Common amp myths

[shakerattleroll]

And how hold are you?

I'm out, not much good can come from this thread.

I'm 23 years hold.

I was only kidding. I just didn't want to get involved in more semantics. Are smiley faces semantics?

Edit 1:I'll play devils advocate. The earth looks flat to me, and therefore it is, cause my eyes told me so.

Edit 2: Some good already came from this thread.

Invalid Link Removed

 

[Count Bassie]

Go back and read post #333.

If no one minds, how do you know which is #333 if you don't count every one up until #333? Or am I just lazy?

 

[pedro]

If no one minds, how do you know which is #333 if you don't count every one up until #333? Or am I just lazy?

Look at the top right corner of each post.

 

[djwackfriz]

TOP 5 THINGS I'VE LEARNED IN THIS THREAD:

1) Watts is watts.

2) People don't like their rigs criticized, presumably because of some Freudian small-wiener fear.

3) I know even less than I thought about sound engineering.

4) If I don't understand an explanation for something technical, I should just zoom-out to a "big picture" stance, and instead insist that it's really all about the real world/the music/my own perception.

5) Fire is hot!

 

[muse]

When you are driving a speaker all Watts are not created equal. An eight Ohm speaker is not the same as a real eight ohm load. The eight Ohm RMS power rating of an amplifier is measured into a real eight Ohm load. A real load means that it is eight Ohms at all frequencies. An eight Ohm speaker on the other hand is only eight Ohms at a few specific frequencies. Over 99% of the audio band the speaker is no where near eight Ohms. A typical eight Ohm speaker will start out at 5 Hz as 6 Ohms. If mounted in a bass reflex cabinet (ported cabinet) it will shoot up to over 50 Ohms at about 30 Hz, then drop down to 8 Ohms at 50 Hz, then shoot back up to 50 Ohms at 80 Hz then drop back down to 8 Ohms at 200 Hz. From 200 Hz through the rest of the audio band (20 kHz) its impedance will increase 6dB per octave (double every time the frequency doubles).
Tube amps have a soft supply that sags with low impedances and returns with high impedances. This means the amp will put out more power into a high impedance than an amp with a hard supply that did not sag. The 8 Ohm real load that the tube amp is rated into causes the supply to sag a lot compared to the supply in a typical solid state amp. So when the tube amp is driving a speaker it can deliver a lot more power to the high impedances it sees than a comparable solid state amp. Of course that assumes the solid state amp has a hard supply as most of them do. But guess what? Some solid state amps have soft supplies.

Just finished reading the whole thread.
So everybody's talking so far only about the nature of sound
a tube amp produces, and how it is perceived as louder
(compression,harmonic dirstortion etc.),
but the last 4 pages nobody commented on this.
Does this also contribute to the perceived loudness and
how much?

 

[shakerattleroll]

TOP 5 THINGS I'VE LEARNED IN THIS THREAD:

1) Watts is watts.

2) People don't like their rigs criticized, presumably because of some Freudian small-wiener fear.

3) I know even less than I thought about sound engineering.

4) If I don't understand an explanation for something technical, I should just zoom-out to a "big picture" stance, and instead insist that it's really all about the real world/the music/my own perception.

5) Fire is hot!

Top thing I learned from your signature:

No one can defeat the quad-laser.

 

[bongomania]

I think a big part of it is that amp companies are not honestly rating SS head outputs so a head rated at 300 might be putting out 150-200 max. Tubes on the other hand, put out a pretty tried and true output. You know how much output a head is going to have by what kind of and how many tubes are in it.

This is false. There is nothing in the theoretical math behind a tube circuit that makes it any more "inherently honest" than a SS amp. Sure you can count tubes and look up the nominal ratings for those tubes, but that tells you nothing about the rest of the circuit, or how much voltage is going to the different parts of those tubes in that specific circuit, or whether the wattage generated is used efficiently, etc.

Also while I will freely agree that manufacturers in general lie about specs, I have not ever seen an instance where I thought the specs were slanted on the basis of the amp being solid state.

