# Preamp tube break up vs Power tube break up



## Jeff Flowerday (Jan 23, 2006)

This isn't really a cut and dried topic for me. It really depends on the amp.

My Hot Cat 15 starts sounding like butt in the Gain Channel, when I start cranking the master. 10 O'clock max. The Clean channel sounds great when you really start pushing the output section though.

My Fenders all need to be cranked up to sound great. They can get a little tubby so you have to EQ them differently when cranked.

My Mini Cat II sings like there was not tomorrow with the Master cranked.


Thoughts?


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## Accept2 (Jan 1, 2006)

I prefer solid state power. I prefer to keep the tube preamp doing all the work, and then have the solid state power the tone cleanly without coloring it in any way............


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## dwagar (Mar 6, 2006)

I prefer the vintage/overdrive to high gain.
For this, with my JTM-60, Marshall recommends pinning the Master Volume, gain about 1/3, channel volume to required vol level. Basically take the Master pot out of the sequence by cracking it to full blast.


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## Adicted to Tubes (Mar 5, 2006)

There are so many opinions about what sounds best out there.Some people like the buzzy preamp distortion ala boogie and some like the classic power tube distortion.The camp is divided here.
My solution is to have a little of both.A JCM800 2204 ciruit cascades two stages together and allows you to preload the pre-amp and feed it to the power section,but it is not like the extra gain stages that boogie uses.It combines the best elements of both together for a most pleasing sound.
Sure,there will be some guys that don't like the 2204 sound,but many do.In the words of many marshall addicts"The JCM800 was marshall's last really good rock amp"
The boogie distortion filled a need at the time he first started cascading gain stages together and adding a master volume.It really depends on what kind of music you want to hear.Most fenders don't sound good with a master volume.

www.claramps.com


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## JamesPeters (Feb 2, 2006)

Adicted to Tubes said:


> There are so many opinions about what sounds best out there.Some people like the buzzy preamp distortion ala boogie and some like the classic power tube distortion.The camp is divided here.


Hold on there, pardner. 

Preamp tube distortion doesn't always sound "buzzy". It can sound remarkably like smooth warm power tube distortion. And power tube distortion can sound just as "buzzy" as anything else too. There's so much in the designs of the amps that's responsible for how the amps sound beyond whether it's just preamp or poweramp distortion.

I prefer a reasonable blend of both, relying more on the preamp for distortion (but in a friendly way) so that the master volume works effectively at varying volumes without changing the sound very much.


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## Emohawk (Feb 3, 2006)

Disclaimer: I'm not an amp tech or an EE or anything like that. But here's my $.02 worth.

In theory, isn't overdriving a pre-amp tube fundamentally the same as overdriving a power tube? All you're doing on either side is hammering the tube with more signal than it was designed to handle without harmonic distortion. To me, it's exactly the same process. Remember - the pre-amp stage is an amplifier too. All the power stage is doing is re-amplifying an already amplified signal. The real trick to tone is how you design the circuit (as James noted) and the personality of the tubes themselves.

I read an article once that talked about building a low-wattage (around 1W) guitar amp using what we call "pre-amp" tubes for both the pre-amp stage and the power stage. Their claim was that it should sound great as long as the pre & power stages were designed well. Logically, it makes sense to me. I don't know how well it would work in practice, but it does make sense.

Kirb


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## Adicted to Tubes (Mar 5, 2006)

I agree about what Mr.Peter's says about pre-amp distortion.It can be very smooth and mellow and many amps have poor sounding power amp distortion.
But you can't argue with people when they sell off their boogies and buy a custom classic amp because they are tired of that type of distortion.
And as I mentioned before with the JCM800,the blend of both can be really great sounding.
Even a poor sounding amp can be tweaked to sound great if you know how.
We are of like mind here,and I was only mentioning what people want from me.I love a properly executed master volume amp.But the circuit design in most Fenders' don't take to kindly to it.
The whole trend behind the recent tube amp boom is directly related to the quality of the sound and the product.The trend swings both ways.Distorted and clean.
Peter's amplification is a respected name in the builder's arena.I hope to be there one day.

www.claramps.com


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## JamesPeters (Feb 2, 2006)

Thanks for the kind words. 



Adicted to Tubes said:


> But you can't argue with people when they sell off their boogies and buy a custom classic amp because they are tired of that type of distortion.


