I can understand your frustration with the non 845 suggestions. However I am curious why you are so determined to use this particular tube.
Is it because of the sound? Have you heard this tube?
Is it because of the way it looks?
Is it because of the increased power over the more usual 45, 50, 2A3 or 300B that would probably work with your Lowthers?
Is it because it's a popular and well known transmitting tube?
We all have our preferences and that is fine and dandy. I'm just curious what are the factors that make you choose this particular tube above all others.
ray
Is it because of the sound? Have you heard this tube?
Is it because of the way it looks?
Is it because of the increased power over the more usual 45, 50, 2A3 or 300B that would probably work with your Lowthers?
Is it because it's a popular and well known transmitting tube?
We all have our preferences and that is fine and dandy. I'm just curious what are the factors that make you choose this particular tube above all others.
ray
I think you joined the DC DIY group. Since you have not heard a SET, ask the group if somebody near Wheaton could let you listen to one. I live up in North East MD so it's a bit far to travel.
Since you are a relatively inexperienced builder, here are a couple of observations about building an 845 amp. It typically uses very high voltages and most designs call for over 1000 volts. Many very experienced builders are too scared to go up into that voltage range since it is very dangerous. As you have seen in the thread on output transformers for an 845, the transformer needs to be rated to handle that voltage.
The high voltage power supply will be large and heavy with chokes that are rated for at least 1000 volts. Your capacitors will also need to handle the voltage as well as the diodes. Such a power supply is not trivial.
You use high efficiency Lowther drivers. The 10 volts that you will need to heat the 845 may result in hum issues if you use AC with a hum pot. Hum would be less of an issue if you had less efficient speakers. The alternative would be to use DC to heat the filaments. The best solution are the Rod Coleman regulators but then you have to build a substantial power supply for each channel to supply the regulators.
Already what I am describing is a serious boat anchor amp which will be quite difficult and expensive to build.
Since you are concerned about linearity, you also need to consider the input tube as well as the tube or mosfet or interstage solution you will need to drive the 845 tube.
Or you can make life easy for yourself and use some of the most linear tubes ever made, the 45, 2A3, 4P1L or 300B which will work fine with your Lowthers. There are plenty of designs using these tubes and as a relative beginner, you will have a much greater likelihood of success and your amp will sound just as good on your speakers as an 845 amp. There are also kits you can buy using some of these tubes which will teach you best practice lessons about layout and wiring. The cost will be much less and you will be able to carry the amp without getting a hernia.
The other point to remember is that once you start building amps, you will find it difficult to stop. There will always be another tube or topology you will want to try so start small and eventually you will have the knowledge and skills to build your 845 amp.
ray
Since you are a relatively inexperienced builder, here are a couple of observations about building an 845 amp. It typically uses very high voltages and most designs call for over 1000 volts. Many very experienced builders are too scared to go up into that voltage range since it is very dangerous. As you have seen in the thread on output transformers for an 845, the transformer needs to be rated to handle that voltage.
The high voltage power supply will be large and heavy with chokes that are rated for at least 1000 volts. Your capacitors will also need to handle the voltage as well as the diodes. Such a power supply is not trivial.
You use high efficiency Lowther drivers. The 10 volts that you will need to heat the 845 may result in hum issues if you use AC with a hum pot. Hum would be less of an issue if you had less efficient speakers. The alternative would be to use DC to heat the filaments. The best solution are the Rod Coleman regulators but then you have to build a substantial power supply for each channel to supply the regulators.
Already what I am describing is a serious boat anchor amp which will be quite difficult and expensive to build.
Since you are concerned about linearity, you also need to consider the input tube as well as the tube or mosfet or interstage solution you will need to drive the 845 tube.
Or you can make life easy for yourself and use some of the most linear tubes ever made, the 45, 2A3, 4P1L or 300B which will work fine with your Lowthers. There are plenty of designs using these tubes and as a relative beginner, you will have a much greater likelihood of success and your amp will sound just as good on your speakers as an 845 amp. There are also kits you can buy using some of these tubes which will teach you best practice lessons about layout and wiring. The cost will be much less and you will be able to carry the amp without getting a hernia.
