Hi everyone!
I've just powered on my SSE for a bench test for the first time.
First let me say THANK YOU to everyone who gave such helpful replies to all my forum posts here lately. I couldn't have managed a build like this without your invaluable assistance. And big thanks to George for creating such a fun and interesting project for all of us.
So, after checking and double-checking all my connections, I powered on my SSE. When there's no music playing, the speakers are dead quiet. And then, when I play some music, it's clear and lush, even from the tiny speakers I'm using to test the SSE with. I'm very impressed so far, and quite happy with the sound.
However I have a question about the heat produced by the tubes. I don't have any experience with tube speaker amps, only tube headphone amps (bottlehead crack). So for all I know, this may be normal behavior. But the tubes are putting out quite a bit of heat.
I don't have a proper IR thermometer, only one used for bodies. It maxes out around 209 degrees Fahrenheit, so it won't give an accurate reading of the tubes, it just says "HI". I'll rummage around in the storage room and see if I can find a proper IR thermometer.
I've got my system configured in the basic triode mode without feedback. Output tubes are EL34. And there's a GZ34 and a ECC81 on the board as well. Tube rectification only, no solid state. Power transformer is a Hammond 274BX, the kind recommended by George on his site. A Triad C-14X choke is present, as well as a motor run cap. Output transformers are Toroidy TTG-EL34SE.
Does this temperature seem normal?
Edit: I found a proper thermometer, and took some measurements by aiming the thermometer at the middle of the tubes. After having the amp on, without signal, for about 10 minutes The EL34 tubes are reading about 380F. If I aim at the top, the EL34 tubes read 411F.
Seems hot, no?
The ECC81 is at 204F, and the GZ34S is at 240F.
I've just powered on my SSE for a bench test for the first time.
First let me say THANK YOU to everyone who gave such helpful replies to all my forum posts here lately. I couldn't have managed a build like this without your invaluable assistance. And big thanks to George for creating such a fun and interesting project for all of us.
So, after checking and double-checking all my connections, I powered on my SSE. When there's no music playing, the speakers are dead quiet. And then, when I play some music, it's clear and lush, even from the tiny speakers I'm using to test the SSE with. I'm very impressed so far, and quite happy with the sound.
However I have a question about the heat produced by the tubes. I don't have any experience with tube speaker amps, only tube headphone amps (bottlehead crack). So for all I know, this may be normal behavior. But the tubes are putting out quite a bit of heat.
I don't have a proper IR thermometer, only one used for bodies. It maxes out around 209 degrees Fahrenheit, so it won't give an accurate reading of the tubes, it just says "HI". I'll rummage around in the storage room and see if I can find a proper IR thermometer.
I've got my system configured in the basic triode mode without feedback. Output tubes are EL34. And there's a GZ34 and a ECC81 on the board as well. Tube rectification only, no solid state. Power transformer is a Hammond 274BX, the kind recommended by George on his site. A Triad C-14X choke is present, as well as a motor run cap. Output transformers are Toroidy TTG-EL34SE.
Does this temperature seem normal?
Edit: I found a proper thermometer, and took some measurements by aiming the thermometer at the middle of the tubes. After having the amp on, without signal, for about 10 minutes The EL34 tubes are reading about 380F. If I aim at the top, the EL34 tubes read 411F.
Seems hot, no?
The ECC81 is at 204F, and the GZ34S is at 240F.
Last edited:
https://drtube.com/datasheets/el34-sed2001.pdf
Allowable spot temperature for an EL34 is 250C = 482F
Allowable spot temperature for an EL34 is 250C = 482F
The valves are thermionic so generate a bit heat by definition.
The hearers alone can take a few watts.
Having said that good ventilation for the valves is recommended.
A lot of valve amps have an open back while being safe.
I had an old Simms-Watts 100 watt PA amp that had an open back and grill on top for the 4 off EL34 valves.
The hearers alone can take a few watts.
Having said that good ventilation for the valves is recommended.
A lot of valve amps have an open back while being safe.
I had an old Simms-Watts 100 watt PA amp that had an open back and grill on top for the 4 off EL34 valves.
Look at the outer metal element (the plate) that surrounds the guts inside the glass in a dark room. There should be no red glow on this element. The rod running down the center (the cathode) of the tube does indeed glow a very hot shade of red.
If there is no glowing spots on the plate you are probably OK. To verify you can measure the voltage on the cathode (pin 8) and the plate (pin 3). These numbers can be used to figure out the actual dissipation (waste heat) in the tube.
If there is no glowing spots on the plate you are probably OK. To verify you can measure the voltage on the cathode (pin 8) and the plate (pin 3). These numbers can be used to figure out the actual dissipation (waste heat) in the tube.
In the case of an SE amp the time when it is not playig music is the worst for dissipation. So giving a bit of welly won't hurt!
I wondered if anyone had considered something like the ignition cutout of modern cars, where the engines go dormant at traffic lights? How about something solid state that monitors the signal and slowly (2 seconds or so) varies the bias of the tube between 'power saver' and 'bring it on'. It could be additional fixed bias so the grid goes more negative when the amp is not doing any work.
There are amps with parallel tubes that are configurable for the amount of tube power they have.
I have a fear that one day there will be some blanket legislation that makes our hobby harder (e.g. minimum efficiency). I wonder how long we will have to have mains supplies up around 230V or 115V, it is only for distribution to the front door. Most higher current appliances can buffer their power needs by stint of being battery powered (e.g. drills, vacuums), so apart from heating and cooking, which could be hardwired electrical supplies, what is left?
I wondered if anyone had considered something like the ignition cutout of modern cars, where the engines go dormant at traffic lights? How about something solid state that monitors the signal and slowly (2 seconds or so) varies the bias of the tube between 'power saver' and 'bring it on'. It could be additional fixed bias so the grid goes more negative when the amp is not doing any work.
There are amps with parallel tubes that are configurable for the amount of tube power they have.
I have a fear that one day there will be some blanket legislation that makes our hobby harder (e.g. minimum efficiency). I wonder how long we will have to have mains supplies up around 230V or 115V, it is only for distribution to the front door. Most higher current appliances can buffer their power needs by stint of being battery powered (e.g. drills, vacuums), so apart from heating and cooking, which could be hardwired electrical supplies, what is left?