Trying to Understand Preamp vs. Power Tubes and their Emulation

[diagrammatiks]

not all power tube sections are configured to distort in the same way.

a class A amp running a single power triode or a triode connected pentode will sound very much like a single 12ax7 distorting.

a class ab amp running 2 pentodes in push-pull doesn't have any readily available analogies using preamp tubes.

however, preamp gain stages can be cascaded easily while power tube stages cannot be cascaded as easily.

[DougH]

Didn't FrequencyCentral do just that?  A pentode-based distortion box?  Let me see if I can dig it up...

Edit: Here it is- http://www.diystompboxes.com/smfforum/index.php?topic=70524.0

The Pentaboost-very interesting

http://www.aronnelson.com/gallery/main.php/v/DougH/distortion/pdriver

[DougH]

Most of what people call "tube tone" is just someone mistakenly attributing some aspect of electric guitar sound to a glass envelope. I wouldn't spend a lot of time agonizing over it, personally. If you are curious about tubes, build a tube pedal or amp and have some fun. I've built several and it's always fun.

[DavenPaget]

So, what's a good way to emulate a cranked power tube? More specifically, a pentode or tetrode -- 6V6, EL-34, or EL-84? MOSFETs are supposed to sound/act very much like a pentode, so should I try stringing a few together, perhaps building a Box of Rock or an Obsidian Overdrive? I don't want too much crunch or buzz, so perhaps only two stages instead of three? Or would a 4049 design be more in line with what I'm after? I don't need or even particularly want a perfect emulation -- just something that has that sort of magic.

MOSFET power amp , if that's what you want . To me , vertical mosfets only shine when they use it through their intended application, which is high power applications .
There's a fantastically warm sound when a mosfet is supplied with a good SMPS , note : only SMPS , transformers won't go well with them .

[jafo]

Most of what people call "tube tone" is just someone mistakenly attributing some aspect of electric guitar sound to a glass envelope.

Well... in our defense, it is a complicated subject, and marketing people have been spreading an awful lot of pro-tube [md]isinfo.

I wouldn't spend a lot of time agonizing over it, personally. If you are curious about tubes, build a tube pedal or amp and have some fun. I've built several and it's always fun.

Eeep -- voltages and currents like that? Nuh-uh! Even if I could afford the parts, I'm not ready to work with anything that touches wall power.

[jafo]

So, what's a good way to emulate a cranked power tube? More specifically, a pentode or tetrode -- 6V6, EL-34, or EL-84? MOSFETs are supposed to sound/act very much like a pentode, so should I try stringing a few together, perhaps building a Box of Rock or an Obsidian Overdrive? I don't want too much crunch or buzz, so perhaps only two stages instead of three? Or would a 4049 design be more in line with what I'm after? I don't need or even particularly want a perfect emulation -- just something that has that sort of magic.

MOSFET power amp , if that's what you want . To me , vertical mosfets only shine when they use it through their intended application, which is high power applications .
There's a fantastically warm sound when a mosfet is supplied with a good SMPS , note : only SMPS , transformers won't go well with them .

Heh... sounds like the only way to get what I'm looking for is to run it for real (i.e., live at high power with a speaker and so forth), at which point I might as well just simplify things and use a tube anyway.

[DavenPaget]

> Well... in our defense, it is a complicated subject, and marketing people have been spreading an awful lot of pro-tube [md]isinfo.
Well ... I went to a guitar shop in the past that kept on dumbing down solid state and kept repeating that tube amps last a generation and that they sound a million times better .
Bullshit , fire up a kustom KG100HFX and tell me if your shit can last .

> Eeep -- voltages and currents like that? Nuh-uh! Even if I could afford the parts, I'm not ready to work with anything that touches wall power.
Why would you need to be worried about that ? You can use starve a tube's plate or use a 555-based SMPS  No harm required , 9/12VDC input and then a tube pedal TADA ! No line power required .

[teemuk]

What makes the difference in how they sound and feel?

One could write a book to answer that.

Study circuits. The stuff you see in amps. Figure out how that stuff works and performs. There are your differences, a huge amount of them depending on each and every circuit design. As said, it's a lot of ground to cover. Worth of at least a book, and several have been written in an attempt to cover the topic.

Sorry to say, there is no "easy way", e.g. an answer to your question that will sum everything in a few simple sentences. Prepare to do you footwork and use many manhours to figure out how circuits work and perform.

[petemoore]

So, what's a good way to emulate a cranked power tube? More specifically, a pentode or tetrode -- 6V6, EL-34, or EL-84?Exactly that and speaker...
 
