Recent content by audiowize
  1. audiowize

    Crack;Bottlehead OTL

    They aren't even close. They will not work without a major redesign of the circuit. They might work a little better in the stock circuit if the LEDs were replaced with resistors, but you'd be moving backwards to use an inferior tube.
  2. audiowize

    Crack;Bottlehead OTL

    The 6C8G is not a substitute for a 6F8G/12AU7.
  3. audiowize

    Crack;Bottlehead OTL

    The Speedball will increase current delivery to the load at the output, which will increase available power. The stock circuit has a ton of voltage swing; that's rarely an issue.
  4. audiowize

    Crack;Bottlehead OTL

    I sure hope the winding isn't 15VA, the Crack amp draws more than 30VA from that winding; the SEX amp draws more. AC and DC current are not the same. The transformer only cares about AC current.
  5. audiowize

    Crack;Bottlehead OTL

    The Crack transformer is also in the SEX amp, and that's the clue to the capacity of the HV winding. From the original SEX amp and Crack 1.0, that indicates a high voltage winding capacity of 72VA and a LV winding capacity of 22VA, so I guess it's only 94VA. This is to keep the transformer...
  6. audiowize

    Crack;Bottlehead OTL

    The stock transformer is spec'd at about 105VA and runs under 50VA.
  7. audiowize

    Crack;Bottlehead OTL

    For those who may consider a larger/cooler running transformer to be some kind of improvement, it's worth remembering that underloading a transformer leads to poor regulation, and poor regulation can leave your 6.3V heater winding putting out far more than 6.3V, which can reduce tube lifetime...
  8. audiowize

    Crack;Bottlehead OTL

    In a Crack with no Speedball, you can run it with no 6080 and plug these tubes in. The 12AU7 will produce the expected plate voltage that's around 75V or so. A 12AX7 is going to show very, very high plate voltage. With or without the Speedball, it's going to be up close to whatever your B+...
  9. audiowize

    Crack;Bottlehead OTL

    This will put tubes in the signal path, but it won't add the "tube" sound IMO. Part of the tube sound comes from the way tube amps interact (or don't interact) with the load your headphones present vs. a solid state amp.
  10. audiowize

    Crack;Bottlehead OTL

    Gift horse, etc.
  11. audiowize

    Crack;Bottlehead OTL

    What would you hope to learn from this?
  12. audiowize

    Crack;Bottlehead OTL

    This sounds like a good idea until you run the amp with the switch on 12V and a 6V tube installed. Either you destroy the tube or the power transformer.
  13. audiowize

    Crack;Bottlehead OTL

    They are in the same family and they do have the same heater voltage, heater current, and pinout. They are otherwise completely different devices and will need very different component values and operating points to work properly.
  14. audiowize

    Crack;Bottlehead OTL

    1. Too much gain. The 12AU7 is already pretty hot, but the 12AT7 and 12AX7 have significantly more gain that is absolutely not desired. 2. Available B+ voltage. The 12AU7 is perfectly fine with 80V on the plate, but a 12AX7 with 80V on the plate will either draw grid current or draw...
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