Today, after "burning in" the 6P36S conversion I made for a couple of days without any issue at all, I went out so I turned it all off. When I got home, I turned the power on, and 2nd output (from left to right) arcs and the power cuts (OCP on ATX). I try again, same result. Same arc, same place. Change the tube. No more issue.
The question is how does a tube that worked perfectly for 48 hours fail on power up the next time? My take away? Bad tube since I'm not an engineer and it tells the story. If however it keeps happening, then bad design, right?
Yet another example of designing, building, tinkering, and generally fooling around with things to see what happens. As long as you have the basic understanding of electricity and how it can easily kill you if you're careless, foolish, or otherwise unlucky, you probably won't get hurt or blow much stuff up other that the odd fuse, diode, resistor, capacitor, transistor...
Only once have I ever got a tube to crack and that was a yellow plating sweep tube that either ran away or lost it's bias. Not sure how to tell, but again changing the tube for another one in the same over engineered circuit (5W resistors where most people would use 1W etc so nothing blew up) the amp worked fine again and still does months later. Sometimes you get a dud tube, not all of them are perfect especially NOS tubes that may have been sitting in a bunker for 70 years or something. That said, if you're tinkering, don't use irreplaceable output transformers etc. but that almost goes without saying. I think the OP will learn as they go. If you have never effed around with ANY electronics at all though? I really suggest starting with simple (read for kids) books on electricity.
Here's the first book on electricity I ever read (but probably a newer revision) for only 6$. https://www.amazon.ca/Wires-Watts-Understanding-Using-Electricity/dp/0684168545
If you're lucky, you might find a copy on your local lending library for anyone who's interested.
I usually assume most people on a DIY forum already have the fundamentals, but that might not be true and we all started at the beginning, right?
Like in programming, no matter what language you want to learn, you'll probably start out with "hello world", not try to write a low level kernel driver.
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Copies available near $4 shipped:
Wires Watts Understanding Using Electricity by Irwin Math - AbeBooks
Ah- click "Destination, rates & speeds" and change your country as needed. I don't see an offer for delivery to Canada under $13.
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And it is probably best to “learn electronics” and make mistakes with transistors and ICs running off a wall wart, or even passive circuits like speaker crossovers first before opening up a tube amp chassis. You will learn more faster if your hands are actually on the circuits, which you cannot do with tubes. You can learn electronics from the ground up with tube circuits, but it goes a lot slower because you literally need to work with one hand tied behind your back. Mistakes much more costly.
THANKS everyone!
I DO appreciate all the ideas. In my first post, I mentioned I will NOT build any amp!
I think this forum can teach me a LOT!
I am thinking to BUY a tube preamp, headphone amp, and possibly hook up the tube preamp to a solid state power amp.
dumb questions.
1. which brands do you like? Primaluna tube preamps? other
2. which brand headphone tube amp? Schiit? woo audio? Feliks audio? all look really really nice!
3. when I do get one, i will ask about tube rolling, something for me to learn about
.4. which SOLID STATE power amp do you like? Pass Labs? McINtosh, other?
With respect, I am NOT going to build any equipment, but would like to learn about tubes!
thanks again!
Bob
I DO appreciate all the ideas. In my first post, I mentioned I will NOT build any amp!
I think this forum can teach me a LOT!
I am thinking to BUY a tube preamp, headphone amp, and possibly hook up the tube preamp to a solid state power amp.
dumb questions.
1. which brands do you like? Primaluna tube preamps? other
2. which brand headphone tube amp? Schiit? woo audio? Feliks audio? all look really really nice!
3. when I do get one, i will ask about tube rolling, something for me to learn about
.4. which SOLID STATE power amp do you like? Pass Labs? McINtosh, other?
With respect, I am NOT going to build any equipment, but would like to learn about tubes!
thanks again!
Bob
dynaco-doctor.com has PAS3 preamp boards, populated, also a transformer wrapped in steel. They don't have cases and there is no picture of the shorting when not selected rotary switch.
Cheapest .015 % hd solid state amps are blown up Peavey PV-4 PV-8c, CS800x, CS800s, CS600. Look on e-bay "amplifier for parts or repair". Complete schematics are available and Peavey sells some of the unique parts. Prices are high now, everybody apparently repairs amps in the winter. I got a PV-4 for $20 including freight last spring. I bid $27 but ebay wouldn't give it to the guy since nobody else bid. $50 in output transistors & new rail caps, works great on my HDTV instead of a Samsung $180 "sound bar" with the "miracle" 3" woofer.
QSC & crown amps are also highly respected, but don't buy a DC300. You don't want DC on a speaker. You can find these a pawnshops musician's exchanges craigslist too, where bands dump their gear when leaving the road.
Don't buy early CS800, rev A,B,C they hiss at 1 or 2 W and have op amps you can only buy from Peavey. Buy the ones with the "wind-tunnel" design, vent grill in the middle of the front.
I learned a lot crawling through a PV-1.3k replacing 124 parts, but no-one needs 650 W/ch for home use.
Dynaco solid state is a laugh, I'm listening a ST-120 right now but it takes a 7 transistor/ch djoffe bias board to make it sound good. Also needs more heatsink. Heathkit AR-15 are not too bad except the possibly laughable amateur soldering.
Don't buy a SWTC tiger anything, they blow up without modification.
Allen S-100 organ SS amps aren't bad either, I've got two working great in a 300 organ at a church I attend. Went to 2 watts in 2017, the donor church wanted rid of the organ, "obsolete". All new e-caps, back to 100 W. Monster heat sinks for fan free 100W hours at a time.
