Morgan Jones tube amp
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fyleow

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I'm contemplating this for my next project. It doesn't look too hard to build without a PCB and just hand wiring the stuff but I am concerned about the power. Since tube amps need a lot of power how dangerous is it to build this amp? I don't want to get electrocuted or anything....

How does it sound compared to the META42? I know that they are different as one is solid state and one is tube but do you think it would be an upgrade? I've never really tried tube amps before so I don't know the signature sound that comes with it...
 
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andrzejpw

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You have to be careful with tube amps. You're running more than 100 volts. I'm also interested in how it compares to the meta42, because I just built one.
 
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fyleow

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Well here is my dillema I just built a META 42 and I'm looking for more challenging projects now. The problem is I am probably better off just upgrading my player (Nomad Jukebox 3) than my amp again. The exception is a Tube amp because they are supposed to give a different "feel". On the other hand I don't want to risk electrocution
.I could try to build ppl's amp but I would need someone to help me out and explain stuff and if I remembered correctly it required two different power supplies to operate. I also have no idea how it sounds compared to the META.

I tried asking for some DAC plans and people were very helpful but most pointed to very complex (at least for me) designs that I had no clue on how to start on.

So now I am just bored. Great soldering skills but no circuit design know how at all
 
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AssafL

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The voltages present in a tube amplifier vary wildly between designs (and so the risk factor), so less risky lower voltage designs should be available.

If you do plan to build a tube amp, remember that capacitors retain voltage across them (while discharging) and can shock you some time after disconnecting the voltage. Also, DO NOT do any measurements or adjustments if you do not fully understand the high voltage circuitry (ask a technician for help). Shorting a high power, high voltage supply is nasty at best...

BTW, Last AudioXpress had a very interesting and dangerous, very complicated power amplifier design. Perhaps this is the time to get an Electronics for Beginners book...
 
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andrzejpw

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CaptBubba

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The best thing to do would be to use a variac to bring the voltage up slowly.

All it takes is a little more caution to work with high voltages. Just use a resistor to discharge all capacitors, and always hold one hand behind your back until you have made sure that no charge is left in the amp. Hook the negaive lead of your mm to the ground of the amp, and then use the hand not behind your back to go around the amp checking voltages.

It is kinda like the difference between playing darts with plastic tipped ones and real, metal-tipped darts. Yes, you are less likely to hurt yourself with the plastic ones, but as long as you use a little common sense with the metal ones, you'll be just fine.
 
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fyleow

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Thanks for all the advice guys. AssafL the Morgan Jones is "only" 200 volts so I guess it's less risky.

Andre I think the main problem with DAC is that all the DAC chips are SOIC only, it becomes very difficult to build unless you have a PCB made. I don't think that is too hard though since the schematic is provided for it.

Unforunately I don't have the link to ppl's amp anymore. I'm also really reluctant to build another SS amp unless I know it's going to be better than my META 42. Tubes interest me but the high voltage doesnt


Capt I read somewhere on Bottlehead that I can just put a resistor in the circuit and it will slowly discharge the capacitors over time. That seems to be an easy way out of it.

In any case I think I will need to get more knowledgable in this field before I start anything. If anyone has some suggestions for books in mind let me know.
 
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braillediver

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I'm really impressed with the MG Head and was looking at the Morgan Jones Tube Amp also. The earmax pro runs $750 and if this is comparable to it I'm game. I keep wanting to make an ultimate META42 for home use but this might be a better choice for the money.

A little caution and common sense is needed. I was thinking about bread boarding it on a piece of plywood until the circuit is working then moving it into an enclosure.

Please keep us/me posted on any progress you’ve made and maybe indicate where you get the parts.
 
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fyleow

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I noticed that the designs shown in the library are only one channel. It mentions adding another tube for stereo but on the completed projects there are only 3 tubes. So how do you make it stereo and were the completed projects shown only mono?

What types of capacitors do i use in the circuit? The only ones I saw were all rated for DC voltage and not AC....

Also I was wondering if the power supply can be bought instead of built myself? If not what kind of transformer is used in the power supply circuits? It doesn't say.

Thanks.
 
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CaptBubba

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Each tube is a dual triode (I think, tired at the moment). Basicly the amp needs 3 triodes/ch, and each tube has two. So you need six triodes for stereo, hence three tubes. I think you can use one tube for the input of both channels, and then use one tube/ch for the output.
 
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fyleow

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I still don't understand though. The diagram has 3 tubes but it says one channel?
 
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CaptBubba

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The diagram shows one and a half tubes. Look next to each of the "tubes" and you will see a thing that says 1/2 Vx. That is one half of tube x.
 
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fyleow

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Ahh ok I see it now. But I'm confused how to wire this thing now for stereo. They should make a diagram for stereo for the dumb people
 
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AssafL

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Sometimes they add the second channel in brackets. I.e. 3 (7) which means pin 3 for left, 7 for right. Sometimes they have the second channel in a pinout table.
If neither exist, you will need the pinout of the valve to identify what is the pinout of the second device in the valve. You will have to wire it exactly the same (only different pin numbers).
 
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fyleow

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I'm thinking of picking up Valve Amplifiers by Morgan Jones to get me started. I think it will help since I am clueless about most of this stuff. Anyone recommend this book for a beginner? Based on the reviews from Amazon it looks like he explains the stuff pretty well.
 
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