Re: so how hot is too hot
It's usually quite OK (speaking generally; I know nothing about the wave 8's), but you might want to try both 4 and 8 ohm taps to see which sounds better. IME, nominal 6R loads usually sound better on the 4R taps, but it depends on what the Z curve of the speaker looks like.
adharvey said:
It's usually quite OK (speaking generally; I know nothing about the wave 8's), but you might want to try both 4 and 8 ohm taps to see which sounds better. IME, nominal 6R loads usually sound better on the 4R taps, but it depends on what the Z curve of the speaker looks like.
Wave - 8
Hi,
Just installed a pair of wave 8 and have noticed the same phenomenon. It is hotter then what I usualy see in tube amps of my design. Two things can be the contributing factors, the tubes are radiating heat on the output transformer (being painted black it acumulates this heat) and the other is a small power transformer that gets hot by itself. Possible cures: reduce the voltage to the tubes filaments to 5.7 v via resistor this will minimize the amount of heat from the tubes, and add a filament transformer under the hood (there is room for this there) to take the load off the main one. Anothr way is to put an aluminum foil on the output transformer facing the tubes, this will radiate the heat back out BUT will hurt cosmetics so it is up to you.
Good luck.
Glass painter.
Hi,
Just installed a pair of wave 8 and have noticed the same phenomenon. It is hotter then what I usualy see in tube amps of my design. Two things can be the contributing factors, the tubes are radiating heat on the output transformer (being painted black it acumulates this heat) and the other is a small power transformer that gets hot by itself. Possible cures: reduce the voltage to the tubes filaments to 5.7 v via resistor this will minimize the amount of heat from the tubes, and add a filament transformer under the hood (there is room for this there) to take the load off the main one. Anothr way is to put an aluminum foil on the output transformer facing the tubes, this will radiate the heat back out BUT will hurt cosmetics so it is up to you.
Good luck.
Glass painter.
Hi,
Sorry to say so but reducing heater voltage is NOT a good idea.
The cause of the heat in the xformer(s) is quite likely a thinnish wire gauge in the xformer(s) with respect to the current draw.
Nothing much you can do about it.
Just put the amps in a well ventilated place, not inside a closed cupboard and plan on replacing electrolytic caps every other 15 years.
Other than that it's nothing I'd worry about.
Cheers,
Sorry to say so but reducing heater voltage is NOT a good idea.
The cause of the heat in the xformer(s) is quite likely a thinnish wire gauge in the xformer(s) with respect to the current draw.
Nothing much you can do about it.
Just put the amps in a well ventilated place, not inside a closed cupboard and plan on replacing electrolytic caps every other 15 years.
Other than that it's nothing I'd worry about.
Cheers,
Hi Frank,
Can you add info regarding why reducing filament voltage by 10% is not a good idea?
According to Steve Bentch work and based on my experiance I have not seen effects on sound, distortion or any other for that matter because of this action (I have several amplifiers running this way). In addition, the manufacturer states that the filament voltage should be the nominal (6.3v) plus or minus 10%.
Thanks.
Glass painter.
Can you add info regarding why reducing filament voltage by 10% is not a good idea?
According to Steve Bentch work and based on my experiance I have not seen effects on sound, distortion or any other for that matter because of this action (I have several amplifiers running this way). In addition, the manufacturer states that the filament voltage should be the nominal (6.3v) plus or minus 10%.
Thanks.
Glass painter.
Hi,
First of all I assumed the WAV amp uses IDHTs.
While I mostly agree with Steve Benchs' experiments, what you do when starvings DHTs for voltage is that you create a new set of curves for the DUT.
This is fine for experimental testing but I can't imagine a manufacturer who's had to use a loadline to determine optimal operating points having this kind of condition in mind.
If ever you have the chance to run some experiments on IDHT triodes you can actually see that you can burn in tubes at reduced heater voltages or increased ones and end up with non-standard curves.
For instance, taking the ubiquitous 6DJ8 and testing it at 5 V on the heater and you'll notice a much reduced emission of the cathode.
Leave it at this voltage for hours in a row and you'll have a dull and lifeless sounding tube for the rest of its life.
Now let's use the same type and put the heater at 7 V. At first the cathode emission will be way too high showing much increased transconductance.
About 10 to 15 minutes later you'll notice an emission that's decreased to about 100% of what you'd see for a 6DJ8 at 6.3 V.
If you now test that same tube that was heated at 7 V but retest it with 6.3 V n the heater you'll notice the DUT won't even come close to what is to be expected. It's emission is only about 70% if we're lucky.
Moreover it will quite probably never return to normal emission.
If we now plot the curves of both DUTs we'll notice that neither one will show a typical curve.We just wasted two perfectly fine tubes...
Tube manufacturers allow for +/- 10% of heater voltage variation to ensure the tube will still work as expected.
And yes, it will work...just NOT optimally.
Also note the word variation used which does not mean permanent deviation.
