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#1
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How to increase 2nd HD?
Hello everyone,
is there a way to slightly increase the second harmonic distortion of a SET or similar single ended amp? Should it be done in the driver stage or the output stage? If you are thinking of reducing NFB, what if the amp has no NFB? I simply want to experiment and find what differences I can or cannot hear. However, I want to do it in a way that leaves the amp performing at its best in all other ways. Thanks for any help, Grant |
#2
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I don't know what's best , but at least this is worth reading .....
http://www.borbelyaudio.com/15wse.pdf (scroll down to page 3.) "Grant Sellek" schreef in bericht om... Hello everyone, is there a way to slightly increase the second harmonic distortion of a SET or similar single ended amp? Should it be done in the driver stage or the output stage? If you are thinking of reducing NFB, what if the amp has no NFB? I simply want to experiment and find what differences I can or cannot hear. However, I want to do it in a way that leaves the amp performing at its best in all other ways. Thanks for any help, Grant |
#3
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Generally, 2H cancels to some extent between driver and output stage
if the driver is inverting. You may find that increasing the 2H of the driver actually decreases it at the output, and vice versa. To increase the 2H of the driver, you could add a cathode bypass cap if you haven't got one already and can accommodate the reduction in gain, or you could decrease its anode resistor, giving a steeper loadline, and then relocate the operating point by changing the bias current and HT voltage. Decreasing the 2H of the driver via the anode resistor won't be so easy cos you will run out of HT voltage. Unless you use an anode choke, or a MOSFET to convert to a mu-follower (if you can find enough HT). You could remove the cathode bypass cap if present. Or you can change valves maybe. Altering the distortion of the output valves might not be so easy because you can't change the load without also affecting the final power output and frequency response unless you change the OPT. Perhaps more details of your particular circuit and valves would help to produce a more focused answer. cheers, Ian "Grant Sellek" wrote in message om... Hello everyone, is there a way to slightly increase the second harmonic distortion of a SET or similar single ended amp? Should it be done in the driver stage or the output stage? If you are thinking of reducing NFB, what if the amp has no NFB? I simply want to experiment and find what differences I can or cannot hear. However, I want to do it in a way that leaves the amp performing at its best in all other ways. Thanks for any help, Grant |
#4
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To increase the 2H of the driver, you could add a cathode bypass
cap.... Decreasing the 2H...remove the cathode bypass cap... oops. Opposite way round. Ian |
#5
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Grant Sellek wrote:
Hello everyone, is there a way to slightly increase the second harmonic distortion of a SET or similar single ended amp? Should it be done in the driver stage or the output stage? If you are thinking of reducing NFB, what if the amp has no NFB? I simply want to experiment and find what differences I can or cannot hear. However, I want to do it in a way that leaves the amp performing at its best in all other ways. Take a look at http://home.netcom.com/~wa2ise/radios/cdtubedsim.gif This is a tube cathode follower running on a low B+ source. The simulation shows a lot of 2H. You could add this circuit to just before the volume control of your amp. The 6111 tube is somewhat similar to a 12AU7. Or use a 6111 submini tube, they come with long leads and are designed to be directly wired into circuits under the chassis. As seen in http://home.netcom.com/~wa2ise/radios/cdtubed.jpg |
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