It is difficult to compare LCT540 and NT1a in details. I am not sure which one is better for silence recordings. Both have same specification of lowest self noise on the market, they have their own characteristics and after my NT1a mod, they seems to have slightly different polar pattern.
I record this audio samples at 24bit/48khz with 45dB gain (40Hz HPF) on MixPre6
In post I increase the gain approximately another 45dB and normalized to -5dB
The outcome is shown on the spectrograms on recording A and recording B. The LCT540 is above. NT1a below.
NT1a is extremely well focused in the mid-range 500hz – 5Khz. which is exactly the frequency where most common birds sing. So NT1a is very good for nature recordings. But sometimes NT1a sounds „flat“ because NT1a is rather poor on low frequency, sometimes like out of phase (which could be as well caused of wrong setup).
I have not a long experience recording with LCT540s, but at the moment the overall sound quality seems to be better than NT1a, especially in lower frequencies which give better „juicy“ sound and „depth feeling“. But at the same time it is not as „clear“ as NT1a in the mid range.
Following audio samples will give some insight how LCT540s compares to NT1a in silence. You can clearly compare the mics self noise which sounds almost equal.. You can also hear how this two microphones pick up the details in two alarm clocks and a pocket radio at the lowest level in ca 2,5m distance, inside ca 45m2 garage. Other background sound is a light gust outside which swipe the garage walls and roof, a fly in the window and a traffic in air and ground in the county. Anyway this is a silence which most people will barely hear anything else than just their own heartbeat. See pictures
How do they withstand humidity or handling noise in windscreen? I can only say this.
Both need DIY shock mount if they should be fit in Rycote windshield. Both are sensitive for handling noise especially NT1a. High humidity is usually not a problem for microphones in Iceland, but there are stories about problem with NT1a in other countries.
I will update this information/comparison as soon as I have got more experience with LCT540s. You can also search for NT1a and LCT540s on this website and listen to nature recordings.
Listening with quality headphones will give best result.
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Lewitt LCT540s Recording A (mp3 256kbps / 7Mb)
Rode NT1a Recording A (mp3 265kbps / 7Mb)
Lewitt LCT540s Recording B (mp3 256kbps / 4,8Mb)
Rode NT1a Recording B (mp3 256kbps / 4,8Mb)
Short comparison of both LCT540S & NT1a
HLJÓÐMYND - SOUNDIMAGE 
Have you ever tried the Rode NT1 instead of the NT1A?
Yes I have compare them both.
They have similar self noise but NT1 is slightly better against handling noise . NT1 sounds probably slightly more „natural“, but NT1a have better focus on the mid range which is often very useful for smallest details in silence recordings. . Both NT1 and NT1a have same „Rode characteristic“. You can buy NT1a as a matched pair, but not NT1
I have use NT1a more probably because one of my NT1 have once produce a strange noise.
Even though it has been repaired, it is hard for me trust this NT1 anymore on the field.
Anyway, one day I will make similar comparison with this two mics as I did here above
Thank you very much for your feedback! I was just listening into some of your nature recordings, well I can’t find the right words, the soundstages are just amazing! Very nice, artwork!
I’m a starter, own a pair of NT1’s build into a DIY Binaural setup, 1xSennheiser MKH8060, Rec. Mixpre3, Zoom F8, Sony PCM D100, all supplied with huge Li ion DIY Batterie array capable of week long lasting recordings, the limitations here in Luxembourg are the environmental noise, airport, highways etc…unfortunately, looking constantly for the interesting and CALM place which seems not to be easy in my region…