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Discussion Starter · #1 ·
I have no idea about tubes, and I was wondering if the number of preamp tubes has anything to do with the amount of gain in an all-tube amp.

I'm thinking of getting a low-wattage combo to experience 'the real thing' (always been a SS user). I'd like a nice, heavy tube distortion at low volumes, and my fear is that a small combo wouldn't have enough gain (am I totally off the mark?)

If more tubes = more gain, how about a 30W single channel combo, 3 preamp tubes, 2 power amp tubes? Would that give me enough gain at bedroom volumes? Of course I'd use other stuff, but I'd like to get my main distortion from the amp.

Sorry for the stupid questions and thanks folks!
 

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Nah,it's not a stupid question at all.

It's quite a complex subject though.
Basically each pre-amp tube has two gain stages but a lot of people prefer the actual drive they get from driving the power-amp tubes at a good volume,which you won't be able to do at bedroom levels.

You can get an Attentuator (THD Hotplate/Marshall Powerbrake etc.) which goes between your tube amp and the speakers and this will allow you to whack up the amps volume comtrol and regulate the actual volume which comes out of your speakers, allowing you to drive your amp hard but without deafening yourself and your neighbours.
This means a lot of extra cost though:(.

Your best bet if you wanted a smallish tube combo would be to run something like an Ibanez Tubescreamer in front of the amp which will push it into saturated overdrive at low volumes.

It also depends on what sort/level of gain you're looking at. What a lot of people call 'high-gain' i consider to be 'mildly-overdriven'.

There's a lot to it, as i said,lol.

The best thing you could do to help with your decision is to try a few of the amps you're considering and see what you think of them. If you do it that way it'd be best to try and use your guitar to test them so you get a true idea of what the end sound will be like.

Good Luck and all the Best.............;)
 

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Discussion Starter · #3 ·
Thanks a bunch! That's what I what I thought.

Does more tubes in the preamp stage mean more preamp gain though? I won't even attempt to get power amp distortion unless I want to be evicted LOL
 

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Generally yes, but you'll usually find 'most' tube amps have either three or four 12ax7 (ECC83) tubes.
A Marshall,for example, will generally have three tubes two of which are gain-stage tubes and the third is an inverter tube.
I'm not very familiar with Mesa-Boogie amps but i think they ususally have four pre-amp tubes.

The gain you end up with will depend a lot on the particular type/make of the amp and the circuitry it uses in the pre-amp section as much as the actual tubes.

People who haven't used tube amps will generally assume that they're going to get one and plug it in and all of their prayers will be answered but unfortunately that rarely happens.

Don't get me wrong, i've used tube amps for many years (ususally Marshalls) and when i've been in a band i've gotten awesome sounds from my rigs but in a home/ bedroom situation it's a lot more difficult to get the same sound from them.

I'm actually considering getting an SS rack pre-amp and running it through a Stereo Tube rack power-amp into two cabs to get the best of both worlds.:)
 

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Its not the tubes, it's what you do with them. There are plenty of "one tube" pedals that are extremely high gain. The same preamp tube (if I'm remembering correctly) can be passed through as many as three times. So you can actually get a greater gain exponent from one tube than two, depending on how you use them. Some amps, like the Marshall JCM900 aren't even getting the high gain distortion from the preamp tube. So tube quantity is irrelevant. Some preamps, like the Carvin Quad X preamp had lots of tubes (five I think) and I don't think they even came close to the high gain chunk of a hot-rodded 2 preamp tube Marshall style circuit, or even the one tube Mesa V-twin for that matter.

First determine how many preamp tubes are actually in the gain stage. Old Fender amps have 4 preamp tubes, but one just operates the vibrato, the other is the driver tube, and the two "gain" tubes are split, one for each input channel. So basically they are a "one tube gain" circuit. That's why when people mod them, they usually bridge the two preamp tubes, and sometimes tap into the vibrato tube, too.

Today's high gain metal sound is so easily approximated in the solid state realm that lots of "tube" amps are using some SS gain circuitry. Without learning about all their different schematics, you just have to use your ear I guess. For example, I think the Hughes & Kettner Tube Factor pedal is awesome, but there's only one tube in there. They might "hybrid" the high gain sound but I don't care, it sounds great. The JCM900 on the other hand, feels like SS overdrive. I can't explain it, but on that amp, you really don't get a good tube vibe until you've cranked the power section, because the preamp section is thin and buzzy. But Mesa's Recto recording pre is thick and smoky even going direct.

All in all, its a good question that I think should be answered with "no, they don't really correlate" although general consensus is that they should.
 

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Actually the JCM 900 SL-X uses 4 preamp tubes with a cascading gain stage for distortion. The rest of them and the later JCM 800s used clipping diodes.

Here's the thing - you can have a 3 tube amp with a cascading gain stage which will get more gain from tubes by running one tube to push the next.

Usually if an amp has preamp tubes in the gain stage, it will have less gain than an amp with 4 preamp tubes. Keep in mind tremolo and reverb almost always require an extra tube, and sometimes even the effects loop has its own preamp tube as well so you have to know what the tubes are used for to figure out how many are in the gain stage.

Peavey 5150s or 5150 IIs (now the 6505 or whatever) have a ton of gain to them if you want a high gain amp.

I have a Marshall Studio 15 (15 watt) with 2 6V6s in the power section and 2 12AX7s in the powersection. I put loud tubes in the preamp and it is not a high gain amp -- sounds just like an old Marshall. I can boost the input (treble booster, tube screamer) and it will have a bit more gain to it though.
 
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