Are tubes

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Victory Pete said:
Is this a trick question? Are you saying tubes dont produce more even harmonics and transistors dont produce more odd harmonics?
VP
Click to expand...

I can build a tube amp that doesn't produce even-order harmonics as its dominant distortion and a transistor amp that does. But I can't build a transformer that does anything but odd-order when saturating.

Here is your logical argument:

- Odd-order harmonics are bad and even-order harmonics are good;

- Transformers only produce odd-order harmonics;

- Therefore, transformers are . . . good :confused:

Get it now?
 
mshilarious said:
I can build a tube amp that doesn't produce even-order harmonics as its dominant distortion and a transistor amp that does. But I can't build a transformer that does anything but odd-order when saturating.

Here is your logical argument:

- Odd-order harmonics are bad and even-order harmonics are good;

- Transformers only produce odd-order harmonics;

- Therefore, transformers are . . . good :confused:

Get it now?
Click to expand...

Are you saying output transformers only produce odd harmonics? Can you produce a link I can study?
VP
 
"No matter how I try, I find my way into the same old jams!" :D


Tom Cruise looks down at his dying father and says, "Father, you came back from the dead to tell me I'm odd?" :eek:
 
I just found this link, It says OT distortion is nasty, so I assume it is odd.
I stated I thought it might be the OT in a MOSFET, I wasnt stating it as fact. I am always willing to learn something new, I just dont like to be insulted.

http://www.tubelab.com/SSopt.htm

VP
 
Victory Pete said:
Are you saying output transformers only produce odd harmonics? Can you produce a link I can study?
VP
VP
Click to expand...

As a general rule, yes! Here, this study linked in your Wikipedia article ought to do:

http://milbert.com/Files/articles/TvsT/tstxt.pdf

I think that paper has some problems, plus it was written in 1972 so some of the test methodology could be done better with modern tools. The latter obviously isn't the author's fault, but his general method was to measure distortion 12dB above the point of 1% THD. That's not particularly fair to the opamp, because opamps are designed not to distort at all until they don't have any choice in the matter, then they hard clip. (By the way, opamp is a circuit topology, not a device, although he does later specify monolithic opamp--those were fairly primitive in 1972). So an amp that is designed to distort should never use an opamp to do that, you'll always get mostly symmetrical hard clipping (hard being much worse than symmetrical).

Anyway, pay special attention to Fig. 4, 6, 8, and 10. What is the dominant distortion in fig. 6? Isn't that a tube? Why is fifth-order and seventh-order distortion more prominent in fig. 10 vs. fig. 8?

Here's some more on transformer saturation:

http://www.opamp-electronics.com/tutorials/core_saturation_2_09_11.htm

Look towards the bottom, there is a little hint on DC causing asymmetrical distortion in a transformer. That's the only way it can happen. I admit I haven't made a careful study of that behavior in guitar amp output transformers, but I don't think it would ordinarily be a large effect (due to limited DC), and I'm pretty sure that couldn't occur in push-pull designs. Some discussion on that here:

http://music-electronics-forum.com/t16762/

So a single-ended transformer output can distort asymmetrically, but we already know that a single-ended tube output is going to potentially have a large amount of even-order distortion all by itself. So do all push-pull output tube amps sound like crap? Discuss.

Again, topology: more important than device selection.

I will give you the further hint that it's not even- vs. odd- which is so compelling, but low vs. high. That's the real issue. People like third-order harmonics; ninth-order, not so much. Transistor designs tend to use lots of transistors to make more linear circuits. They have low distortion of all types--until they clip, which they will do hard and fast. You can't use 20 tubes in a tube amp due to cost and maybe heat, but if you wanted to, you could make an extremely linear tube amp (until it clipped). Actually you could do much better with even six tubes than is commonly done.

If you don't want a linear amp . . . don't do that!
 
