I believe it is supposed to be 230V everywhere in the EU. UK and Ireland were 240 but went down to 230. Europe was 220 went up to 230.
Well that is something I have not been able to verify for myself (in all of the EU countries 😉.
But here in the Netherlands the voltages are consistently closer to 230 than 220. And transformer winders wind for 230V primaries.
But here in the Netherlands the voltages are consistently closer to 230 than 220. And transformer winders wind for 230V primaries.
I base my statement on the anecdotal evidence of a German neighbour of mine. He came from Berlin about 15yrs ago and now lives in Ireland. He said he was amazed at how quickly bulbs self destructed in Ireland over Berlin. Things may very well have changed considerably since then.
I also read a report about how long Tungsten bulbs could be made to last if undervoltaged, but as usual the exact reference is lost in the mists of the internet.
Shoog
I also read a report about how long Tungsten bulbs could be made to last if undervoltaged, but as usual the exact reference is lost in the mists of the internet.
Shoog
Harmonisation
It's a great European paper exercise. British mains used to be 240V +/-6%. It is now 230V +10% -6%. Guess what? That means that the existing 240V just sneaks in (unless it was right at the top of its +6%). Just ask yourself how much money it would cost to go round all the substations changing taps on the transformers to genuinely convert from 240V to 230V.
As it happens, I measured the mains at work yesterday: 250V.
To get back on topic. As far as hum is concerned, you only need DC heaters in RIAA stages. (And even there you can get away with AC if you do your heater wiring really carefully and select an input valve with low heater/cathode leakage.)
Evenharmonics: Leave no stone unturned, no wires untwisted.
Bas Horneman said:
It's a great European paper exercise. British mains used to be 240V +/-6%. It is now 230V +10% -6%. Guess what? That means that the existing 240V just sneaks in (unless it was right at the top of its +6%). Just ask yourself how much money it would cost to go round all the substations changing taps on the transformers to genuinely convert from 240V to 230V.
As it happens, I measured the mains at work yesterday: 250V.
To get back on topic. As far as hum is concerned, you only need DC heaters in RIAA stages. (And even there you can get away with AC if you do your heater wiring really carefully and select an input valve with low heater/cathode leakage.)
Evenharmonics: Leave no stone unturned, no wires untwisted.
Redd 47 AC Heater Termination Hell using ef86/E88cc
.I have just finished a tedious turret board- built Redd 47 , that 'photographs extremely well',..but, using this 6K49VG-460 volt transformer with a 6.3 volt secondary, fails to supply 6.3-7. volts to 'Two' tubes', namely, the E88cc and the EF86. I have 2.5 amps of current available, but have not been able to reconcile how to terminate- this' often 'overlooked topic. I build Microphone systems with OB2's that sound better than Neumann.. but when it comes to providing "AC" 6.3 voltage to -two 'differing tubes' such as is found on the REDD 4 7, I can only get 3.5 volts on both. I have only done DC discreet choke fed shunt regulation for filament and have no experience in AC heater design with different tubes. 1. First attempt - simple parallel- ( load to pin 4 and 5- both tubes..)no ground ref.. gave me a steadily changing '5-7volt' on the E88cc and '4- 5.1 volts' on the EF86(receiving current last..). 2. Second shot, I changed to the Guitar Amp approach where you short 4 to 5 and then use "9" on the E88cc as the other terminal.. with the same on the EF86- except using pin "7".
3. Third attempt, I -now have 3.5 volts --across load , with E88cc pins 4 and 5 tied together, other lead to "9" , with the EF86 simply going to pins 4 and 5- however with a ground reference.There is no center tap, so I built out two 5 watt Ohmite resistors to signal ground and took my 7 volts from their. Also, can I not 'clamp' this with some simple voltage clamp at 6 volts? Across the load?..The transformer is "6K49VG" Hammond(La2A) and is capable- more so than I (ha..) with a 460 volt secondary @50ma/6.3v@2.5A WITH CT for B+. I have great B+ voltage at 294volts and I'm using an AMI Tab Funkenwerk BV8r at .6.5:1 for input and output- since they are around.. Input secondary load resistor is 63k. Output is 10k over secondary. Any help with this Multiple Tube AC Heater dilemma would be appreciated!
