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#1
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Getting started with DIY tube amps
Greetings, good sirs. I'm interested in getting started in building my
own tube amplifiers and could use your learned advice on what is the most effective way to educate myself in the hobby and get started building. I'm just out of college, but apart from a robotics course I took in gradschool (which was mainly a programming course), I have no electronics or engineering experience. Audio-wise, I do have what I would call a hi-end system, but the only tubed component I own is an Audio Electronic Supply PH-1 phonostage, at least for now. My level of knowledge is probably best described by the fact that I can identify the parts on a circuit diagram, but I'm not sure what the significance is of the way they are combined. I figure I'd probably be best served by reading a book or two on the subject of DIY electronics or on basic electronics. At that point, I'd hopefully be comfortable enough to try building a quick project just to get the hang of soldering and such. I'm thinking an inexpensive tube radio kit would be perfect for this, as if I happen to botch it, it'd be no big loss. Assuming this was a success, I imagine I would then be prepared for my first foray into serious amp building, and should choose a schematic online to use as a guide. So, some questions I have a - Am I being overly cautious in my approach? That is, is building tube amps simple enough to just jump into it with minimal education? - What kind of tools should I buy? Obviously, I'll at least need a soldering iron, wire cutter, and screwdriver, but what else? - Do any of you who have built Andre Jute's amps have any comments on the experience or final product? - What are some other good online sources of information and schematics that you guys frequent? |
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#2
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"Bruce C. Miller" wrote: Greetings, good sirs. I'm interested in getting started in building my own tube amplifiers and could use your learned advice on what is the most effective way to educate myself in the hobby and get started building. I'm just out of college, but apart from a robotics course I took in gradschool (which was mainly a programming course), I have no electronics or engineering experience. Audio-wise, I do have what I would call a hi-end system, but the only tubed component I own is an Audio Electronic Supply PH-1 phonostage, at least for now. My level of knowledge is probably best described by the fact that I can identify the parts on a circuit diagram, but I'm not sure what the significance is of the way they are combined. I figure I'd probably be best served by reading a book or two on the subject of DIY electronics or on basic electronics. At that point, I'd hopefully be comfortable enough to try building a quick project just to get the hang of soldering and such. I'm thinking an inexpensive tube radio kit would be perfect for this, as if I happen to botch it, it'd be no big loss. Assuming this was a success, I imagine I would then be prepared for my first foray into serious amp building, and should choose a schematic online to use as a guide. So, some questions I have a - Am I being overly cautious in my approach? No. Caution with tubes prolongs life expectancy, since even a humble tube preamp could kill anyone who is careless. You must learn serious respect of high voltages. That is, is building tube amps simple enough to just jump into it with minimal education? Start with building a simple one triode line stage stereo amp. But first you have to get some idea of how a triode works, its electrode impedance behaviours, and for that you need to read old books. get a copy of the Radiotron Designer's Handbook, 4th Ed, 1955. Experiments and observations about circuit gain, feedback usage, input and output impedances, distortion, etc, can all be made when closely observing the simple action in your preamp. The preamp project will teach you abour power supplies. If you attempt to construct anything, and you are not asking many questions as you proceed, then you are not learning anything. The question ** WHY!!! ** should arrise in the un-initiated about 20 times a day, and keep you awake all night, until you realize you have "got it" and the books start to make sense. You won't learn anything just from books, and you need to be doing, not just reading. Electronics is all about grasping lots of interrelating mental concepts. - What kind of tools should I buy? Obviously, I'll at least need a soldering iron, wire cutter, and screwdriver, but what else? At least a digital multimeter, and an oscilliscope. If you are going to make your metal work, maybe you can buy pre-made chassis but you'll need hole cutters, and drills, electric drill, files, and so forth. - Do any of you who have built Andre Jute's amps have any comments on the experience or final product? I have not built a "juey " ( yet ) , but a sample of what can all be done by one man alone can be seen at http://www.turneraudio.com.au There are other sites where much better craftmanship is viewable. - What are some other good online sources of information and schematics that you guys frequent? The rec.audio.tubes archives have a lot of Q&A discussions which have links. Reading all the past discussions is a long process and one you won't understand much, but gradually you will learn more, and a visit to the links and sites will give you some idea where to go on the net for info. But the old books describe the basics the best. But read alone without a teacher, they are damned hard to understand, and the math used constantly to describe electronic behaviour is a PITA, since almost all of it defies common sense, but not eductated scientific good sense. Without the basics learnt well first, you will really struggle to make much sense of the world of analog audio. So you need to become facile with basic LCR behaviour, transformer behavoir, tube and solid state device character, measurement procedures, like thinking in terms of dB, and all about Ohm's Law. That's just a few. You need to have a passionate urge to succeed to know what is really going on. You must never assume a single solitary thing before you understand it. You need the eye for detail. You need the patience for details. You need to realize that what you make is the result of a wholistic approach. You may feel proud of what you have made if it worth being proud of. You may need an understanding girlfriend. Patrick Turner. |
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#3
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The best way to start at your level is get a kit product that gives a little
background and read up on the theory to understand what you are doing. Bottlehead stuff is good for this, and fairly inexpensive, but there are a lot of other choices as well. Usually people recommend starting with upgrading one of the veritable Dynaco line, but that is not going to give you as much understanding as a full ground up kit. Tools: Get a solder station--not gun. Good foreign versions (like Hanko) can be had for $70. Get a good digital voltmeter. Fluke 179 is a reasonably priced model, or look for foreign knock offs that can be had for 1/2 the price. MAKE sure the meter can read 1000VDC--many foriegn models stop at 600VDC. Next most important tool in the line up is a scope. Your surplus shops can get you an analog starter scope for under $50--dual trace and 20MHz is all that is needed for audio. If you can afford it--the Velleman PC-500 and signal generator give you a lot of real flexibility in circuit testing (www.velleman.be ) Finally, get a decent tube tester, don't get a cheapo. For the price, the Precision 612 model is good value and available for about $60 on ebay. Other reasonalbe models to look can be found at http://www.tone-lizard.com/Tube_Testers.html Good luck--this hobby is a lot of fun. Keep your eyes out for yard sales--lots of great tubes, amps, radios, and test equipment can be found for a song. My Hickok 539C was picked up for $20 at a yard sale. "Bruce C. Miller" wrote in message oups.com... Greetings, good sirs. I'm interested in getting started in building my own tube amplifiers and could use your learned advice on what is the most effective way to educate myself in the hobby and get started building. I'm just out of college, but apart from a robotics course I took in gradschool (which was mainly a programming course), I have no electronics or engineering experience. Audio-wise, I do have what I would call a hi-end system, but the only tubed component I own is an Audio Electronic Supply PH-1 phonostage, at least for now. My level of knowledge is probably best described by the fact that I can identify the parts on a circuit diagram, but I'm not sure what the significance is of the way they are combined. I figure I'd probably be best served by reading a book or two on the subject of DIY electronics or on basic electronics. At that point, I'd hopefully be comfortable enough to try building a quick project just to get the hang of soldering and such. I'm thinking an inexpensive tube radio kit would be perfect for this, as if I happen to botch it, it'd be no big loss. Assuming this was a success, I imagine I would then be prepared for my first foray into serious amp building, and should choose a schematic online to use as a guide. So, some questions I have a - Am I being overly cautious in my approach? That is, is building tube amps simple enough to just jump into it with minimal education? - What kind of tools should I buy? Obviously, I'll at least need a soldering iron, wire cutter, and screwdriver, but what else? - Do any of you who have built Andre Jute's amps have any comments on the experience or final product? - What are some other good online sources of information and schematics that you guys frequent? |
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#4
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"Bruce C. Miller" wrote in message oups.com... Greetings, good sirs. I'm interested in getting started in building my own tube amplifiers and could use your learned advice on what is the most effective way to educate myself in the hobby and get started building. Welcome, it's a fascinating and rewarding hobby. I'm just out of college, but apart from a robotics course I took in gradschool (which was mainly a programming course), I have no electronics or engineering experience. Audio-wise, I do have what I would call a hi-end system, but the only tubed component I own is an Audio Electronic Supply PH-1 phonostage, at least for now. My level of knowledge is probably best described by the fact that I can identify the parts on a circuit diagram, but I'm not sure what the significance is of the way they are combined. That's a good point from which to start I figure I'd probably be best served by reading a book or two on the subject of DIY electronics or on basic electronics. At that point, I'd hopefully be comfortable enough to try building a quick project just to get the hang of soldering and such. I'm thinking an inexpensive tube radio kit would be perfect for this, as if I happen to botch it, it'd be no big loss. Assuming this was a success, I imagine I would then be prepared for my first foray into serious amp building, and should choose a schematic online to use as a guide. The definitive book on the subject is the Radio Designers' Hand Book by Langford Smith,. The 4th edition is now in print again. But it's a bit heavy going. For a practical person, maybe: VALVE AMPLIFIERS by Morgan Jones. Published by Newnes (ISBN 0 7506 4425 7) THE PRINCIPALS OF POWER by Kevin O'Connor. Published by Power Press. London. Canada (ISBN 0 9698 6081-1) THE BEGINNER'S GUIDE TO TUBE AUDIO DESIGN By Bruce Rozenblit Published by Audio Amateur Press. (ISBN 1-882580-13-3) When you have read those you will know a lot about tube audio, and if you have any questions, this is a very good place to ask them:-) - What kind of tools should I buy? Obviously, I'll at least need a soldering iron, wire cutter, and screwdriver, but what else? A good DVM (Fluke is excellent) A signal generator A dual beam scope. A variac. These are the basic tools. But the list is as long as you want it to be:-) Iain |
