Building a Tube Amp

On a sunny day (Wed, 15 Oct 2008 16:53:55 +1000) it happened "ZACK" wrote in :

VDR (Voltage Depndent Resistors) across the transformer?

I suppose that people who don't know much about electronics can do all sorts of weird stuff.

Have any big hits been done this way?

Guitar distortion seems to be another fringe thing.

John

--

    Boris Mohar

message

(which

amp

Of course. We are talking about the subjective opinions of people who are probably drugged-out most of the time and hearing-impaired all of the time. None of which involves electronic design.

John

Depends. Not all tubes are designed to have cool anodes, some run the anodes quite hot, like x-ray tubes. Some have spinning anodes to prevent spot heating. But in a discussion about the modest power levels for an audio amp (as long as it's not PA) I'm guessing glowing anodes are a bad thing. As for pushing the envelope, glass envelopes benefit tremendously from reduced operating temperature, so running anodes red hot in a glass tube is a bad idea IMO.

Glowing cathodes are easy to see on tubes like the 6080. I'm guessing the reason people don't put coolers over power tubes is that they want to see the glow...

[snip] [snip]

Nonsense! You compared a toooob amplifier against some cheesy Radio Shack solid state amplifier.

If you prefer the "warm" sound of a toooob amplifier go right ahead, but don't offend our sensibilities with words like "sound quality".

...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

     Liberals are so cute.  Dumb as a box of rocks, but cute.

Hey, at least its galvanically isolated ;)

M

I'm trying to remember now. I believe it was KT88's that I set the bias just at the hint of a plate glow ;-)

...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
 I love to cook with wine     Sometimes I even put it in the food

How long do they last?

There have been some acoustic-based isolated power couplers, usually solid-rod piezo things. Probably more efficient than a tube-amp/speaker/microphone combo.

John

This was, like, 1958... they lasted until I became a solid state convert ;-)

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at

| 1962 |

Liberals are so ignorant... They don't even know the definition of ignorant

Ever hear of a 6L6 operating upside down in a pail of water, running 800 V on the plate?

Tam

On a sunny day (Wed, 15 Oct 2008 12:13:41 -0400) it happened "Tam" wrote in :

No, but I do remember a similar tubes in the Ampex quadruplex video recorder VR1000 head drive mounted upside down, and un-soldering themselves from the socket, falling down. That happened when the cooling fan failed, and the air flow detection (some vane) also failed.

If you like tubes, look at the cabinet to the left of the recorder console, see the capstan and head drive amps, modulator, demodulator, servo... Had to keep that lot running.....

My "little" brother (who turns 54 or so this year) has been a musician for decades. He has a little story about that. They used to play while high - he says, "It sounded real good to _us_! Then we heard ourselves on tape while we were straight, and all said, "OOps!"" (or something to that effect.)

Cheers! Rich

OK, now imagine you're an audio electronics designer, and these kinds of people are deciding if your stuff is any good or not.

No thanks.

John

I will leave the microphone claim for someone else to have fun with, but a typical home speaker is around 1% efficient (electrical watts to acoustic watts). A JBL Model 4675C 1200W cinema screen loudspeaker system is 6.3% efficient.

--
Guy Macon

Not necessarily. After being a long time valve man, its surprising just how good some ss effects can be.

I used to use a tube amp, but now can't be f%^&%ed with the weight. I now use a Marshall AVT150 transister job, although it does have one ECC83 in it. However, not for its distortion. I am happy with it, that is after I had to cut and rewire its effect loop as the damm f%^*&sh£$ "design" techs at Marshal have no idea that a || loop is useless in a guitar amp. Like, if I am using its pre-amp distortion, how the f^&* do you insert a volume pedal in the loop and expect it to control the sound down to zero. Or like, insert a noise gate and have it actually work?

~~~~~

Different.

You know the one about meat and poison?

Kevin Aylward

I know quite a bit about electronics, and while I tend to be the fellow who gets rid of the ground loops, wires up the patch bay or balances the ground currents, I have worked with many mixing engineers and I assure you that the microphone in front of the amplifier is the standard way of recording rock lead guitar.

Yes. The vast majority of billboard 100 rock guitar hits were done that way.

No it isn't. it is a standard audio engineering thing.

--
Guy Macon

Sure, that combo is insane. I'll add "" tag next time :)

M