People often gripe about an amp they tried being "underpowered" or "not able to produce the watts they claim" when actually the problem was often caused by incorrect gain staging, incorrect assumptions about volume/gain knob position, failing to perceive the pre-voicing (inherent EQ shaping) of amp designs even when set "flat", failing to RTM and understand what knob settings are "flat" for that amp, etc. etc. etc.

 

[Count Bassie]

Look at the top right corner of each post.

So this quote comes from post #15...

 

[shakerattleroll]

This is false. There is nothing in the theoretical math behind a tube circuit that makes it any more "inherently honest" than a SS amp. Sure you can count tubes and look up the nominal ratings for those tubes, but that tells you nothing about the rest of the circuit, or how much voltage is going to the different parts of those tubes in that specific circuit, or whether the wattage generated is used efficiently, etc.

Also while I will freely agree that manufacturers in general lie about specs, I have not ever seen an instance where I thought the specs were slanted on the basis of the amp being solid state.

People often gripe about an amp they tried being "underpowered" or "not able to produce the watts they claim" when actually the problem was often caused by incorrect gain staging, incorrect assumptions about volume/gain knob position, failing to perceive the pre-voicing (inherent EQ shaping) of amp designs even when set "flat", failing to RTM and understand what knob settings are "flat" for that amp, etc. etc. etc.

Gain staging? That's just semantics.

 

[NKUSigEp]

-1 for reading comprehension. The myth listed in the OP, and propagated by millions of ignorant people, is that tube watts are different from solid state watts.

But that's what I was saying (in some roundabout, illogical way), a watt is a watt is a watt is a watt. But since when is volume measured in watts? I know what you're getting at, but your argument at face value is useless because you're talking about watts in reference to volume.

 

[pedro]

So this quote comes from post #15...

No post #370. Look right above where it says

Join Date: Apr 2000
Location: Madison, WI.

 

[fdeck]

I think the technical definition of "loudness" is a red herring until we prove that there is an effect -- what it consists of and what its magnitude is. Until then all we have are varying claims ranging from modest to hyperbolic, and explanations ranging from mundane to magical.

If two amps sound different, then they will deliver different waveforms to a load. Any engineer who understands tube amps can show us the waveforms and end the debate. If real world signal and load conditions are necessary to illustrate the effects, then use those conditions in your tests.

I am willing to agree that tube power amp effects are probably real, but of unknown magnitude due to the wide range of subjective claims. Modest claims are probably true, hyperbolic claims are probably false, and reality is probably somewhere in between.

So far, nothing jumps out at me as a reason to get excited about tube power amps, except for the headroom afforded by a soft power supply. But a few dB of headroom still doesn't tip the scales, pound for pound, or dollar for dollar, compared to a switchmode amp. I also don't know which tube power amps have soft power supplies, or if all of them do.

Meanwhile, I am taking a skeptical position, because I think that measured waveforms are the only way out of the thicket.

I design scientific instruments for a living. If someone claims that two instruments give noticeably different results (an issue that I obviously take very seriously), and they don't have hard data to show me, then I will either suggest a way to obtain the data, or just send them away. Sometimes it takes a few attempts to refine a test so that it is unaffected by extraneous factors.

So far in my life I have never regretted ignoring claims that can't be backed up by either empirical data or a plausible explanation.

And if you don't believe me, read post #379.

 

[bongomania]

But since when is volume measured in watts? I know what you're getting at, but your argument at face value is useless because you're talking about watts in reference to volume.

Pretty much every bassist at the beginning of their career thought watts = volume. Tell me that's not true. Now tell me people don't still talk about getting more watts in order to get more loudness. You see where I'm going- "since when" is since the dawn of time so to speak, and continues to this moment, among people who don't know better.

And I'm not talking about watts in reference to volume, I'm talking about volume in reference to watts- the difference is that people are saying tube amps give you more volume per watt, and I'm saying that's only a fraction of the story, and that "one specific solid state amp by itself" is not a definition of "any solid state amp" or the capabilities of solid state when used in an educated way, based on the number of watts.

 

[fdeck]

but the last 4 pages nobody commented on this. Does this also contribute to the perceived loudness and
how much?

