Film-Tech Forum ARCHIVE: Vacuum tube amplifier for iPod

This is topic Vacuum tube amplifier for iPod - a joke? in forum Film-Yak at Film-Tech Forum ARCHIVE.

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Posted by Michael Schaffer (Member # 1204) on 08-02-2006, 07:20 PM:

http://www.akihabaranews.com/en/news-12197-Vacuum+tube+amplifier+for+IPOD.html

Posted by Floyd Justin Newton (Member # 1316) on 08-02-2006, 07:44 PM:

Uh.... [Confused]

Posted by Charles Greenlee (Member # 3856) on 08-02-2006, 09:05 PM:

Neat, I like the sound tube aduio produces. It's not "accurate", so I wouldn't consider it for motion picture (though THX still probably would certify it for the right price), but cool as a novelty. However, I don't have that cond of money to blow on something like that. I don't even have a stereo in my car.

Posted by Greg Mueller (Member # 17) on 08-03-2006, 08:42 AM:

I saw one like that on "I Want That" on HGTV last night. Really expensive. Little tiny tubes and xfmrs. Novel but silly

Posted by Aaron Sisemore (Member # 145) on 08-03-2006, 02:53 PM:

Greg, the amp you're talking about sounds a lot like the
ZVEX iMP amp:

Videos about the iMP amp

-Aaron

Posted by Bill Enos (Member # 440) on 08-03-2006, 06:36 PM:

That little amp looks a lot like one I bought from LaFayette in the early '60s for $17.

Posted by Cameron Glendinning (Member # 3516) on 08-03-2006, 09:15 PM:

Its cute [Smile]

I'm not sure why a valve amp would not be acurite? I was under the impression that most valve amps worked better because the designs where less flexible than transistor designs. Also when a tube amp is driven into distortion it is a harmonic distortion and at least musical rather than the noise created when transistor amps are driven too hard.

Ive been told by many that now days there is no real difference in quality between a well designed mosfet and a tube amp as the circuit design may be the same.

I wonder if you could hear the difference between a downloaded and a home recorded mp3?

Posted by Mark Gulbrandsen (Member # 72) on 08-03-2006, 09:36 PM:

Cameron is correct about the harmonic content... tube amps generate mainly even harmonics which are not hard on the ears. Its one of the main reasons that tube equipment sounds like it does. There are also many single ended MOSFET class A micro amps that also sound great for this purpose. The tubes used in the IMP AMP are mil spec Raetheon tubes that were designed for guided missle use with a 100,000 hr plus life span. They have a wire lead base and have to be soldered into place in the circuit.

Cameron and Michael you both might be interested in this site... there are many similar DIY amp projects over there. There are many high end designs available over there.

DIY Audio

Mark

Posted by Charles Greenlee (Member # 3856) on 08-03-2006, 10:52 PM:

What about the phenomenon known as tube hiss and tube hum. Or is that more of a symptom of a poorly designed tube circuit. Tube's operate very similarly to FETs, the voltages and poles have been changed to protect the innocent, but the logic is similar.

Speaking of logic, I did some hard studying during my digital circuits class on them. Being that the first (electronic) computer used them, I figured for one of my projects, I'd use tubes to build a couple of basic logic gates. The others did it using solid state components. Building an logic gate, with a regulated output isn't easy, and takes up a good share of the breadboard. However, it worked, and worked well, but not so well at TTL-compatible 5V so I used 24V. It even worked with TTL circuits after a buffer. My instructor had me wire it on a PCB so he could keep it to use it as an example, comparing the same circuit in Tubes, solid-state, and ICs.

I have much respect for tubes, but reference material and guides are very hard to come by anymore, whereas you can get digital ICs books and solid state book everywhere. If I could find some good material, I'd love to start playing with them again.

Posted by Greg Mueller (Member # 17) on 08-04-2006, 09:02 AM:

Yep, that's it Aaron. It has blue leds which light up the plexiglass and dim and brighten with power consumption

Posted by Mark Gulbrandsen (Member # 72) on 08-04-2006, 09:12 AM:

FYI, The blue LED's are used to bias the tubes. Unfortunately they chose the noisier of the LED family to do that. Normally T-1 red LED's are the quietest for that purpose. Blue looks nifty though. I have the schematic of that amp on my puter at home.

Mark

Posted by Will Kutler (Member # 770) on 08-04-2006, 01:40 PM:

Charles...

Unless I am mistaken, the "hum" that you are speaking of is not from valves. That comes from failing E-Caps. If that "hum" is audiable, one should not operate equipment until those caps are replaced. Otherwise "minor" things like transformers will be destroyed.

Posted by Cameron Glendinning (Member # 3516) on 08-04-2006, 08:26 PM:

Mark

You were right, I loved the site [Wink]

Posted by Charles Greenlee (Member # 3856) on 08-05-2006, 03:38 AM:

Isee, well I guess that's cool. I've always wanted to mess with tubes in an audio application. So far, my experince has been limited to building the logic gates, and building an X-ray generator our of a couple of beam triodes I had laying around(bought them in error while trying to get parts for the logic gates).