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#5
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Welcome to the tube Bruce,
Like you i'm a beginner. I only have few moths more of experience. And i can advice you also to read the RDH4, VALVE AMPLIFIERS, Menno van der veen 'Hi end tube amplifiers' very good also. Yes you need a very good digital multimeter with a high internal impedance (30MOhm at least), and a good scope if you want to see the truth. Those are quite expensive. I borroved them in my company, but now i realise that i can't work without them. You also need a lot of time. Reading those books is hard. Sometimes i read 3 times the same chapter to get it. You also need internet connection ;-), here on RAT they know very well my stupid questions. You also need 8ohm 50w resistor for the testing. I began rebuilding few amplifiers (quad II, fisher 500c), that was quite easy and i learned a lot i think by observing how they were made. It also reminded me the basics of how to read electrical diagram. And VERY IMPORTANT : you need plastic gloves, to take the measures when the amp is running. THAT SAVES YOUR LIFE. Luc. |
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#6
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Iain M Churches wrote: "Bruce C. Miller" wrote in message oups.com... Greetings, good sirs. I'm interested in getting started in building my own tube amplifiers and could use your learned advice on what is the most effective way to educate myself in the hobby and get started building. Welcome, it's a fascinating and rewarding hobby. I'm just out of college, but apart from a robotics course I took in gradschool (which was mainly a programming course), I have no electronics or engineering experience. Audio-wise, I do have what I would call a hi-end system, but the only tubed component I own is an Audio Electronic Supply PH-1 phonostage, at least for now. My level of knowledge is probably best described by the fact that I can identify the parts on a circuit diagram, but I'm not sure what the significance is of the way they are combined. That's a good point from which to start I figure I'd probably be best served by reading a book or two on the subject of DIY electronics or on basic electronics. At that point, I'd hopefully be comfortable enough to try building a quick project just to get the hang of soldering and such. I'm thinking an inexpensive tube radio kit would be perfect for this, as if I happen to botch it, it'd be no big loss. Assuming this was a success, I imagine I would then be prepared for my first foray into serious amp building, and should choose a schematic online to use as a guide. The definitive book on the subject is the Radio Designers' Hand Book by Langford Smith,. The 4th edition is now in print again. But it's a bit heavy going. For a practical person, maybe: VALVE AMPLIFIERS by Morgan Jones. Published by Newnes (ISBN 0 7506 4425 7) THE PRINCIPALS OF POWER by Kevin O'Connor. Published by Power Press. London. Canada (ISBN 0 9698 6081-1) THE BEGINNER'S GUIDE TO TUBE AUDIO DESIGN By Bruce Rozenblit Published by Audio Amateur Press. (ISBN 1-882580-13-3) When you have read those you will know a lot about tube audio, and if you have any questions, this is a very good place to ask them:-) - What kind of tools should I buy? Obviously, I'll at least need a soldering iron, wire cutter, and screwdriver, but what else? A good DVM (Fluke is excellent) A signal generator A dual beam scope. Should be 'Dual Trace Scope'. Dual beam means two guns & deflection systems in the CRT. Fairly rare & expensive. Examples are HP 132A, TEK 555 & Philips 3250 (I think). All obsolete now. Not sure if anyone even makes a true dual beam scope anymore. Digital techniques do the same function much better except in rare cases. Cheers, John Stewart A variac. These are the basic tools. But the list is as long as you want it to be:-) Iain |
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#7
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Patrick Turner wrote:
"Bruce C. Miller" wrote: - Am I being overly cautious in my approach? No. Caution with tubes prolongs life expectancy, since even a humble tube preamp could kill anyone who is careless. You must learn serious respect of high voltages. I've seen this on many a website and in books. Have there really been cases of electrocution deaths as a result of home stereo equipment, particularly recently? That is, is building tube amps simple enough to just jump into it with minimal education? Start with building a simple one triode line stage stereo amp. But first you have to get some idea of how a triode works, its electrode impedance behaviours, and for that you need to read old books. get a copy of the Radiotron Designer's Handbook, 4th Ed, 1955. I've seen copies of this book on ebay... Guess I'll pick one up then. Experiments and observations about circuit gain, feedback usage, input and output impedances, distortion, etc, can all be made when closely observing the simple action in your preamp. The preamp project will teach you abour power supplies. If you attempt to construct anything, and you are not asking many questions as you proceed, then you are not learning anything. The question ** WHY!!! ** should arrise in the un-initiated about 20 times a day, and keep you awake all night, until you realize you have "got it" and the books start to make sense. You won't learn anything just from books, and you need to be doing, not just reading. Electronics is all about grasping lots of interrelating mental concepts. - What kind of tools should I buy? Obviously, I'll at least need a soldering iron, wire cutter, and screwdriver, but what else? At least a digital multimeter, and an oscilliscope. If you are going to make your metal work, maybe you can buy pre-made chassis but you'll need hole cutters, and drills, electric drill, files, and so forth. I imagine I could pick up most of this stuff used on ebay. Hopefully for not too much money. My wallet is still hurting from the last round of hifi purchases. - Do any of you who have built Andre Jute's amps have any comments on the experience or final product? I have not built a "juey " ( yet ) , but a sample of what can all be done by one man alone can be seen at http://www.turneraudio.com.au There are other sites where much better craftmanship is viewable. - What are some other good online sources of information and schematics that you guys frequent? The rec.audio.tubes archives have a lot of Q&A discussions which have links. Reading all the past discussions is a long process and one you won't understand much, but gradually you will learn more, and a visit to the links and sites will give you some idea where to go on the net for info. But the old books describe the basics the best. But read alone without a teacher, they are damned hard to understand, and the math used constantly to describe electronic behaviour is a PITA, since almost all of it defies common sense, but not eductated scientific good sense. Without the basics learnt well first, you will really struggle to make much sense of the world of analog audio. So you need to become facile with basic LCR behaviour, transformer behavoir, tube and solid state device character, measurement procedures, like thinking in terms of dB, and all about Ohm's Law. That's just a few. I assumed as much. That's why I didn't want to just start by buying a kit amp with step-by-step instructions where it was mostly just a soldering exercise, though I don't think that would hurt. You need to have a passionate urge to succeed to know what is really going on. You must never assume a single solitary thing before you understand it. You need the eye for detail. You need the patience for details. You need to realize that what you make is the result of a wholistic approach. You may feel proud of what you have made if it worth being proud of. Sounds alot like my current profession of programming. I always say something similar to beginners just getting started in CompSci. But, I suppose it's true about many fields. You may need an understanding girlfriend. Yes, not many females in the hobby, I've noticed. Or most any hobby for that matter. |
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#8
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tubesforall wrote: The best way to start at your level is get a kit product that gives a little background and read up on the theory to understand what you are doing. Bottlehead stuff is good for this, I might do just that. Bottlehead stuff does look very nice. The only thing are the dumb names for some of their components. S.E.X. amp? You'd think they were marketing to 12 year old boys. and fairly inexpensive, but there are a lot of other choices as well. Usually people recommend starting with upgrading one of the veritable Dynaco line, but that is not going to give you as much understanding as a full ground up kit. Tools: Get a solder station--not gun. Good foreign versions (like Hanko) can be had for $70. Get a good digital voltmeter. Fluke 179 is a reasonably priced model, or look for foreign knock offs that can be had for 1/2 the price. MAKE sure the meter can read 1000VDC--many foriegn models stop at 600VDC. Next most important tool in the line up is a scope. Your surplus shops can get you an analog starter scope for under $50--dual trace and 20MHz is all that is needed for audio. If you can afford it--the Velleman PC-500 and signal generator give you a lot of real flexibility in circuit testing (www.velleman.be ) Finally, get a decent tube tester, don't get a cheapo. For the price, the Precision 612 model is good value and available for about $60 on ebay. Other reasonalbe models to look can be found at http://www.tone-lizard.com/Tube_Testers.html Thanks for the good advice. Looks like just collecting all the tools I'll need will be a quest in itself. Good luck--this hobby is a lot of fun. Keep your eyes out for yard sales--lots of great tubes, amps, radios, and test equipment can be found for a song. My Hickok 539C was picked up for $20 at a yard sale. But for every one nice yard sale find, you have to sift through literally mountains of useless junk. Hardly worth the effort, when I can just get the same thing on ebay for maybe 3x the yard sale price, but save many hours doing so (which I could spend going to work and making 100x the yard sale price). It'd be ok if yard sales were fun, but for me, they're not  |
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#9
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"Bruce C. Miller" wrote in message oups.com... But for every one nice yard sale find, you have to sift through literally mountains of useless junk. Hardly worth the effort, when I can just get the same thing on ebay for maybe 3x the yard sale price, but save many hours doing so (which I could spend going to work and making 100x the yard sale price). It'd be ok if yard sales were fun, but for me, they're not There's a lot of junk on e-Bay too, at 3x the price. Iain |
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#10
