Tortuga Preamps

I have owned two LDR preamps. Extremely happy with mine.

Oz

The data seems to indicate significant distortion

Been there and done that with "active forced matching".

I use "quad matched" sets of the far more expensive NSL32RS2S "sorted" LED/LDR’s which also go lower in impedance than the non "S" version, then none are "over rev’d" as they all "rev" the same.

By using "active forced matching feedback type circuitry", which btw measures the the output resistance of the ldr’s, makes it an active preamp not true passive.

KISS: spend the "man hours to quad matched them" at different points, and then they all "rev" at the same, and also stay totally passive, and sound better for it.

https://www.digikey.com.au/products/en?keywords=NSL-32SR2S

https://www.digikey.com.au/product-detail/en/advanced-photonix/NSL-32SR2/NSL-32SR2-ND/5039808


Cheers George

George, 

Sounds interesting! Did you swap out these LEDs in a build or preexisting Tortuga. Please elaborate:-)

Does quad matching lower the distortion?

George manufactures the Lightspeed Attenuator. One of the the best bargains in audio. I have owned one for 10 years it seems. My old friend Pubul57 (RIP) started this thread years ago to discuss the Lightspeed:

https://forum.audiogon.com/discussions/lightspeed-attenuator-best-preamp-ever?highlight=lightspeed%2...