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Post by cedarchoper58 on Jun 4, 2020 14:17:28 GMT -5
I was going to try some different tubes (12AX7's) in my 67 black face pro reverb in V2 which is V1 on the reverb channel and was wondeing what is the difference in tone and sound in the tubes that the plates are about 1/3" apart vs the ones that are farther apart aprox 5/8" thks
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Post by Peegoo 🏁 on Jun 4, 2020 15:24:36 GMT -5
Construction of the tube can affect the tone, but there are no accepted conventions that stipulate how the plate spacing affects tone.
The best advice is to try as many different tubes as you can and find the one that appeals most to your ears.
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Post by cedarchoper58 on Jun 4, 2020 18:19:04 GMT -5
what does the term long plate and short plate mean. I have heard short plate is for guitar amps and long is for other like radios
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Post by Peegoo 🏁 on Jun 5, 2020 21:50:08 GMT -5
Short plates were developed because less mass of the shorter plate--ideally--would be less prone to microphonics, especially in combo amps.
In practice, however, this is not necessarily the rule because the various tube makers all have different tolerances for fit of the internal components. Adding to the problem is how the tubes are used: rough handing, hard use, excessive heat, and many heat/cool cycles all contribute to the tube's internal components loosening up over time and creating noise in the signal.
Some long plates are noisy and some short plates are noisy. Some tubes become microphonic over time, and some stay nice and quiet despite one's determined efforts to the contrary.
The brand and type of tube does matter to how an amp sounds, though. For example, a Mullard 12AX7 may not sound as good to you as an identical-spec Phillips 12AX7 in a specific amp. But in a diffferent amp, the Mullard may be the better-sounding tube to your ears.
Back in the 50s, 60s, and 70s, when a tube blew, a guitar player would go to the local TV shop or Radio Shack, buy a tube and stick it in there, and go play guitar.
Taste testing preamp tubes was never really a thing; about the only time a player swapped tubes is if V1 got a little microphonic: they'd swap V1 and V2 and they'd go play guitar (amps sound best when V1 is quiet). The concept of matched power tubes didn't become a thing until the 1980s...much of it was marketing wank and it still is. It's just another item in the litany of things guitar players can obscess over and spend their money on.
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Post by cedarchoper58 on Jun 6, 2020 15:00:06 GMT -5
Short plates were developed because less mass of the shorter plate--ideally--would be less prone to microphonics, especially in combo amps. In practice, however, this is not necessarily the rule because the various tube makers all have different tolerances for fit of the internal components. Adding to the problem is how the tubes are used: rough handing, hard use, excessive heat, and many heat/cool cycles all contribute to the tube's internal components loosening up over time and creating noise in the signal. Some long plates are noisy and some short plates are noisy. Some tubes become microphonic over time, and some stay nice and quiet despite one's determined efforts to the contrary. The brand and type of tube does matter to how an amp sounds, though. For example, a Mullard 12AX7 may not sound as good to you as an identical-spec Phillips 12AX7 in a specific amp. But in a diffferent amp, the Mullard may be the better-sounding tube to your ears. Back in the 50s, 60s, and 70s, when a tube blew, a guitar player would go to the local TV shop or Radio Shack, buy a tube and stick it in there, and go play guitar. Taste testing preamp tubes was never really a thing; about the only time a player swapped tubes is if V1 got a little microphonic: they'd swap V1 and V2 and they'd go play guitar (amps sound best when V1 is quiet). The concept of matched power tubes didn't become a thing until the 1980s...much of it was marketing wank and it still is. It's just another item in the litany of things guitar players can obscess over and spend their money on. thanks so the pre tubes that the plates are farther apart are long correct. On the power tube subject how much of a mis match is acceptable? say if there is 5ma diiference then one tube would be set hot and the other cold thus making one at risk of melt down
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gunny
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Post by gunny on Jun 6, 2020 18:53:06 GMT -5
quote: thanks so the pre tubes that the plates are farther apart are long correct. >>> NO. Long plates have lengthier plates; it has nothing to do with the spacing inside the glass envelope.