Now, imagine we'd feed that tube at -10% already and the mains fluctuates another 5-10%, where do we end up?
Outside manufacturer tolerances I reckon...
This applies mainly to all IDHT I know of, the higher the transconductance the more obvious the effect.
DHTs are a different kettle of fish all together, I've seen 2A3s that were dull sounding at 2.5 V and came to life at 3 V and lasted for many years. YMMV.
Hope this helps,
First of all I assumed the WAV amp uses IDHTs.
While I mostly agree with Steve Benchs' experiments, what you do when starvings DHTs for voltage is that you create a new set of curves for the DUT.
This is fine for experimental testing but I can't imagine a manufacturer who's had to use a loadline to determine optimal operating points having this kind of condition in mind.
If ever you have the chance to run some experiments on IDHT triodes you can actually see that you can burn in tubes at reduced heater voltages or increased ones and end up with non-standard curves.
For instance, taking the ubiquitous 6DJ8 and testing it at 5 V on the heater and you'll notice a much reduced emission of the cathode.
Leave it at this voltage for hours in a row and you'll have a dull and lifeless sounding tube for the rest of its life.
Now let's use the same type and put the heater at 7 V. At first the cathode emission will be way too high showing much increased transconductance.
About 10 to 15 minutes later you'll notice an emission that's decreased to about 100% of what you'd see for a 6DJ8 at 6.3 V.
If you now test that same tube that was heated at 7 V but retest it with 6.3 V n the heater you'll notice the DUT won't even come close to what is to be expected. It's emission is only about 70% if we're lucky.
Moreover it will quite probably never return to normal emission.
If we now plot the curves of both DUTs we'll notice that neither one will show a typical curve.We just wasted two perfectly fine tubes...
Tube manufacturers allow for +/- 10% of heater voltage variation to ensure the tube will still work as expected.
And yes, it will work...just NOT optimally.
Also note the word variation used which does not mean permanent deviation.
Now, imagine we'd feed that tube at -10% already and the mains fluctuates another 5-10%, where do we end up?
Outside manufacturer tolerances I reckon...
This applies mainly to all IDHT I know of, the higher the transconductance the more obvious the effect.
DHTs are a different kettle of fish all together, I've seen 2A3s that were dull sounding at 2.5 V and came to life at 3 V and lasted for many years. YMMV.
Hope this helps,
Hi Frank,
Thanks for the info. it was very interesting to read.
As I stated before, I have a 50bm8 amp running at 45 v filament currently running with no impact on sound (as much as I know) and I had several others that worked well - until I took them apart for other projects, but after reading your mail I will test it again.
Thanks.
Glass_painter
Thanks for the info. it was very interesting to read.
As I stated before, I have a 50bm8 amp running at 45 v filament currently running with no impact on sound (as much as I know) and I had several others that worked well - until I took them apart for other projects, but after reading your mail I will test it again.
Thanks.
Glass_painter
Hi,
Ah...if I'm not mistaken the 50BM8s' heater was designed for series operation ( several heaters strung together daisy chain) in radio and TV service.
If that's the case it will work as long as it can draw its required current (100mA in this case), voltage isn't as critical here. Current draw is.
I'd need to refresh the little I know about it though, never took any interest in those particular TV tubes but most audio tubes have equivalents using different heater voltages for this kind of service.
If my guesswork is correct it could well explain why you don't hear a difference at lower heater voltage.
Cheers,
Ah...if I'm not mistaken the 50BM8s' heater was designed for series operation ( several heaters strung together daisy chain) in radio and TV service.
If that's the case it will work as long as it can draw its required current (100mA in this case), voltage isn't as critical here. Current draw is.
I'd need to refresh the little I know about it though, never took any interest in those particular TV tubes but most audio tubes have equivalents using different heater voltages for this kind of service.
If my guesswork is correct it could well explain why you don't hear a difference at lower heater voltage.
Cheers,
Hi,
Most TV tubes at a given point in history had a heater designed for stringed operation.
The idea was to save on powerxformers by putting the heaters in series so you ended up with, say, 115 VAC for a TV set in the U.S. using a combination of tubes.
As you may have noticed the higher the voltage the lower the current consumption making for better efficiency. Less power consumption was the main target.
How this was achieved technically I don't quite remember but a book on the history of the electron tube should explain it.
Or perhaps someone else remembers the details?
Sorry if I'm not much help to you here...
Cheers,
Most TV tubes at a given point in history had a heater designed for stringed operation.
The idea was to save on powerxformers by putting the heaters in series so you ended up with, say, 115 VAC for a TV set in the U.S. using a combination of tubes.
As you may have noticed the higher the voltage the lower the current consumption making for better efficiency. Less power consumption was the main target.
How this was achieved technically I don't quite remember but a book on the history of the electron tube should explain it.
Or perhaps someone else remembers the details?
Sorry if I'm not much help to you here...
Cheers,
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