The other point to remember is that once you start building amps, you will find it difficult to stop. There will always be another tube or topology you will want to try so start small and eventually you will have the knowledge and skills to build your 845 amp.
ray
Ray, you have somehow made me rethink. I looked at few of the amp pictures available. Perhaps I should rethink. That 1KV is a bummer. This should be something I should do perhaps 2-3 years later if I am not happy with other designs.
Claudiomas showed this Italian designer and I saw his completed amps , too bulky.
I want to experience the NFB amp and I guess a lot of options available in MOSFET arena too.
Claudiomas showed this Italian designer and I saw his completed amps , too bulky.
I want to experience the NFB amp and I guess a lot of options available in MOSFET arena too.
You probably would get fine results with one of the following.
Tubelab SE | Tubelab
Amplifiers for Loudspeakers | Bottlehead
Of course, there are many other easy to build solutions.
ray
Tubelab SE | Tubelab
Amplifiers for Loudspeakers | Bottlehead
Of course, there are many other easy to build solutions.
ray
My experience with 845 (set) (1000V) with 'lampizator' types of speakers with alnico magnets is that linearity is good up to 0.25 watts.
Kinku, it is better to 'mess-up' on a kit operating at 250 V than carbonizing components with 1000V, a bad solder joint, thermal problems on the hot socket. Component failures are more likely to happen at 1000V.
I started to modify 845 amplifiers, then built transistors amps, then tube kits, etc., I re-built tube gears (not amplifiers) up to 10000V with anti-arc corona on every HV connection and it is quite dangerous, hydrogen tubes also emits radiations.
You can achieve a more linear sound using smaller triodes in parallel in push-pull.
The 845 tube is unique in the distortion and compression effects it generates, not because of linearity. The 300B is more linear.
High sensitivity Lowther's will probably be a great match, however it will still have an immense (and pleasurable) compression and distortion effect on the sound.
Kinku, it is better to 'mess-up' on a kit operating at 250 V than carbonizing components with 1000V, a bad solder joint, thermal problems on the hot socket. Component failures are more likely to happen at 1000V.
I started to modify 845 amplifiers, then built transistors amps, then tube kits, etc., I re-built tube gears (not amplifiers) up to 10000V with anti-arc corona on every HV connection and it is quite dangerous, hydrogen tubes also emits radiations.
You can achieve a more linear sound using smaller triodes in parallel in push-pull.
The 845 tube is unique in the distortion and compression effects it generates, not because of linearity. The 300B is more linear.
High sensitivity Lowther's will probably be a great match, however it will still have an immense (and pleasurable) compression and distortion effect on the sound.
Kinku,
If you ever do build an 845 amp, the power supply is not as daunting as some would have you believe.
The choke(s) do not have to be rated for 1000VDC. You don't need to put the choke(s) in the + high voltage line. As a safe alternative, you can put the choke(s) in the negative line and they are just as effective. Do a search and you will find a circuit for reference.
The 845 filament only needs 10VDC @ 3A. Not a big deal to make a DC filament supply. For a nice starter amp, this supply does not have to be regulated.
Not all 211 or 845 amps are boat anchors. I've seen 300B amps turned into boat anchors.
Do your homework and make a decision based on your needs. You'll find as you begin to build amps that your needs will change and so will your amp choices.
If you ask for an opinion, you'll get way more feedback than you ever dreamed of as you have already learned.
If you ever do build an 845 amp, the power supply is not as daunting as some would have you believe.
The choke(s) do not have to be rated for 1000VDC. You don't need to put the choke(s) in the + high voltage line. As a safe alternative, you can put the choke(s) in the negative line and they are just as effective. Do a search and you will find a circuit for reference.
The 845 filament only needs 10VDC @ 3A. Not a big deal to make a DC filament supply. For a nice starter amp, this supply does not have to be regulated.
