we can make a decision if a version with fewer turns should be tried. The other difference is Steve has 8 ohm speakers opposed to johns 16 ohm so the turns ratio will be increased from 25:1 to 35:1 to make up for that difference.

Some 2:1 transformers to load the RS241. I'm doing two versions of this and am shooting for target inductances of 30 and 50. From the looks of it, the 50hy should be -1dB at 30hz and the 30hy -1dB at 50hz. (Steve has subs that kick in at 100hz.) Preliminary sweeps of the two versions show the 50hy versions remain behaved up to about 60K and the lower turn version go to 100K. By comparison the versions for SB's linestage have fewer turns yet and behave out to near 200K (all with 50 ohm source and no load) so a predictable pattern is forming. (in addition to the fewer turns, the 3:1 ratio of SB's version is also a bit of a help in extending the top end.

Your listening tests of these two versions should shed some light on the tradeoff between low and top end performance. Another thing I'll be watching for is if some sort of pattern shows up with gap size.

Can One of you guys do a quick schematic of the linestage and the amp (just one channel of the signal) the part values are not needed, but a general picture would be a big help in looking at the "big picture". How are the RS241's and the 75TL biased?

Steve Kaufman
Posts: 35
Joined: Wed Jan 26, 2005 6:00 am
Location: Fort Collins, Colorado

Post by Steve Kaufman »

Hi Dave

I'm back from Alaska. Thanks for getting everything together. The C3/4 are raring to go. I'll talk to Johnny about those schematics.

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