sure, i am starting with the power supply, redesigning the power traffo so that instead of one 780 volt ht windings. there will be three 260 volt windings instead. feeding individual bridges and psu caps stacked one on top of the other......just as boldname said...
got the idea here: Champ 1000 Watt Tube Amp
measure the voltage in the output secondary... you will find it to be constant 0 for neutral and couple volts for the other.
Quality OPT's for 211's or 845's, from reputable makers, already have the operating voltage taken into consideration.
Maybe the Coriolis Effect might improve the sound if you switch hemispheres?
Relevant to the topic, if you build a 845 tube amp you will reach about 20 watts and it will not be very good and cannot function properly without feedback.
If you take the same amplifier, get the HT+ to 1200V and the bias quite high, then you inject decent feedback like in a Kt88 amplifier and drive the tube into grid current (be ready for quasi-pentode driver with local feedback, dedicated power) you can achieve greatness. However expect such a design to require something like 10 transformers per mono-block. And be ready to invest in a high quality output transformer, hammond and edcor are not doing too great in SET , without ultralinear and with 10K impedance. (they work quite well in ultralinear and under 8 K )
Addendum: I am sure the efforts are worth it and a great 845 triode will sent all other PP amps to shame, but it comes at a price, and for this price I prefer to invest in speakers and be happy with a el34 25 watts amp.
If you take the same amplifier, get the HT+ to 1200V and the bias quite high, then you inject decent feedback like in a Kt88 amplifier and drive the tube into grid current (be ready for quasi-pentode driver with local feedback, dedicated power) you can achieve greatness. However expect such a design to require something like 10 transformers per mono-block. And be ready to invest in a high quality output transformer, hammond and edcor are not doing too great in SET , without ultralinear and with 10K impedance. (they work quite well in ultralinear and under 8 K )
Addendum: I am sure the efforts are worth it and a great 845 triode will sent all other PP amps to shame, but it comes at a price, and for this price I prefer to invest in speakers and be happy with a el34 25 watts amp.
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I think that is not necessary 10 transformer and NFB.
But depend of properly definition. Airtight in this case is out of properly function.
When you implement NFB you change your amp from HIFI to MIDFI. expense money after NFB in capacitors or good transformer are ridiculous.
300B and 845/211 are very linear tubes in SET to me dont need. Only the 6c33 maybe need in this case same people like with or without. But this is not a exact science, always are personal opinions.
If someone is venturing into building an amp of this caliber then to be honest, I don't think the price of Chinese 845 tubes is that bad. www.thetubestore.com - Shuguang 845 Audio Tubes $89 per tube. I haven't had any troubles with the pair I'm running right now.
I think probably everything you need to know is in a few Tubelab articles.
Read both of these all the way through. The 845 shines when your driver can deal with the 845 drawing grid current.
845 SE | Tubelab
Power Drive | Tubelab
This seems overly generalized and dismissive to me..
My experience with an 845 zero feedback design has been excellent.
I'm running an amp much like Tubelab's design with mosfet source follower's feeding the 845's, and I LOVE it. To my ears with my pair of Klipsch Forte's, it's excellent.. Though I suppose maybe I enjoy the sound of "junk" or something.. Who knows. I don't have a lot to reference the sound of this amp to, other than a few low power IDHT SET amps I've built prior to this one.
845 and low power
Hi Kinku,
I second your choice to build a 845 amp - I have been also thinking about doing the same thing. However, I draw the line at 700V for power supply at the moment. Yes, that is ridiculously low for an 845, you can barely get 11W at such low U. I have no idea what it will sound at such sleeper voltage... but 11W is already more than plenty for my 96-97dB speakers.
