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anyone ever duilt a simple TUBE AMP ?

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Hello folks, the title says it all.

I'm pretty sure that there's a fellow guitarist around here who built, tested and approoves some simple schematics to a tube amp.

I'd like to build one, a simple one so I could buy the parts easily and etc.

 

alec_t

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Reloadron

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What's a tube amp? Do you mean a valve amp? :)

Yeah, I have built a few in my day. Likely because transistors were in their infancy as to availability and God's gift to me was the 6L6. I still have all my old tube manuals and circuit books.

Ron
 

audioguru

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I made an amplifier with vacuum tubes about 48 years ago. It sounded great when its output tubes were new but in 2 or 3 months they didn't match anymore and neeeded replacement. It cost too much to keep replacing worn out tubes.
Then I bought a solid state stereo receiver. It is old but it still works perfectly today.
 

KeepItSimpleStupid

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I have a friend who has built a few. Mostly from old SAM's Photofact schematics. He has modified some. He only keeps the ones he likes. he likes building the power supply separate.

I've fixed a number of tube amps and had an old 50 W mono Fisher amp when I was a kid. The 6l6/1614 rules. The KT88 is a popular tube too.

Here are some kits that are available: http://tubedepot.com/kitshifi.html

I hope your pockets are deep.
 
Yeahh well that's the thing. That's why I want to build one, and stay away from those expensive kits. I could probably make the power supply but that would be overkill as I don't have the tools but I expect it to be the most expensive piece of the puzzle; but could I take a psu from another thing/machine ?
 
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bountyhunter

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My first stereo amp was a tube amplifier called a Bell Stereophonic 30-30 which was 30W/channel. It was so old, it had inputs for both RIAA and EUR compensation for records.

It's not worth the misery it's going to take to build one.
 
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Nigel Goodwin

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Yeahh well that's the thing. That's why I want to build one, and stay away from those expensive kits. I could probably make the power supply but that would be overkill as I don't have the tools but I expect it to be the most expensive piece of the puzzle; but could I take a psu from another thing/machine ?
The problem is the cost - in particular the transformers.

You can build a far higher quality transistor amp for less than the cost of one of the transformers required.
 

Reloadron

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I just read this story a week ago or so. The guy building the amps is literally a few miles from me, I should go check his place out. As to building a vacuum tube power supply most of the stuff is available including the transformer for the B+ supply. The link is a nice read.

Ron
 

alec_t

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I'm sure it would be much simpler and cheaper to make a solid state amp, with extra components to emulate the distortion of the old tube amp. Dunno why, but musicians seem to like the 'character' that adds.
 

audioguru

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You can buy "vacuum tube" amplifiers that are actually solid state but have glowing vacuum tubes on top for the show.
 

ronsimpson

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Dunno why, but musicians seem to like the 'character' that adds.
Even/Odd harmonics:
Tube (valve) amplifiers make harmonics where there are already harmonics in the music. It sounds 'natural'.
A transistor amp adds harmonics where there should not be harmonics in the music. The total distortion is much less just more noticeable.

When a tube amp is over driven it distorts 'softer' than the hard clipping of a transistor amp.

I should know better than to talk about audio, just under a post from AudioGuru.
 

audioguru

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Even/Odd harmonics:
Tube (valve) amplifiers make harmonics where there are already harmonics in the music. It sounds 'natural'.
Adding harmonics to music is distortion, it is not natural, it is awful. A vacuum tube and a transistor both cause even harmonics and both types in the push-pull output stage cause odd harmonics. But the vacuum tube amplifier has an output transformer that has phase shift so not much negative feedback can be used.
A solid state amplifier has no output transformer so its phase shift is very low. Its open-loop gain and negative feedback can be very high to cancel distortion. It sounds natural.

When a tube amp is over driven it distorts 'softer' than the hard clipping of a transistor amp.
Amplifiers should never be over driven. They should have some "headroom". Aren't the ceilings in your home much higher than your head?
Guitar amplifiers normally smash their heads on their ceiling.

I should know better than to talk about audio, just under a post from AudioGuru.
You are darned right! But I have heard very good sound from vacuum tube hi-fi amplifiers, not from guitar amplifiers.
 

alec_t

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When a tube amp is over driven it distorts 'softer' than the hard clipping of a transistor amp.
But hard clipping can be avoided by diligent use of compression/gain control. That could also reduce/prevent harmonic generation. I'd bet wiser heads than mine have already looked into this. I'm sure that with enough design effort a solid state amp could be made to give an output audibly indistinguisahble from a tube amp.
 

alec_t

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Amplifiers should never be over driven.
Tell that to a pop musician!!
 

Nigel Goodwin

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I'm sure that with enough design effort a solid state amp could be made to give an output audibly indistinguisahble from a tube amp.
Why would you want to lower the quality of a transistor amp to try and make it sound like a valve one?.

Fair enough for guitar amps, you're often looking for low quality and VERY high distortion, but not for normal use.
 

tcmtech

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Here is a place that still caries a good number of vacuum tubes and output transformers specifically for replacement in stock and custom made tube amps.:D

http://www.parts-express.com
 

ronsimpson

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I agree any distortion is not good.
Music is not a simple sign wave. It usually is a collection of harmonics. 1, 2, 3, 4x, etc. Harmonic distortion form a amplifier that adds to the harmonics content aligned with the instrument is very hard to hear. Adding energy at the harmonics, increases the sound level, sounds louder, and thus your ear may think it is 'better'. http://gabevee.tripod.com/harmonics.html A 0-distortion transistor amplifier, while not adding harmonics in normal operations, when over driven will add energy at frequencies not aligned with the music. This is easy to hear the distortion.

Amplifiers should never be over driven. YES. Sitting in you living room listing to caned music---YES. In a live consort there is never that much ceiling. That is why I have limiters. Limiters in mic inputs, limiters on power amps and on recorders. I know limiters add distortion but that is very small compared to the distortion of a power amplifier out of control. If you have ever heard FM, CD or tape music you have heard the effects of 'limiting' and 'compression'.

I have never found any two Audio Gurus that agreed on everything (anything). I expect no to little agreement here.
 

alec_t

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Why would you want to lower the quality of a transistor amp to try and make it sound like a valve one?.
Personally I wouldn't. That's just for the folk who prefer the distortions of 'valve sound'.
Fair enough for guitar amps
I thought that's what we are talking about here. The OP refers to a 'fellow guitarist'.
Adding energy at the harmonics, increases the sound level, sounds louder
Isn't that simply treble boost ?
 
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