Thank you!Read and liked
Thank you!Read and liked
Maybe this was mentioned earlier in this thread, but I did not see it if it was:
The biggest difference I hear when listening to speakers driven by a tube output stage vs. solid state is related to Ohms-law interactions between the higher output source impedance of a typical tube amp and the load impedance of the speaker, which varies with frequency. Many tube amps introduce a frequency response artifact from the interaction of their high-ish output source impedance with the speaker's load impedance. Have a look at the following two graphs- the black trace shows amplifier output power output as affected by speaker load impedance interacting with the amplifier's source impedance:
PRIMALUNA DIALOGUE AMPLIFIER - TUBE from https://www.stereophile.com/content/primaluna-dialogue-premium-power-amplifier-measurements
± 8.5 dB response variation !
PARASOUND INTEGRATED AMP - SOLID STATE from https://www.stereophile.com/content/parasound-halo-integrated-integrated-amplifier-measurements
± 0.125 dB response variation nearly two orders of magnitude lower variation than the Primaluna!
One can argue about low-order harmonics that tubes can inject into the sound, etc etc but those effects are very small in magnitude compared to this source impedance- speaker load impedance "Ohm's law interaction." I mean, ±8.5 dB of frequency response variation is a pretty huge coloration.
Not all tube output stages show such high source impedance, but with the recent fashion of avoiding negative feedback we see more and more tube amps with high output source impedance. This is fine, but people who prefer this sound need to understand that they are using their amplifiers as a TONE CONTROL.
(Actually I rather like the way a pair of 2-way speakers I built using a 5.25" SEAS magnesium cone woofer and a SEAS Millenium tweeter sound on an Audioromy FU29 tube amp which shows EXACTLY this kind of coloration. But I KNOW I am using the amp as a tone control. The other thing I like about the amp is that when it is clipping in the low bass it still sounds OK, the amp doesn't produce all kinds of high-order trash. This is a system I use for casual listening. It sounds "nice" but not neutral or accurate. I wouldn't say it sounds especially "musical" either, it just sounds "nice.")
That is partly true. Partly because this only f-s up the damping factor.
As tube amps deliver power rather than voltage they react differently to higher impedance swings compared to only a lower damping factor.
Power delivery is due to voltage and current capability into load(impedance). The current flow in the resistive component of the load, determined by the impedance, will produce power. I don't understand that tube amps deliver power rather than voltage. Without voltage there is no power delivery in amps. Ohms law. I'm sure you meant something different to what you said.
What the guy was essentially saying is that the vintage HiEff speakers were designed to work at their best with higher output impedance (tube) amps.
Nope what I said is correct. Tube amps supply power.
An example. A SS amp provides 30 W into 8 ohm and 15W in 16 ohm.
A 30W rated tube amp rated 30W in 8 ohm can supply 25W in 16 Ohm so substantially more (granted depends on the design) .
I've listened to several tube amps over the years but the only one I actually owned was the Wheatfield HA-2, a SET OTL headphone tube amp that I used to drive Sennheiser HD580s, whose 300+ ohm impedance makes them a good load for an OTL amp.I would like to know what is the scientific reason behind the "attractiveness" of tubey sound.
My impression is as below: ...
...
Yep, and the term "OTL" refers to the ones that don't. "Output Transformer-Less". These may be more transparent (no transformer in the signal path) but generally, they can only drive high impedance loads.Most tube amps have tapped output transformers so deliver the same power into a resistive load be it 4, 8, or 16 ohms....
Most tube amps have tapped output transformers so deliver the same power into a resistive load be it 4, 8, or 16 ohms.
A small qualification to that - they deliver the same power into the load that has been selected. They don't do that if a nominally 16 Ω speaker (with the transformer set to that load) drops to 8 Ω at some frequency.
When I plumbed my 'scope to the amp's output it burned the probe's ground lead in two. At least it didn't fry the amplifier... Folk using subs like REL that add a ground wire need to be careful to follow their manual and not attach it in that case.
One consequence of this important point is you can't trust the frequency response measurements of a high output impedance amplifier. It might be flat as measured by the manufacturer. But conventional headphones or speakers have varying impedance with frequency, which will change the impedance ratios and thus the frequency response.A small qualification to that - they deliver the same power into the load that has been selected. They don't do that if a nominally 16 Ω speaker (with the transformer set to that load) drops to 8 Ω at some frequency.
One consequence of this important point is you can't trust the frequency response measurements of a high output impedance amplifier. It might be flat as measured by the manufacturer. But conventional headphones or speakers have varying impedance with frequency, which will change the impedance ratios and thus the frequency response.
So when it comes to tube amps just because it "measures flat" doesn't mean it actually has flat frequency response when it's driving an actual headphone or speaker. I believe this is a contributing factor to tube amps sounding more different when driving different headphones, and if the impedance vs. frequency curves for headphones shares some common characteristics (such as impedance peaking in a certain frequency range) this could also contribute to what people think of as the characteristic "tubey" sound.
I deliberately avoided mentioning OTL in general and Futterman specifically due to bad experiences in a previous life... It wasn't all bad, but when it was bad, it was really bad.
I’ve seen current amplifiers and voltage amplifiers. You seem to be saying that the output response of a tube amplifier is power. Voltage signal in. Power signal out. I know a simple triode sure doesn’t do that. Explain.Nope what I said is correct. Tube amps supply power.
An example. A SS amp provides 30 W into 8 ohm and 15W in 16 ohm.
A 30W rated tube amp rated 30W in 8 ohm can supply 25W in 16 Ohm so substantially more (granted depends on the design) .
So around resonance frequencies of speakers more power (and thus voltage) is available. That's simply how tube amps work.