I have repaired, modified, designed from scratch countless tube amps for the past two decades (SE, PP - strictly tubes only, no solid states). I had excellent mentors locally who had 20-50 years of experience working with tube gear. During those two decades, I have been zapped several times. Was I so careless? Nope. When you smoke the solder fumes a lot, sooner or later you will get zapped. (Maybe 1 zap per 200 hours of working on gear.) That's inevitable, part of the learning curve. BTW, my every single zap has been an accidental short to the chassis. And each was a distinct experience, so do not generalize after one shock!
Of note, if I wore long sleeves, I would not have had any zaps! However, long sleeves does not insulate against 1kV - on the other hand, it will melt on you and make the burn much more severe.
While any electric shock can be deadly, as you go higher in stored energy and voltage, the chance is greatly magnified. Check out PSVANE's website for their 211,845 tubes. When a manufacturer advertises its own product with the words "instant death" on his own commercial site, that's a decent indication that it's a big no-no for a starter project. Even when you survive, those voltages leave permanent injuries.
I am confident that by now I have good enough practices to handle 1kV land. But I am deadly frightened that someone else gets electrocuted by it. Children and pets. For them, 1kV in the 10uF+ range (845) is instant death. I had my nephew yank out a power tube from the 450VDC DC Darling amp when it was on. Were it an 845 DIY amp, I would be now in jail. My friend's sons were cracking open his KT88s in his amp with a hammer. Stuff like that happen, and people can and will get exposed to lethal voltages.
I warmly recommend that you build up at least 4-5 years of experience with building and using 450V range, having people around in the house, and weather a couple accidental zaps from that level. And please, do not try to get zapped!!! Avoid it at all costs! - but build enough, and you will have it coming. Your body does communicate to you when you get close to death. If you have the feeling you are lucky to be alive after 450V zap, then stay 450V land. Never ever go to kV land before getting a bite at 400-500V. Get to know your body first. My mentors mantra: if your meter cannot measure it, don't build it!
I'm trying to prepare you, not to scare. 800V+ in audio power amps is deadly serious land. It is safe if you know the rules, but you have to know them as second nature, not leaning as a newbie. Making a mistake at 400V you risk a nuisance. Make same mistake at kV and you risk death. Or, if you are more sensitive, it's probable death or permanent injury vs sure death.
As 400V range has a set of additional rules compared to 50V land, 1kV has another set of safety rules and practices on top of 400V practices. Have someone experienced with that voltage guide your hands in person. Only then will it be safe. Go there only when working on 400V is second nature, and you can ensure the safety of others in the household. (Absolutely no kids or drunk people around, nor unsupervised-unsuspecting adults.)
People usually build an 845/211/GM70/etc amp as a challenge to crown their amplifier building career. kV land is the final frontier. Not the beginner, neither the intermediate step.
Alas, will it sound better than a 0.75W SET amp with the right speakers? Maybe it does, maybe not. Audio experience is highly subjective, and it also changes as you age.
Hi Kinku,
I second your choice to build a 845 amp - I have been also thinking about doing the same thing. However, I draw the line at 700V for power supply at the moment. Yes, that is ridiculously low for an 845, you can barely get 11W at such low U. I have no idea what it will sound at such sleeper voltage... but 11W is already more than plenty for my 96-97dB speakers.
I have repaired, modified, designed from scratch countless tube amps for the past two decades (SE, PP - strictly tubes only, no solid states). I had excellent mentors locally who had 20-50 years of experience working with tube gear. During those two decades, I have been zapped several times. Was I so careless? Nope. When you smoke the solder fumes a lot, sooner or later you will get zapped. (Maybe 1 zap per 200 hours of working on gear.) That's inevitable, part of the learning curve. BTW, my every single zap has been an accidental short to the chassis. And each was a distinct experience, so do not generalize after one shock!
Of note, if I wore long sleeves, I would not have had any zaps! However, long sleeves does not insulate against 1kV - on the other hand, it will melt on you and make the burn much more severe.