That type of situation could have a lot less to do with whether it's preamp or poweramp distortion though, and that was my point. A lot of people will sell a Boogie and buy something with just as much preamp distortion that sounds better for their tastes. (And Dual Rectifiers aside, some might even prefer the smooth preamp overdrive of the Boogie Mark I/II to some amps which rely on output tube distortion and don't sound as thick/rich.)

Anyway it's easy to assume that a classic Marshall might be better suited to their tastes because of power tube distortion, since everyone assumes that's the biggest part of the Marshall sound, but you might also be surprised to learn just how much of that distortion is in the phase inverter and not the output tubes. The PI is a preamp tube, so if it can sound like "natural power tube distortion" in the PI, why not in the preamp. (As well as other compression/distortion sounds which remind people of power tube distortion.) I'm not just saying this about my own designs, but there are a number of other amps I've noticed which sound very natural in their distortion character. When it comes to old-school designs it's one thing, but with some later designs (especially with some small-volume amp builders who are really trying to do something different), you'd be surprised what's out there.



Adicted to Tubes said:


> I love a properly executed master volume amp.But the circuit design in most Fenders' don't take to kindly to it.


I do take your point in a general sense. But as an amp builder you have the opportunity to put preconceptions like that behind you and do something different.

:rockon:


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## Adicted to Tubes (Mar 5, 2006)

Yes,there are a lot of pre-concieved ideas out there.I guess it's up to guys like us to break the mold.
In fact,the Fender long tailed pair phase inverter does add a lot of gain to the circuit.I rather like the sound of the princeton with it's split load inverter.
But push-pull aside,I am delving into the single ended realm with some interesting results.


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## JamesPeters (Feb 2, 2006)

Adicted to Tubes said:


> Yes,there are a lot of pre-concieved ideas out there.I guess it's up to guys like us to break the mold.
> In fact,the Fender long tailed pair phase inverter does add a lot of gain to the circuit.I rather like the sound of the princeton with it's split load inverter.
> But push-pull aside,I am delving into the single ended realm with some interesting results.


SE is cool, it definitely has its own thing going on. But it has its limitations too, which can be frustrating (especially if people expect the amp to have "tons of gain" and still sound just as deep/broad as p-p amps they're used to). Split-load PIs sound cool; their sound can be imitated in the preamp section but it's very touch-and-go and pretty much requires redesigning the preamp.

Lots of fun stuff.  We'll have to hang out one of these days...


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## Adicted to Tubes (Mar 5, 2006)

Yeah,we should meet.I heard from Kevin Herring that you can talk up a storm!


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## JamesPeters (Feb 2, 2006)

Adicted to Tubes said:


> Yeah,we should meet.I heard from Kevin Herring that you can talk up a storm!


Lies, LIES I tell you!


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## Adicted to Tubes (Mar 5, 2006)

Meet me at L&M and we'll do coffee.


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## JamesPeters (Feb 2, 2006)

Adicted to Tubes said:


> Meet me at L&M and we'll do coffee.



Do you work there? I figured I'd know you by now if that were the case...although I don't go there nearly as often as I used to.

I was there yesterday however, buying some [email protected] Gibson-style 3-way switches. $18 my @ss...

If you want to keep your anonymity safe, email me your name so I know who you are next time.


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## Adicted to Tubes (Mar 5, 2006)

No i don't work there! I couldn't live on the peanuts they pay those guys!
Everone there knows me though.
I'm going there today with one of my 18 watt combos to give them a test drive.About 3PM or so.
I don't like anonymity.If someone wants to talk to me I'm right here.:food-smiley-004:

www.claramps.com


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## JamesPeters (Feb 2, 2006)

Adicted to Tubes said:


> No i don't work there! I couldn't live on the peanuts they pay those guys!
> Everone there knows me though.
> I'm going there today with one of my 18 watt combos to give them a test drive.About 3PM or so.
> I don't like anonymity.If someone wants to talk to me I'm right here.:food-smiley-004:
> ...


Ok, oh ye who won't tell me his name. 

Sorry but I'm on the other side of the city (72 Ave NE) and I have to work today, so I won't be able to go there.


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## Adicted to Tubes (Mar 5, 2006)

Sorry Peter,the name is Keith McneilevilGuitar:

www.claramps.com


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## Adicted to Tubes (Mar 5, 2006)

Speaking of power tube and preamp breakup,I just modified an 18 watt TMB circuit and it has the best of both.It has far more touch-response and dynamics than an ordinary TMB by far.I am a believer in blending the two together in a unique way.


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## JamesPeters (Feb 2, 2006)

Adicted to Tubes said:


> Sorry Peter,the name is Keith McneilevilGuitar:
> 
> www.claramps.com


Hi Neil! I'm James.


