Looking for help with a Hybrid guitar amp, this is a modeling amp, solid state 120 watt and a tube pre amp 1 watt, using a single 12AX7 tube. The amp is going on seven years old and have been considering replacing the tube, after reading about different tubes which one would be the best, I keep seeing the same comments "After break in, the tube sound great". Not being a EE a 1 watt pre amp input (or output) will the tube ever break in, or are the voltages supplied to the tube the same whether its 1 watt or 65 watts. VOX VT120+
thanks for your help,
Matt
thanks for your help,
Matt
This amplifier uses an ECC83/12AX7 pre amp valve.
Valves do not 'break in', they wear out slowly. When they get old and low emission, they sound different to new as they do not produce as much voltage swing without distortion as they run out of electrons available from the cathode.
If it works as you like it, there is nothing wrong.
If you replace it with another ECC83, it may not sound any different or it might. No way of telling without experimenting.
The only known issues is the anode load resistors if really early manufacturing date tend to drift in value, having a possible effect as 'breaking in'.
The pre amp amplifies and compresses the signal and is not responsible for power, that is the responsibility of output stage voltage and current gain stages.
Valves do not 'break in', they wear out slowly. When they get old and low emission, they sound different to new as they do not produce as much voltage swing without distortion as they run out of electrons available from the cathode.
If it works as you like it, there is nothing wrong.
If you replace it with another ECC83, it may not sound any different or it might. No way of telling without experimenting.
The only known issues is the anode load resistors if really early manufacturing date tend to drift in value, having a possible effect as 'breaking in'.
The pre amp amplifies and compresses the signal and is not responsible for power, that is the responsibility of output stage voltage and current gain stages.
Thanks 'JonSnell Electronic' for your input, mostly wanted to experiment with some tube tones. I see that Amazon sells kits of several tube manufactories so you can switch tubes and listen for differences. My modeling amp sounds very different than full solid state modeling amp, so the tube makes a difference. This is a hobby for me and a single tube or 2 isn't going to break the bank. There is a lot of difference to tube designs.
jazbo8 you sound more like a troll then a (moderator really?) this is my very first post, any question is valid, there are at least 5 you tube projects comparing tone quality, noise and such for this tube type and large difference in sound and all for $20 bucks. this is a hobby I'm having fun, why don't you try answering my technical question, does the wattage (power) go through the tube or is it modulated by the tube, on the newer model you can control the bias hot or cold what does this mean?
I have a Fender Super Champ XD, which is a similar idea vaguely to your Vox amp. The SCXD has a digital effects front end which feeds into a simple all-tube amplifier. If I use the clean channels it is a simple 12ax7 preamp feeding into a 6V6 two-tube power stage. There isn't any tube distortion from my preamp, but if driven loud then the output tubes will distort.
What you've got is that 12ax7 tube preamp running into a solid state power amp. Your power amp won't distort. If I understand correctly, you may be able to drive your 12ax7 into true tube distortion, whereas my amp won't do that.
Anyhow, I have tried swapping out different tubes including preamp tubes. Yes, there is a difference in tone between different brands of tubes. I've had the same result swapping the 12ax7 tube in an ART-TUBE preamp, where the cheap oem tubes sounded a bit harsh but swapping in a different tube helped it sound a lot nicer.
There are several different manufacturers of compatible preamp tubes, but many different labels put on them. It is a long time since I've looked at it in detail, so I'd advise you to internet search different brands "Who makes JJ Tubes", "Who makes Ruby Tubes", etc etc.
There are also different flavors of the tubes. 12AX7, 12AY7, etc. Your amp can probably operate using different flavors, though it isn't guaranteed. You shouldn't smoke the amp, but I would advise you to visit some Vox amp forums and ask about particular tubes you want to swap in if they aren't 12AX7. Some tubes will be quieter, some will distort when pushed less hard, and others will remain clean even when pushed pretty hard.
Be aware there is a high level of cork sniffery involved in tube amps! Lots of snobbery for different brands, different eras, different amp topologies, etc. And just like everything else guitar amp related, lots of words with vague meanings. Is it creamy or is it luscious? Fat? Warm but bright? Round yet crisp?
tubedepot.com and thetubestore.com are reputable suppliers.
Don't expect incredible differences, but I have found audible improvements using modern production tubes priced at reasonable levels. Be sure to research who actually manufactures the brands you are considering.
