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Originally Posted by cafe zeenuts /img/forum/go_quote.gif
Btw what pre-amp tube are you using, 6SL7 or 6SN7???
FYI the 6SL7 will have a higher gain than 6SN7...
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I would be supercareful swapping 6SN7 and 6SL7. Although they are pin compatible an operating point for 6SN7 dosnt really work right for a 6SL7, and vice versa.
With the common plate resistors used for a 6sn7 & reasonable B+ (less than about 320V) 1/2 to 2/3 of the gain of the 6sl7 disappears attempting to drive a hopelessly small plate resistor. Running a 6sl7 in a circuit designed for a 6sn7 generally winds up eeking less than 3db more gain out of the tube and putting WAY too much current through it. You dont get much more gain in parctice, and put excessive stress on the tubes.
Quote:
Originally Posted by FallenAngel /img/forum/go_quote.gif
Almost all amps (except for a few tube amps) will have problems with no load.
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In headphonia its not that bad: there are very few headphone amps that are not stable with no load.
White cathode followers, simple cathode followers, and plate followers with gobbs of global feedback as used in headphonia are generally are stable into an infinite load.
The buffers on the outputs of tube/SS hybrid amps are generally stable into an infinite load.
The VAST majority of transformer coupled tube amps are stable into an infinite load unless you go crazy and CRANK the volume without a headphone attached; even then you may still be OK. There are a couple in this category that do rely on the load for stability, but there are only a couple (like 2 and nobody around here has mentioned them on this site since about 2006) and when necessary they come with DIRE warnings not to run them unloaded.
SRPP amps are also generally stable into infinite loads although certainly "out of their element" being run into an impedance more than a few times away from their optimization points.
The "pure" SS amps are also generally stable into infinite loads.
Some amps run into trouble hard core style when the outputs are momentarily shorted plugging in/out. In these amps it is not the fact that they are run unloaded that causes fireworks, but the shorted output.
To be sure there are a couple headphone amps that are NOT stable with no headphone connected, but they are rare enough to be considered the exception rather than the rule. The warning is to insure that the 2 or 3 amps known for blowing up when the headphones are plugged in/out hot dont get plugged hot.
Quote:
Originally Posted by oinkbanana /img/forum/go_quote.gif
but typically i'd assume since I also got signal dropping out (volume cutting) completely .. no load = bad!! amp damage.
:deep breath:
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The output stage on the LD6 is a simple cathode follower. It is totally OK to run with no load.