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"Bruce C. Miller" wrote: Patrick Turner wrote: "Bruce C. Miller" wrote: - Am I being overly cautious in my approach? No. Caution with tubes prolongs life expectancy, since even a humble tube preamp could kill anyone who is careless. You must learn serious respect of high voltages. I've seen this on many a website and in books. Have there really been cases of electrocution deaths as a result of home stereo equipment, particularly recently? Despite my caution during what i do daily for a living, I still get the occasional boot from a B+ supply, or from the mains which I thought was turned off, or forgot to think about or turn off. The worst shock i got was from an old radio when i was 17, which sent me across the room and the radio to the ceiling, then the floor. Amazing how 500v livens up dem throwin muscles. One day I just might get one too many, and I'll be discovered days later. That is, is building tube amps simple enough to just jump into it with minimal education? Start with building a simple one triode line stage stereo amp. But first you have to get some idea of how a triode works, its electrode impedance behaviours, and for that you need to read old books. get a copy of the Radiotron Designer's Handbook, 4th Ed, 1955. I've seen copies of this book on ebay... Guess I'll pick one up then. Experiments and observations about circuit gain, feedback usage, input and output impedances, distortion, etc, can all be made when closely observing the simple action in your preamp. The preamp project will teach you abour power supplies. If you attempt to construct anything, and you are not asking many questions as you proceed, then you are not learning anything. The question ** WHY!!! ** should arrise in the un-initiated about 20 times a day, and keep you awake all night, until you realize you have "got it" and the books start to make sense. You won't learn anything just from books, and you need to be doing, not just reading. Electronics is all about grasping lots of interrelating mental concepts. - What kind of tools should I buy? Obviously, I'll at least need a soldering iron, wire cutter, and screwdriver, but what else? At least a digital multimeter, and an oscilliscope. If you are going to make your metal work, maybe you can buy pre-made chassis but you'll need hole cutters, and drills, electric drill, files, and so forth. I imagine I could pick up most of this stuff used on ebay. Hopefully for not too much money. My wallet is still hurting from the last round of hifi purchases. Well, if you are to build anything, you need to tool up. I started makin things as a kid. My old man enchoraged all that. I've had a reasonable tool set all my life, and had 30 years in the one now cluttered workshop with rather a lotta gear. So it takes time to get stuff if you can't afford new gear. I made my own millivilt meter, low distortion oscillator, distortion tester that gets down to 0.002%, and quite a few other gadgets. I read heaps. Some of the most inspiring info appeared in Wireless World, where I found many circuit ideas. If you can sit in a university achives library for a few days with a photocopier, its amazing what you will find. - Do any of you who have built Andre Jute's amps have any comments on the experience or final product? I have not built a "juey " ( yet ) , but a sample of what can all be done by one man alone can be seen at http://www.turneraudio.com.au There are other sites where much better craftmanship is viewable. - What are some other good online sources of information and schematics that you guys frequent? The rec.audio.tubes archives have a lot of Q&A discussions which have links. Reading all the past discussions is a long process and one you won't understand much, but gradually you will learn more, and a visit to the links and sites will give you some idea where to go on the net for info. But the old books describe the basics the best. But read alone without a teacher, they are damned hard to understand, and the math used constantly to describe electronic behaviour is a PITA, since almost all of it defies common sense, but not eductated scientific good sense. Without the basics learnt well first, you will really struggle to make much sense of the world of analog audio. So you need to become facile with basic LCR behaviour, transformer behavoir, tube and solid state device character, measurement procedures, like thinking in terms of dB, and all about Ohm's Law. That's just a few. I assumed as much. That's why I didn't want to just start by buying a kit amp with step-by-step instructions where it was mostly just a soldering exercise, though I don't think that would hurt. Kits rarely teach you anything, because you are not challenged to work it all out from basic first principles. When they sent guys to the moon in 1969, they didn't build a rocket kit. They all sat down and worked out what it would take. You need to have a passionate urge to succeed to know what is really going on. You must never assume a single solitary thing before you understand it. You need the eye for detail. You need the patience for details. You need to realize that what you make is the result of a wholistic approach. You may feel proud of what you have made if it worth being proud of. Sounds alot like my current profession of programming. I always say something similar to beginners just getting started in CompSci. But, I suppose it's true about many fields. You may need an understanding girlfriend. Yes, not many females in the hobby, I've noticed. Or most any hobby for that matter. Let's hope you are her hobby. But your'e right, women simply ain't into men's business If it wasn't for male minds and fascination with wheels and electricity, we'd be stuck way back at about 1005. And women didn't much care to build many wooden sailing ships, so america wouldn't have been discovered. Plenty of women into fashion, culiniary, quilt making, and all sorts of things that are women's business. A glance through almost any city's yellow pages lists all sorts of women's organisations that I would not be seen dead at. Women are of course rather unfathomable, and they see us the same way, and even though a triode is simple when you understand its workings, they would never see how a triode works, and become bored after 10 minutes if they learned. Young sheilas need what they cannot understand, and we need them, while we are young, otherwise the planet would just all be old folks and we'd be no more, and that would give the other species a chance. Of course if you sail through life withou needing people, just liking them for what they are, it upsets many sheilas. But the fact is that not any one of us is indispensible. My ex wife said to me after she left me that had she stayed any longer she'd have "kicked my hi-fi speakers in the cones". I was a gentleman of course, averse to arguing about where a sheila should locate her presense or how she should construct her allegances, and opened the door for her when she left.... I have seen many relationships based on shared activities, some last and some don't, but my parents stayed with each other for 35 years until my old man died and in all that time niether shared any hobbies, except sharing life itself with all its joys and problems. At 15 I was building radio telephones using old radio parts. But by 18 I drifted right away from electronics because I thought it nerdy, and I spent 25 years as a construction contractor. Maybe I made more money than had I persued electronics. Who knows. I never met any women through work. There are vitually none in physical activity clubs like cycling clubs and so on. But these days the fascination with timber and steel and bricks is over, and I am returned to triodes, and happy to spend a day in my work shed. Most women I need are simply quite unimpressed by anything to do with electronics. Most have appalling sound gear, but they hear more from those poor systems than us men hear from our good systems. And so many women don't like the Internet, but lerve their mobile phones. I don't have a mobile, and don't watch TV. One can never hope to find someone like oneself. You will only find someone who is different, and that shouldn't hinder anyone socially, if you can value differences. At the young end of life there is much attraction of opposites, and toleration of differences, denial of them even, with good and bad consequences..... But at the other end of life, finding someone tempting is all that much harder, because temptation will avoid you, as most passion amoungst women has faded. Patrick Turner. |
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#11
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"Bruce C. Miller" wrote: tubesforall wrote: The best way to start at your level is get a kit product that gives a little background and read up on the theory to understand what you are doing. Bottlehead stuff is good for this, I might do just that. Bottlehead stuff does look very nice. The only thing are the dumb names for some of their components. S.E.X. amp? You'd think they were marketing to 12 year old boys. Sexing up the old texts and old knowledge to attract the attaractable is part of the age in which we live. Even new knowledge is sexed up, like weapon capabilities of the Iraqis, "We all could be bombed by Sadam in 45 minutes".... yeah, sure man, and all that trendy mindless BS led to the chase for Iraq's oil. Anyway, with all due respect to Bottlehead, there are otheer places to find the nitty gritty about tube use. Anyone incapable of staying focused for longer than 10 seconds need not try to be good at electronics, they won't make it. and fairly inexpensive, but there are a lot of other choices as well. Usually people recommend starting with upgrading one of the veritable Dynaco line, but that is not going to give you as much understanding as a full ground up kit. Tools: Get a solder station--not gun. Good foreign versions (like Hanko) can be had for $70. Get a good digital voltmeter. Fluke 179 is a reasonably priced model, or look for foreign knock offs that can be had for 1/2 the price. MAKE sure the meter can read 1000VDC--many foriegn models stop at 600VDC. Next most important tool in the line up is a scope. Your surplus shops can get you an analog starter scope for under $50--dual trace and 20MHz is all that is needed for audio. If you can afford it--the Velleman PC-500 and signal generator give you a lot of real flexibility in circuit testing (www.velleman.be ) Finally, get a decent tube tester, don't get a cheapo. For the price, the Precision 612 model is good value and available for about $60 on ebay. Other reasonalbe models to look can be found at http://www.tone-lizard.com/Tube_Testers.html Thanks for the good advice. Looks like just collecting all the tools I'll need will be a quest in itself. Good luck--this hobby is a lot of fun. Keep your eyes out for yard sales--lots of great tubes, amps, radios, and test equipment can be found for a song. My Hickok 539C was picked up for $20 at a yard sale. But for every one nice yard sale find, you have to sift through literally mountains of useless junk. Hardly worth the effort, when I can just get the same thing on ebay for maybe 3x the yard sale price, but save many hours doing so (which I could spend going to work and making 100x the yard sale price). It'd be ok if yard sales were fun, but for me, they're not Learn to meet people who are already into electronics, often radio hams are sources of gear they no longer want. Garage and yard sales don't yeild much; the good gear never makes it out to the yard. I have aquired a tonne of old second hand junk, donated over the years by various ppl. I have never used Ebay. I watcjed and waited for cheap sales when they came up. Older analog test gear say 20 years old and still working fine is quite ok to begin with. All the gear made 20 years ago is obsolete now, but perfect for fiddling round with a few tubes for audio. Its all