| Quote (Mwah @ May 28 2006,11:01) | ||
Tom, you're right. That's why the point of (audible) distortion is much higher on the dial. |
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| No, no tube bypass on my MIC200. Apparently the thing isn’t one of those “dual path” units with both solid state and tube preamp. Everything goes through the glass. That’s why changing the tube changes the sound so much. |
| Quote (TomS @ May 29 2006,09:41) | ||||
So, forgive the stupid question, but if it simply means that distortion happens at 8 rather than 6, but the amplification of 8 with the UA7 equals the amplification at 6 with the AX7, then don't we get the same basic problem? A lack of clean gain? Or (here I am treading on little knowledge) does biasing have something to do with it?
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Hi Everyone:
My knowledge of the 9-pin mini dual triode series of tubes is somewhat different then what is puplished in today’s Data bases…
My tube manuals and what I am to believe goes this way…
The 12AX7 series of tubes has an amplification factor of 100
The 12AT7 series of tubes has an amplification factor of 60…
The 12AU7 series of tubes has an amplification factor of 20…
Now, haveing said that… each series of tubes has a different Plate-Load impedience… along with other factors that determine how the circuit design causes the triode to behave…
Some common tubes is each series are…
12AX7 is the same as ECC83 in that series…
12AT7 is the same as ECC82 in that series…
12AU7 is the same as ECC81 in that series…
Other specs. being equal…
But some references that I’ve seen as of late don’t appear to group these tubes quite that way…
Lets face IT… Tubes weren’t designed and built for anything else but the Military… IT became an after-the-fact, to design/build amplifiers for public use, with them…
The manufacture of tubes “Died” when the Military moved into “Solid State” electronics…
Bill…
So, Bill, would there be any value in swapping out a 12ax7 and replacing it with a 12au7? Would there be any improvement in sound quality that is attributable to the amount of gain (rather than, say, replacing a bad sounding sovtek 12ax7 with a good sounding NOS RCA 12au7)?
Hi TomS:
What I would do as a suggestion, that is… Would get all the 9-pin dual troide tubes and “Log” them somehow… But don’t stick any tape on them… or paper /tape and come up with a “Gradeing System”… For example… 1-10 and assign numbers to the tubes as you try them out… First Noise Floor… then, the Frequency Response… and then… whatever else is important to the audible qualities you consider is important to you…
You might just find that “Magic” tube for your application… IT might just be any old tube you thought would never BE-the-ONE… Microphonic Tubes meaning When a tube warms up they “Ring” or make “Nioses” when you tap on them are not a good quality you want to use… But a good “Noise” floor is a good quality you’re looking for when you Crank up the Knobs is something that is acceptable… But… However, you just might want the dirtiest rottenest sound you can get for that “Magic” Track… After you’ve “Graded” your 9-pin tubes you can put your fingers on that tube… any time you want…
Bill…