.I have just finished a tedious turret board- built Redd 47 , that 'photographs extremely well',..but, using this 6K49VG-460 volt transformer with a 6.3 volt secondary, fails to supply 6.3-7. volts to 'Two' tubes', namely, the E88cc and the EF86. I have 2.5 amps of current available, but have not been able to reconcile how to terminate- this' often 'overlooked topic. I build Microphone systems with OB2's that sound better than Neumann.. but when it comes to providing "AC" 6.3 voltage to -two 'differing tubes' such as is found on the REDD 4 7, I can only get 3.5 volts on both. I have only done DC discreet choke fed shunt regulation for filament and have no experience in AC heater design with different tubes. 1. First attempt - simple parallel- ( load to pin 4 and 5- both tubes..)no ground ref.. gave me a steadily changing '5-7volt' on the E88cc and '4- 5.1 volts' on the EF86(receiving current last..). 2. Second shot, I changed to the Guitar Amp approach where you short 4 to 5 and then use "9" on the E88cc as the other terminal.. with the same on the EF86- except using pin "7".
3. Third attempt, I -now have 3.5 volts --across load , with E88cc pins 4 and 5 tied together, other lead to "9" , with the EF86 simply going to pins 4 and 5- however with a ground reference.There is no center tap, so I built out two 5 watt Ohmite resistors to signal ground and took my 7 volts from their. Also, can I not 'clamp' this with some simple voltage clamp at 6 volts? Across the load?..The transformer is "6K49VG" Hammond(La2A) and is capable- more so than I (ha..) with a 460 volt secondary @50ma/6.3v@2.5A WITH CT for B+. I have great B+ voltage at 294volts and I'm using an AMI Tab Funkenwerk BV8r at .6.5:1 for input and output- since they are around.. Input secondary load resistor is 63k. Output is 10k over secondary. Any help with this Multiple Tube AC Heater dilemma would be appreciated!
DC heaters were used in hi-fi gear in the 60s. The Brenell hi-fi tape link had DC heaters.
http:// http://www.schimmel.talktalk.net/tape/brenzone/vlink2.jpg
Cheers
Ian
http:// http://www.schimmel.talktalk.net/tape/brenzone/vlink2.jpg
Cheers
Ian
The Brenell was quite unusual in that respect, I don`t know of any other domestic kit that used DC heaters at that time. EMI and Leevers Rich professional machines on the other hand, used DC back in the early fifties - probably much other studio gear as well.
Not a myth. This applies to DH types, and is related to the "disappearing cathode" phenomenon. The plate voltage, as seen from the cathode, isn't very high, five volts or so. The voltage differential along a DH cathode can go positive, during negative grid downswings, and low Ip. That part of the cathode simply "disappears", and alters the characteristic from a 1.5 law device to a 2.5 or even a 3.5 law characteristic with nastier harmonics that don't roll off with increasing frequency as fast. This may be why some find 45s (2.5V heater) to sound better than 300Bs (5.0V heater). Some evidence that undervolting 300Bs makes for sonic improvement even though it sacrifices output.
Of course, none of that applies to indirectly heated cathodes, and why such cathodes are called "unipotential". There, undervolting the heaters just exposes the cathode to more positive ions that will ruin it that much faster. Best to run IDH types within their heater voltage spec.
No references, just experience. I had some special light bulbs designed for 277V. To use them, I wound up an autotransformer to double the line voltage to 240V -- 33V below the design voltage. I couldn't tell any difference so far as light color or brightness, but one bulb lasted over six years before it burnt out.
I'd use DC for heaters if doing a project involving low level signals: the phonos you mentioned, the front end of a receiver (regen, or the RF preamp, and mixer) however, past the first IF, AC heating. For higher level designs (audio amp designed to accept the ~1.0Vrms of a CD player, etc) DC isn't necessary.
At one time I had problems with light bulbs not lasting but 6 months (around 1986 or 1987). I had the power board install a stripchart to monitor my line voltage and when they picked it up they said it only reached 134V and that was acceptable. I started buying Polish made light bulbs rated at 130V instead of standard 115V bulbs. The 130V bulbs lasted for at least a year and often up to two years before going out.
Several years later I saw a lineman working a line across from my house and told him of my problem. He offered to take a look at it. While he was up the power pole at the transformer (service only to my house) he had me switch on the microwave, toaster over, and some other appliances one at a time.
He determined that the ground of the transformer was faulty. This resulted in erratic swings of the line voltage at the house under differing load conditions. One side that was loaded would see a 15V or more drop while the other side saw a comparable increase. He put in a work order and had the transformer replaced. My problems went away and those 130V light bulbs lasted several years more before I ran out and could not buy more.