being junked for the latest gear with more features and automation and PC interface ability. And its fast becoming a digital world, and analog is becoming the poor relation in electronics. Even the latest amplifiers are PWM and the size of a cigarette pack, yet able to to handle 200 watts, since they are so efficient. ( But the audio enthusiasts in the clubs I know loathe all this crap, and tell me their tube amps are still better with music, despite the heat, weight, cost, and fiddles. They still demonstrate to me the wonders of well done vinyl........) I started my pile of stuff 11 years ago. I didn't have a PC until nearly 5 years ago. I was well schooled and tooled when i got my PC. Then i quickly realized that if i wanted to do spectrum analysis, I could use an old PC with W95, quite adequate, and have an oscilliscope program and find out more faster about the wave forms than I see now. I have a home brew spectrum analyser for sifting out 2H, to 10H harmonics of 1 kHz, and IMD products, but it'd be faster if I did it with a PC. I built my own pink noise source and tunable active RC bandpass filter for testing speakers, very necessary it is, and I'd love a laptop fitted out with something that shows the profile of a response in a second, rather than the 15 minutes it takes me to record dots along the band on paper in a book. But its portable, and reliable, and confirms my doubts about poor sound when i have speakers to repair or have to do a home visit to determine the bad news about someone's pet system. I can't afford a laptop. I got an analog 20MHz dual trace CRO which I don't use now because I find I get by quite OK now with a much older single trace, all discrete and transistors, and fixable if it goes wrong. The dual trace CRO with about 20 14 pin ICs and countless other parts is/was a bitch to service. I very nearly built my own CRO, I have all the necessary parts to build 3 if I wanted to, but why? I wanted to focus on build fine amps, not reproductions of valve driven CROs. I have to earn a living. But I did find the time for the other test gear. Building test gear teaches you about precision and noise. And about opamps, transistors, and it broadens one's experience, thus training the brain to think more deeply, becuse to be good with electronics, you have to be prepared to accept or find the non obvious, and realize many things are going on even in a simple circuit. There are very very few people I know locally who I could discuss tube craft with. After getting a PC, I learnt that to enjoy discussions about what i do, I had take part in the only real and deep level tube audio discussions i know of here at r.a.t, a *worldwide* group of enthusiasts. Most blokes don't want to discuss much. Patrick Turner. |
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"Bruce C. Miller" ha scritto nel messaggio oups.com... Greetings, good sirs. I'm interested in getting started in building my own tube amplifiers and could use your learned advice on what is the most effective way to educate myself in the hobby and get started building. I'm just out of college, but apart from a robotics course I took in gradschool (which was mainly a programming course), I have no electronics or engineering experience. Audio-wise, I do have what I would call a hi-end system, but the only tubed component I own is an Audio Electronic Supply PH-1 phonostage, at least for now. My level of knowledge is probably best described by the fact that I can identify the parts on a circuit diagram, but I'm not sure what the significance is of the way they are combined. I figure I'd probably be best served by reading a book or two on the subject of DIY electronics or on basic electronics. At that point, I'd hopefully be comfortable enough to try building a quick project just to get the hang of soldering and such. I'm thinking an inexpensive tube radio kit would be perfect for this, as if I happen to botch it, it'd be no big loss. Assuming this was a success, I imagine I would then be prepared for my first foray into serious amp building, and should choose a schematic online to use as a guide. So, some questions I have a - Am I being overly cautious in my approach? That is, is building tube amps simple enough to just jump into it with minimal education? Nobody ever died 'cos he was overly cautious. Building tube stuff is easy, but common sense says that it is much better starting from the bottom up. - What kind of tools should I buy? Obviously, I'll at least need a soldering iron, wire cutter, and screwdriver, but what else? One or two small, good quality pliers with long, narrow tips (one straight, one 45°) to get into the smaller spaces. Buy a good welding iron, You can sell it afterwards if You don't like this game. - Do any of you who have built Andre Jute's amps have any comments on the experience or final product? Not built, but it seems a very sensible project. Sound is a matter of taste. - What are some other good online sources of information and schematics that you guys frequent? Duncan Amps, VT52.com, http://www.tubedata.info/ , http://www.dogstar.dantimax.dk/tubestuf/ Triode Electoronics... there are so many good ones. |
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#13
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I think the yard sale world depends on where you are. Here in Portland I
find great stuff regularly at yard sales. WHat I do is ask if they have old radio or audio equipment. About 1 out of 4 has something that they thought no one would want--like a nice pair of monoblock Eico HF-20's I recently got for $2. Another sale yielded about 30,000 tubes for $15--of which about 2000 were high quality audio. And all of my good vinyl comes from yard sales. That said--you have to enjoy yard and estate sales, or it is really a drag. My wife collects vintage clothes, so it's a way for us to spend an enjoyable Saterday morning together. "Patrick Turner" wrote in message ... "Bruce C. Miller" wrote: tubesforall wrote: The best way to start at your level is get a kit product that gives a little background and read up on the theory to understand what you are doing. Bottlehead stuff is good for this, I might do just that. Bottlehead stuff does look very nice. The only thing are the dumb names for some of their components. S.E.X. amp? You'd think they were marketing to 12 year old boys. Sexing up the old texts and old knowledge to attract the attaractable is part of the age in which we live. Even new knowledge is sexed up, like weapon capabilities of the Iraqis, "We all could be bombed by Sadam in 45 minutes".... yeah, sure man, and all that trendy mindless BS led to the chase for Iraq's oil. Anyway, with all due respect to Bottlehead, there are otheer places to find the nitty gritty about tube use. Anyone incapable of staying focused for longer than 10 seconds need not try to be good at electronics, they won't make it. and fairly inexpensive, but there are a lot of other choices as well. Usually people recommend starting with upgrading one of the veritable Dynaco line, but that is not going to give you as much understanding as a full ground up kit. Tools: Get a solder station--not gun. Good foreign versions (like Hanko) can be had for $70. Get a good digital voltmeter. Fluke 179 is a reasonably priced model, or look for foreign knock offs that can be had for 1/2 the price. MAKE sure the meter can read 1000VDC--many foriegn models stop at 600VDC. Next most important tool in the line up is a scope. Your surplus shops can get you an analog starter scope for under $50--dual trace and 20MHz is all that is needed for audio. If you can afford it--the Velleman PC-500 and signal generator give you a lot of real flexibility in circuit testing (www.velleman.be ) Finally, get a decent tube tester, don't get a cheapo. For the price, the Precision 612 model is good value and available for about $60 on ebay. Other reasonalbe models to look can be found at http://www.tone-lizard.com/Tube_Testers.html Thanks for the good advice. Looks like just collecting all the tools I'll need will be a quest in itself. Good luck--this hobby is a lot of fun. Keep your eyes out for yard sales--lots of great tubes, amps, radios, and test equipment can be found for a song. My Hickok 539C was picked up for $20 at a yard sale. But for every one nice yard sale find, you have to sift through literally mountains of useless junk. Hardly worth the effort, when I can just get the same thing on ebay for maybe 3x the yard sale price, but save many hours doing so (which I could spend going to work and making 100x the yard sale price). It'd be ok if yard sales were fun, but for me, they're not Learn to meet people who are already into electronics, often radio hams are sources of gear they no longer want. Garage and yard sales don't yeild much; the good gear never makes it out to the yard. I have aquired a tonne of old second hand junk, donated over the years by various ppl. I have never used Ebay. I watcjed and waited for cheap sales when they came up. Older analog test gear say 20 years old and still working fine is quite ok to begin with. All the gear made 20 years ago is obsolete now, but perfect for fiddling round with a few tubes for audio. Its all being junked for the latest gear with more features and automation and PC interface ability. And its fast becoming a digital world, and analog is becoming the poor relation in electronics. Even the latest amplifiers are PWM and the size of a cigarette pack, yet able to to handle 200 watts, since they are so efficient. ( But the audio enthusiasts in the clubs I know loathe all this crap, and tell me their tube amps are still better with music, despite the heat, weight, cost, and fiddles. They still demonstrate to me the wonders of well done vinyl........) I started my pile of stuff 11 years ago. I didn't have a PC until nearly 5 years ago. I was well schooled and tooled when i got my PC. Then i quickly realized that if i wanted to do spectrum analysis, I could use an old PC with W95, quite adequate, and have an oscilliscope program and find out more faster about the wave forms than I see now. I have a home brew spectrum analyser for sifting out 2H, to 10H harmonics of 1 kHz, and IMD products, but it'd be faster if I did it with a PC. I built my own pink noise source and tunable active RC bandpass filter for testing speakers, very necessary it is, and I'd love a laptop fitted out with something that shows the profile of a response in a second, rather than the 15 minutes it takes me to record dots along the band on paper in a book. But its portable, and reliable, and confirms my doubts about poor sound when i have speakers to repair or have to do a home visit to determine the bad news about someone's pet system. I can't afford a laptop. I got an analog 20MHz dual trace CRO which I don't use now because I find I get by quite OK now with a much older single trace, all discrete and transistors, and fixable if it goes wrong. The dual trace CRO with about 20 14 pin ICs and countless other parts is/was a bitch to service. I very nearly built my own CRO, I have all the necessary parts to build 3 if I wanted to, but why? I wanted to focus on build fine amps, not reproductions of valve driven CROs. I have to earn a living. But I did find the time for the other test gear. Building test gear teaches you about precision and noise. And about opamps, transistors, and it broadens one's experience, thus training the brain to think more deeply, becuse to be good with electronics, you have to be prepared to accept or find the non obvious, and realize many things are going on even in a simple circuit. There are very very few people I know locally who I could discuss tube craft with. After getting a PC, I learnt that to enjoy discussions about what i do, I had take part in the only real and deep level tube audio discussions i know of here at r.a.t, a *worldwide* group of enthusiasts. Most blokes don't want to discuss much. Patrick Turner. |
