LarryF

I couldn't find a schematic for the mic, even on the Shure site. Wiring 2 jumped to 4 will increase the pin 3 bias to 5 Volts equivalent, which might give you more headroom. I am kind of in the dark without a schematic. LEF

From the Lectrosonics FAQ section under Support: The Sanken CUB-01 boundary mic does not seem to have the usual FET output stage and also seems to have a large capacitor across the power supply lead (bias lead). This means that it can’t be wired as the usual three wire microphone with the SM. The wiring below seems to work well and is fully compatible with our other transmitters. Our pin 1 to Sanken shield (ground). Our pin 2 to Sanken black wire (5 Volt power). Our pin 3 to a 511 Ohm resistor and the other end to Sanken white wire (audio). This matches well to our 300 Ohm input input while providing a satisfactory 811 Ohms to the Sanken mic. Our pins 4 and 5 no connections.

Yes, the resistor is a requirement. Newer digital Lectro units have the resistor in the transmitter and switch it into circuit when DPA is menu selected. Best Regards, Larry Fisher.

You can certainly do that. The transmitter has enough gain range to handle a minor 6dB change in level. As you asked, you just need less gain in the transmitter. You won't lose 6 dB of SPL handling in the mic since the servo circuit in the transmitter will compensate for the decreased or increased current draw of the mic as you vary the resistance. Best Regards, Larry Fisher

Any value from 2K to 4K is just fine with the lower value giving 6 dB more output. 3.9k is a standard resistor value. Best Regards, Larry Fisher

It shouldn't be RF overload. Those model units were tested for overload with the transmitter and receiver antennas touching. The receiver AGC circuits were checked to make sure they had more than enough attenuation capability in the receiver to prevent any possible of RF overload. It's a good thought though, since some digital systems are not as forgiving. Best Regards, Larry Fisher

Also, cable losses at UHF would become a big factor as you stretch cable around a set. LEF

Many years ago, I setup a leaky antenna system and had poor results. As a receiver antenna, it has very low gain and depending on the placement, any weak signal picked up "leaks" out before it gets back to the receiver. As a transmitting antenna, it has very low radiation efficiency. The reason it can work in a tunnel is that it's the only practical, cheap way to get a uniform signal into a tunnel. In a tunnel setup, you can use a relatively powerful, AC powered transmitter that overpowers the poor antenna efficiency. That could work on a set if you used a booster amp (Probably not legal). Trying to use a 50 mW transmitter with a leaky antenna would give poorer results than a good medium gain antenna at the transmitter. YMMV Best Regards, Larry Fisher

The SNA600a is 2:1 only at the band edges. When defining bandwidth, the 2:1 value is a commonly accepted bandwidth definer. Inside that bandwidth, the SNA600a SWR is much lower on the order of 1.2:1. Keep in mind, a tunable bandwidth may be useful in attenuating undesired RF. "Different horses for different courses" . Best Regards, Larry Fisher

The headphone output is quiet and can be used as a line level (1 Volt) output. It is just lower impedance than most line level outputs, which is never a bad thing. I'm missing what is the reticence to use it as a line level output. (??). It's a minor point but G3/G4 receivers do not have matching equalization and compander time constants to the Lectro IFB. It certainly will work, though. Best Regards, Larry Fisher

The loss at our frequencies is on the order a quarter of a dB or less. In sum, fuggedaboutit. LEF p.s. Buying two 50 foot cables and using a coupler to make an occasional 100 foot cable is more space efficient and cheaper than buying a 50 and 100 foot cable.

Hi Derek, The EBL batteries have 95% of the Energizer runtime. For instance, if you have 6 hours of run time on the Bunny Brand, that's 360 minutes. The EBL 95% is 5% less time or .05 x 360 =18 minutes less. So you'd have 5 hours and 42 minutes compared to 6 hours. Or you can just subtract 1/20th of the run time. Regards, LEF p.s. The reason I didn't do run times is we have many transmitters at various power levels and single and dual batteries. In retirement, I'm getting to be pretty lazy.

I bought some disposable AA lithiums from Amazon and tested for power capacity. Total power was a better benchmark since average voltage and Amp hours varied by 8% or so across the three brands. Total power makes more sense due to the switching "power" supplies in Lectro transmitters, since they are like a DC transformer with power in equal to power out (less small losses). I bought Eveready as a reference, NINMA since they claimed 3500 mAh, and EBL since I recognized the brand as a larger seller of battery products. The testing rig was a computer controlled battery tester made by West Mountain Radio. The test current was a constant 400 mA similar to Lectro transmitter current drain. I also calculated cost, corrected for power capacity using prices off Amazon. Amazon has coupons and scheduled delivery discounts that will vary over time. The corrected costs are as of today, 15 Oct 2023 for 24 batteries purchased at a time. Eveready Ultimate Lithium: 4.418 Watt hour 100% (reference) $2.79 2.79 corrected EBL Lithium: 4.212 Wh 95% $1.62 1.70 corrected NINMA Lithium: 4.146 Wh 94% $1.75 1.86 corrected Conclusions: The off brand lithiums would be a cost viable choice if you don't need the last few minutes of run time. A situation where NiMh won't run long enough but an Eveready Lithium is more time than you need. The NINMA brand had the highest current capacity but the average voltage was 8% lower. That reduced its power capacity. Eveready had the highest average voltage making it the highest capacity. EBL had good current and voltage putting it in the middle. EBL was the most cost effective. YMMV Best Regards, Larry Fisher

3500 mAh is correct

The difference is in initial battery voltage. The lithium is higher voltage so the current draw is lower due to the fact that the power supply in the unit is a switching power supply. Switchers convert power in to power out. So a higher voltage can draw less current for a given power in. For instance, a switching power supply running from a 12 Volt battery could draw 5 Amps and put out 5 Volts at 12 Amps, if it were 100% efficient. 60 Watts in for 60 Watts out. The switchers we employ, are chosen for high efficiency of course. All this to say, if a unit needs 600 milliWatts to operate, that would be 500 mA at 1.2 Volts (NiMh) but only 400 mA at 1.5 Volts (lithium). And all this is complicated by the fact that the lithium starts out at 1.5 Volts and then gradually falls to 1 Volt or less before dying and the NiMh stays at 1.2 Volts until suddenly collapsing. Best Regards, Larry Fisher