While any electric shock can be deadly, as you go higher in stored energy and voltage, the chance is greatly magnified. Check out PSVANE's website for their 211,845 tubes. When a manufacturer advertises its own product with the words "instant death" on his own commercial site, that's a decent indication that it's a big no-no for a starter project. Even when you survive, those voltages leave permanent injuries.
I am confident that by now I have good enough practices to handle 1kV land. But I am deadly frightened that someone else gets electrocuted by it. Children and pets. For them, 1kV in the 10uF+ range (845) is instant death. I had my nephew yank out a power tube from the 450VDC DC Darling amp when it was on. Were it an 845 DIY amp, I would be now in jail. My friend's sons were cracking open his KT88s in his amp with a hammer. Stuff like that happen, and people can and will get exposed to lethal voltages.
I warmly recommend that you build up at least 4-5 years of experience with building and using 450V range, having people around in the house, and weather a couple accidental zaps from that level. And please, do not try to get zapped!!! Avoid it at all costs! - but build enough, and you will have it coming. Your body does communicate to you when you get close to death. If you have the feeling you are lucky to be alive after 450V zap, then stay 450V land. Never ever go to kV land before getting a bite at 400-500V. Get to know your body first. My mentors mantra: if your meter cannot measure it, don't build it!
I'm trying to prepare you, not to scare. 800V+ in audio power amps is deadly serious land. It is safe if you know the rules, but you have to know them as second nature, not leaning as a newbie. Making a mistake at 400V you risk a nuisance. Make same mistake at kV and you risk death. Or, if you are more sensitive, it's probable death or permanent injury vs sure death.
As 400V range has a set of additional rules compared to 50V land, 1kV has another set of safety rules and practices on top of 400V practices. Have someone experienced with that voltage guide your hands in person. Only then will it be safe. Go there only when working on 400V is second nature, and you can ensure the safety of others in the household. (Absolutely no kids or drunk people around, nor unsupervised-unsuspecting adults.)
People usually build an 845/211/GM70/etc amp as a challenge to crown their amplifier building career. kV land is the final frontier. Not the beginner, neither the intermediate step.
Alas, will it sound better than a 0.75W SET amp with the right speakers? Maybe it does, maybe not. Audio experience is highly subjective, and it also changes as you age.
what an essay!! Though, a word of wisdom, the KV range is certainly not for a tube beginner, unless you have years of experience in electronics hence general practice of applying ideas/thoughts with staying within the safety common sense.
But, I think, buying a pre-manufactured one is still a good idea for intermediate level, learn it first and then mod it best to your preferences: most of metal job has already been completed so you perfect the circuitry part.
But, I think, buying a pre-manufactured one is still a good idea for intermediate level, learn it first and then mod it best to your preferences: most of metal job has already been completed so you perfect the circuitry part.
I didnt see any mention of Line Magnetic? You might find one used in your budget..
https://www.stereophile.com/content/line-magnetic-audio-lm-518ia-integrated-amplifier
https://youtu.be/q9ux_TROwns
https://youtu.be/6Q9aXt2PWU4
https://www.stereophile.com/content/line-magnetic-audio-lm-518ia-integrated-amplifier
https://youtu.be/q9ux_TROwns
https://youtu.be/6Q9aXt2PWU4
Stay away from that MA845. It comes with no mains earth connection which is the first mod required. It runs 915V HV across 2 series connected 450V caps with inadequate voltage sharing resistors. Mine blew an output tranny (primary to secondary short) which took out an 845 output tube. Sounded pleasant up to moderate listening levels but was sickly sweat (excessive 2H distortion) at higher levels. That was due to inadequate driver.
I have new output trannies, new 845s , new power trannies on the shelf to rebuild it. The popular wisdom from the old guys is that 845 sound best when cathode to anode voltage is above 1100 Volts, so 1250 V supplies for cathode biased amp, 1100 will do for fixed bias. A search of this forum might help - there was a published design for driving parallel 845 for greater than 50 Watts out. Driver design should not be too difficult, you need to drive significant grid (miller) capacitance but 845 perform well in Class A1, it is not necessary to drive them to Class A2 with grid current.