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#14
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For a good dual trace scope I recommend any of the Tek 466 series. It was
made in the '70's but is absolutely bullet proof. You can't fry the front end by accidentally hitting the 5mv setting with 400VDC. "John Stewart" wrote in message ... Iain M Churches wrote: "Bruce C. Miller" wrote in message oups.com... Greetings, good sirs. I'm interested in getting started in building my own tube amplifiers and could use your learned advice on what is the most effective way to educate myself in the hobby and get started building. Welcome, it's a fascinating and rewarding hobby. I'm just out of college, but apart from a robotics course I took in gradschool (which was mainly a programming course), I have no electronics or engineering experience. Audio-wise, I do have what I would call a hi-end system, but the only tubed component I own is an Audio Electronic Supply PH-1 phonostage, at least for now. My level of knowledge is probably best described by the fact that I can identify the parts on a circuit diagram, but I'm not sure what the significance is of the way they are combined. That's a good point from which to start I figure I'd probably be best served by reading a book or two on the subject of DIY electronics or on basic electronics. At that point, I'd hopefully be comfortable enough to try building a quick project just to get the hang of soldering and such. I'm thinking an inexpensive tube radio kit would be perfect for this, as if I happen to botch it, it'd be no big loss. Assuming this was a success, I imagine I would then be prepared for my first foray into serious amp building, and should choose a schematic online to use as a guide. The definitive book on the subject is the Radio Designers' Hand Book by Langford Smith,. The 4th edition is now in print again. But it's a bit heavy going. For a practical person, maybe: VALVE AMPLIFIERS by Morgan Jones. Published by Newnes (ISBN 0 7506 4425 7) THE PRINCIPALS OF POWER by Kevin O'Connor. Published by Power Press. London. Canada (ISBN 0 9698 6081-1) THE BEGINNER'S GUIDE TO TUBE AUDIO DESIGN By Bruce Rozenblit Published by Audio Amateur Press. (ISBN 1-882580-13-3) When you have read those you will know a lot about tube audio, and if you have any questions, this is a very good place to ask them:-) - What kind of tools should I buy? Obviously, I'll at least need a soldering iron, wire cutter, and screwdriver, but what else? A good DVM (Fluke is excellent) A signal generator A dual beam scope. Should be 'Dual Trace Scope'. Dual beam means two guns & deflection systems in the CRT. Fairly rare & expensive. Examples are HP 132A, TEK 555 & Philips 3250 (I think). All obsolete now. Not sure if anyone even makes a true dual beam scope anymore. Digital techniques do the same function much better except in rare cases. Cheers, John Stewart A variac. These are the basic tools. But the list is as long as you want it to be:-) Iain |
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Bruce C. Miller wrote:
Patrick Turner wrote: "Bruce C. Miller" wrote: - Am I being overly cautious in my approach? No. Caution with tubes prolongs life expectancy, since even a humble tube preamp could kill anyone who is careless. You must learn serious respect of high voltages. I've seen this on many a website and in books. Have there really been cases of electrocution deaths as a result of home stereo equipment, particularly recently? It happens every so often. But respect (not fear, but knowledge of what high voltage can do and how to avoid it happening) goes a long way. Things like keeping the other hand in your pocket. You really don't want to take a hit across your heart, it might stop beating. After a while safety becomes second nature and you know what you can and cannot do to stay safe. |
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"robert casey" wrote in message link.net... Bruce C. Miller wrote: Patrick Turner wrote: "Bruce C. Miller" wrote: - Am I being overly cautious in my approach? No. Caution with tubes prolongs life expectancy, since even a humble tube preamp could kill anyone who is careless. You must learn serious respect of high voltages. I've seen this on many a website and in books. Have there really been cases of electrocution deaths as a result of home stereo equipment, particularly recently? It happens every so often. But respect (not fear, but knowledge of what high voltage can do and how to avoid it happening) goes a long way. Things like keeping the other hand in your pocket. You really don't want to take a hit across your heart, it might stop beating. After a while safety becomes second nature and you know what you can and cannot do to stay safe. When I was young, the chap who introduced me to valve audio felt some kind of responsibility for his actions, and built me a "discharge box" which I still have and use often. It comprises of a small 300VDC panel meter, with a 10k 20W resistor, and a neon across it which strikes at 70V. It has two flying leads, one red, one black with a switch mounted in the face of the box, to switch the pos side. One connects the box across the reservoir cap in the amp, before one starts work, and switches it on to discharge the amp psu after the mains supply is switched off. A simple but very effective safety device. Iain |
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Bruce C. Miller wrote:
- Do any of you who have built Andre Jute's amps have any comments on the experience or final product? Dear Mr Miller, I built one of Andre Jute's amps. "Triple Threat" is a push-pull class A EL34. It sounds impressive and measures well. I also have an Audiolab transistor amplifier and Mr Jute's amp is of comparable quality but easier to listen to for hours on end. I am always very keen to settle in my listening room and switch it on. Mr Jute has published much easier designs for DIY construction. I am collecting parts to build his "KISS Ultrafi" design with 300B as my ultimate amp. KISS stands for "Keep it simple, Stupid". Have you looked at Mr Jute's "SEntry"? That must be as inexpensive and simple to build as a good tube amp gets. I've also built Mr Jute's "Impresario" speakers. The result is so good that I'm seriously considering building the expensive Fidelio horns he recommends to go with my "KISS Ultrafi". Yours sincerely, Frank B. |
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Bruce,
Before you take any advice from "frankbte" you should know that Frank is a sockpuppets that Mr. Jute speaks through from time to time. "Frank's" postings are all the same, i.e. a sycophant with nothing but fawning praise for Mr. Jute and his doings, real or imaginary. It's the moral equivalent of shill-bidding. "Frank" never has much else to say of a tube-related nature. But you can count on him to appear, much like the visual aura that precedes a migraine . .. . Is it clever, pathetic, or psychopathological? Because Mr. Jute takes liberties with respect to facts, I'd take his technical recommendations with a grain of salt. One doesn't know if an amp Mr. Jute has built and Frank "auditioned" is real or the abstract product of an overactive imagination . . . . |
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Google for "dan garstecki" to get an idea of the type of person who uses
sock puppets on usenet. Adam |
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Yo, Frank, I don't think the T113 Triple Threat is suitable for
newbies. A fully developed PP amp like the T113 is really not a first construction project: too many parts, too fiddly, too easy to get wrong. That particular amp depends for its tone and silence on the block film caps with the little PCB feet from RS. It really needs a PCB rather than hardwiring. The two KISS amps, T39 Ultrafi and and its less expensive sister T44 Populaire are simple enough for a novice to build. But I don't fancy telling a novice to splash out on gennie WE and Mullard tubes that he might ruin for the T39, or even for Chinese 300B and Russian 6SN7 equivalents that he might blow up for the T44. Bruce should first consider his speakers. If he has suitable speakers or is willing to build suitable speakers, perhaps my Impresario that you liked, then he can consider an SE amp. My T201 SEntry that you suggest is, as you say, cheap and cheerfully easy to build. All the parts except the output transformers can be ordered from a mainstream electronics supply house. The output trannies can be universal Hammonds or UBTs or, upmarket, Lundahls which will be infinitely reuseable. The power tranny can be 2x115 to 2x115 isolation tranny, cheap by mailorder. In the proto I built out of my junkbox, I used two filament trannies face to face (230V in, 6V out, into 6V in 230V isolated out), total cost twelve bucks, with the spare windings used for the heaters of three tubes. All this fits into a 17x10x4 Hammond ali box, ten bucks, with space to fit. Yo, Bruce, I'm Andre Jute and I have built a few amps designed by Andre Jute and others. I liked some of them. (Now watch that little sorehead Yaeger -- crooked garage trader who is sore because I exposed one of his scams -- come tell us I am a sock puppet! Anyone who has a good word to say for me is sock puppet. Beware.) You shouldn't really even consider an amp until you have considered your speakers seriously and bought or built really good quality speakers. They will cost as much or more than a good amp, and they will determine what sort of amp you should have. The articles you might want read while you consider your speakers are near the beginning of http://members.lycos.co.uk/fiultra/T...mp%20INDEX.htm and the Impresario speaker and SEntry amp are available from http://members.lycos.co.uk/fiultra/JUTE%20ON%20AMPS.htm Good luck. Andre Jute wrote: Bruce C. Miller wrote: - Do any of you who have built Andre Jute's amps have any comments on the experience or final product? Dear Mr Miller, I built one of Andre Jute's amps. "Triple Threat" is a push-pull class A EL34. It sounds impressive and measures well. I also have an Audiolab transistor amplifier and Mr Jute's amp is of comparable quality but easier to listen to for hours on end. I am always very keen to settle in my listening room and switch it on. Mr Jute has published much easier designs for DIY construction. I am collecting parts to build his "KISS Ultrafi" design with 300B as my ultimate amp. KISS stands for "Keep it simple, Stupid". Have you looked at Mr Jute's "SEntry"? That must be as inexpensive and simple to build as a good tube amp gets. I've also built Mr Jute's "Impresario" speakers. The result is so good that I'm seriously considering building the expensive Fidelio horns he recommends to go with my "KISS Ultrafi". Yours sincerely, Frank B. |
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Hi Iain,
A simple but very effective safety device. Great idea. Additionally, I use to put a PSU cap discharger in almost all amps I build, too: http://www.tubes.mynetcologne.de/roe...fety_e.html#a2 Small, cheap, effective. Especially when for maintenance purposes the output tubes may have been pulled, and PSU cap voltage will fall very slowly ... such a situation actually happened to me because I simply depended on the thought that the output tubes will suck the PSU caps empty. They will, of course, when they are heated. They won't, of course, if they are not present, or/and if one uses sandstate rectification and switches that damp amp on only for seconds (so the tubes don't heat up, but the PSU caps are under full B+). The PSU cap voltage did hit me two days (!) after that switch-on. I have learned my lesson =:-) Tom -- When in doubt, use brute force. - Ken Thompson |