BTW triodeelectronics.com still has ST70 and MkIII MkIV dynaco tube amp clone kits. The instructions tell you where to route every wire to avoid hum. There are a million upgrades for these online since so many were sold. I'm having trouble with a 7199 after 49 years, they are expensive, have a triple 6sc7? board to put in which allegedly sounds better. Not urgent, the upgraded ST120 and CS800s sound better, use less electricity, and don't have the problem of one of the new 6CA7 output tubes I bought in 2012 shorting after 12 hours on.
Cheapest .015 % hd solid state amps are blown up Peavey PV-4 PV-8c, CS800x, CS800s, CS600. Look on e-bay "amplifier for parts or repair". Complete schematics are available and Peavey sells some of the unique parts. Prices are high now, everybody apparently repairs amps in the winter. I got a PV-4 for $20 including freight last spring. I bid $27 but ebay wouldn't give it to the guy since nobody else bid. $50 in output transistors & new rail caps, works great on my HDTV instead of a Samsung $180 "sound bar" with the "miracle" 3" woofer.
QSC & crown amps are also highly respected, but don't buy a DC300. You don't want DC on a speaker. You can find these a pawnshops musician's exchanges craigslist too, where bands dump their gear when leaving the road.
Don't buy early CS800, rev A,B,C they hiss at 1 or 2 W and have op amps you can only buy from Peavey. Buy the ones with the "wind-tunnel" design, vent grill in the middle of the front.
I learned a lot crawling through a PV-1.3k replacing 124 parts, but no-one needs 650 W/ch for home use.
Dynaco solid state is a laugh, I'm listening a ST-120 right now but it takes a 7 transistor/ch djoffe bias board to make it sound good. Also needs more heatsink. Heathkit AR-15 are not too bad except the possibly laughable amateur soldering.
Don't buy a SWTC tiger anything, they blow up without modification.
Allen S-100 organ SS amps aren't bad either, I've got two working great in a 300 organ at a church I attend. Went to 2 watts in 2017, the donor church wanted rid of the organ, "obsolete". All new e-caps, back to 100 W. Monster heat sinks for fan free 100W hours at a time.
BTW triodeelectronics.com still has ST70 and MkIII MkIV dynaco tube amp clone kits. The instructions tell you where to route every wire to avoid hum. There are a million upgrades for these online since so many were sold. I'm having trouble with a 7199 after 49 years, they are expensive, have a triple 6sc7? board to put in which allegedly sounds better. Not urgent, the upgraded ST120 and CS800s sound better, use less electricity, and don't have the problem of one of the new 6CA7 output tubes I bought in 2012 shorting after 12 hours on.
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THANKS everyone!
I DO appreciate all the ideas. In my first post, I mentioned I will NOT build any amp!
I think this forum can teach me a LOT!
I am thinking to BUY a tube preamp, headphone amp, and possibly hook up the tube preamp to a solid state power amp.
dumb questions.
1. which brands do you like? Primaluna tube preamps? other
2. which brand headphone tube amp? Schiit? woo audio? Feliks audio? all look really really nice!
3. when I do get one, i will ask about tube rolling, something for me to learn about
.4. which SOLID STATE power amp do you like? Pass Labs? McINtosh, other?
With respect, I am NOT going to build any equipment, but would like to learn about tubes!
thanks again!
Bob
I understood your position when I posted the link I did. If you read the book a few pages at a time it is 'colorfully' written and pretty easy to digest.(Fun with 3D glasses too!) Once you get through the first few chapters you'll have some understanding of what's going on inside the tube. Not that it makes a lot of difference in terms of just buying and trying a tube but it will give you a sense of some of the possible variables inside the tube that can make a difference to what you hear. After that, all you need is access to a listing of tube equivalents . . . which can easily be found in many forms.
Also, some tube types have more equivalents/alternatives than others so if you're heading into this with the main intent to try lots of different tubes then you'll be happier if you research the possibilities before you buy the preamp.
Old Bob,
If your main goal is to make an informed decision for your planned purchase by learning about tubes, my suggestion is to get the book "Designing high fidelity tube preamps" by Merlin Blencowe. This book has been published 2016 and still in print. The old (and free) classics that have been suggested previously are excellent books and some of them are much better at explaining the physics, but I assume that you are more interested in practical aspects such as the differences between capacitor types and design choices, and also you are asking informations about the tube preamp section and not the power amp. Starting from chapter 2 of this books you will find many answers to the questions you may have. This book is focused on audio, instead of the radio focus of most older books, and it does describe today's electronic landscape. If you choose to dive deeply on this book and you have enough technical background, you may even design a preamp yourself that fullfills your exact specifications and taste and only costs a fraction of a comparable commercial product. But even from a quick read you may gather enough information to do a first evaluation of a commercial product and put the sales pitch in the right context. You will learn, as example, that tube rolling can't turn a bad product in a gem, and why.
If your main goal is to make an informed decision for your planned purchase by learning about tubes, my suggestion is to get the book "Designing high fidelity tube preamps" by Merlin Blencowe. This book has been published 2016 and still in print. The old (and free) classics that have been suggested previously are excellent books and some of them are much better at explaining the physics, but I assume that you are more interested in practical aspects such as the differences between capacitor types and design choices, and also you are asking informations about the tube preamp section and not the power amp. Starting from chapter 2 of this books you will find many answers to the questions you may have. This book is focused on audio, instead of the radio focus of most older books, and it does describe today's electronic landscape. If you choose to dive deeply on this book and you have enough technical background, you may even design a preamp yourself that fullfills your exact specifications and taste and only costs a fraction of a comparable commercial product. But even from a quick read you may gather enough information to do a first evaluation of a commercial product and put the sales pitch in the right context. You will learn, as example, that tube rolling can't turn a bad product in a gem, and why.
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