PaulyT said:
It's on the same page that I mentioned about the other deviations from the parts list:
http://www.tubelab.com/
Scroll down towards the end...there is a big section on the Tubelab SE. About those resistors, he says "Increase the grid stopper resistors on the 5842 (R31 and R32) from 1K to 4.7K ohm. These resistors should be carbon composition if at all possible."
So he updated the value, but left them as metal film. I think you will be OK. Do what I do: create a spreadsheet or text file of parts you would like to have the next time you make a Digikey/Mouser order. Next time, pick up a few OD472JE-ND's and have them on hand in case you have issues.
I put my 5842s up on socket savers in preparation for upcoming chassis construction. With the 4.7k CCs there, I have not encountered any oscillation issues that I can detect. If you are using the stock sockets, you should be fine with the metal films.
http://www.diyaudio.com/forums/showthread.php?postid=1853638#post1853638
Oh, I see it now, thanks. It's kind of a pain when instructions are spread out over multiple pages, and not even grouped under the individual design sections...
I'm not going to use socket extenders since I'm not going for any particular tube height equivalence. They'll all be inside one big box anyway.
But just for my own edification, why are carbon resistors preferable here?
I'm not going to use socket extenders since I'm not going for any particular tube height equivalence. They'll all be inside one big box anyway.
But just for my own edification, why are carbon resistors preferable here?
PaulyT said:
I asked a similar question in my thread:
how can a resistor sound good
Nine pages later - I still didn't get a clear answer. The only thing I took from it is that the individual designers experimented with different resistor types in different parts of their circuit and found that some performed better than others...
Metal film resistors are constructed by depositing a metal film on a ceramic base. The film is then cut in to a spiral to give the correct resistance. This spiral can be inductive. Carbon composite is non inductive, hence better for reducing oscillations as stoppers. That is my understanding...
I missed this too. So now I have two parts to order... Still not enough to get over the $5 handling charge... The digikey part number for a carbon 4.7k 1/4w is OD472JE-ND.
George's site has so many pages that are hard to get to, it's actually fun to go back and see where some odd page might lead me. I spent some time the other day reading about some of the drag races and car shows that he attended.
for some reason a line from an old text only unix game comes to mind:
"You are in a maze of twisty little passages, all alike"
If you are reading George - its all in good fun
PaulyT said:
You mean something like this?
Personally, I would use that on top of shallower chassis that covers the board and other parts except for the tubes. That way, it can keep the dust off of it and let the tube's heat dissipate outside. Then the cage will protect the tubes while letting it vent.
Evenharmonics said:
Thanks! Yup, that's kind of the general idea. Ideally I'd like to have a clear plexiglass front so you can see all this stuff I'm spending so much time and $$ on... But yes, I want to have one big enclosure that contains the entire board+tubes and transformers, choke, run cap, etc. Not sure if/where I can find something big enough for all that, hence my thinking I'd end up building my own somehow.
Suggestions are welcome though. Do you know how big those dynakit enclosures are? They don't seem to list detailed specs on their site...
oldmanStrat said:
Yeah, I did that too, fun indeed. Saw the car he's rebuilding almost completely from scratch. I reached two conclusions: 1) he is a smart guy with too many simultaneous projects, and 2) he never wears a shirt.
Ha! I've played that one too... wasn't that Zork? Except I played that (originally) on an Atari 800.
PaulyT said:
Yeah, I did that too, fun indeed. Saw the car he's rebuilding almost completely from scratch. I reached two conclusions: 1) he is a smart guy with too many simultaneous projects, and 2) he never wears a shirt.
LOL - I'd have to agree!
When I first played the game it was called "adventure". We would run it on the command line of a PDP 11... this was back in the early '80s.
PaulyT said:
Yeah, I did that too, fun indeed. Saw the car he's rebuilding almost completely from scratch. I reached two conclusions: 1) he is a smart guy with too many simultaneous projects, and 2) he never wears a shirt.