MOSFETs are supposed to sound/act very much like a pentode, so should I try stringing a few together, perhaps building a Box of Rock or an Obsidian Overdrive?
   So are Jfets and CMOS though, the clips of the BOR sounded hard', and my OO had crazy gain sound.
I don't want too much crunch or buzz, so perhaps only two stages instead of three?
  From the description of the desired tone, mention of 4 stages instead of 2 or 3 is made. First stage may contribute to gain, but mainly sets up the second/third stages for input or output distortion, then it'll probly want a TC or whatever, then the fourth stage...loosely stated, more than one stage clipping 'easy over' tends to be smoother/less buzzy at "Xgain" setting than pushing just one stage harder to do all the distorting.
  Or would a 4049 design be more in line with what I'm after? I don't need or even particularly want a perfect emulation -- just something that has that sort of magic.
  Abracadabra ! ! 'Smooth' has accompanied many a 4049 build, 5vsupply for the chip and a boost of some sort to push it's input a bit harder than a SC does...
  Any of these circuits or active components have probably been called magic at some time, CMOS does have it's own set of unique qualities, and in my case does a really nice 'set sound' that has the convincing 'tubi-ness' tone to it.
  These non-specific statements are broad, vague and don't mean much compared to an actual application-review.

[Gus]

Look up the MM guitar amp schematics
Some are an IC solid state preamp to IC PI then cascode transistor tube class B or AB(I believe I read it is a class B output I have not worked on a MM to check if this is true) transformer output.

Also try a solid state amp like a 10Watt practice amp into a good 2X12, 4X12 etc.

Read MAC's post in this thread.

[mrmoo1337]

What makes the difference in how they sound and feel?

One could write a book to answer that.

Merlin B published a phenomenal tube preamp book that is highly recommended, still waiting on his power amp book that the world wants him to write. 

[DavenPaget]

I have tried my 10watter's stock sound and TL072 sound , definitely cleaned up compared to the 4558 ,
10watter's line output into my Alpine MRV-F400 , EPIC !  ( I used a JBL GT82 8" sub )
30 watter's ( modelling amp ) , slight amount of bass . Definitely quite thin .
Line output into Alpine MRV-F400 , WTF WHERE DID THAT WARMNESS COME FROM ? My 30watter amp was pretty warm from the beginning , i just love the mosfets they used in the alpine .
Yep , mosfets sound absolutely like a tube amp when done properly , i dragged my uncle's tube stereo amp to compare .
The alpine was warmer 

[jafo]

Lots of good info and pointers -- it's like Christmas came early. Thanks, all!

[jafo]

Look up the MM guitar amp schematics
Some are an IC solid state preamp to IC PI then cascode transistor tube class B or AB(I believe I read it is a class B output I have not worked on a MM to check if this is true) transformer output.

Err, which "MM" do you mean? Google found quite a few differing ones, alas...

Also try a solid state amp like a 10Watt practice amp into a good 2X12, 4X12 etc.

Read MAC's post in this thread.

Quoth mac:

It's the power tube + output transformer duo what many pros like.
Of course it depends on the design, can sound like crap.

Absolutely. I have a keyboard amp (some SS Peavy thing) which sounds great, even on guitar, when run at full volume. I always thought it was just this one amp, and was embarrassed to admit that I like how it sounds, but now I'm convinced that good tone comes from good design, not the specific parts.

[jafo]

  Or would a 4049 design be more in line with what I'm after? I don't need or even particularly want a perfect emulation -- just something that has that sort of magic.
  Abracadabra ! ! 'Smooth' has accompanied many a 4049 build, 5vsupply for the chip and a boost of some sort to push it's input a bit harder than a SC does...
  Any of these circuits or active components have probably been called magic at some time, CMOS does have it's own set of unique qualities, and in my case does a really nice 'set sound' that has the convincing 'tubi-ness' tone to it.
  These non-specific statements are broad, vague and don't mean much compared to an actual application-review.

Unscientific and imprecise they may be, you've convinced me that I have to build something with hex inverters soon. That, and something with submini pentodes. And something with strongly driven MOSFETs. And a few more small projects...

[jafo]

> Eeep -- voltages and currents like that? Nuh-uh! Even if I could afford the parts, I'm not ready to work with anything that touches wall power.
Why would you need to be worried about that ? You can use starve a tube's plate or use a 555-based SMPS  No harm required , 9/12VDC input and then a tube pedal TADA ! No line power required .

Neat! Plus, I could use said SMPS for the MOSFET project you suggested above.

[jafo]

One could write a book to answer that.

Reading through yours right now, incidentally... great stuff, and superbly well written, but most of it is beyond my current understanding.

[Gus]

a link
http://www.music-man.com/techinfo/old-amps.html

[jafo]

a link
http://www.music-man.com/techinfo/old-amps.html

Cool, many thanks. I was pretty sure you meant Music Man, but there was a reference to some Randall amps and a few amps by a guy known only by the initials MM. And some M&M amps.

[DavenPaget]

MM amps are definitely music man amps .