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PostPosted: 27 Dec 2013, 20:38 
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Joined: 05 Nov 2010, 21:07
Posts: 702
Location: South East US - Tennessee
EdV wrote:
Aloha,

......Can tubes be installed in the horizontal position?

....With all of the grounding issues I read about is there any advantage to running a separate earth ground out of the chassis?
Ed


Can tubes be installed horizontally? Yes. There are a few older types (filamentary cathodes (DHT)) that you need to consider the alignment so the filament, which is also the cathode, does not droop towards the plate. One such tube would be the 300A/B. You can find the information regarding mounting position from the tube data sheet, and you can find most of those on Frank's Electron Tube Database.

Grounding... My first question would be, where would you then go with that "separate" earth ground? UNLESS you're connecting a phonograph, there is no benefit to having a separate earth ground lead. You would connect that lead to the grounding terminal of the phonograph.

As far as expanding your knowledge, there are a number of good books you can look at. I would suggest, however, you start with a basic electronics tutorial so you can learn the various terms, symbols, and generally how things work. After that, you can look at some more advanced stuff such as Vacuum Tube Theory Basics Tutorial. For an in depth look at tubes and applications, you can look at Herbert J. Reich's Theory and Application of Electron Tubes . :!: CAUTION: It's a l-o-n-g read and chock full of algebraic formulae, but it fully explains everything you ever wanted to know about tubes including design applications. Covers power supplies, amplifiers, etc. It is considered by many to be THE vacuum tube "bible". ;) Another good read is the RCA Receiving tube Manual, issue 30. While generally intended as a cross reference for tubes, it contains a lot of good information regarding tubes, how to calculate loads, etc. Not as in depth as Herbert Reich's book, but is a good fundamental resource.

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The key to a successful build is to keep the smoke IN the circuit.
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We cannot solve our problems with the same thinking we used when we created them. - Albert Einstien
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LM380 Bridged Guitar Amp, Oatley K301 Phono Pre-amp, Oatley K272 Headphone Amp, Tube proto-board


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PostPosted: 29 Dec 2013, 22:27 
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OK. Something to address that's popping up as of recent: "Stability of heater power supplies"
There seems to be some misconception that there needs to be some "elaborate" schemes for powering the filaments of tube projects.

IN THE BEGINING, there was darkness. A deep, cold darkness. We lit the way with candles or oil. Then a great inventor gave birth to the electric light bulb. Shortly following, that same man invented the vacuum tube, first the diode, then the triode. These were early filamentary cathode types. Course, we know this man was Thomas Edison. Course, he had to have a power source, right? Yes, and it was DC (direct current). Then, one day, another famous inventor introduced us to a different form of voltage: Alternating Current (AC). As time went on, AC became the standard power source, much to Edison's dismay. You see, Edison, using a DC generator built by the man who would give us AC, felt DC was the best way to power the world. He was wrong. But I digress. However, there is a point here. While DC, in the form of batteries, was the predominant power source early in tube tech. With the success and growth of the AC power grid, battery powered "sets" slowly became replaced with AC powered sets. Now, granted, early radio and TV did not put a whole lot of design of super clean power supplies, they were clean enough for the average user. The one place they focused very little design effort was in the filament supply. Why? IT WAS NOT NECESSARY. The same holds true today. Filaments are nothing more than resistive loads, nothing more, unless you're dealing with 5U4GB or 300B or the few other popular DHTs. In those few types (DHTs), the filament is also the cathode. Which opens up a whole other can of worms. However, DHT filament supplies need not be extravagant, though there are some design considerations that go with having to combine filament power with cathode bias. But since most of the tube set being hobbied together now are non-filamentary cathode types, that is they have separate filament and cathode elements, it is only necessary to provide either AC or DC at the appropriate voltage and current capability for the filament. 6 - 6.5v for the "6volt" types and 12.3 to 12.8 for the "12volt" types. Too much shortens filament life, to low sets up a condition called "starvation" - the tube isn't quite warm enough for efficient operation. So, folks, when designing your filament supplies, just focus on getting the proper voltage. Don't worry about "stability". Don't worry about "cleanliness". Is the voltage correct and are you providing enough current for the total draw. How do I know my total draw? Simple. Using the tube data sheets for your particular tube (type and manufacture), find the filament current. Then take those values and add them all up, that's your total draw. Multiply that sum by 1.5 and that should get you a good source current you need to provide. For example, if your total draw is 1 amp, you need to use a power transformer that can muster 1.5amps. That 1.5 multiplier is the absolute MINIMUM value. You DO have to consider inrush current. Cold filaments pull slightly more current than when they're warm. It doesn't hurt to go bigger. Now, I'm not going to get in to the AC vs DC argument here. I have my preference and my own reason for that. Just remember the KISS principle (no, not the killer rock group): Keep It Simple, Stupid. The most KISS way is a dropping resistor in series with the rest of the circuit. It'll even absorb some of the inrush, thereby easing the initial load on the power transformer.