All electronic components have a life that is related to power dissipation. The hotter you run them, the shorter the life. The converse is also true. The cooler you run them, the longer they last. Just don't run them so low that you are out of the required parameter range.
Several years later I saw a lineman working a line across from my house and told him of my problem. He offered to take a look at it. While he was up the power pole at the transformer (service only to my house) he had me switch on the microwave, toaster over, and some other appliances one at a time.
He determined that the ground of the transformer was faulty. This resulted in erratic swings of the line voltage at the house under differing load conditions. One side that was loaded would see a 15V or more drop while the other side saw a comparable increase. He put in a work order and had the transformer replaced. My problems went away and those 130V light bulbs lasted several years more before I ran out and could not buy more.
All electronic components have a life that is related to power dissipation. The hotter you run them, the shorter the life. The converse is also true. The cooler you run them, the longer they last. Just don't run them so low that you are out of the required parameter range.
Dynaco PAS-2 and 3 both used DC heaters as did gear from HH Scott, Fisher and many others.. My ReVox G36 MKIII uses DC heaters for all critical low level stages as well.
Rectifiers were often selenium for filament heating and fixed bias if used.
I have had serious problems with hum.
The power supply needed better and separate decoupling to each stage.
I had one problem where the rectifier diodes for the HT were glitching at 100Hz.
I had used slow diodes, replacing them with fast ones removed the problem.
I had another problem where even changing the heaters to DC didn't get rid of hum.
I then noticed my mains transformer was too close to the valves.
I was getting 40mV out of the first stage valve. This amplified through the second stage by a factor of 20 and gave massive hum on output.
I redesigned the pcb and the hum went to a minimal value.
I also found it important to keep inputs to valves short as possible to reduce pick up.
Elevated heaters to about 50VDC helps too.
The power supply needed better and separate decoupling to each stage.
I had one problem where the rectifier diodes for the HT were glitching at 100Hz.
I had used slow diodes, replacing them with fast ones removed the problem.
I had another problem where even changing the heaters to DC didn't get rid of hum.
I then noticed my mains transformer was too close to the valves.
I was getting 40mV out of the first stage valve. This amplified through the second stage by a factor of 20 and gave massive hum on output.
I redesigned the pcb and the hum went to a minimal value.
I also found it important to keep inputs to valves short as possible to reduce pick up.
Elevated heaters to about 50VDC helps too.
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it is alsways a good idea to look at hum with an oscilloscope. If it is 100Hz or harmincs therefof then it likely comes from after the rectifiers. if it is 50Hz then it is most likley nothing to do with the supplies but rather is magnetic coupling from a transformer. I NEVER use a steel chassis because it is an excellent conductor of magnetic fields.
Cheers
Ian
An interesting test for Op Tx coupling,
Remove the output tubes and power the amp..see if you get hum through the speakers....Just make sure you don't over volt the caps on the supply with lower current draw.
Regards
M. Gregg
Remove the output tubes and power the amp..see if you get hum through the speakers....Just make sure you don't over volt the caps on the supply with lower current draw.
Regards
M. Gregg
If you want DC regulated heaters (which i think are a good idea) then there are 2 further options we need to discuss:
- voltage regulation
- current regulation
There is some concern (with no facts or evidence to justify it) that DC will shorten heater life. If you are worried - use current regulation. With AC, or DC voltage, there will always be a current surge on power up. With DC current regulation - no current surge. This will actually increase heater life.
- voltage regulation
- current regulation
There is some concern (with no facts or evidence to justify it) that DC will shorten heater life. If you are worried - use current regulation. With AC, or DC voltage, there will always be a current surge on power up. With DC current regulation - no current surge. This will actually increase heater life.
I have used DC voltage controlled but made the transformer have just enough VA not to allow massive current flow.
The same goes for AC powered heaters, don't over rate the transformer or massive current will flow.
The same goes for AC powered heaters, don't over rate the transformer or massive current will flow.
AC heaters for me....
and you can still make your amp hum free...
tried dc but so far i have learned that going dc
is no guarantee for a hum free circuit,...
and you can still make your amp hum free...
tried dc but so far i have learned that going dc
is no guarantee for a hum free circuit,...
Exactly.
I have multiple amps with AC heaters, all hum free. I just built a SS amp and it has more hum than any of the valve builds.
If you jump to DC as a first option it is very likely that you will have failed to optimize the real source of the hum and this will degrade the overall performance of the amp.
Shoog
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