heathkit w-5m renovations [boondoggle edition] quantum vacuum deep dive
- Thread starter sae-7125
- Start date
sae-7125
Super Member
that should be all for now until amp 2 of 2 is located or the out-txf situation is resolved. updates to the v1.0 design will be random but there are a few flaws to adjust. or go in a slightly different direction with a fresh pair of w-5m's.
going with a lower b+ might not be such a good idea. looking at the voltage drop(s) inside the out-txf from b+ to each anode is of concern. with higher voltage, less current is needed to achieve the same wattage. less current = less voltage drop internally and less heat is generated, internally. the txf windings are a massive heat sink but why make things hotter than they should be.
going with a lower b+ might not be such a good idea. looking at the voltage drop(s) inside the out-txf from b+ to each anode is of concern. with higher voltage, less current is needed to achieve the same wattage. less current = less voltage drop internally and less heat is generated, internally. the txf windings are a massive heat sink but why make things hotter than they should be.
sae-7125
Super Member
the benefit of lower current when calculating 315r/312r voltages (resistances shown in bias sim snapshot post #340).
350v 50ma= 17.5w = 15.75v and 15.60v = 0.787w + 0.780w internally
400v 45ma= 18.0w = 14.17v and 14.04v = 0.637w + 0.631w
450v 40ma= 18.0w = 12.60v and 12.48v = 0.504w + 0.499w
500v 35ma= 17.5w = 11.02v and 10.92v = 0.385w + 0.382w
so... one of the early design fork solutions several pages ago involving mains full tap with one diode per side and padding resistors even on the center tap is starting to look like a prospective successor to this v1.0 mutant proof of concept. running b+ higher, around 530v 30ma each side (16w), and eliminating the series reducer caps plus fine tuning the power off pop.
the tube rectifier and choke will still be out of the equation for improved mains-txf survival and circuit sanity without inductive kickback threat. also utilizing the timed relay soft start circuit, ct connected, since it will be extremely beneficial for reducing power-on surge/over-voltage/kaboom-potential.
350v 50ma= 17.5w = 15.75v and 15.60v = 0.787w + 0.780w internally
400v 45ma= 18.0w = 14.17v and 14.04v = 0.637w + 0.631w
450v 40ma= 18.0w = 12.60v and 12.48v = 0.504w + 0.499w
500v 35ma= 17.5w = 11.02v and 10.92v = 0.385w + 0.382w
so... one of the early design fork solutions several pages ago involving mains full tap with one diode per side and padding resistors even on the center tap is starting to look like a prospective successor to this v1.0 mutant proof of concept. running b+ higher, around 530v 30ma each side (16w), and eliminating the series reducer caps plus fine tuning the power off pop.
the tube rectifier and choke will still be out of the equation for improved mains-txf survival and circuit sanity without inductive kickback threat. also utilizing the timed relay soft start circuit, ct connected, since it will be extremely beneficial for reducing power-on surge/over-voltage/kaboom-potential.
sae-7125
Super Member
the performance of amp 1 of 2:
it has no problem commanding half of the bench 2.2 system. bass extension and clean highs without fatigue are apparent. zero perceivable noise/hiss at idle, cant really hear if the amp is turned on even with an ear to a ribbon tweeter or bass hungry woofer. power-off pulse/pop is minimal depending on woofer surround flexibility.
thin rubber surround on a decent quality bookshelf speaker has minimal pull-in and no audible power-off sound. the bench bookshelf hack job speakers use scrap subwoofers from a monitor audio powered sub and their surrounds are rigid enough to show zero signs of power-off pop/pulse/woofer-pull.
it has no problem commanding half of the bench 2.2 system. bass extension and clean highs without fatigue are apparent. zero perceivable noise/hiss at idle, cant really hear if the amp is turned on even with an ear to a ribbon tweeter or bass hungry woofer. power-off pulse/pop is minimal depending on woofer surround flexibility.
thin rubber surround on a decent quality bookshelf speaker has minimal pull-in and no audible power-off sound. the bench bookshelf hack job speakers use scrap subwoofers from a monitor audio powered sub and their surrounds are rigid enough to show zero signs of power-off pop/pulse/woofer-pull.
sae-7125
Super Member
with v1.1 on the r&d to-do list, i wonder if focusing on a 5ma/4ma/3+3ma type of v1/v2 loading scheme would be ideal, just to hear what happens. no need for an output protection relay if there is no pulse to warrant the use on one...
looking at the brimar 12au7 spec sheet and the 3rd harmonic distortion graph, although under different anode/g1 parameters, it looks like a lower wattage across the triode (250mw) can be beneficial. still seems weird how ~46v across v1.2 can still sound good and bark with authority.
looking at the brimar 12au7 spec sheet and the 3rd harmonic distortion graph, although under different anode/g1 parameters, it looks like a lower wattage across the triode (250mw) can be beneficial. still seems weird how ~46v across v1.2 can still sound good and bark with authority.