Building the housing

[BigDumbDinosaur]

Dajgoro wrote:

I bought the letraset from ebay.

Extremely off-topic:
I apologize for this extremely off topic post, but i kinda don't know who else to ask...

I am wondering which tubes should i buy for the preamp stage, i need some ECC82, but which one are good? Ebay gives me this choice: http://www.ebay.com/sch/i.html?_nkw=ecc ... &_osacat=0
My budget is kinda limited to the first half of the page...

My experience in the last several years is that the Eastern European (e.g., Russian) tubes tend to be more consistent in behavior than the Chinese products. In particular, Chinese tubes tend to have issues with microphonics and off-spec transconductance. The latter could be important if you are trying to get consistent gain between channels.

Of course, if you can find NOS tubes, especially British or American made, you will be much happier. None of the current crop of tubes is nearly as good as those made back in the day.

[GARTHWILSON]

Quote:

As for the rub on method, i just take the sticker and apply it on the housing with pressure, and then i remove it and the letter is there permanently, or what?

They're not really "stickers."  You won't find anything adhesive.  Put the desired letter into position, and without moving the clear backing relative to the surface you want to transfer the letter to, run a ball-point pen over the letter, covering the entire letter, leaving none of it undone.  The pressure will transfer it.  When you remove the transparent backing, the letter will not be stuck to the backing at all.  It's not like adhesive stickers.  You'll have plenty of extra ones to practice with before doing "the real thing."

On the tube-versus-solid-state thing, see the video at http://www.youtube.com/watch?v=BYTlN6wjcvQ .  It starts out with a lecture at a conference and then goes to demonstrations from quality digital audio equipment in his studio that let him manipulate the exact amounts of different negative characteristics the golden-ears people said were major problems, and you can see if it is or not.  (Since YouTube compresses the audio, he gives the URL to download the uncompressed wave files.)  In the lecture, he tells of a comparison with a tube amp and a solid-state amp in front of a room full of audiophiles, with an A-B switch.  The engineers mostly chose the solid-state amplifier, while the golden-ears people said the tube amp sounded better.  The thing about it is that the tube amp didn't even work, and the cords that went to it were only stapled onto the back, and both sides of the switch actually went to the solid-state amp!

[Dajgoro]

Well then, i now can start mounting the front panel, since i wont be using any kind of paint mask...

GARTHWILSON wrote:

Quote:

On the tube-versus-solid-state thing, see the video at http://www.youtube.com/watch?v=BYTlN6wjcvQ . It starts out with a lecture at a conference and then goes to demonstrations from quality digital audio equipment in his studio that let him manipulate the exact amounts of different negative characteristics the golden-ears people said were major problems, and you can see if it is or not. (Since YouTube compresses the audio, he gives the URL to download the uncompressed wave files.) In the lecture, he tells of a comparison with a tube amp and a solid-state amp in front of a room full of audiophiles, with an A-B switch. The engineers mostly chose the solid-state amplifier, while the golden-ears people said the tube amp sounded better. The thing about it is that the tube amp didn't even work, and the cords that went to it were only stapled onto the back, and both sides of the switch actually went to the solid-state amp!

As for tube amps, i haven't been able to hear the "warm sound" and i have been listening for almost two years... What i can hear is effects off low quality mp3 compression, once i found a website with two songs for comparison, and there i could hear the aliasing... As for sound cards, i know that my cheap sound card can't reproduce frequencies greater than 12khz correctly, i did a simple test, and when it pases 12khz, it starts generating some sort of harmonics that are clearly audible, and visible on the scope...

[GARTHWILSON]

Quote:

As for tube amps, i haven't been able to hear the "warm sound" and i have been listening for almost two years... What i can hear is effects off low quality mp3 compression, once i found a website with two songs for comparison, and there i could hear the aliasing... As for sound cards, i know that my cheap sound card can't reproduce frequencies greater than 12khz correctly, i did a simple test, and when it pases 12khz, it starts generating some sort of harmonics that are clearly audible, and visible on the scope...

I ought to look into MP3 algorithms, but I haven't so far.  When our son MP3's things, he can select how much compression and audio quality he wants.  Since it's mostly just speech and not music, he can go for a very low data rate and still get good sound.

As for sound cards though, the man demonstrates later in the video, with very enlightening tests, that most sound cards (not necessarily yours) are much better than anyone's ability to tell the difference from a top-of-the-line one.  You can't hear harmonics of 12kHz though.  That would be 24kHz, 36kHz, 48kHz, etc., which are beyond the human hearing range.  You might be hearing some type of distortion products though, ones that come through at lower frequencies than the 12kHz.

