jacco, since mercury wetted is ******* illegal now (the best), and teledyne micro relays are hard to find (silba would use them in a second if you couldn't get them at all...), my personal fave is NEC. they make an excellent 12V small signal pc mountable relay. hi rel, gold plated, etc. and you don't have to buy them on ebay. i don't know the exact part # but they are not hard to find. there is a korean licensee that make local versions. i have no prob with them. we are using them in the relay attenuators we make.
is that a help?
is that a help?
Sure, for me it's fun to see a specialty preamp with relays for once.
I've got both plenty of documentation on relays and various types in volume numbers, some as exotic as it gets.
Thanks for the reply, wishing you and the family Merry-X too and a happy continuation in Malmö.
Next time (if) i catch you in the flesh, i'll take you to a better French cafeteria, in return for a longer talk, deal ?
I've got both plenty of documentation on relays and various types in volume numbers, some as exotic as it gets.
Thanks for the reply, wishing you and the family Merry-X too and a happy continuation in Malmö.
Next time (if) i catch you in the flesh, i'll take you to a better French cafeteria, in return for a longer talk, deal ?
LOL. When was the last time they were worth something? Enjoy them yourself if you can and don't ask the mob for recognition. You won't get it.
Ouch, Touchy.
You probably missed the Muppet show episode about the Cat that went to the Dogs.
.
And a beautiful family you have! Please forget the little gaff and all the best. Nothing beats cafeteria food in the UK.
...read the book instead?
_-_-bear
There's nothing like hearing WSB read it to you. There are scattered portions all over, worth seeking out.
I did. I can only remember this one:
YouTube - I Hope That Somethin' Better Comes Along - Rowlf the Dog and Kermit the Frog
To stay on topic I say... Hi, Mr Morrison! I seem to remember building the 2A3 Loftin-White SE amp (long time ago).
The h-k diode will only be reverse biased if the heater is made more positive than the cathode. I wouldn't leave ANYTHING floating. If there is significant signal on the cathode I like to use a separate heater winding but maybe that's overkill in some cases.
Depending on the transformer but yes, absolutely. It's even different if you fix one end of the winding vs. the other. Try it with a bifilar would input transformer, for example.
Cheers,
Michael
Back off topic, one you didn't see on Sesame Street, Rowlf the Dog as Kermit's heroin connection: YouTube - kermit sings hurt
John
ahh, i shouldn't do this, but it's too late now.
one addition piece of information about the heater cathode voltage rating...
as far as the "parasitic diode" goes, the heater is the emissive part, and the cathode becomes the anode. the current flows from heater to cathode, when the rating is exceeded in the positive direction. this "diode" is not a high performance part. but it creates electrical/chemical activity in the environment of the cathode which is destructive. a vacuum tube is only as good as its emission.
raising the heater with respect to ground only helps when the cathode is at ground potential. in a cathode follower, or self biased stage, the cathode is not at ground potential. hence the need to "lift" the heater string to somewhere near the cathode level. the real problem arises when one is using dual tubes, and perhaps several of them, all on a common heater string. it doesn't take much imagination to see the possible interconnection of stages through the low level chaos of the heater to cathode interface. this is usually a much bigger deal at RF than audio... where early failures are more of an issue. i maintain that grounding the heater is rarely wise. and it's so easy to lift or drop it a few or many volts. of course for AC signals, it is often important to "ground" the heater string. AC powered heaters is a particular concern in this case... but it is so easy to attach the heater string to a self biased stage, or a divider, and then bypass with a suitable cap. a long heater string with small signal and power tubes sharing 6 amperes of ac or dc current is nothing to have on ground.
its perfectly ok to have the cathode flying around... as long as its within ratings. it is also often ok to let the heater float to the cathode level on its own... which it will because of the parasitic C. many regulators are made this way... it is NOT necessary to ground reference the heater in every application.
jc
one addition piece of information about the heater cathode voltage rating...
as far as the "parasitic diode" goes, the heater is the emissive part, and the cathode becomes the anode. the current flows from heater to cathode, when the rating is exceeded in the positive direction. this "diode" is not a high performance part. but it creates electrical/chemical activity in the environment of the cathode which is destructive. a vacuum tube is only as good as its emission.