What you've got is that 12ax7 tube preamp running into a solid state power amp. Your power amp won't distort. If I understand correctly, you may be able to drive your 12ax7 into true tube distortion, whereas my amp won't do that.
Anyhow, I have tried swapping out different tubes including preamp tubes. Yes, there is a difference in tone between different brands of tubes. I've had the same result swapping the 12ax7 tube in an ART-TUBE preamp, where the cheap oem tubes sounded a bit harsh but swapping in a different tube helped it sound a lot nicer.
There are several different manufacturers of compatible preamp tubes, but many different labels put on them. It is a long time since I've looked at it in detail, so I'd advise you to internet search different brands "Who makes JJ Tubes", "Who makes Ruby Tubes", etc etc.
There are also different flavors of the tubes. 12AX7, 12AY7, etc. Your amp can probably operate using different flavors, though it isn't guaranteed. You shouldn't smoke the amp, but I would advise you to visit some Vox amp forums and ask about particular tubes you want to swap in if they aren't 12AX7. Some tubes will be quieter, some will distort when pushed less hard, and others will remain clean even when pushed pretty hard.
Be aware there is a high level of cork sniffery involved in tube amps! Lots of snobbery for different brands, different eras, different amp topologies, etc. And just like everything else guitar amp related, lots of words with vague meanings. Is it creamy or is it luscious? Fat? Warm but bright? Round yet crisp?
tubedepot.com and thetubestore.com are reputable suppliers.
Don't expect incredible differences, but I have found audible improvements using modern production tubes priced at reasonable levels. Be sure to research who actually manufactures the brands you are considering.
Hey there, chill out, will ya... I have the same type of amp and am just telling you what I think. If you want to try swapping the tube, go ahead and don’t let me stop you. The output power comes from the chip amp, where the 12AX7 plays a minor role. By changing its bias, you can adjust how the tube behaves, i.e., its clipping/overdrive characteristics, whether that is more useful than than just changing the drive level is debatable.
In amps like this the tube is mainly there so they can claim tube-iness in their marketing. The tube is not in the middle of a tube amp like in some Marshall or Fender product. In my opinion, the tube is not a major contributor to this amp's tone. But tubes are not that expensive, if you want to try several, go ahead.
Product comparisons of 12AX7s are usually based on all tube amp circuits and generally those as used in high overdrive situations.
Product comparisons of 12AX7s are usually based on all tube amp circuits and generally those as used in high overdrive situations.
Welcome to the forum.
Perhaps, but a misguided question deserves an honest answer. Jazbo8 gave you an honest answer. And tubes don't break-in.
Be cautious what you believe. The majority of audio-related information on the 'Net is complete nonsense. The equivalent of reading sheep-entrails to predict the future. Utter, complete, ridiculous, absurd, nonsense.
As for different sounds when "tube rolling", they may exist, and yet have no useful significance. Tubes have parameter spreads, factory production variations that all manufactured products have. If you happen to plug in two tubes (both of the same nominal type, say 12AX7), one of which has a mu on the low end of the manufacturing spread, one with a mu at the high end, you will hear more gain and (in a guitar circuit) maybe more distortion from the high mu one.
So far, so good; we have heard a change in sound triggered by an entirely random change in tube parameters. The mistake is to then attribute that change to the brand name, and assume that all brand X tubes sound like this, and all brand Y tubes sound like that.
The sensible engineering approach is to achieve the tone you want with potentiometers (gain controls), or by varying other parts of the circuit design, rather than by randomly swapping tubes and hoping by accident to find one you like.
Sigh. Gramma used to say "You can catch more flies with honey than with vinegar."
Nobody owes you any favors. Ask nicely, most people here are kind, and enjoy helping, and they might do you a favor.
This is not the kind of question that can be meaningfully answered in a sentence or two, so I'm going to point you at a really good resource instead. Reading this will give you a great starting point and answer some of your questions: The Valve Wizard
The rest of the Valve Wizard website is packed with useful information too.
-Gnobuddy
Something else to keep in mind when rolling tubes. it is appealing to get a Sovtek, a JJ, an EH, a Chinese, a "Mullard", etc, and have a side by side and assume that the differences are due to brand. But if you line up a half dozen Sovteks, or a half dozen JJs, you might find just as much difference between them as between two brands in the first experiment.
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