Batty Posted May 16, 2020 Share Posted May 16, 2020 43 minutes ago, iant said: Thermistors as surge protection in power amps are a bit of a concern.They can cause power supply modulation effects along with other potential problems.See Rod Elliotts full discussion.https://sound-au.com/articles/inrush.htm#s61 Nelson Pass uses them.... 1 Link to comment Share on other sites More sharing options...
mwhouston Posted May 16, 2020 Share Posted May 16, 2020 Just now, Batty said: Nelson Pass uses them.... He is just copying me. 2 Link to comment Share on other sites More sharing options...
Guest iant Posted May 16, 2020 Share Posted May 16, 2020 (edited) 1 hour ago, Batty said: Nelson Pass uses them.... See Rod Elliotts full discussion.https://sound-au.com/articles/inrush.htm#s61 Edited May 16, 2020 by iant Link to comment Share on other sites More sharing options...
kranky Posted May 16, 2020 Share Posted May 16, 2020 Mark not a 45 but a close cousin. 2 Link to comment Share on other sites More sharing options...
mwhouston Posted May 16, 2020 Share Posted May 16, 2020 1 hour ago, kranky said: Mark not a 45 but a close cousin. I’m salivating. One better than a threesome. 2 Link to comment Share on other sites More sharing options...
kranky Posted May 16, 2020 Share Posted May 16, 2020 Yes sorry for posting the pic. Have you tried the 4P1L tubes in a pre as i have found them to be excellent, as good as 01A just not as detailed but a dam site cheaper. 1 Link to comment Share on other sites More sharing options...
DQ828 Posted May 16, 2020 Share Posted May 16, 2020 Valve porn The easy bits done, I removed some winds and took the opportunity to replace the leads with something a little more friendly. I better pull my finger out and order the wire for the 150v. If this works I might encase it in resin 3 Link to comment Share on other sites More sharing options...
Red MacKay Posted May 16, 2020 Share Posted May 16, 2020 5 hours ago, DQ828 said: Valve porn The easy bits done, I removed some winds and took the opportunity to replace the leads with something a little more friendly. I better pull my finger out and order the wire for the 150v. If this works I might encase it in resin Awesome work! Link to comment Share on other sites More sharing options...
Martykt Posted May 16, 2020 Share Posted May 16, 2020 9 hours ago, kranky said: Mark not a 45 but a close cousin. They look really old, around what year would they have been manufactured? Link to comment Share on other sites More sharing options...
mwhouston Posted May 16, 2020 Share Posted May 16, 2020 5 hours ago, kranky said: Yes sorry for posting the pic. Have you tried the 4P1L tubes in a pre as i have found them to be excellent, as good as 01A just not as detailed but a dam site cheaper. Like to stay with tubes I can get at a moderate price. And I never build one of anything, well rarely, generally three. I’d even go for some modern Chinese 45s if I could find them. I like the modern Chinese tubes. I have used lots and always vely happy. Link to comment Share on other sites More sharing options...
Batty Posted May 16, 2020 Share Posted May 16, 2020 (edited) 18 hours ago, Guest iant said: See Rod Elliotts full discussion.https://sound-au.com/articles/inrush.htm#s61 Thermistors should only be used by themselves where the protected equipment draws a relatively constant power after it has settled down after power is first applied. While very convenient, NTC thermistors have a number of limitations. OK in a Class A power amp then. Edited May 16, 2020 by Batty 2 Link to comment Share on other sites More sharing options...
kranky Posted May 16, 2020 Share Posted May 16, 2020 Martykt, they are from the 1920s, on one tube there is a sticker with a stamp dated 1928. These tubes are known as an 01A. For more info on this tube or most tubes go to. Vinylsavor Thomas Mayer Tube UX201a. Steve. 1 Link to comment Share on other sites More sharing options...
SumonKabir Posted May 18, 2020 Share Posted May 18, 2020 (edited) Finally finished my 6sn7 preamp. not a bad outcome considering 50% material was recycled. Thanks a lot mwhouston for schematics. Edited May 18, 2020 by SumonKabir 15 Link to comment Share on other sites More sharing options...
DQ828 Posted May 18, 2020 Share Posted May 18, 2020 Last night I finally got around to testing the RPi Streamer using 5v power bank. I'll have to say it was a worthwhile experiment as I believe there was a noticable improvement in the SQ. I'm planning to set the Powerbank/Charger up so when I turn the DAC on, the charger for the PB is disconnect from the AC Mains, hence removing the PSU switching element. I'll probably put another trigger outlet in the DAC to achieve this. When I bought the original PB I stuffed up and bought one that wont supply power while charging so in the switchover the Streamer would get turned on and off, not what I wont. So of course I forked out more money get get a BP that does what I need. Just another thing to add to the list Link to comment Share on other sites More sharing options...