The actual voltage you use will depend upon the Output Trannies you have. Required primary impedance rises rapidly with B+.
I am not fussed about high voltage but I did my electronics training in a major hospital and routinely worked on Surgical Diathermy with 2,000 V on the output tube anodes.
These days I am a Senior Electronic Design Engineer, that means I have to write OH&S procedures etc. in addition to the actual electronic design. If I were writing a procedure for this I would say minimum of 2 persons to be present - not to be worked on alone.
Went looking for driver circuits - This one is likely to be great, if you don't mind some SS.
http://www.diyaudio.com/forums/tubes-valves/224912-845-driver-circuit-2.html
Cheers,
Ian
I have new output trannies, new 845s , new power trannies on the shelf to rebuild it. The popular wisdom from the old guys is that 845 sound best when cathode to anode voltage is above 1100 Volts, so 1250 V supplies for cathode biased amp, 1100 will do for fixed bias. A search of this forum might help - there was a published design for driving parallel 845 for greater than 50 Watts out. Driver design should not be too difficult, you need to drive significant grid (miller) capacitance but 845 perform well in Class A1, it is not necessary to drive them to Class A2 with grid current.
The actual voltage you use will depend upon the Output Trannies you have. Required primary impedance rises rapidly with B+.
I am not fussed about high voltage but I did my electronics training in a major hospital and routinely worked on Surgical Diathermy with 2,000 V on the output tube anodes.
These days I am a Senior Electronic Design Engineer, that means I have to write OH&S procedures etc. in addition to the actual electronic design. If I were writing a procedure for this I would say minimum of 2 persons to be present - not to be worked on alone.
Went looking for driver circuits - This one is likely to be great, if you don't mind some SS.
http://www.diyaudio.com/forums/tubes-valves/224912-845-driver-circuit-2.html
Cheers,
Ian
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First of all, this HV warning is a conspiracy to keep you from building...
To another suggestion, to get somebody to build one for you, you are not going to get anything more than a research project. If you set out to pay some labour rate over a dollar an hour it is going to be expensive....let alone the components.
First things first, get after Ray, and listen to some SE amps. That process in and of itself is fun. Learn what it means to find the 'right' speakers, and what to look for in that regard. I listened to many of them, and decided they're not for me. I have built a small handful of projects, and I see no need to go pushing over about 600V of B+.
Was kidding about HV Conspiracy Theory, really, 1kV is nothing to mess with until you have gotten experience and proper instruction. Tube amps are all about low impedance energy storage; their PS can dump a significant current into you once you establish a connection.
cheers,
Douglas
To another suggestion, to get somebody to build one for you, you are not going to get anything more than a research project. If you set out to pay some labour rate over a dollar an hour it is going to be expensive....let alone the components.
First things first, get after Ray, and listen to some SE amps. That process in and of itself is fun. Learn what it means to find the 'right' speakers, and what to look for in that regard. I listened to many of them, and decided they're not for me. I have built a small handful of projects, and I see no need to go pushing over about 600V of B+.
Was kidding about HV Conspiracy Theory, really, 1kV is nothing to mess with until you have gotten experience and proper instruction. Tube amps are all about low impedance energy storage; their PS can dump a significant current into you once you establish a connection.
cheers,
Douglas
Two of my friends bought 845 Chinese amps. One of them just collects dust because his flea power Yamamoto 45 amp trashed it big time. My other friend has very good experience with his, but he had bias stability issues with one of the 845 tubes - but he has vast experience working with amps.
If you look at building amps as a journey, and you ae lookin for SE, it's best to start with 2A3 / 300B / 45 / 1626 / EL34 / 807. DHT / IDHT both can sound great. The first step is to build an amp, and find the speakers that work with it. While we are all fascinated by the amps, without the right speakers you will miss out most of their potential. Find the speakers that sound like heaven with a 1-2W amp. Those will bring out the true potential from higher power SET DHTs like 845 amps. If you want a 845 just to power power hungry speakers, then you'll get stuck in dealership sound land.
