Brian Beck said:
It depends on how dark the room is
For most of my testing and listening, I set the bias so that each 833's plate dissipated about 160W, well below the max ratings. In a brightly lit room, I don't notice a glow (although you can make it out if look closely). With the lights off, there is a dull red glow. When I've cranked up the juice to 400 W per tube, a glow is apparent in a lit room. As long as you are within ratings for natural (non-forced) air flow, a glowing plate is no cause for concern. By the way, the hot graphite plate, in conjunction with coatings applied to it, acts as a getter, sucking up residual gases.
Plate glow is how the 833's shed much of their heat, through the glass envelope by IR radiation. The concern at high power is to keep the plate and grid terminals cool enough to protect the lead seals against failure. RCA recommends a 2" diameter blower nozzle pointed directly at the top of the tube between the terminals to accomplish the cooling at high power use. The use of heat radiating/exchanging connectors on the grid and plate connections that have heat dissipating fins is helpful.
That depends on the operating conditons for the tube. At 1500 volts and 200 to 300 Ma I found a 5K ohm load to be ideal, with power output approaching 175 watts. Over 200 watts was available at 275 mA of bias current. If you operate at higher voltage and lower current a higher load impedance is needed.
It will be hard to find a transformer for this amp.
I did some experimenting with a custom made 5K ohm transformer. The results are here:
http://www.tubelab.com/833SE.htm
It will be hard to find a transformer for this amp.
I did some experimenting with a custom made 5K ohm transformer. The results are here:
http://www.tubelab.com/833SE.htm
The power gain of any tube is highly dependent on the circuit that it is in. The 833A is one of the largest tubes used in audio amplifier designs. It requires voltage levels far in excess of those used in typical designs. Because of this special components and techniques must be used. An output transformer for an amp of this magnitude is hard to find and usually must be custom made. An amp of this nature should only be attempted by those who are extremely well skilled in the art of vacuum tube amplifier design and construction. Even if you can get through the lethal voltages without getting fried, the amplifier will probably not work very well, and could casue a severe shock and fire hazard for everyone living in your house! If you have not built a few tube amplifiers before, DO NOT EVEN THINK OF STARTING WITH AN 833A.
Read this entire thread, and follow all of the links to see what others have done to tame this beast. Then ask yourself if you are capable of doing this sucessfully. Look at the picture of my test amp, there is a 1/4 inch thick sheel of Lexan between me and the amp, and a large fire extinguisher nearby! If something like this doesn't scare the crap out of you, you have no business building one!
A project of this magnitude will cost some serious money and time. Will you give up on the entire hobby if you fail? Start with a project that you WILL finish. Then you will want to build another one.
http://www.tubelab.com/833SE.htm
Read this entire thread, and follow all of the links to see what others have done to tame this beast. Then ask yourself if you are capable of doing this sucessfully. Look at the picture of my test amp, there is a 1/4 inch thick sheel of Lexan between me and the amp, and a large fire extinguisher nearby! If something like this doesn't scare the crap out of you, you have no business building one!
A project of this magnitude will cost some serious money and time. Will you give up on the entire hobby if you fail? Start with a project that you WILL finish. Then you will want to build another one.
http://www.tubelab.com/833SE.htm
tubelab is correct that building a 833 or something equally crazy costs a lot of money and is quite dangerous.
you cannot just use any wires, for example. Military grade wires and connectors are used. So you either order from the military/aerospace catalogue and pay $60 for just one connector and you probably need about 8 or more, or hunt surplus on Ebay.
As long as you wear high voltage gloves, I don't think constructing a 833-like amp is any more complex than a 2a3 amp. Everything are just a lot bigger, heavier, and more expensive.
Also, I don't think you can necessarily breadboard the amp either, as all the components must be secured, soldered, and mounted before you even consider powering it up. So, triple check and than quad check everything.
you cannot just use any wires, for example. Military grade wires and connectors are used. So you either order from the military/aerospace catalogue and pay $60 for just one connector and you probably need about 8 or more, or hunt surplus on Ebay.
As long as you wear high voltage gloves, I don't think constructing a 833-like amp is any more complex than a 2a3 amp. Everything are just a lot bigger, heavier, and more expensive.
Also, I don't think you can necessarily breadboard the amp either, as all the components must be secured, soldered, and mounted before you even consider powering it up. So, triple check and than quad check everything.
tubelab.com said:
My advice is to build it, charge a fortune for it. They WILL come and buy it. Zero doubt on that.
I've done the odd custom amp for some groups, that ended up nearly creating the 'sound' of that particular album. (they ended up in the studio) *
If this 833 does what you say it does..then it WILL be in great demand, as it will 'define' a 'space' for a given sucessful artist, who's already been everywhere. That new sound that they are dying for, they -will- pay ANYTHING for.
You know this, so make it and sell them, at exorborant prices. get the fame and at the same time you put nice steaks on the table.
*disclaimer: I can't design my way out of the bathroom closet, but I CAN mod the *** off of anything.
rcavictim said:
Is it perhaps revealing that military quality connectors and cables cost a lot less than audiophile quality interconnects?! Could it be that outrageous profiteering is being employed in the audio interconnect biz? Tell me this ain't so.
well think about it: the people that are used to paying $600 for a toilet seat only want to pay $60 for a titanium frame, silver plated plug.
Banned
Joined 2002
Banned
Joined 2002
Re: 833 tube need helo
That only works with BJTs. For VTs, you need to draw loadlines.
The 833A won't work as a Class A1 amp. It's a high gain xmtr tube with such a high u-factor that you'll never get it to pull enough current to work at all well if you don't give it enhancement bias and work it as a Class A2.
zzzz_alexander said:
That only works with BJTs. For VTs, you need to draw loadlines.
The 833A won't work as a Class A1 amp. It's a high gain xmtr tube with such a high u-factor that you'll never get it to pull enough current to work at all well if you don't give it enhancement bias and work it as a Class A2.
agent.5 said:
Tubelab did. He didn't even have a proper 833A socket.
Of course, it's not something I would want to do. After all, what am I going to do with a 175W amp anyway? I don't need to fill an entire arena with sound, and the 25 watter I have now is more than loud enough to P.O. the neighbours if I really run it flat out.
I have breadboarded the 833A supporting it on heavy #10 AWG solid copper wires from a filament xfmer with small hose clamps to the filament terminals with good success.
BTW-1, don't run an 833A this hot for more than tens of seconds or you will end up with a holy anode.
BTW-2, don't run an 833A at all if you don't have a lot of experience in high voltage practise.
BTW-1, don't run an 833A this hot for more than tens of seconds or you will end up with a holy anode.
BTW-2, don't run an 833A at all if you don't have a lot of experience in high voltage practise.