[Dajgoro]

GARTHWILSON wrote:

Quote:

You can't hear harmonics of 12kHz though. That would be 24kHz, 36kHz, 48kHz, etc., which are beyond the human hearing range. You might be hearing some type of distortion products though, ones that come through at lower frequencies than the 12kHz.

I didn't mean hi frequency harmonics, i can hear some sort of harmonic in the range of 1-5KHz.

[GARTHWILSON]

Harmonics are, by definition, integer multiples.  One thing you might be hearing though is intermodulation distortion products (heterodynes), so for example 12kHz and 13.5kHz will produce a 1.5kHz intermodulation distortion product if the linearity is not adequate.  Another possibility is aliasing, where the sampling is not fast enough to give an adequate representation of the input signal.  (There's a six-second recording of a sawtooth wave near the bottom of the page, with and without aliasing problems.)  Another possible problem is jitter in the sampling clock, but the amount of jitter in your sound card probably won't be enough to give you as big a problem as you're getting.  Page 3 of the ap. note referenced has a diagram that makes the jitter problem quickly understandable.

[Dajgoro]

I guess it aliasing then, it sound similar to the sawtooth wave recording...

[BigDumbDinosaur]

GARTHWILSON wrote:

The thing about it is that the tube amp didn't even work, and the cords that went to it were only stapled onto the back, and both sides of the switch actually went to the solid-state amp!

Aah, the old placebo effect! That's funny.

[PaulF]

There is now a very easy way to get a high quality front panel for home-built projects.

Start by drawing up your front-panel on a CAD package. Print it out on a decent printer. Then put it on the front of your project and cover it with a sheet of transparent adhesive-backed plastic.

The result is a high quality, durable front panel that looks really great.

[Tor]

As for tube amps, at least there's one area where there's no question about the difference: Guitar amplifiers. There the amp itself is part of the sound, you're not after pure amplification at all, you want to hear what the amp adds by overdriving it. Overdriving a solid state amp sounds totally different. So vacuum tubes never went away, there was never a period where solid state "took over" for tubes, when it comes to guitar amplifiers.
Of course there are solid state amps out there too, lots of them. But they don't replace tube amps, they simply provide a different sound. The only solid-state option for tube amps are so-called "modelling" amps, in which you basically use a digital computer to try to model the sound of known tube amps. They manage that to some extent, but it's not the same. I own both, and the modelling amp has its uses, but it's not a tube amp.

(Acoustic guitar amplifiers though - there you don't want to hear the amplifier colouring the sound at all, so solid state is (generally) the rule there.)

-Tor

[ElEctric_EyE]

Now that is an interesting point about distortion.
Maybe some type of distortion is the 'difference' people are hearing when the amplifiers are not being overdriven. Not the commonly measured distortions like THD or IM, some other type.

[BigDumbDinosaur]

Tor wrote:

As for tube amps, at least there's one area where there's no question about the difference: Guitar amplifiers. There the amp itself is part of the sound, you're not after pure amplification at all, you want to hear what the amp adds by overdriving it. Overdriving a solid state amp sounds totally different. So vacuum tubes never went away, there was never a period where solid state "took over" for tubes, when it comes to guitar amplifiers.

Specifically, when you "overdrive" a tube amp, you drive the output stage into incipient clipping, which adds some even-order harmonic distortion to the sound. Doing the same thing with a solid state amp results in "hard" clipping, which generates disagreeable odd-order harmonic distortion. With solid state amplification, as soon as you go off the linear part of the gain curve the distortion hits, and hits hard. Tube circuits make the transition much more gradually, which not only produces a more pleasant effect, it gives the musician greater control.

Quote:

(Acoustic guitar amplifiers though - there you don't want to hear the amplifier colouring the sound at all, so solid state is (generally) the rule there.)

No reason for that. In general, tube amps are as linear as their solid state counterparts and often have better transient response, producing a more natural sound. As long as the amp is operated in the linear part of its gain curve it won't color the sound.

[Dajgoro]

PaulF wrote:

There is now a very easy way to get a high quality front panel for home-built projects.

Start by drawing up your front-panel on a CAD package. Print it out on a decent printer. Then put it on the front of your project and cover it with a sheet of transparent adhesive-backed plastic.

The result is a high quality, durable front panel that looks really great.

What exactly is the adhesive-backed plastic?

[BigEd]

Probably
http://www.amazon.co.uk/Cover-Film-For- ... 0TBYL46/2/

[Dajgoro]

I used that for my school bocks, and i remember that all of them had bubbles left, no matter how carefully i would apply the plastic...