Victory Pete said:
I just found this link, It says OT distortion is nasty, so I assume it is odd.
I stated I thought it might be the OT in a MOSFET, I wasnt stating it as fact. I am always willing to learn something new, I just dont like to be insulted.

http://www.tubelab.com/SSopt.htm

VP
Click to expand...

Everybody gets insulted here all day long. Some dude just insulted me on another board. Oh well.

That circuit looks similar in concept to that ZOTL patent we were kicking around the other day . . . in this case, they are trying to avoid the foibles of a typical output transformer by avoiding low-frequency saturation. Question is, do you want to avoid low-frequency saturation? That's more of a question for bassists than guitarists, I think. Guitarists tend to like it, while suffering the effects somewhat less. Bassists, it would depend on their style. It does make one wonder why you'd want to bother with the transformer at all if you seek to avoid saturation. Feed a power tube on full blast into dummy load and then a MOSFET output stage instead.

I have separately raised the issue of using a small interstage transformer in a FET amp (or small-signal tubes) and saturating the crap out of it. That's cheaper and lighter than the same effect in a real output transformer, but it would probably be thought of as a caricature of transformer sound, just like starved-plate tube stuff is. Still, I'd be surprised if no one has done a guitar pedal with that technique. I have a preamp that can be tweaked thusly; I can't be bothered with doing boutique pedal quality artwork, so somebody else will have to do that.
 
mshilarious said:
As a general rule, yes! Here, this study linked in your Wikipedia article ought to do:

http://milbert.com/Files/articles/TvsT/tstxt.pdf

I think that paper has some problems, plus it was written in 1972 so some of the test methodology could be done better with modern tools. The latter obviously isn't the author's fault, but his general method was to measure distortion 12dB above the point of 1% THD. That's not particularly fair to the opamp, because opamps are designed not to distort at all until they don't have any choice in the matter, then they hard clip. (By the way, opamp is a circuit topology, not a device, although he does later specify monolithic opamp--those were fairly primitive in 1972). So an amp that is designed to distort should never use an opamp to do that, you'll always get mostly symmetrical hard clipping (hard being much worse than symmetrical).

Anyway, pay special attention to Fig. 4, 6, 8, and 10. What is the dominant distortion in fig. 6? Isn't that a tube? Why is fifth-order and seventh-order distortion more prominent in fig. 10 vs. fig. 8?

Here's some more on transformer saturation:

http://www.opamp-electronics.com/tutorials/core_saturation_2_09_11.htm

Look towards the bottom, there is a little hint on DC causing asymmetrical distortion in a transformer. That's the only way it can happen. I admit I haven't made a careful study of that behavior in guitar amp output transformers, but I don't think it would ordinarily be a large effect (due to limited DC), and I'm pretty sure that couldn't occur in push-pull designs. Some discussion on that here:

http://music-electronics-forum.com/t16762/

So a single-ended transformer output can distort asymmetrically, but we already know that a single-ended tube output is going to potentially have a large amount of even-order distortion all by itself. So do all push-pull output tube amps sound like crap? Discuss.

Again, topology: more important than device selection.

I will give you the further hint that it's not even- vs. odd- which is so compelling, but low vs. high. That's the real issue. People like third-order harmonics; ninth-order, not so much. Transistor designs tend to use lots of transistors to make more linear circuits. They have low distortion of all types--until they clip, which they will do hard and fast. You can't use 20 tubes in a tube amp due to cost and maybe heat, but if you wanted to, you could make an extremely linear tube amp (until it clipped). Actually you could do much better with even six tubes than is commonly done.

If you don't want a linear amp . . . don't do that!
Click to expand...

Okay thanks, I will study this. Greg L probably has already read it all.
VP

P.S. I do have a clue!
 
mshilarious said:
As a general rule, yes! Here, this study linked in your Wikipedia article ought to do:

.....................!
Click to expand...

Dude, don't waste your time with him apart from to bait him. The guy is a first rate cock and an ignorant one at that. You should remember that from your modding days.;)
 
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