SumonKabir Posted May 18, 2020 Share Posted May 18, 2020 On 16/05/2020 at 5:20 PM, kranky said: Yes sorry for posting the pic. Have you tried the 4P1L tubes in a pre as i have found them to be excellent, as good as 01A just not as detailed but a dam site cheaper. Yes, I was surprised with $10 tube. Amazing 3D imaging and balanced output. There is only svetlana 4p1L what I can find. Looks like not many manufacturers made them. Link to comment Share on other sites More sharing options...
kranky Posted May 18, 2020 Share Posted May 18, 2020 10 hours ago, SumonKabir said: Yes, I was surprised with $10 tube. Amazing 3D imaging and balanced output. There is only svetlana 4p1L what I can find. Looks like not many manufacturers made them. I am not sure if the 4P1L was made in other plants in the USSR. Another tube which is similar is the 2P29L but is covered by a metal casing. $10 dollars a tube is still cheap, I purchased 100 of each around 10 years ago for $1 a pop. Happy Building. Steve. 1 Link to comment Share on other sites More sharing options...
muon* Posted May 19, 2020 Share Posted May 19, 2020 Had to hunt down a fault in Matt's Muji DAC, of course it turned out to be something simple but it alluded me for a while. Also changed the electrolytic caps around the digital chips for larger Polymers, replaced the decoupling caps on the TDA1541 for larger value Polystyrene and changed the 10uf electrolytic caps around the Sparko Op Amps to 100uf Silmics. 3 1 Link to comment Share on other sites More sharing options...
MattyW Posted May 19, 2020 Share Posted May 19, 2020 (edited) 16 minutes ago, muon* said: Had to hunt down a fault in Matt's Muji DAC, of course it turned out to be something simple but it alluded me for a while. Also changed the electrolytic caps around the digital chips for larger Polymers, replaced the decoupling caps on the TDA1541 for larger value Polystyrene and changed the 10uf electrolytic caps around the Sparko Op Amps to 100uf Silmics. Looking forward to hearing this once more. It's a truly wonderful sounding unit after a few mods: NOS reclock module, Holland made TDA1541 S1, rhodium plated brass solderless RCA's with tellurium copper center pin, Sparkos and Burson OPAMPS, some Arizona Blue Cactus caps, Miflex KFPM-1 bypassed with Duelund Silver Bypass caps and the Neotech UPOCC wires. Will be very interesting to see how these other improvements on the digital side change things, Course it's better value for money to buy a DAC from the Abbas Audio range. Edited May 19, 2020 by MattyW Link to comment Share on other sites More sharing options...
mwhouston Posted May 23, 2020 Share Posted May 23, 2020 A pair of Jim’s Audio F5 brds I just populated. Apart from matched input FETs and power FETs a pretty standard brd. with standard parts. 1 Link to comment Share on other sites More sharing options...
mwhouston Posted May 23, 2020 Share Posted May 23, 2020 Made too many of these. Universal tube preamp PS. 250VHT and 25v filament. Voltages required for each preamp is configured in the preamp. One PS powers four of my preamp from 5V heater and 100VHT requirement to 24V and 250VHT requirements. Save a few hundred dollars each preamp. Neatest build so far. Link to comment Share on other sites More sharing options...
aussievintage Posted May 23, 2020 Share Posted May 23, 2020 17 minutes ago, mwhouston said: Made too many of these. Universal tube preamp PS. 250VHT and 25v filament. Voltages required for each preamp is configured in the preamp. One PS powers four of my preamp from 5V heater and 100VHT requirement to 24V and 250VHT requirements. Save a few hundred dollars each preamp. Neatest build so far. Seeing only one transformer, I am wondering, either you use the transformer backwards and power the board from a 12/24 AC plugpack, or you are just using the transformer normally for the low voltage, and rectifying the HT direct from the mains? 1 Link to comment Share on other sites More sharing options...
mwhouston Posted May 23, 2020 Share Posted May 23, 2020 1 minute ago, aussievintage said: Seeing only one transformer, I am wondering, either you use the transformer backwards and power the board from a 12/24 AC plugpack, or you are just using the transformer normally for the low voltage, and rectifying the HT direct from the mains? 24V 1A wall wart then, as you said, backwards into the step down (24V) for HT. Filament voltage directly rectified and filtered. 1 Link to comment Share on other sites More sharing options...
tubularbells Posted May 23, 2020 Share Posted May 23, 2020 Some Holton magic arrived yesterday.... 2 Link to comment Share on other sites More sharing options...
aussievintage Posted May 23, 2020 Share Posted May 23, 2020 5 minutes ago, mwhouston said: 24V 1A wall wart then, as you said, backwards into the step down (24V) for HT. Filament voltage directly rectified and filtered. Yes, same as I do for my phono amps then. Works extremely well and saves on transformer costs. I usually don't regulate the DC filament/heater voltage btw (you don't mention it either), as a simple power resistor to drop the voltage, due to the constant load, works nicely. 1 Link to comment Share on other sites More sharing options...
mwhouston Posted May 23, 2020 Share Posted May 23, 2020 9 minutes ago, aussievintage said: Yes, same as I do for my phono amps then. Works extremely well and saves on transformer costs. I usually don't regulate the DC filament/heater voltage btw (you don't mention it either), as a simple power resistor to drop the voltage, due to the constant load, works nicely. Should add I choke the HT with a 5H 50mA Hammond which sitS off the brd:- CLCRC then in the preamp -RC. Total of 400uf+ for HT and 9400uf+ for the heaters. Link to comment Share on other sites More sharing options...
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