I achieved very good results replacing the SDA circuit inductor and low frequency inductors of my SDA SRS 1.2TL's with Solen perfect lay inductors. Those modifications are discussed in the threads listed in the reference section below. Unfortunately, Solen does not make inductors with wire size and DCR values equivalent to those in the 1.2TL's high frequency circuit. Forum member RickTfromAZ suggested Jantzen perfect lay inductors might be suitable. The required values for the HF circuit were two 0.4 mH 22 AWG inductors (0.68 ohm DCR) and one 0.7 mH 25 AWG inductor (1.69 ohms DCR). Solen makes a 0.4 mH 22 AWG inductor (0.64 ohm DCR). Solen does not make a 0.7 mH 25 AWG inductor. In place of the original 0.7 mH inductor, I tried a Jantzen 0.65 mH 26 AWG, which did not work, then a Jantzen 0.75 mH 26 AWG which did work after it was unwound to 0.7 mH.
The Jantzen 0.4 mH 22 AWG and unwound 0.7 mH 26 AWG inductors provided a more detail, particularly with vocals, than the original 0.4 mH 22 AWG inductors. The Jantzen 0.65 mH 26 AWG inductors were not appropriate substitutes for the 0.7 mH 25 AWG original inductors. There were detrimental bass effects: loss of weight, detail, and articulation. Tactile sensation was also diminished. Vocals and solo instruments in the center also appeared to move backward a couple of feet. The 0.7 mH inductor is in series with tweeter number 4 (4th from the top), which is the next to "main" tweeter number 3. Therefore changes in that tweeter's circuit branch would be the most sonically obvious with increasing frequency.
The Solen inductors sounded better than the original inductors right from the beginning and got better with time. The Jantzen inductors produced harsh highs and smeared bass upon first listening. The sound significantly improved after five hours of play time. All detrimental artifacts were gone after an additional 12 hours of music play. I could not find a specified break in time for the Jantzen inductors. I did not bother to ask them since, unlike Solen, they do not appear to like to communicate directly with customers. Solen recommends a break in time of 100 hours for their perfect lay inductors. I did not condition the Jantzen inductors on the Cable Cooker as I did the Solens. I didn't feel like going through the numerous removal and install iterations.
These were special order items from Parts Express. The 0.4 mH inductors cost $2.86 each. The 0.75 mH inductors cost $1.89 each. Lead time is typically eight weeks. I received the 0.4 mH and 0.65 mH coils in 2.5 weeks because Parts Express included my order as part of a large order from Jantzen. The second order for the 0.75 mH inductors took seven weeks for delivery. Bev Ruggiero handled my order and she was a pleasure to work with.
Fun With FedEx
Two things in life are certain:
1. A watched pot will never boil.
2. A long awaited package will be
D. lost or,
E. all of the above.
Imagine my surprise after checking the FedEx tracking website and finding that my inductors had been delivered at the expected time of day...but not to me. When I called FedEx to find out where the package had been delivered, I was given the delivery address, which the agent admitted did not match the ship to address. My package was delivered to another address on the same street. The agent said she would have the driver redeliver the package, but I declined as it was just down the street and I could easily pick it up in 10 minutes. This was preferable to waiting another day for the driver to deliver it to yet another wrong address on a different street. The next day, another FedEx agent left a voice mail informing me that they were in the process of retrieving my misdelivered package and they would have it to me within two days. I really didn't want to call the agent back and tell her my merchandise was already in my possession...but I did it anyway because I'm trying to get to Heaven. The agent was profusely appreciative of my efforts as her FedEx colleague had noted that the package had been misdelivered, but had not noted that I was going to pick it up myself.
Perfect Lay vs. Bobbin Wound Inductors
Figure 1. The three bobbin wound inductors on the left center of the crossover circuit board were replaced
with Jantzen perfect lay inductors. These were the last three legacy components left from the original
Figure 2. Bobbin wound original 0.7 mH inductors at top, 0.7 mH perfect lay replacements below.
Bobbin wound inductors are susceptible to microphonics (electrical noise introduced by mechanical vibration). Perfect lay inductors significantly reduce the effects of mechanical vibration by tightly winding and bonding the wire coils.
Jantzen 0.75 mH Inductor Unwinding
Jantzen's product options for the original 0.7 mH 25 AWG inductor were a 0.65 mH 26 AWG and a 0.75 mH 26 AWG. I was reluctant to order the larger value and unwind due to concern about compromising the mechanical integrity of the coil. After receiving the 0.65 mH coils, and noting their failure in listening tests, I saw that the wire could be carefully peeled off the coil without destabilizing the binding.
Figure 3. The SDA shrine is a nice place to unwind.
Figure 4. Unwound inductor ready for installation.
Unwinding inductors is not something I recommend without accurate devices for measuring inductance and direct current resistance (DCR). An MCP BR2822 LCR meter was used to measure inductance and a Fluke 8050A multimeter was used to measure DCR. The first inductor measured 0.756 mH with 1.84 ohms DCR. Twenty-four inches of wire was removed to reduce the inductance to 0.7 mH and 1.75 ohms DCR. The second inductor measured 0.750 mH with 1.78 ohms DCR. Twenty-two and three-quarter inches of wire was removed to reduce the inductance to 0.7 mH and 1.72 ohms DCR. Nominal values for inductance and DCR were 0.75 mH and 1.81 ohms.
A 26 AWG wire has a resistance of 0.0034 ohms per inch, at an ambient temperature of 20 degrees C (68 degrees F). The temperature in my work area was 72 degrees F, but I will use the 0.0034 ohms per inch figure for illustrative purposes. For the first inductor, 24 inches of wire removed equates to:
24 inches x 0.0034 ohms/inch = 0.0816 ohms of resistance lost.
1.84 ohms - 0.0816 ohms = 1.76 ohms. The multimeter measured 1.75 ohms DCR after cutting.
For the second inductor, 22.75 inches of wire removed equates to:
22.75 inches x 0.0034 ohms/inch = 0.07735 ohms of resistance lost.
1.78 ohms - 0.07735 ohms = 1.70 ohms. The multimeter measured 1.72 ohms DCR after cutting.
After cutting, I was faced with the tedious task of removing the orange polyamide insulation. For larger, stiffer wire, I would just grind off the insulation with a Dremel sanding wheel. For delicate, hair-thin (0.016" diameter) 26 gauge wire, I carefully scraped off the insulation with a sharp new box cutter razor blade. The wire end was laid on the back of a metal baking sheet. The process was complicated due to the small size of the wire and the fact that the brownish-orange insulation color was close to the color of the copper wire. I used an 8X magnifying lens to check my progress after each scrape. If you want to try this unwinding exercise and you aren't experienced in this sort of thing, you might want to order several more inductors than you need...just in case.
Figure 5. Custom SDA SRS 1.2TL crossover circuit board with high quality close tolerance parts. No wonder
you produce Such Good Sound.