Recent content by Tortuga Audio

  1. Tortuga Audio

    Preamp ramblings: Active, Passive, TVCs, Birds, And Bees

    Based on that observation my guess is: unity gain opamp input buffer -> LDR attenuator (probably just a shunt if it's a single LDR per channel) -> unity gain opamp output buffer. I would describe that as a solid state unity gain active preamp. Odd that it comes up in the context of a passive preamp.
  2. Tortuga Audio

    Preamp ramblings: Active, Passive, TVCs, Birds, And Bees

    If only because we've done quite a bit of work with LDRs and buffer stages, my guess is they're probably discrete mosfet or jfet transistors configured as input and output buffers. We use an LSK170 JFET along with a constant current source as the core of our output buffer stage.
  3. Tortuga Audio

    Preamp ramblings: Active, Passive, TVCs, Birds, And Bees

    My understanding (and it's just only that, since I've not taken one apart and verified first hand) is that the truth does use an LED plus photoresistor (an LDR by any other name) for volume control. LDRs are notoriously challenging to maintain channel balance over time and much effort usually...
  4. Tortuga Audio

    Preamp ramblings: Active, Passive, TVCs, Birds, And Bees

    This is often raised as a potential issue with resistive passive attenuation but as a practical matter we rarely see this as a primary constraint since as long as the IC run between the preamp and amp is kept to say 6-8 feet or less the filtering knee is kept well above 20 kHz. For most home...
  5. Tortuga Audio

    Preamp ramblings: Active, Passive, TVCs, Birds, And Bees

    Those measurements are a testament to how irrelevant measurements can be (beyond a certain point) when compared to the subjective experience of actually listening and experiencing the sound with your own ears. Meanwhile we are 2 generations down the road since those measurements were made....by...
  6. Tortuga Audio

    Tone controls?

    First time I played Adele's first album on my living room rig I thought something had gone wrong with the DAC or the tubes were going in the preamp buffer. Sounds great in the car or even an iPad but the recording and/or mastering was rough. //Morten
  7. Tortuga Audio

    Hello From Southwest Florida

    Hi All, My name is Morten Sissener and I own/operate Tortuga Audio, a small audio design/manufacturing company here in Southwest Florida specializing in light dependent resistor (LDR) based preamplifiers. Several customers recommended me to WBF so I decided to join up. I look forward to...
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