raising the heater with respect to ground only helps when the cathode is at ground potential. in a cathode follower, or self biased stage, the cathode is not at ground potential. hence the need to "lift" the heater string to somewhere near the cathode level. the real problem arises when one is using dual tubes, and perhaps several of them, all on a common heater string. it doesn't take much imagination to see the possible interconnection of stages through the low level chaos of the heater to cathode interface. this is usually a much bigger deal at RF than audio... where early failures are more of an issue. i maintain that grounding the heater is rarely wise. and it's so easy to lift or drop it a few or many volts. of course for AC signals, it is often important to "ground" the heater string. AC powered heaters is a particular concern in this case... but it is so easy to attach the heater string to a self biased stage, or a divider, and then bypass with a suitable cap. a long heater string with small signal and power tubes sharing 6 amperes of ac or dc current is nothing to have on ground.
its perfectly ok to have the cathode flying around... as long as its within ratings. it is also often ok to let the heater float to the cathode level on its own... which it will because of the parasitic C. many regulators are made this way... it is NOT necessary to ground reference the heater in every application.
jc
Hi ! JCM, I am very glad to meet you in ETF-2010. Your presentation
was impressive to me.
I have completed the schematic design of a Class-D with a tube voltage
pre-amplifier which uses negative voltage power supply and input
transformer for the common purpose of your presentation.
Please see following my Web.
http://ja1cty.servehttp.com/class-d/ClassD-theory.gif
http://ja1cty.servehttp.com/class-d/ClassD-AMP.gif
was impressive to me.
I have completed the schematic design of a Class-D with a tube voltage
pre-amplifier which uses negative voltage power supply and input
transformer for the common purpose of your presentation.
Please see following my Web.
http://ja1cty.servehttp.com/class-d/ClassD-theory.gif
http://ja1cty.servehttp.com/class-d/ClassD-AMP.gif
I will freely admit I'm a noob, but what is the advantage of the twin rectifier tubes with the SS diode rectification in this PS? I noticed this PS uses two tubes while his other designs used a single tube.
I'm very intrigued and love the idea of a soft-start for a high current, HV PS. Do the tubes limit the amount of current that can pass through the solid state diodes once they are up to operating points? If the tubes are a limiting device, what is the advantage of the addition of the SS diodes, why not just use a tube for the rectifier with a standard FW CT secondary?
I need a PS for +400V and -400V split rails that can deliver more current than most of the shunted designs I have seen so I'm interested in this PS design, using the B+ filtering techniques for both rails. What is the upper limit of current that each rail could provide? I need about 300mA-400mA per rail if I really crank up the bias levels. I can add MOSFET discrete regulation after the filters.
TIA for helping a noobie understand the application and advantages of this unique supply.
I'm very intrigued and love the idea of a soft-start for a high current, HV PS. Do the tubes limit the amount of current that can pass through the solid state diodes once they are up to operating points? If the tubes are a limiting device, what is the advantage of the addition of the SS diodes, why not just use a tube for the rectifier with a standard FW CT secondary?
I need a PS for +400V and -400V split rails that can deliver more current than most of the shunted designs I have seen so I'm interested in this PS design, using the B+ filtering techniques for both rails. What is the upper limit of current that each rail could provide? I need about 300mA-400mA per rail if I really crank up the bias levels. I can add MOSFET discrete regulation after the filters.
TIA for helping a noobie understand the application and advantages of this unique supply.
Hi!
Instead of putting the two tube rectifiers in the ground rail, I would have built a hybrid bridge, using the tubes instead of the two silicon diodes in the upper part of the bridge. This would provide the same soft start but woould add the better switching behaviour of the tubes
Best regards
Thomas
The advantage of the full wave bridge over the FW CT scheme is the simpler power transformer which only needs to provide half the secondary voltage.
Instead of putting the two tube rectifiers in the ground rail, I would have built a hybrid bridge, using the tubes instead of the two silicon diodes in the upper part of the bridge. This would provide the same soft start but woould add the better switching behaviour of the tubes
Best regards
Thomas
Thanks Thomas.
Wouldn't placing a tube rectifier in the top of the bridge impose the current limitation of the chosen rectifier tube and require a larger secondary voltage in the winding to accommodate the voltage drop across the tube?
The way I'm interpreting the circuit, there is no voltage drop other than the usual couple of volts across the SS diodes and the circuit should be able to deliver far more current than the usual 250mA or less that most rectifier tubes are rated to pass.
But there are two in parallel so that threw me. I didn't know if the current limitation of the tubes still applied and if the two tubes in parallel doubles the available current.
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