Haha...yeah he does like to go shirtless...he's in FL afterall. I could never survive down there...humidity just kills me. I was also intrigued by some of his car pages as he actually knows something about the cars I drive....
PaulyT said:
"It is pitch black. You are likely to be eaten by a grue."
Zork II. I played it for hours on end on our first home "PC": a Xerox 860 (CP/M) with dual 8" floppy drives! It was a hoot.
Yeah, my friends and I were really into those text adventures. You can actually get a modern windows application that acts as an inteprepter for those old Infocom adventure game files, my best bud from high school actually wrote one not too many years back. We even found collections of the files somewhere, might even have been from ex-Infocom folks. I think I have most of them stashed away on my PC somewhere.
Ok, another part I missed in my initial reading of the instructions. Looks like I will need to find an additional larger heatsink for the D1+U1 pair, since I will be running 300B's, right? Are there digikey parts for this? I have some old computer bits&pieces, I might be able to find something...
Anything with the right spacing will do...actually it's the regulator (the 5-pin device) that needs attention. The dual Schottky will be happy with just the original heat sink, so as long as you manage mount the regulator to the aux heat sink, it will be fine. The regulator has thermal protection, so it will simply switch off if it overheats. I clamped a squangle to the original heat sink when I had shutdown problems.
As pointed out a carbon comp resistor is non inductive, and most metal film resistors are spiral cut which makes them an inductor, a lossy inductor. That said most carbon comp resistors are noisier than metal film resistors, and the worst place to put a noisy resistor is on the grid of the input tube. Which do you use? That depends! If your input wiring is clean and routed away from the PC board, I would use the metal film resistor (that's what is in my amps). The 5842 tube is capable of operation at 200 MHz or more and it will oscillate if you give it a chance. Since I can't control what people will do with their amps (and I have seen some strange stuff) I tend to recommend the conservative approach.
Yes, the board assumes "standard" sized parts. As manufacturers use materials capable of higher temperature operation, resistors get smaller for a given power rating. I have seen resistors rated for 2 watts that are the same size as a half watt carbon comp from the 1970's. If you actually run 2 watts through it, it will operate at about 75 degrees C. The little parts are a bit funny looking, but seem to make less noise than the old larger parts.
I used 5 watt resistors in most of my earlier builds. They get pretty warm, but there have been no issues with them. I have noticed a strange upward creep in the negative supply voltage over the past 4 years. I have notes that I took during the development of the board that show a negative supply voltage in the -140 range with the small transformer (45 amp) and - 180 volts on 300B amps. People are now reporting voltages from -230 to -260 volts. I believe that this is related to the rather distorted line voltage that we are now receiving. My line voltage is routinely at 10 to 12% distortion, and the voltage is usually 122 volts or higher. This makes R6 and the mosfets run hot. My last board builds used a 6.5 watt Dale resistor. They get hot, but this is normal. R6 dissipates 4+ watts, even a 10 watt resistor will get hot.
I haven't built a single amplifier since mid 2007
Life's little gotchas got me pretty good last year, but 2009 has been somewhat better. I plan to build a few amps this year (although I may sell most of them) starting with a Tubelab SE. I started construction on a conventional looking Tubelab SE using socket extensions to raise the tube sockets 1.5 inches over a year ago. It was never finished, and I sold the populated PC board that I made for it. So, I have the wood and Lexan cut, the BIG Edcor OPT's, a motor run cap, a choke (cheap Triad with end bells added) some tubes, and a Hammond 272JX power transformer. I may order a "rknize" Edcor, if it fits my (already drilled) Lexan top plate. Anyone got the dimensions? It has been a while since I spent some time tweaking out one of these boards, and now since I get to build a new one, I will have a chance. It is possible that some component values need revisiting.I know that my web site has become disorganized. Sometimes I can't even find stuff on my own site! I started the web site about 6 years ago using Front Page and just kept adding to it until it got out of hand. I started doing a completely new site using Expression Web, but never found the time to finish it. I know analog, digital, and RF design. I can write enough "C" or assembly to build embedded systems, but I don't claim to know much about web site design, and my organizational skills suck! I am not familiar with Joomla, but I found their web site and will check it out.