Not all 211 or 845 amps are boat anchors. I've seen 300B amps turned into boat anchors.
Do your homework and make a decision based on your needs. You'll find as you begin to build amps that your needs will change and so will your amp choices.
If you ask for an opinion, you'll get way more feedback than you ever dreamed of as you have already learned.
The Dietmar works, better than original, but needs more power supply regulation circuitry. Not sure whether transformer is the limiting factor. The 845 is the triode to do, as it can deliver 20 watts per channel, so it can go quite loud even without horns
$1500 budget for an 845 is severely lacking. There will be compromises at every step and the end result will be not too far from a chinese amp. As a learning exercise it may be great, as means to listen to music, not so much. For this budget there are great SS amps to be built.
As always, nothing diy beats used for value.
As always, nothing diy beats used for value.
1000 volts is not the same as 400 volts in terms of safety.
There is a sticky at the top of this forum about working with ultra-high voltages (over 1000 volts). Read it.
http://www.diyaudio.com/forums/tubes-valves/30172-safety-practices-general-ultra-high-voltage.html
There are other very linear transmitting tubes out there that will sound just as good as an 845. Look for GM70, 813 and GK71. There are numerous schematics operating at well under 1000 volts using these tubes.
ray
There is a sticky at the top of this forum about working with ultra-high voltages (over 1000 volts). Read it.
http://www.diyaudio.com/forums/tubes-valves/30172-safety-practices-general-ultra-high-voltage.html
There are other very linear transmitting tubes out there that will sound just as good as an 845. Look for GM70, 813 and GK71. There are numerous schematics operating at well under 1000 volts using these tubes.
ray
As a fairly inexperienced builder I wouldn't go near 1kv. My current amp has 390v on the plate and I wouldn't use a probe in that, I always connected my DVM with clips while the amp was off and then turned it on and stood back. It helps to have multiple DVMs when using that method, they are cheap enough. Now that I have Alexa to control the power I don't even need to touch the switch, except to have an emergency power off switch if things start to smoke or glow bright red.
Anyway, why not use 300B? I guess like everyone else I don't understand the insistence on 845, especially for an amateur.
I plan on building an Amity, and $1500 isn't enough for a DIY build. Those transformers get expensive.
Anyway, why not use 300B? I guess like everyone else I don't understand the insistence on 845, especially for an amateur.
I plan on building an Amity, and $1500 isn't enough for a DIY build. Those transformers get expensive.
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This is true; however, within any practical amplifier with a 1000V supply there is this little device called a capacitor. Come into contact with that 1000V and that pesky little capacitor will discharge a whole lot of electrons that equate to more than 0.00001A. So in general, the 1000V amplifier will always be an equal or greater risk than a 400V amp. Amps are not built without capacitor storage.
Duration of applied current is also of concern, ref. IEEE 80, 367 and 1590 provide some good data on what the human body can take when considering both ampere level and time. I am not afraid of working with 10 kV, but have a ton of respect of the danger it poses. I never assume it is current limited to micro ampere levels.
400v DC or 800 volts DC a both well into instant penalty mode. Even 40v DC will give you a hug like a bear.
A 400v DC valve amp is 400v DC all the way through the output valves to the transformer. The better 800v DC is also designed as a 2 x 400 volt DC in the power supply to combine to 800v DC into the 845 output valves onward to the transformer. The big 845 can deliver enough watts to avoid having to use high efficiency speakers, eg horn mid. But a 300B with a horn CD mid is probably the best choice for safety and reasonable listening levels. If it must be the 845 800 volts is adequate.
I really can't believe the stigma about 1000 volt power supplies. I have learned people will debate anything for no reason other than to be heard.
If you are cautious and learn how to work with electronics, the danger is minimised. Any hobby can be dangerous.
I guess a lot of you will not be building Tesla Coils...
All men die, but not all men live.
If you are cautious and learn how to work with electronics, the danger is minimised. Any hobby can be dangerous.
I guess a lot of you will not be building Tesla Coils...
All men die, but not all men live.
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