In post #432 you mentioned an issue with the hall chip in combination with 3N type opto would need some sort of gain stage to maintain Iq stability vs supply and temp.
Recently the Wizard disclosed that he calls a different opto for bias duty in the XA25. The best part is that by his infinite wisdom, Srajan managed to publish a very interesting photo of the secret part, just enough to show that it is an 8 pin dip complete with a perfect blur on the part number nobody can read.
I suspect the 8 pin dip to be a 6N type with very high CTR that would very likely overcome the issue of #432. Another piece of crumb towards Halley Babelfish Pucks.
Recently the Wizard disclosed that he calls a different opto for bias duty in the XA25. The best part is that by his infinite wisdom, Srajan managed to publish a very interesting photo of the secret part, just enough to show that it is an 8 pin dip complete with a perfect blur on the part number nobody can read.
I suspect the 8 pin dip to be a 6N type with very high CTR that would very likely overcome the issue of #432. Another piece of crumb towards Halley Babelfish Pucks.
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With the pucks, @ ~2A Iq, sim shows 0.1A Iq drift with 11-35V supply and 150mv offset drift with 3V supply variation.with IXYS pucks ...
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waidaminit!
rummaging through zillion iterations of Babelfish XA25 ....... dummy ZM tried that approach some moons ago (in sim only) and I found already developed solution for pucks (last schm (again - sim only!) I posted in berserker F4 thread) with CMirrors -superior in multiple ways - Iq , offset stability in temp and rails change domain , same as bias stability after long burst
so , time will tell ....... we are young , and we'll try them all in vivo
rummaging through zillion iterations of Babelfish XA25 ....... dummy ZM tried that approach some moons ago (in sim only) and I found already developed solution for pucks (last schm (again - sim only!) I posted in berserker F4 thread) with CMirrors -superior in multiple ways - Iq , offset stability in temp and rails change domain , same as bias stability after long burst
so , time will tell ....... we are young , and we'll try them all in vivo
too bad that driving them through buffer-xformer combo is not looking promissing
I also considered that approach, but there are fundamental problems. If the pucks are operated common-drain (source followers), then the transformer secondaries must produce the same large voltage swing as the puck output, which is too much for any of the line transformers. That leaves us with operating the pucks in common-source mode and fighting the puck gate capacitances, particularly Ciss. We really want to operate the pucks as followers.
Yes. I forgot that the auto-transformer has a swing per winding that is total-swing/N-windings. That means for 20 Watts and a transformer with 4 windings each winding sees 5V peak.
The Jensen JT-123-FLPCH datasheet http://www.jensen-transformers.com/wp-content/uploads/2014/08/jt-123-flpch.pdf, shows distortion vs. level for a test circuit with 2 windings in series as the primary and 2 windings in series for the secondary. The maximum output level is +20dBu = 11V peak, or 5.5V peak per winding. The 20Hz distortion is 1%, but decreases to below .01% above 70Hz.
The Jensen JT-123-FLPCH datasheet http://www.jensen-transformers.com/wp-content/uploads/2014/08/jt-123-flpch.pdf, shows distortion vs. level for a test circuit with 2 windings in series as the primary and 2 windings in series for the secondary. The maximum output level is +20dBu = 11V peak, or 5.5V peak per winding. The 20Hz distortion is 1%, but decreases to below .01% above 70Hz.
some house-cleaning
superduper nice small xformers of Yore, which I put in my little Jewel, they are working, but their contribution to overall heat of amp simply becomes too high
they were not buzzing, but they're simply too hot for my liking
who knew - supposedly 120VA jobbies, but evidently purely intended to feed B Class amp (being exactly pulled from pair of these), and juicing 60W for DEFiSIT channel is simply too much
just a remainder of little Cuties .......
superduper nice small xformers of Yore, which I put in my little Jewel, they are working, but their contribution to overall heat of amp simply becomes too high
they were not buzzing, but they're simply too hot for my liking
who knew - supposedly 120VA jobbies, but evidently purely intended to feed B Class amp (being exactly pulled from pair of these), and juicing 60W for DEFiSIT channel is simply too much
just a remainder of little Cuties .......
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So, I've sent e-mail to my guys at Trafomatic and ordered pair of new ones
these - 150VA, single 24Vac secondary, decreased flux, static shield, magnetic shield, black finishing tape
addition of small NTC board, so each having own mains NTC
they're practically cold per se
these - 150VA, single 24Vac secondary, decreased flux, static shield, magnetic shield, black finishing tape
addition of small NTC board, so each having own mains NTC
they're practically cold per se
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