I came to the "too many projects" conclusion about 5 years ago when my father passed away, and Sherri's stepdad passed away the following year. We spent about two years going through their lifetime collection of "stuff" and unfinished projects. We realized that each of us has more projects than we could complete in TWO lifetimes, so some had to go. We have been going through our own "lifetime collection" and selling or giving away the projects and "stuff" that we realistically will never get to. Yes, I recently gave away a 2 KILLOWATT Crown audio amplifier, a dead McIntosh (really ugly) and a bunch of other stuff and my tube collection has been pared from over 100,000 to less than 20,000. I am not done yet.
The Challenger is another one of those unfinished projects. The previous owner had rebuilt the motor and transmission, but had no clue! I got it cheap, and pulled the motor for a rebuild. I kept finding more problems which got the snow ball rolling. The car has been unfinished for about 10 years now, and I haven't had the time to touch it in 4 years. All of the hard mechanical stuff is done, the car runs but has no interior or wiring and I am using a tool box for a seat. Not exactly street legal. I don't see time to finish it any time soon, but I can't bring myself to sell it, yet.
One of the things that I inherited from my father is his propensity to sweat. 5 minutes outside in the Summer will leave me soaking wet. We grew up in Miami and did not have air conditioning until I was in high school. We didn't have a clothes dryer either, laundry was hung outside to dry. I was one of three messy boys. We had a lake in the backyard and getting wet was a daily occurrence. Shirts and shoes were not needed or encouraged when going outside to play, or around the house. OK, 40+ years have elapsed, but I haven't changed much. I tend not to wear shoes or a shirt around the house or yard, and I still jump in the pool whenever I feel like it even in January!
I spent the day outside today mowing the lawn and fixing Sherri's car. The thermometer in the shade on the front porch topped out at 96 degrees, and it was a typical sweltering June day zero breeze and 85% humidity.
I did spend a few years tinkering with the Dodge Turbo 2.2 in "L" bodied cars. There were several others at work who had similar cars and we all autocrossed them. This was front wheel drive racing with American cars long before the import "sport compact" scene had begun. One of the guys who we hung with at the autocross races actually quit his day job and got a sponsor so that he could race Neon ACR's professionally. When I first started building my first turbo car, I had a carburated 1982 OMNI with a blown transmission. Direct Connection published a book dealing with these cars. I called the phone number listed in the book and got to speak to Carroll Shelby. He was extremely helpful and convinced me to stuff a 160 HP turbo motor in place of that old 82HP wheezer. That car reached 154 MPH, bouncing off of the 7200 RPM rev limiter in fifth gear. Just another hobby that I no longer have time for.
tubelab.com said:
Dimensions, including the little extra on the Edcor end bells: 3-7/8"H x 3-1/4"W x 4-1/4"D
The Hammond 193J end bells fit perfectly to it, so I imagine any of their chokes/transformers with the same core lamination size will also work. With those bells, the height and width are 3-3/4" x 3-1/8". The footprint is 2.5" x 3".
I hear ya there. My minimopar site is very dated and rather unruly. It's all done in raw HTML. I've recently switched to WordPress for my personal site, but am also looking to Joomla to ease maintenance of other sites I maintain.
My motivation to work on cars is not at all what it once was. The CSX has been sitting for two years now, think...
Ditto
Joomla doesn't guarantee an organized web site, but it does simplify creation and management. One nice thing is that you can have many people contributing content - and you can assign access permissions to each. There are also forum, web store etc plugins for just about anything you can imagine.
For ten years I auto crossed and club raced my Porsche 944S2... most fun you can have with your pants on
But that hobby is way too expensive to maintain in this economy ... once the car sat for over a year with out me even starting it, I knew it had to go to a better home.Now playing with tube amps and guitars substitutes for apexing the bus stop at Watkins Glen
I envy your weather - we have had an unusually cold and rainy spring/June here in the northeast.
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