That's interesting news. I bet those Slagles have been improved since the ones I owned. It really does sound better than S&B. I give it my recommendation without even hearing the newer version. Dave is good.
If you want to roll your own from my recipe, I looked around and found some info for for making these items. You too can have a $2K performing pair of AVC's and $3K performing pair of MC step-ups (judging with my ears against other products I heard on the market) for about $400 in parts, and have enough to do another pair of all of them for a buddy. But there's some difficulties to overcome.
First is finding a decent coil winder that works, one you can borrow if not own, capable of letting you handle 32 AWG wire if you have a careful smooth winder and a steady hand (and patience). This must have a turn counter because you will need to know the exact turn count all the time. Maybe you should stay with 24 AWG to prevent awkward motion from breaking the wire. That's still very good wire if it's Cardas, for example.
I recommend getting really quality magnet wire, preferably Cardas. It actually does sound smoother, more detailed and a little sweeter than Rat Shack type cheap magnet wire. And pure copper is always my favorite even if my Urushi cartridge uses silver clad copper (but so little of it).
You will need to buy about 500 ft of wire to get all these projects done, maybe 1000' to be safe if you're a klutzy winder just learning.
Now to source the hard pieces: The laminations - I can only recommend Magnetic Metals lams (www.magmet.com). Ask for a couple of lbs. of 21E1 laminations of grade 8406 and another couple of pounds of 21E1 lams of grade 8414. This will get you SuperPerm 80 (AKA HyPerm 80 in generic sense), but don't trust this to any other manufacturer because I cannot account for slightly different formulations that could be important.
For the bobbins, get them at Cosmo Corporation (www.cosmocorp.com). The part number to buy is 1-1254-0-000-00-0. Description for this is "for lams EI-21 x 5/8".
For the channel frames, go to Bahrs Die and Stamping Co., Inc. (www.bahrsdie.com). The part to order on their website is "1/2 x 5/8 channel frame", style 1. You might have to speak to a representative for these items. A lot of people want to get them by just asking for free samples. You need to be a corporation to do that and be nice following the rules.
I recommend a full single winding of 2000 turns. For -3 dB, you would send the input to the top of that coil, the 2000th turn, and then tap out on winding 0.707*2000=1414 turn. I recommend taps every 2.0-2.5 dB apart. Less than that and there's too many taps that will make a horrible rats nest out of it along with too many switch positions required. More dB apart means too coarse a series of volume steps for most people. You will need to do the proper math and have all windings taps pulled out and labelled appropriately so you don't lose where they go.
The taps can be free of splices by running a twisted loop out from the transformer at the tap position, and use a solder pot to melt the magnet wire insulation at the end.
Use a quality switch for these. I went to Michael Percy to buy a stereo ladder multiposition switch. The cost was a bit high, but so well worth it with a very high quality contact and smooth operation and lasting durability. I forgot the name of those switches he sells.
Plan ahead accordingly. I chose to wind up from the low taps on the inner core and moving out from there. The first tap was just one turn, or 1/2000th voltage out as voltage in. Amazingly excellent sound from that huge ratio. Wind end to end along the width of the bobbin and try to remain flat. The beauty of this simple winding scheme is, well, it's ease of construction, and you still get all the bandwidth. No fancy winding technique that amateurs can't try for themselves.
For the 1:10 MC step-up, use the same materials but wind 200 turns for the input (a tap out to the input) and then wind the rest of the 2000 turns for the output. Place these tranformers in a magnetic iron shielding box and maybe add a big extra layer of unmolested mu metal for a second magnetic shield. This is where microvolts of signal are happening and magnetic shielding is the challenge here.
Stacking the lams is another new trick to learn, so be patient on this. Again I recommend using 5 of the thin 8406 lams and then 1 of the thicker 8414 lams. Repeat this pattern all across the transformer.
You do not need to seal or varnish the lams after they are installed. The high nickel lams pretty much won't corrode in a home environment that steel lams could.
Good luck if you try this project.
Kurt