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## Adicted to Tubes (Mar 5, 2006)

Duh! I'm the dislexic amp builder! James,I've got it.
Good thing I'm not dislexic with amps,because my latest is a real killer!

www.claramps.com


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## Imported_goods (Mar 4, 2006)

*What type of break-up does my amp have?*

I'm really bad at understanding all of the science and technology behind tube amps, so I was wondering if one of you gentleman might explain to me how you can tell whether the beak-up is coming from the pre-amp or power section of the amp.

For example, right now I have two low-wattage tube amps (one made by Electrosonic Amps, the other by Thomas Winfield Amps) which are master-volume only. I presume that when I push the amps into overdrive territory that it's the power tubes that are breaking up?

But what about amps that have separate gain and master volume controls? If you turn the gain to 10 but leave the master volume at, say, 3, are you getting distortion from the pre-amp only?

 

(And please don't ask me if my amps are Single-Ended, Push-Pull or Class A...whenever I try to really understand those concepts I feel like a preschooler at a neuroscience convention)


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## Adicted to Tubes (Mar 5, 2006)

You've basically answered the question yourself.If the amp only has a master or volume control,and you have to turn the amp all the way up to get it to distort,then it's power tube distortion.With a gain and a master,the gain pre-loads the preamp section and the master feeds it to the output section.It allows you to get distortion at a lower volume level.And like James Peters has stated,pre-amp distortion does not need to be buzzy.But unfortunately not all amp makers build their amps to sound like that.


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## JamesPeters (Feb 2, 2006)

Unfortunately I can't tell when the power tube distorts on an amp unless I know its design already. It's possible as the "volume" is turned up, the preamp is distorting more (and the PI, if it exists, is also distorting), before the power tubes are distorting. At some point I'd assume the power tubes are distorting, but exactly where on the "volume" knob that happens, I couldn't tell you.


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## Imported_goods (Mar 4, 2006)

Thanks for the info!

If I were to use pre-amp tubes that are supposed to be "tamer", i.e. 12AU7's instead of 12AX7's, would it affect how much gain I would get from my amps? That is, I presume that changing the pre-amp tubes would only affect the gain IF the break-up is coming more from the pre-amp section, and not from the power tubes?

And does the fact that the break-up is coming from the pre-amp section or power section affect how touch-sensitive the amp is?

Sorry if the questions are naïve or confusing...


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## Adicted to Tubes (Mar 5, 2006)

You need to identify what amp you have first.Is it a push-pull circuit or a single ended circuit?Then how many pre-amp tubes does it have? either way,the first 12AX7 is where the inputs are connected to unless you have a two channel amp.The pre-amp adds the gain to the circuit and the power section amplifies it.If you use a 12AU7 in the first pre-amp position it will lower the gain for the entire amp.It will have less volume and will likely break up less too.i would not suggest using a 12AU7 in any position other than the first ,because the loss of gain might be too much.Some amps respond very well to the change and other's lose too much.It will hurt nothing to try it.
The pre-amp sets the stage for the rest of the amplifier.It can be biased hot or cold just like the output section.


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## Imported_goods (Mar 4, 2006)

Again, thanks for the info.

12AX7's it is, then. I'm not sure at all whether the amps are single-ended or push-pull, but they have exactly the amount of gain that I want, so I'll just leave 'em as they are!


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## Adicted to Tubes (Mar 5, 2006)

I am not familiar with the amp models you mentioned.It would be cool to hear some more about your rig.


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## david henman (Feb 3, 2006)

...in order to facilitate power tube breakup, would it make sense to use power tubes that break up early combined with preamp tubes that break up late?

i play through a traynor ycv40wr with (thankfully) no master volume on the clean channel.


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## JamesPeters (Feb 2, 2006)

david henman said:


> ...in order to facilitate power tube breakup, would it make sense to use power tubes that break up early combined with preamp tubes that break up late?
> 
> i play through a traynor ycv40wr with (thankfully) no master volume on the clean channel.


Possibly. The sound of the amp will significantly change by doing that, and you still don't have complete control over when one type of distortion happens as opposed to the other.

FWIW, whether it's preamp or poweramp distortion isn't important. If you like the sound of the amp, that's important.

I know of an amp that has distortion which occurs in the following order as the volume is turned up--poweramp, phase inverter, preamp. When people use the amp, they love the sound of it turned up--when it gets the most preamp distortion blended into the sound. I find it a bit ironic since people associate the sound of that amp more with power tube distortion.


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