Also, you can learn a lot by building / modding 300-450V B+ amps. Your learning curve will be super restricted with a 845.
cheers,
Janos
If you look at building amps as a journey, and you ae lookin for SE, it's best to start with 2A3 / 300B / 45 / 1626 / EL34 / 807. DHT / IDHT both can sound great. The first step is to build an amp, and find the speakers that work with it. While we are all fascinated by the amps, without the right speakers you will miss out most of their potential. Find the speakers that sound like heaven with a 1-2W amp. Those will bring out the true potential from higher power SET DHTs like 845 amps. If you want a 845 just to power power hungry speakers, then you'll get stuck in dealership sound land.
Also, you can learn a lot by building / modding 300-450V B+ amps. Your learning curve will be super restricted with a 845.
cheers,
Janos
I started with the 300b and quickly moved on to a GM70 at 1150v. I wanted to build with the 845 but found the GM70 to be much easier to implement. I initially spent a minimum of 4K for a pair of monoblocks and quickly upgraded from there. I ended up with an outstanding amplifier that outperforms commercial amps in the 20k range. It's truly a boat anchor as each monoblock weighs in excess of 120lbs with two HV supplies. It sounds like a 300b amp on steroids. I have seen a couple designs using a HV pentode driver that would save you another HV power supply so that may be worth researching.
All I can say is keep your hands out at those voltages. I simply clip my testing equipment in prior to energizing, do the same and you'll never get hurt. Wear safety glasses as well.
All I can say is keep your hands out at those voltages. I simply clip my testing equipment in prior to energizing, do the same and you'll never get hurt. Wear safety glasses as well.
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Excellent advice! I have 3 meters, hook them up to the test points and then turn the amp on with a variac. One meter is always on the high voltage.
If I need to measure something else, then power down, wait for HV to drop to safe levels, reconnect one meter, power up and measure.
Highly recommend to have one good Fluke meter, and additional 2-3 cheapo multimeters. It's so much easier, safer and faster than having just 1 meter and scrambling around!
BTW, a variac with a current meter is a must. Thanks to it, I never had anything blown up on the testbench. Was lucky to pick up a Heathkit variac for 5$ in a thrift store a good while ago. ;
Janos
Ming da
Hi All..regarding Chinese amps..
A late response but....
I can agree that some Chinese product is of poor quality..
However..
I have been the UK disti for Ming Da now for 7 years.. I have never had a failure on arrival...All amps get inpsected, tested and soaked...No build errors are found..
Ming Da is a small family run business, they wind all their own transformers in house.. They buy the best parts they can and have 27 years experience making them! I visit the factory twice a year and help with new model designs..Their build quality is some of the highest Point to Point I have seen..All properly grounded and safely wired!!!
So they are NOT all bad..
Who would have bought a Japanese car 40 years ago..Now Honda and Toyota are some of the best car brands around!
I also design and manufacture my own tube products and have learned from them as they learn from me!
So please do not condem all China products!!
Hi All..regarding Chinese amps..
A late response but....
I can agree that some Chinese product is of poor quality..
However..
I have been the UK disti for Ming Da now for 7 years.. I have never had a failure on arrival...All amps get inpsected, tested and soaked...No build errors are found..
Ming Da is a small family run business, they wind all their own transformers in house.. They buy the best parts they can and have 27 years experience making them! I visit the factory twice a year and help with new model designs..Their build quality is some of the highest Point to Point I have seen..All properly grounded and safely wired!!!
So they are NOT all bad..
Who would have bought a Japanese car 40 years ago..Now Honda and Toyota are some of the best car brands around!
I also design and manufacture my own tube products and have learned from them as they learn from me!
So please do not condem all China products!!
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