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Thread: Tube amp....It's alive....and so am I!

  1. #1
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    Tube amp....It's alive....and so am I!

    Last October I finished my first electric guitar for my 16 year old son. http://sawmillcreek.org/showthread.p...ghlight=guitar
    We were encouraged enough by the sound that we thought it merited a tube amplifier, but the CFO (LOML) wouldn't "buy" into our enthusiasm . The fiscally acceptable solution was to build one....a 3 watt, Class A "night light" from mostly salvaged parts. We used the chassis and power transformer from a 1939 Stromberg Carlson radio. This project has me way out of my element, but after several weeks of headscratching, several revisions to the schematic, and several feet of solder up in smoke, she finally glowed and sang to us tonight! Woo Hoo!

    It seemed like every tube amp website I looked at had huge "WARNINGS!" about how the high voltages of these things can kill you if you don't know what you're doing. So with one hand safely tucked in my pocket, I poked and prodded enough to gain some confidence that this thing wasn't wasn't going to become a turbo charged pacemaker for anyone. All systems go so far, but there's still much work to be done. The plan is to clean up the layout, then stuff the whole thing in a box from a 1928 American Bosch radio. I'll post some pics once it's presentable.....right now I'm just happy that it works and that no one got fried!
    Last edited by scott spencer; 12-13-2006 at 08:44 PM.
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  2. #2
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    Awesome. The guitar thread definitely belonged in the OT forum, but I think maybe this thread should go in the Neander forum. Very few people make their own tube amps. When you figure out how to convert a woodworking lathe into a LP cutting lathe to cut your own records, that one goes in the Turning Forum.
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  3. #3
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    Very neat Scott, does your 16 year old and friends think dad is a square, or do they think he is a bit cool

    Cheers!
    The pessimist complains about the wind; the optimist expects it to change; the realist adjusts the sails.
    William Arthur Ward

  4. #4
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    Cool news to see you got 'er done, Scott. I'll bet it sounds nice and rich at lower volumes, and good and crunchy when it's cranked up.

    Regarding the high voltages, I learned about that (and about how capacitors store electricity) as a teenager replacing the power switch on my old Fender Deluxe Reverb. I had unplugged it, and was in the process if removing the broken switch, when my hand bumped something and ZAP! I was given a healthy shock. I scratched my head, double checked to see that it was unplugged, the went back after the switch. ZAP! again. I was thoroughly confused, since I couldn't figure out what I was touching to get the shock, and how I was getting shocked after unplugging the amp.

    Long story short, I found that the clipped-off end of one of the wires to the switch was still hot, and my hand had been brushing against the little bit of copper that was exposed on the end of the wire. When I finally tracked it down and put my voltmeter on it, it still had several thousand volts hanging around in the capacitor, waiting for the next ZAP!
    When the going gets weird, the weird turn pro. - Hunter S. Thompson
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  5. #5
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    Question...

    Thanks for the "plug" gang! Many thanks to Tom Pritchard and Ahmet Becene for answering countless questions. I'd probably have curly hair and Marty Feldman eyes if not for you guys!

    QUESTION FOR YOU GUITAR PLAYERS: (love that emoticon! ...wonder who's idea that was Vaughn?! )

    This amp lacks reverb. Danelectro has some effects pedals for < $20...my son has the "Overdrive" and "Distortion" pedals, which he likes....which of their pedals is closest to reverb..."Echo" or "Chorus"? ...and what's the "Flange" do?

    There's a pic of the box she's going into below:
    Attached Thumbnails Attached Thumbnails boschampbox.jpg  
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  6. #6
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    Echo would be the closest to a Reverb. Both Chorus and Flanging also have pitch bending involved which doesn't sound much like Reverb. You could probably pick up a Spring Reverb Unit specifically made for guitar amps for next to nothing though.
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  7. #7
    Sounds like a fun project, Scott. But I am curious as to why you wanted a tube amplifier in this day a age, other than the parts were available at the right price.

  8. #8
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    Quote Originally Posted by Ken Garlock View Post
    Sounds like a fun project, Scott. But I am curious as to why you wanted a tube amplifier in this day a age, other than the parts were available at the right price.
    Tubes have a distinctive sound character that you can't get from transistors IMO....plus tubes glow in the dark! The tube sound is often richer and sweeter, and has better resolution of fine detail than transistors. I'm pretty new to guitar amps and the tube appeal to that application, but tubes also have a more refined character when they get driven past their normal operating capabilities and distort...they distort alot more gracefully. Distortion can be a desirable sound in a guitar amp, and the circuitry is often developed with high gain in mind so the distortion can be minimized/maximized with a knob or a switch. Distortion in a solid state amp has to added with a separate electronic circuit and it's just not the same.

    As always, which you "like" best is a matter of opinion, but I'm definitely a tube fan. Tubes are alive and well in the highend audio world, and are very popular as musical instrument amplifiers. They will usually fetch a premium, and there's still a huge market willing to pay for the tube benefit.
    Last edited by scott spencer; 12-13-2006 at 08:36 PM.
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  9. #9
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    scott, not to sidetrack your thread.....(i can`t play any insturment) but tube amps are considered by many to be the absolutely best way to reproduce sound and even with my ol` deaf ears i`ve gotta agree...if a fellow ever gets a chance to hear a good tube amp run through good speakers he`ll most likely not be happy with the ic amps everybody makes now ever again..
    [SIZE="1"] associated with several importers and manufacturers.[/SIZE]

  10. #10
    Gentlemen, I think I have heard that song before.

    Let me give you my position, and then let's let it go, OK?

    A tube amp by necessity requires an output transform to match the high impedance of the output tubes (3 to 6 thousand ohms) to the low impedance of the speakers (4 to 16 ohms.) A transformer is an inductor, and as such has a built-in shock absorber type response.

    A transistor output is by its nature a low impedance output, may be even lower than one ohm. There is no output transformer to get in the way.

    The name of the game in amplifiers and speakers is for the amp to put the speaker cone where it wants it and at the time it wants it. Ideally you would want your amp almost touching the speaker cabinet in order to keep the impedance between the amp output and the speaker cone to an absolute minimum. Of course, that would produce some undesirable effects like micro phonics or even feedback.

    Due to its output transformer, a tube amp by nature cannot provide the tight control of the cone that a low impedance transistor output can. As a result you get "mellow" sound instead of the crispness of a transistor output.

    Sure there are people who like "mellow" sound, and some are even willing to pay $24,000 for a tube amp, and over $10,000 for a preamp. I wonder if those people get their entertainment from spending the money rather than from using the equipment.

    Then there is distortion. Introducing a distortion generating device into the amp input makes all of our discussion a moot point. The seems to be a tendency to take a guitar, give it to a simulation of a human being that needs a haircut, bath, and rehab, to see how many unnatural sounds can be generated. (What a roll model!) The last great guitarist was Chet Atkins, the rest need to take some lessons in the proper use of the instrument.


    So who is getting the best sound? In the final analysis, we both are because we are hearing what we each regard as the better sound.

    It has been nearly 50 years since I built a tube type amplifier, a pair of KT88s with 12AX7s driving, and with a good old Heathkit preamp running the show. One Christmas break I built a Carlson speaker cabinet out of 3/4" oak plywood. (The first time I used Waterlox for a finish.) Why a Carlson design, because their ads in the mags said "a box is not a musical instrument."

    At last I am done bloviating. This post is worth what you paid for it.

    Your neighborhood curmudgeon.

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