There was a brief discussion many pages ago, following post #227, which is worth looking at. And my response in post #240.

The "soft" power supply of a tube amp might allow reproduction of a waveform with a brief transient attack (e.g., a bass note) at a higher maximum amplitude than the amplitude of a continuous waveform. The graphs in post #227 suggest the gain might be a few dB.

One thing to note is that there is no obvious compression (reduction of overall gain, as opposed to hard clipping) in the tube amp.

 

[bongomania]

One thing to note is that there is no obvious compression (reduction of overall gain, as opposed to hard clipping) in the tube amp.

I noticed that (as you might imagine ), which is why I then asked if he was sure the same amount of gain was being applied at the input of both amps. Those pictures did a lot to illustrate the difference in performance between a static load and a reactive one, but I think that's all they really demonstrated (based on the data presented so far).

 

[fdeck]

I noticed that (as you might imagine ), which is why I then asked if he was sure the same amount of gain was being applied at the input of both amps. Those pictures did a lot to illustrate the difference in performance between a static load and a reactive one, but I think that's all they really demonstrated (based on the data presented so far).

I was somehow able to persuade myself that the gain didn't matter, because all I was really looking at was the two traces on the left hand graph, and both are presumably displayed at the same vertical scale.

That's a snazzy scope that can display a stored waveform while measuring another waveform. To do that in my shop, I am stuck resorting to stupid computer tricks.

Now, a counter argument (can't just let something be settled, can we?). In the patent for Peavey's "DDT" compression scheme, the text states that hard clipping of the first couple waves of a transient note isn't objectionable. However, I don't know what data led the inventor to that conclusion.

 

[bongomania]

I was earlier speculating in my mind that the manufacturers of both amps might have used a static load to determine the wattage rating, which could indicate that the tube amp under a reactive speaker load would actually be higher wattage. Not "more powerful per watt", but in fact higher wattage.

I repeat though, that's just speculation.

 

[pedro]

whoooooossshhh!!!

(pedro looks up to see what it was that just went over his head.)

 

[fdeck]

I was earlier speculating in my mind that the manufacturers of both amps might have used a static load to determine the wattage rating, which could indicate that the tube amp under a reactive speaker load would actually be higher wattage. Not "more powerful per watt", but in fact higher wattage.

I repeat though, that's just speculation.

I suspect they would have used the mainstream test in both cases RMS voltage into a dummy load, quoted as a power rating. The correct way of saying it is such a mouthful that people just say "RMS."

The tube amp under a reactive load at the frequency of the impedance peak could have actually been putting out less power. The higher output voltage was probably indicative of drawing much less current from the power supply.

 

[wallybill]

Thus, the solid state amp is not "less loud" because it is solid state, but rather because it lacks processing that is inherent to most tube amps. Ergo tube amps are louder if you don't know how to do anything other than plug your bass into the amp and turn the gain knobs.

This is the basis for poor old George's "tube vs. SS" experience, and since he doesn't know how the signal is processed he can only rely on what results you get just by plugging in and turning up. Never mind that the B2RE is widely reviled as a terrible, weak, inefficient amp, completely irrespective of it being SS.

If people want to change their position to "between a tube amp and an equal-wattage SS amp, used by someone who just plugs in and turns it up, the tube amp will be louder", then yeah, obviously. But to then say "tube amps are inherently louder" is false, because an SS amp can be made to be equally loud without adding any wattage; and to go further and say "tube watts are louder than solid state watts" is obviously false.

Aha! Now that makes much sense to me. I've never had much luck with a compressor on my rig (for some reason I can tune one in pretty well for drums through the PA). I do believe I now understand why my 300 watt tube amp "sounds" louder than my 1,000 watt SS amp. I'm one of those "just plugs in and turns it up" guys.
On another note, I was told that a SS amp had blown my speakers by putting DC voltage into them. It was a loaner amp while mine was getting fixed. The tech then said something along the lines of "crud - this amp is seriously screwed up." The good folks at Peavey actually repaired the speakers under warranty. But told me not to do that again.