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Hi Patrick,
Older analog test gear say 20 years old and still working fine is quite ok to begin with. All the gear made 20 years ago is obsolete now, but perfect for fiddling round with a few tubes for audio. Sometimes old gear even can be extremely practical and faster than "modern" stuff. For example, after having already a few (good) DVMs and quite a good 15 y/o scope, I bought me a VTVM (Heathkit IM-18E, for less than 20 Euros on German Ebay, including 30KV probe, complete manual and a spare NIB EAA91/6AL5 recto tube (the other one is plain and common ECC82/12AU7). Now I can measure through amps on the bench at audio freqs MUCH faster than with a scope, and my DVMs would display only rubbish at for example 20kHz anyway. This simple VTVM definitely was one of the best "investments" I made regarding my tube hobby. Probably essential for tube radio restauration work (measuring through IF freq stages), too. Tom -- this is my favourite sig, since there is no reference to Kibo, Discordianism or The Church of the Subgenius in it. |
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wrote:
Yo, Frank, I don't think the T113 Triple Threat is suitable for newbies. A fully developed PP amp like the T113 is really not a first construction project: too many parts, too fiddly, too easy to get wrong. That particular amp depends for its tone and silence on the block film caps with the little PCB feet from RS. It really needs a PCB rather than hardwiring. The two KISS amps, T39 Ultrafi and and its less expensive sister T44 Populaire are simple enough for a novice to build. But I don't fancy telling a novice to splash out on gennie WE and Mullard tubes that he might ruin for the T39, or even for Chinese 300B and Russian 6SN7 equivalents that he might blow up for the T44. Mr Jute, I have read some of your writings on the KISS amp, but as I stated earlier, it is my intention to read up on some basic electronics and on tubes a bit before jumping into building anything. That way I'll be able to understand what it is I'm doing while doing it. Hopefully, by then you'll have had the chance to post the rest of your writings on the subject. Bruce should first consider his speakers. If he has suitable speakers or is willing to build suitable speakers, perhaps my Impresario that you liked, then he can consider an SE amp. My T201 SEntry that you suggest is, as you say, cheap and cheerfully easy to build. All the parts except the output transformers can be ordered from a mainstream electronics supply house. The output trannies can be universal Hammonds or UBTs or, upmarket, Lundahls which will be infinitely reuseable. The power tranny can be 2x115 to 2x115 isolation tranny, cheap by mailorder. In the proto I built out of my junkbox, I used two filament trannies face to face (230V in, 6V out, into 6V in 230V isolated out), total cost twelve bucks, with the spare windings used for the heaters of three tubes. All this fits into a 17x10x4 Hammond ali box, ten bucks, with space to fit. That's a good point. Currently, I own a pair of Spendor s6e's which are much too low sensitivity for anything SE. As much as I'd like to build my own speakers from the ground up, I'm thinking I'll probably need to get a kit of some kind, as a result of my lacking skills in woodworking and the like. Aesthetically, I think the Hammer Dynamics speakers are quite nice and can look quite breathtaking with certain woods. I may also forego speaker construction all together and pick up a pair of pre-built single driver speakers of some variety. Though they can be had for reasonable prices, I'm hoping I can find the courage to construct (preferably, successfully) a pair myself, mostly for pride-related reasons. Yo, Bruce, I'm Andre Jute and I have built a few amps designed by Andre Jute and others. I liked some of them. (Now watch that little sorehead Yaeger -- crooked garage trader who is sore because I exposed one of his scams -- come tell us I am a sock puppet! Anyone who has a good word to say for me is sock puppet. Beware.) Indeed, you do seem to have acquired quite the cadre of detractors. You shouldn't really even consider an amp until you have considered your speakers seriously and bought or built really good quality speakers. They will cost as much or more than a good amp, and they will determine what sort of amp you should have. Considering the amount of free time I have to dedicate to my hobbies, I should have many months to decide on this. I'll likely spend the next few months just collecting tools. The articles you might want read while you consider your speakers are near the beginning of http://members.lycos.co.uk/fiultra/T...mp%20INDEX.htm and the Impresario speaker and SEntry amp are available from http://members.lycos.co.uk/fiultra/JUTE%20ON%20AMPS.htm Good luck. Andre Jute Thanks. I'll also mention that I enjoy reading your thoughts on food, wine, bicycling, and other sundry subjects. You're probably a busy man, no doubt. But if you find the time to post more on these issues, either here or on your website, I'm sure you'll have plenty of readers. It's hard to find anything online written with any sense of cultural refinement. |
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Jon Yaeger wrote:
Bruce, Before you take any advice from "frankbte" you should know that Frank is a sockpuppets that Mr. Jute speaks through from time to time. "Frank's" postings are all the same, i.e. a sycophant with nothing but fawning praise for Mr. Jute and his doings, real or imaginary. It's the moral equivalent of shill-bidding. "Frank" never has much else to say of a tube-related nature. But you can count on him to appear, much like the visual aura that precedes a migraine . . . Is it clever, pathetic, or psychopathological? Because Mr. Jute takes liberties with respect to facts, I'd take his technical recommendations with a grain of salt. One doesn't know if an amp Mr. Jute has built and Frank "auditioned" is real or the abstract product of an overactive imagination . . . . At my current knowledge level, I'm afraid I can't really tell if a design is poor or not (at least by looking at a circuit diagram). I've place some bids on ebay for books recommended here, and hopefully I'll be able to contribute to such discussions soon  As for the subject of Mr. Jute's mental stability, I'm also entirely without opinion. He does seem to have excellent writing ability and is able to cook up a nice looking meal though. Most net.k00k's I've had the displeasure of reading on usenet typically weren't of this variety, though certainly anything is possible. |
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Patrick Turner wrote:
Women are of course rather unfathomable, and they see us the same way, and even though a triode is simple when you understand its workings, they would never see how a triode works, and become bored after 10 minutes if they learned. Young sheilas need what they cannot understand, and we need them, while we are young, otherwise the planet would just all be old folks and we'd be no more, and that would give the other species a chance. Of course if you sail through life withou needing people, just liking them for what they are, it upsets many sheilas. But the fact is that not any one of us is indispensible. My ex wife said to me after she left me that had she stayed any longer she'd have "kicked my hi-fi speakers in the cones". I was a gentleman of course, averse to arguing about where a sheila should locate her presense or how she should construct her allegances, and opened the door for her when she left.... I have seen many relationships based on shared activities, some last and some don't, but my parents stayed with each other for 35 years until my old man died and in all that time niether shared any hobbies, except sharing life itself with all its joys and problems. At 15 I was building radio telephones using old radio parts. But by 18 I drifted right away from electronics because I thought it nerdy, and I spent 25 years as a construction contractor. Maybe I made more money than had I persued electronics. Who knows. I never met any women through work. You just need the right kind of job. Unfortunately those types of jobs are usually mindless, dead-end jobs. But, if you can handle working at clothing stores, call centers, or resturants, there's usually plenty of females to choose from. In every computer-related job I've had, all of my direct coworkers and 95% of the ones I saw only occasionally were all men, and usually of the middle-aged, balding variety. Sometimes I do lament that my youth is being squandered away in a windowless office somewhere, but I doubt the realistic alternatives are much better. We can't all be astronauts, spies, and ninjas. There are vitually none in physical activity clubs like cycling clubs and so on. But these days the fascination with timber and steel and bricks is over, and I am returned to triodes, and happy to spend a day in my work shed. Most women I need are simply quite unimpressed by anything to do with electronics. Most have appalling sound gear, but they hear more from those poor systems than us men hear from our good systems. And so many women don't like the Internet, but lerve their mobile phones. I don't have a mobile, and don't watch TV. I'm currently single, myself. Definitely has it's pluses. Not having to own a TV is one. Women love TV. If you live with one, they'll insist on it. Then they'll sit there and watch American Idol. But if you watch them watching it, it doesn't make them happy, just less unhappy. I also don't own a cellphone. Most of the guys I work with are bugged constantly on theirs by their wives. Cell phones definitely make good leashes. One can never hope to find someone like oneself. You will only find someone who is different, and that shouldn't hinder anyone socially, if you can value differences. At the young end of life there is much attraction of opposites, and toleration of differences, denial of them even, with good and bad consequences..... But at the other end of life, finding someone tempting is all that much harder, because temptation will avoid you, as most passion amoungst women has faded. Oh, I know... I know... What seems like a great idea, and actually requires a lot of work to get, usually ends up with you holding shopping bags and sitting on a bench in the mall hallway, while wifey spends your speaker money on another pair of shoes  |
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#27
