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I just ordered the MK3 premium update driver. Looking further into the B+ regulated module, I noticed that the screen is disconnected from the transformer disabling the ultra-linear mode and tying it to a regulated voltage. I understand the difference between Triode Mode and Ultra-linear Mode, but I don't know what trying the screen to a regulated voltage buys me. Any education offered will be welcomed
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That will make the outputs run in true tetrode (or pentode depending on the tube)mode. You can get a little more power that way, but some say the amp doesn't sound as good.
Fixed screen will give the same power as UL and (sorry - beg to differ) will sound better than UL _IF_ the screen supply is driven by an low impedance - wide bandwidth power supply. This is a topology used by ARC for years - in their case, they used a tube series pass regulator. I use a lower impedance wider bandwidth ss regulator.
Thanks Joe for taking the time to respond. I guess the sound being better or worst is in the "Ear of the Beholder". If I am not mistaken, the topology is from Mike Maida of National Semi many years ago using s 317 cascaded to a HV BJT. Being a Power supply Engineer all my life I am familiar with the designs. There are updated designs using lower dropout regs and FETs. The 317 is one of those regulators still available today in many packages and will be used for many a year to come. I just repaired a supply from the 60s and it used a LM117/883B part.
Thanks for the reply. Is the increase in power in relation to Triode or Ultra-linear Mode, given that Triode Mode produces about 60% of the power of the Ultra-Linear Mode, does tying the screen to a regulated voltage increase the power relative to Triode or Ultra-Linear?
Yes if running pure triode mode, your output power drops 50-60 percent. I think Joe was referring to UL vs regulated screen, not triode mode.
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