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Post by Leftee on Jun 6, 2020 19:02:55 GMT -5
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pdf64
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Post by pdf64 on Jun 8, 2020 6:00:25 GMT -5
On the power tube subject how much of a mis match is acceptable? say if there is 5ma diiference then one tube would be set hot and the other cold thus making one at risk of melt down In the context of a push-pull pair or quad of power tubes, almost certainly not, but the query is too generic to be certain. A functional tube doesn't redplate at idle unless the bias is way too hot, its plate is dissipation way over its limit. * No 2 tubes of the same type are ever EXACTLY the same, especially power tubes. And even 2 that are super close in every aspect will probably diverge to some degree at least as they are used. Hence the benefit of buying tubes from a vendor that subjects them to a burn in process. Generally, for a set of big octal power tubes in AB1 fixed bias, if one's idling at 30mA (plate or cathode current) and another at 35mA, in itself the discrepancy doesn't matter. Those currents should increase massively as signal is applied, eg perhaps up to 200mA. As long as all tubes are out of cut off (eg >10mA) and the greater current doesn't equate to a plate dissipation of more than 70% of its design centre limit / 60% of its design max limit, then the bias can be considered acceptable; it can be varied within that range according to taste. By big octal I mean the 6L6 family (includeds 5881, 6L6GB/WGB/GC, KT66), EL34, KT88, 6550. For smaller power tube types, eg 6V6, EL84, those number will be scaling back a bit. * Note that a gassy or otherwise bad tube might not be able to idle stably, eg current creeps up and up. And tubes can become gassy by being run too hot.
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avspecialist
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Formerly Known As: avspecialist
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Post by avspecialist on Jun 11, 2020 20:22:16 GMT -5
Picking tubes is hit and miss. Sometimes it’s fairly noticeable and sometimes it’s subtle. I really like the Performance series for the Tube Store.
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Post by pcalu on Jun 25, 2020 7:38:18 GMT -5
Those above that said it comes down to the amp, I have to 100% agree.
Currently, I think there are some really decent new production tubes on the market. With many, I can't tell the difference between my NOS and the new production. (in many cases I prefer the new... I can't tell if the NOS I have is worn out, or the new fits the amp better...
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Post by Peegoo 🏁 on Jun 25, 2020 10:47:36 GMT -5
I can't tell if the NOS I have is worn out, or the new fits the amp better... Unless you test a tube and compare the results with OEM specs, there's no way to know if a tube is worn out. Of course, however, when an amp starts to sound lifeless/lacks sonic dimension, it's a good bet the tubes are worn out or the filter caps have drifted. Modern big-production amps are made to work best with modern tubes. An amplifier with a circuit that's thoughtfully designed will contain the tubes with which it works best, so stick with these. Most boo-teek makers usually recommend a brand/type that will keep the amp sounding best; sometimes these recommendations include NOS tubes if the circuit was built around them. I've never paid extra for matched power tubes.
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Post by LTB on Jun 26, 2020 3:52:40 GMT -5
* Note that a gassy or otherwise bad tube might not be able to idle stably, eg current creeps up and up. And tubes can become gassy by being run too hot. Gassy referring to leak letting air inside, correct?
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pdf64
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Post by pdf64 on Jun 26, 2020 5:32:28 GMT -5
* Note that a gassy or otherwise bad tube might not be able to idle stably, eg current creeps up and up. And tubes can become gassy by being run too hot. Gassy referring to leak letting air inside, correct? Possibly but not so much. I think the issue is more usually due to impurities eg gas atoms / molecules that are trapped within the structures and coatings used within the tube at manufacture. Over time these become released. Hopefully the getter silvering catches and traps them so they can’t cause trouble. But the hotter the tube structures run, the more get released. They tend to be ions, positive charge, and so are attracted to the control grid, causing a tiny but problematic positive current that works against the bias and raises the cathode current. This mechanism sets the limiting value of grid circuit resistance provided in the tube type info. Note that the 220k grid leak used in guitar amps is above the 6L6 etc 100k limit; hence the benefit of keeping their dissipation in check.
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