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Tom Schlangen wrote: Hi Patrick, Older analog test gear say 20 years old and still working fine is quite ok to begin with. All the gear made 20 years ago is obsolete now, but perfect for fiddling round with a few tubes for audio. Sometimes old gear even can be extremely practical and faster than "modern" stuff. For example, after having already a few (good) DVMs and quite a good 15 y/o scope, I bought me a VTVM (Heathkit IM-18E, for less than 20 Euros on German Ebay, including 30KV probe, complete manual and a spare NIB EAA91/6AL5 recto tube (the other one is plain and common ECC82/12AU7). Now I can measure through amps on the bench at audio freqs MUCH faster than with a scope, and my DVMs would display only rubbish at for example 20kHz anyway. This simple VTVM definitely was one of the best "investments" I made regarding my tube hobby. Probably essential for tube radio restauration work (measuring through IF freq stages), too. Tom Yeah, the old vtvms are great for tube work. Generally they won't blow up like some SS test gear when measuring the high voltages of tube circuits, like say an SE amp with 1,200v at the anode, and with a signal voltage of 700vrms, which gives a total 2,200v peak with respect to 0V. I built my own volt meter with bandwidth from 2 Hz to 1MHz, and which has a broadband amp attatched with BW 10 to 30MHz, and a gain of 20, so that voltages smaller than a mV ban be determined amoungst the usual noise in signals that small. It has a fet follower input, with six ranges from 0-10mVrms to 0-1,000Vrms. It'd be a bit more conveneient to have intermediate ranges of 0-32mV, 0-320mV also, because measuring at 1/10 of the meter scale is a little inaccurate, but still ok for most I do. The broadband amp is a sziclai pair of 2N222, with NFB, very simple, it is only needed to make a few volts output max. Some old dude just gave me an AWA vtvm, but *very* grimy, with a stuck meter needle, so its probably stuffed like the AVO meters he also donated. The AVO volt and resistance meter, or multimeter is a beuatiful peice of work inside, lke the AWA vtvm. One AVO had no meter, and is in good condition inside, other did ahve a meter inside, but it had been soaked in water for some time and after stripping down the beautifully made meter movement the needle and coil moved OK but alas the coil was open someplace, so I chucked it out; I don't have a 1955 new meter laying around to suit. I kepts the box without the meter, maybe I find another in working condition.... Most of this old gear suffered and perished through abuse and neglect. Tube testers, which I don't believe anyone needs for audio nearly always have several bad faults within due to wrong settings with shorted tubes, and the switches have over heated and become intermittent. I have 3 testers, donated or bought for 50c, and all are crapped out...... After awhile one remembers to check the voltages that you *might* be measuring and using the high voltage range before prodding the circuit. It saves meters. I also built a simple cathode follower in a box to buffer my SS signal generator, which is another audio essntial, because I found that I would accidently touch the direct coupled sig gene output to something with high voltage, and poof, the gene's output transistors would die instantly with a jolt of 300v from a tube circuit. I also banished the damn direct coupling, put in RC coupling, and installed a resistance in series with the gene output, and although I have repaired the sig gene 3 times in the first 2 years i had it, it has lasted now for 7 years. It really ought to have diodes on the transistor emitter outputs to the rails of +/- 15v, so that any incoming voltage spike is clamped by the diodes to never exceed the rail voltage, and thus prevent backward current in the bjts, which zap them instantly. So basically, all test gear should have protection built in. A lot just doesn't. Patrick Turner. -- this is my favourite sig, since there is no reference to Kibo, Discordianism or The Church of the Subgenius in it. |
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#28
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Tom Schlangen wrote: Hi Iain, A simple but very effective safety device. Great idea. Additionally, I use to put a PSU cap discharger in almost all amps I build, too: http://www.tubes.mynetcologne.de/roe...fety_e.html#a2 Small, cheap, effective. Especially when for maintenance purposes the output tubes may have been pulled, and PSU cap voltage will fall very slowly ... such a situation actually happened to me because I simply depended on the thought that the output tubes will suck the PSU caps empty. They will, of course, when they are heated. They won't, of course, if they are not present, or/and if one uses sandstate rectification and switches that damp amp on only for seconds (so the tubes don't heat up, but the PSU caps are under full B+). The PSU cap voltage did hit me two days (!) after that switch-on. I usually have a resistance across the power supply rails to 0V so that I'd never get caught like you days later. One expects rails to be high when farnarkling around on the amp. The discharge idea above is good, but the relay wants to be well rated for the DC voltage which is across it at all times when the amp is on. 240v rated relays are commonly available, but having one with 600v across it is asking for trouble, so I won't use that idea of yours, since I can't find any relays *rated* for indefinite exposure to 1,000V which is what is wanted. In a pair of very high power tube amps I worked on there was 705 uF charged up to 500v in the separate amp chassis. If somebody yanks out the umbilical cord suddenly from the PSU, there is that 500v on two of the plug pins, and it is dangerous, even though the resistors will pull the voltage down eventually. The speed at which the voltage needs to be pulled down should be within 1/10 of a second, so that anyone can handle the plug pins right after pulling the plug out. Its an impossible dilemna, so I will be moving all the C2 of the CLC into the power supply enclosures, but will have 1 uF from the the CT of the OPT to 0V and this will discharge real quick. The umbilical cable impedance is low because it is a pair of 10 amp rated copper wires. The 2 uF is only needed to shunt the cable inductance at HF. So thus a 3 year old should be able to touch or suck the cable plug if he pulls it out just due to curiosity. I have learned my lesson =:-) We never ever fully learn our lessons though, we still farnarkle around with boxes full of volts to a ripe old age...... Patrick Turner. Tom -- When in doubt, use brute force. - Ken Thompson |
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#29
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"Bruce C. Miller" wrote: wrote: Yo, Frank, I don't think the T113 Triple Threat is suitable for newbies. A fully developed PP amp like the T113 is really not a first construction project: too many parts, too fiddly, too easy to get wrong. That particular amp depends for its tone and silence on the block film caps with the little PCB feet from RS. It really needs a PCB rather than hardwiring. The two KISS amps, T39 Ultrafi and and its less expensive sister T44 Populaire are simple enough for a novice to build. But I don't fancy telling a novice to splash out on gennie WE and Mullard tubes that he might ruin for the T39, or even for Chinese 300B and Russian 6SN7 equivalents that he might blow up for the T44. Mr Jute, I have read some of your writings on the KISS amp, but as I stated earlier, it is my intention to read up on some basic electronics and on tubes a bit before jumping into building anything. That way I'll be able to understand what it is I'm doing while doing it. Hopefully, by then you'll have had the chance to post the rest of your writings on the subject. As I suggested, start with a one triode line stage amp on a chassis about 500mm long x 200 mm wide. That way you can always add a phono amp or other stages, and keep the PSU away from the siganl preamp. After that you may feel a little more comfortable and confident about a power amp. Bruce should first consider his speakers. If he has suitable speakers or is willing to build suitable speakers, perhaps my Impresario that you liked, then he can consider an SE amp. My T201 SEntry that you suggest is, as you say, cheap and cheerfully easy to build. All the parts except the output transformers can be ordered from a mainstream electronics supply house. The output trannies can be universal Hammonds or UBTs or, upmarket, Lundahls which will be infinitely reuseable. The power tranny can be 2x115 to 2x115 isolation tranny, cheap by mailorder. In the proto I built out of my junkbox, I used two filament trannies face to face (230V in, 6V out, into 6V in 230V isolated out), total cost twelve bucks, with the spare windings used for the heaters of three tubes. All this fits into a 17x10x4 Hammond ali box, ten bucks, with space to fit. That's a good point. Currently, I own a pair of Spendor s6e's which are much too low sensitivity for anything SE. How do know this is true? I have built a few SE amps for customers with speakers on around 89bB/W/M and there is no shortage of power headroom. But they are all over 25 watts. A lone 300B may not suit your listening levels. But I know guys who find a 300B amp is fine for all their music, they are not deaf, and although their speakers hover around the 89 dB mark, they still prefer a 300B and its maximum of 8 watts. As much as I'd like to build my own speakers from the ground up, I'm thinking I'll probably need to get a kit of some kind, as a result of my lacking skills in woodworking and the like. Aesthetically, I think the Hammer Dynamics speakers are quite nice and can look quite breathtaking with certain woods. I may also forego speaker construction all together and pick up a pair of pre-built single driver speakers of some variety. Though they can be had for reasonable prices, I'm hoping I can find the courage to construct (preferably, successfully) a pair myself, mostly for pride-related reasons. Fair enough. Yo, Bruce, I'm Andre Jute and I have built a few amps designed by Andre Jute and others. I liked some of them. (Now watch that little sorehead Yaeger -- crooked garage trader who is sore because I exposed one of his scams -- come tell us I am a sock puppet! Anyone who has a good word to say for me is sock puppet. Beware.) Indeed, you do seem to have acquired quite the cadre of detractors. The Internet is a place where clashes of personality are inevitable, and its best to try yo ignore much of what isn't advice on how to build a tube amp. After 4 years on the Net I have become more immune to critics, and if any one of them wants to tell me to go eat my own poop, I will ask them if I should cook it first, andcould they suggest a wine to go with such a meal, and would they like to join me. There have been some rather protracted feuds and clashes between various individuals on this group that seem to have gone on for 10 years now. Be not worried, it is in men's nature to have a combative and competitive attitude all day long everyday, and in all activities, and at all times. The most illustrious and lasting friendships I have ever had revolved around competitiveness, and it still goes on. The guys I play chess with take no prisoners. But largely we are a happy bunch. My competitive nature and that of my friends' do not lead us to fisticuffs over issues of wrong chess moves, and when I cycled competively, I didn't push anyone off the road to win, something quite common amougnst younger eager riders of ungentlemany persuasions. I know, because I was shoved off a road by a youngster charging to the line in a sprint; lucky I wasn't killed, and this was a sunday morning local club race. So some people have a lot to learn to control their natural urges to kill anyone who gets in their way, or to beat the daylight out of anyone who dares to disagree.. All I would ask of all is that when anyone become offended, they should weigh up what the heck they might get out of spending a pile of verbal and keyboard energy in flaming forever and ever. Usually, it isn't much worth having, even if they are right. You shouldn't really even consider an amp until you have considered your speakers seriously and bought or built really good quality speakers. They will cost as much or more than a good amp, and they will determine what sort of amp you should have. Considering the amount of free time I have to dedicate to my hobbies, I should have many months to decide on this. I'll likely spend the next few months just collecting tools. The articles you might want read while you consider your speakers are near the beginning of http://members.lycos.co.uk/fiultra/T...mp%20INDEX.htm and the Impresario speaker and SEntry amp are available from http://members.lycos.co.uk/fiultra/JUTE%20ON%20AMPS.htm Good luck. Andre Jute Thanks. I'll also mention that I enjoy reading your thoughts on food, wine, bicycling, and other sundry subjects. You're probably a busy man, no doubt. But if you find the time to post more on these issues, either here or on your website, I'm sure you'll have plenty of readers. It's hard to find anything online written with any sense of cultural refinement. Cultural Refinement. What an entity. Patrick Turner. |
