Fascinating and I think some of this is actually being absorbed into my stubborn brain. I inherited my dad's Dynaco Mk III monoblocks and replaced all the caps and resistors, replaced the circuit boards with restoration boards (exact circuitry etc.), replaced the selenium rectifiers with diodes, biased the amps, replaced the tubes that needed replacing, but I am woefully ignorant of the principles behind the design. I'm beginning to understand what I don't understand. Anyway, thanks! The amps sound pretty darn good btw.
Just goes to show that you can take the boy out of electronics but you can't take the electronics out of the boy. I really enjoyed watching the video even if the technology is a bit before my time.... I surely hope that I'm still talking about electronics and trying to improve on something even if I'm on my death bed... To me... This is my purpose in life and I will continue till my last breath... Thanks for the wonderful series on tube amplification I'm really enjoying everything that you have to say.
Crossing the screen grids to opposite tube plates exacerbates the "kink". it increases distortion, but it also increases power. McIntosh might be correcting that by cathode loading. Manley amplifiers use the cathode loading to this day, but I've never had a chance to play with the concept. I think cathode loading with "ultra linear" connection might just be the happy compromise between power and low distortion. The only caveat, is that more amplitude is needed from the driver stage. I don't think that's a problem, since most of these designs employed "booster" stages between the phase splitters and the grids of the power tubes. That should be more than enough amplitude to cover the gain of the tubes, plus, the cathode swings from either cathode loading on transformers, or just simple cathode follower resistors. I saw the crossed screen grid design before and tried it. It ended up over driving the screen grids, causing them to glow, so I put in resistors, which protected the tubes, but it still didn't help the distortion problem. I've long since abandoned the idea.
I built the 6V6-12 Watt Low Distortion amplifier noted in the video (August 1958) and I'm happy with the results. I used Magnetic Components Classic 35W Ultra-Linear Output transformer (40-18080). Seems when I use the 12K (R1) it really knocks the volume down considerably. Is it possible the difference in output transformer will drastically change the feedback resistor value? Also, is the 6V6 cathode resistor (250 ohm) based on the specific output transformer in the schematic? Seems like the tubes might be running on the high current side, but the amplifier sounds great! Thank you for your videos and appreciate any guidance you might offer.
Thank you Tom! I finally understand the distortion/power trade that occurred years ago. You did an outstanding job putting this presentation together!
This was the very best information on tube amp for this newbie thanks so much
These are superb! thank you for doing this series.
Thankyou. Fascinating and great explanation
Fascinating and I think some of this is actually being absorbed into my stubborn brain. I inherited my dad's Dynaco Mk III monoblocks and replaced all the caps and resistors, replaced the circuit boards with restoration boards (exact circuitry etc.), replaced the selenium rectifiers with diodes, biased the amps, replaced the tubes that needed replacing, but I am woefully ignorant of the principles behind the design. I'm beginning to understand what I don't understand. Anyway, thanks! The amps sound pretty darn good btw.
I'd like to second all the "thank you"s and compliments. Brilliant!
Just goes to show that you can take the boy out of electronics but you can't take the electronics out of the boy. I really enjoyed watching the video even if the technology is a bit before my time.... I surely hope that I'm still talking about electronics and trying to improve on something even if I'm on my death bed... To me... This is my purpose in life and I will continue till my last breath... Thanks for the wonderful series on tube amplification I'm really enjoying everything that you have to say.
Very nice videos thank you so much!
Wow, what a nice class on tube amplifiers, thank you very much sir.
Very enjoyable. Thanks!
gr8 explanation, thanks for sharing
That was excellent.
Nice turntable!
Crossing the screen grids to opposite tube plates exacerbates the "kink". it increases distortion, but it also increases power. McIntosh might be correcting that by cathode loading. Manley amplifiers use the cathode loading to this day, but I've never had a chance to play with the concept. I think cathode loading with "ultra linear" connection might just be the happy compromise between power and low distortion. The only caveat, is that more amplitude is needed from the driver stage. I don't think that's a problem, since most of these designs employed "booster" stages between the phase splitters and the grids of the power tubes. That should be more than enough amplitude to cover the gain of the tubes, plus, the cathode swings from either cathode loading on transformers, or just simple cathode follower resistors. I saw the crossed screen grid design before and tried it. It ended up over driving the screen grids, causing them to glow, so I put in resistors, which protected the tubes, but it still didn't help the distortion problem. I've long since abandoned the idea.
Mind blowing!!!!
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I built the 6V6-12 Watt Low Distortion amplifier noted in the video (August 1958) and I'm happy with the results. I used Magnetic Components Classic 35W Ultra-Linear Output transformer (40-18080). Seems when I use the 12K (R1) it really knocks the volume down considerably. Is it possible the difference in output transformer will drastically change the feedback resistor
value? Also, is the 6V6 cathode resistor (250 ohm) based on the specific output transformer in the schematic? Seems like
the tubes might be running on the high current side, but the amplifier sounds great! Thank you for your videos and appreciate any guidance you might offer.
Maybe i am asking too much ? I seek a circa 10 W stereo amp for hi fi using low voltage. Could you name one i can build ? I do thank you.