Oh. And that "other" inventor I referenced? None other than Nicola Tesla. The REAL father of radio, and just happens to be the father of the modern AC electric power grid. Not to mention a myriad of other inventions we use every single day.

:beerchug: Cheers!

_________________
The key to a successful build is to keep the smoke IN the circuit.
-Les

We cannot solve our problems with the same thinking we used when we created them. - Albert Einstien
_________________________________
LM380 Bridged Guitar Amp, Oatley K301 Phono Pre-amp, Oatley K272 Headphone Amp, Tube proto-board


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 Post subject: Re: Info for beginners!
PostPosted: 15 May 2014, 07:24 
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Joined: 11 Jan 2013, 09:13
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Location: Barrio Garay, Almirante Brown, Buenos Aires, Argentina
91lieb wrote:
4: Large capacitors can hold a charge for a long period of time which means a circuit can be live even when it is disconnected from the mains/power source, discharge them by shorting them with a resistor for a few seconds, I use a 10 Ohm 10W wire-wound resistor.


I prefer to use a normal filament lamp (or more of them in series to get the necessary voltage) to discharge caps, some of them may become faulty if high current (charge or discharge) is passed through them. Also, lamps tell me when caps are really discharged, and they stay here using crocodile clips until next power on. I use it when repairing high voltage AC frequency converters..

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PostPosted: 21 Sep 2014, 13:54 
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First I'd like to introduce myself. I've been fascinated by electronics since the President's initials were LBJ. I've been fortunate enought to have some great teachers over the years, including several WWII vets. My first year of High School was also my teachers, who had been recently laid off from NASA after worknig on the design of the Voyager transmitters. I pretty much lived and breathed in "Electric Shop" as it was called back then.

Though not a "beginner", in those days tubes were being phased out. Most of what I did were repairs on tube TV's, phonos, radios, etc. But after years of "board swapping" as a medical equipment tech, I longed to do some of the playing around I did back then. Lo and behold! All of you great folks "keeping the filaments glowing". Since about the beginning of the year I've poured over countless forums, schematics, books and how-tos. I'm currently in the process of breadboarding my first amp, concocted from pieces of others I've seen and based on the stuff I've hoarded over the years. Thank God (Al Gore? :D ) for the internet! Thusfar I have avoided asking questions directly and have been able to find what I need to piece together this first amp.

Which brings me to my "beginner" question. The RCA manual has several amps in it's back section. The 30-watt and 50-watt ones call for an output transformer with a "5000 ohm plate-to-plate tube load". I also found a chart on one site that listed "Push Pull Plate to Plate" "Primary Load Impedance" for the 6L6 as 10,000 ohms. The book lists "plate to plate", the chart lists "primary load". Edcor lists it's transformers as (example) " push-pull tube output transformer for 10K Ohms", but doesn't differentiate. Since these things aren't cheap, I was hoping someone with more experience that I could elaborate on the different terminology.

Now, to give a little back. I've found a couple of vendors I haven't seen mentioned. One is "Surplus Sales of Nebraska". They have quite a selection in parts, and even some surplus military power supplies (I bought 2). The other one is "www.esrcvacuumtubes.com". They currently have a 10 for $10 sale on some tubes. I bought 10 5GH8s, 25CU6s and 12CU6s for 30 bucks!

The first picture is of my home made breadboard with the driver (6SQ7, credit to Wes Kinsler) and putput stage (6DQ6B) I've also tried 6BQ6s and they work fine, but seem to have a little less bass. You can also find the 12, 17 and 25 volt versions much cheaper. My power transformer is an medical grade one from a xenon light source. It has 2 120 volt windings and a 24 volt that I will be using with 25DQ6s. I'll use a seperate 12.6 volt transformer for the filaments of the preamp tubes, possibly even solid state voltage regulators to reduce hum. I did have a tone control section (6SN7) and a Mag pre-amp (6F5 and 6Q7) on the board. These worked great, but I disconnected them to play around with different output tubes without getting "squealed" at and "thumped" at!