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#30
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"Bruce C. Miller" wrote: Patrick Turner wrote: Women are of course rather unfathomable, and they see us the same way, and even though a triode is simple when you understand its workings, they would never see how a triode works, and become bored after 10 minutes if they learned. Young sheilas need what they cannot understand, and we need them, while we are young, otherwise the planet would just all be old folks and we'd be no more, and that would give the other species a chance. Of course if you sail through life withou needing people, just liking them for what they are, it upsets many sheilas. But the fact is that not any one of us is indispensible. My ex wife said to me after she left me that had she stayed any longer she'd have "kicked my hi-fi speakers in the cones". I was a gentleman of course, averse to arguing about where a sheila should locate her presense or how she should construct her allegances, and opened the door for her when she left.... I have seen many relationships based on shared activities, some last and some don't, but my parents stayed with each other for 35 years until my old man died and in all that time niether shared any hobbies, except sharing life itself with all its joys and problems. At 15 I was building radio telephones using old radio parts. But by 18 I drifted right away from electronics because I thought it nerdy, and I spent 25 years as a construction contractor. Maybe I made more money than had I persued electronics. Who knows. I never met any women through work. You just need the right kind of job. Unfortunately those types of jobs are usually mindless, dead-end jobs. But, if you can handle working at clothing stores, call centers, or resturants, there's usually plenty of females to choose from. In every computer-related job I've had, all of my direct coworkers and 95% of the ones I saw only occasionally were all men, and usually of the middle-aged, balding variety. I have become "unemployable" at 57, because employers want a lot these days, including a glowing resume about all the successes one has had in other "real jobs". But I have been self employed for 25 years now, and I am too indepenadant to work in a team at a restaurant or at a bank or in the public service. Balding is no shame. There is an old Turkish saying," where there grows no grass, there is good ore to be mined ". Sometimes I do lament that my youth is being squandered away in a windowless office somewhere, but I doubt the realistic alternatives are much better. We can't all be astronauts, spies, and ninjas. I saw office work as like being in jail when i was 25. I was only happy when outside, and with men who actually did something real, and I liked being the boss. I was a foreman by age 25, and happy to lead, if anyone dared to follow. I am content to have been a constructive person in my youth. My knees tell me I must have done a lot, so triodic constructions will have to do for now. There are vitually none in physical activity clubs like cycling clubs and so on. But these days the fascination with timber and steel and bricks is over, and I am returned to triodes, and happy to spend a day in my work shed. Most women I need are simply quite unimpressed by anything to do with electronics. Most have appalling sound gear, but they hear more from those poor systems than us men hear from our good systems. And so many women don't like the Internet, but lerve their mobile phones. I don't have a mobile, and don't watch TV. I'm currently single, myself. Definitely has it's pluses. Not having to own a TV is one. Women love TV. If you live with one, they'll insist on it. At 38 I found a 26 yr old with whom I shacked up with for a year. What a year. Really good it was. She didn't like tele at all, but after some time realised I found some comfort of relaxation with the tele at that time of my life when i watched the damn thing after a hard day's slog. Trouble was she liked other guys a little too much, even when i bonked the bitch 6 times a week, for hours at a time. But nobody was enough for her. She had to leave, TV wasn't of any major significance to me. Larger issues were of course. I have mainly lived alone, and TV has become a waste of time, programs have become abysmal; I refuse to watch most, such as Survivor, and soaps, and I am totally intolerant of the adds, and TV is a home invasion, and I don't need TV to relax after construction work. People in real life matter more. Why should I watch other folks doing their life on TV when i should be doing my life? Women like to tour around travelling. When they get where they go, people gawk at them, and relieve them of their money, and they come back poor. Why didn't they stay put; wasn't there a lot to do? But nearly all the women I knew when i was young had the travel bug, and at 30 owned virtually nothing, and couldn't settle down. Women like aimless self indulgences. Then they'll sit there and watch American Idol. But if you watch them watching it, it doesn't make them happy, just less unhappy. I also don't own a cellphone. Most of the guys I work with are bugged constantly on theirs by their wives. Cell phones definitely make good leashes. I have no mobile either. No need. No use having what you don't need. This makes me a "minimalist", and rather unmarriageble. Nobody has convinced me to be otherwise, but i ain't going to put on the agony, and put on the style, at great expense, and for whimsical reasons, for anyone. One can never hope to find someone like oneself. You will only find someone who is different, and that shouldn't hinder anyone socially, if you can value differences. At the young end of life there is much attraction of opposites, and toleration of differences, denial of them even, with good and bad consequences..... But at the other end of life, finding someone tempting is all that much harder, because temptation will avoid you, as most passion amoungst women has faded. Oh, I know... I know... What seems like a great idea, and actually requires a lot of work to get, usually ends up with you holding shopping bags and sitting on a bench in the mall hallway, while wifey spends your speaker money on another pair of shoes Women have two thumbs. I refuse to go under either of them. I also now happily share my house with a 41 yr old lady to whom I am not attracted at all, but who is a delight to get on with. She rents half the house which I don't use, and that pays all the basic expenses I have, so I get to spend time on the Net, rather than drive a taxi to make ends meet. After divorcing a very lack lustre run-around wife 28 years ago, I have shared my house which I worked hard to buy with a long list of mainly happy people. As a craftsman, I liked suburban security, its nothing to be ashamed of, as the avant garde or resteless drifter brigades would have us believe, and I have had the privelige of much experience that I wasn't going to trade for some bothersome damn marriage. I am not averse to marriage, its a wonderful way to be, but there's never been a dame who convinced me it would be as good as it is possible for it to be, and there certainly was never a sheila who could ever cook as well and as repeatedly keenly as my mother or their own mother. I only once married someone because it semed like the right thing to do, but that's never enough reason. What semed right went wrong after a year, but I had no regrets though, since nothing ventured, nothing gained, nothing learnt, nothing experienced. Oscar Wilde wrote that basically a good marriage should be like a one night stand that lasts 40 happy years, but only 1% of the population now would ever realize his perception. Oscar was gay, of course, and I am not, but nevertheless, his wit, humour, and perceptions are relevant still. Along with Pillars Of Wisdom by T.E.Lawrence, every young man should read something by Oscar Wilde. I've allowed some things to just grab me. Like tube craft. It did forawhile when i was young until I needed real work to make some real money for motorcycles and to fund outings with women. Women never say "just lie down here luvvy, it won't costyer anyfink". That is the least said sentance in the English Language. Then Building Construction got my interest, and I even got a Building Certificate at night school during 6 years after work. Better than TV or the pub. I witnessed so many mates doing drugs, getting ****ed every night of the week, riding too fast, some got killed, some got married too early, got divorced, but I studied and learnt and saved, so that by 27 I had 1/3 of the price of a decent house in the bank. I could afford to marry anyone willing, and have them stay at home with the kids. Such was my good management, and concoction of stable boring ideas I had. The catch was to find someone willing, committed, functional, mildly exciting, not too ugly, not dysfunctional, but that wasn't ever going to be easy, since most young women in this town in 1974 and then full of mainly public service employees thought men in the construction industry to be uncouth, dirty, and untouchable. Women don't much like reality. Like many fellas, I am fascinated by electricity, and the wonderment still holds for me. A month ago I took out 6 women within the one fortnight, but every single one had not had a man for years, and didn't know how to plan to. None had any dreams either. What a lot of sexless old dullards. They got no oomf. There are hundreds more to choose from, but I'm in no hurry. Patrick Turner. |
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#31
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"Patrick Turner" wrote in message ... The discharge idea above is good, but the relay wants to be well rated for the DC voltage which is across it at all times when the amp is on. 240v rated relays are commonly available, but having one with 600v across it is asking for trouble, so I won't use that idea of yours, since I can't find any relays *rated* for indefinite exposure to 1,000V which is what is wanted. A relay is not so good here. I have a single pole switch, rated at 15A. It's not automatic, as a relay would be, but I have got into the routine of: "PSU HT off, box on, wait 5 secs, neon goes out, volts drop to zero, proceed. In a pair of very high power tube amps I worked on there was 705 uF charged up to 500v in the separate amp chassis. If somebody yanks out the umbilical cord suddenly from the PSU, there is that 500v on two of the plug pins, and it is dangerous, even though the resistors will pull the voltage down eventually. That's probably the reason why separate psu's are not often seen in domestic applications, although many broadcast and studio amps had them, rack mounted below the amp. I saw such an amp, made in Germany, about a year ago. It did not carry a CE mark. They all seemed to use a "safety loop" from one side of the mains switch which went along the umbilical to a link between two pins on the male multiway connector at the amp end, and back again. This meant that the amp psu would not start if the umbilical was not in place, or one end was disconnected. In this part of the world (Scandinavia) insurance companies will not give approval for an amp with a separate psu over 300VDC, even though the psu has a female chassis connector, and so one could not actually touch the contacts from the outside. Iain |
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