The other 2 pictures are of the "Collins Power Supply" from Nebraska Surplus, $85. It uses 2 3B22s and a 6X4. I'll re-wire the relay socket as a power outlet, and put delay relays on the amp chassis. "Electronic Goldmine" has some 24vac coil delay relays with 0-10 second delay. Replace the 1meg pot on those with a 10 meg resistor and you have a fixed delay of 100 seconds. Less than $10 each.

Now, if I could just avoid real work :bawling:

Cliffystones


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PostPosted: 19 Mar 2015, 16:25 
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Joined: 14 Mar 2015, 16:58
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Hi everyone

Greetings from a beginner from South Africa. I am an engineer (recent graduate), but have never dealt with valve amplification (or anything to do with valves (or in fact audio) at all), though I've been fascinated by this for a long time. I'm looking to start with some basic audio projects (such as a small 12AU7 preamp that I've seen mentioned a few times). I've spent a lot of time on these forums and with other sources, and understand the majority of what I'm reading, but have a question which might seem really idiotic to the rest of you, but here goes:

Most schematics that I've consulted say something along the lines of 'ONLY ONE CHANNEL SHOWN', and was wondering how the other is hooked up in these cases? If it's RCA or some other configuration with two physical connections for output, would I just double up the schematic and connect one to each (and if so, how would the input be connected?), or am I missing something fundamental?

Please, if at all possible, link me to some resources or something which would make this understandable to someone with zero experience.

Thanks in advance,

Daniel


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PostPosted: 20 Mar 2015, 19:29 
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Joined: 21 Sep 2014, 12:07
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I think you need to better understand what "channels" means. One for mono or "Hi-Fi", 2 for stereo, 4 for quadraphonic, etc. You can actually make 2 seperate amps, hook one to the left speaker, one to the right. Your source has multiple outputs usually. An older piece of stereo equipment will have 2. Nowadays you'll see these surround setups with 6-8 seperate channels and a subwoofer.

You can just build the one channel as a seperate amp, then a second. What these schematics mean is that the componets for the amplifier portion need to be built in duplicate times the number of channels you desire. The only section you need not duplicate is the power supply, but it must be connected to the same points on both channels to supply the DC to power the amp sections.

I would suggest that you aquire or download some manufacturer's schematics from some older stereo amps or recievers. One of the good things about troubleshooting stereo amps is that if only one channel is bad, you have another working channel to compare readings with.

I hope I have helped, and wasn't to annoyingly simpleton in my approach.

Cliff Shelby
Castle Rock, Colorado


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PostPosted: 21 Mar 2015, 14:29 
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Joined: 14 Mar 2015, 16:58
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Thanks so much. That's exactly what I needed to know :)

Daniel


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PostPosted: 03 Apr 2015, 16:45 
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Joined: 03 Apr 2015, 15:20
Posts: 1
Hi. There are a lot of attention to safety and it's very good! I am a beginner and for a time engaged in the construction of NP-100v12 - 12AU7 / IRF510 project. And first what I encountered, how to safely make PCB at home. And, beginners need, safe and no hard chemicals. Not going to talk about how to put a picture, it can further protect it to make a marker for CD. Next, we need to citric acid, common salt and hydrogen peroxide, that's all. So, take the container is lowered into the workpiece, pour hydrogen peroxide, sprinkle or pour lemon juice and sprinkle salt, salt is the catalyst for the reaction of her a lot will not, pour more, then follow the process. For hands safe, but better than a blank check tool. The process takes different times, depending on the thickness of the copper coating. I hope that someone that will be useful. Thank you.


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PostPosted: 24 Apr 2015, 01:46 
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Joined: 29 Oct 2014, 12:32
Posts: 95
Location: Russia Komi republic
Greetings! I'm from Russia. Lamp with me for a long time. It all started with my hobby - I play guitar. So I met with tube amps. Now I started to the world of Hi-Fi. Almost finished forevatt preamp. So my question is another question "ONLY ONE CHANNEL SHOWN". Lamp 12au7 this dual triode. I can make a connection for two tubes mirror for easy wiring? I drew what I ask. Of course, the connection of heaters remains the same, that I can understand. Thanks in advance! Yours!


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PostPosted: 24 Apr 2015, 07:23 
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Joined: 04 Nov 2013, 21:18
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Location: Florida
I just draw both channels for my own clarity... I have to see the whole thing to understand it...

Image

Image

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