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Differences between tube amps and solid-state amps - How do I know which one to get? - Page 3

post #31 of 77

Just refering to the Zana Deux, which is a SET and OTL amp. Low output impedance is achieved by global feedback(nfb) or else it would be 90 ohms. So SET and OTL are not mutually exclusive.

 

OTL and OCL are more of the coupling methods used to achieve blocking of DC from getting into your headphones. Zana Deux for example is OTL but is capacitor coupled to achieve DC blocking. Transformer coupled tube amps are generally OCL.

 

I think push pull is best explained here http://www.head-fi.org/t/595246/difference-between-push-pull-and-balanced

 

As for hybrid, it refers to tube amps(usually for voltage gain) used in combination with a transistor output to achieve low impedance and high current.

 

edit: looks ima beaten to the punch


Edited by firev1 - 3/14/14 at 3:40am
post #32 of 77
Quote:
Originally Posted by firev1 View Post
 

Just refering to the Zana Deux, which is a SET and OTL amp. Low output impedance is achieved by global feedback(nfb) or else it would be 90 ohms. So SET and OTL are not mutually exclusive.

 

OTL and OCL is more of the coupling method used to achieve blocking of DC from getting into your headphones. Zana Deux for example is OTL but is capacitor coupled to achieve DC blocking. I think transformer coupled tube amps are generally OCL.

 

Just a pair of comments to complete what was said:

 

- Output impedance of the Zana 2 without feedback is about 50 ohms. You have to // the plate resistor and the internal resistance of the tube.

 

- Transformers do a lot more than just removing the offset. They convert voltage to current. It's a big deal since tubes are mostly high voltage/low current devices. The problem with OTL isn't only output impedance, it's also often limited current delivery.

 

- Actually, transformer coupled amps can also be cap coupled, if using the parafeed topology (Mapletree's design for example)

post #33 of 77

Wow thanks chaps. I truly appreciate it that you've replied back in easy to understand terms. I'll definitely read up on the links more to read up. Yes the ZD output impedance is achieved by the global feedback. My Zana Deux is the original with the 12 ohm Zout and with Craig's guidance the tech installed by adding a 1k resistor in parallel to the 4.7k in the NFB (and a switch so that I can get the same ZDSE functionality).

 

Quote:

The problem with OTL isn't only output impedance, it's also often limited current delivery.

 

 

This is where I further demonstrate my ignorance but aren't the two related anyway (I=V/R)? The reason for my curiosity about this is that my Alpha Dogs sounded somewhat "slow" on my ZDSE in comparison to my hybrid TUR-06 and the explanation provided to me was that it was because the ZDSE is an OTL and couldn't deliver the current that the ADs needed. However it seems the ZDSE, despite being an OTL, doesn't have such a high output impedance as other OTLs amps and therefore should be able to deliver higher current than other OTLs. i.e. poor current isn't the explanation why the ADs sound slow on the ZDSE?

 

Again, if I've asked a stupid question, I apologise, still learning.

post #34 of 77

Output impedance and current delivery are indeed related but not quite the same thing.

 

 

 

 

Let's take an example: In a simple cathode follower configuration, both a very powerfull low gain (µ), high current (low rp) tube and a  weak high gain, low current (high rp) tube could have the same output impedance (formula is rp/µ+1). The first tube will be able to push a lot more current into the load, as long as you can increase the input signal in proportion.

 

Btw, reducing output impedance through feedback only reduces the impedance seen by the load, it doesn't actually reduce the power "lost" inside the amplifier. It doesn't allow more current to be provided, it just reduces the variations in frequency due to a high output impedance.

post #35 of 77
Quote:
Originally Posted by 00940 View Post

- Transformers do a lot more than just removing the offset. They convert voltage to current. It's a big deal since tubes are mostly high voltage/low current devices.

I don't know that "convert voltage to current" is the best way to describe it. "Trade voltage for current" would perhaps be better. EDIT: on second thought, I don't think either of these really work and suggest people not think of transformers in that way.

Basically (and I'm not saying this specifically to you but just generally), transformers transform voltage by the turns ratio (the ratio of the number of turns of wire on the primary versus the number of turns on the secondary) and transforms impedance by the square of the turns ratio.

The loads we typically want to drive with tubes, such as headphones and loudspeakers have a much lower impedance than the tube wants to see and the output impedance of the tube is higher than we want to drive those loads with as well.

5,000 ohms isn't an uncommon load impedance for tubes. So if we want to drive a 50 ohm headphone load, that's a ratio of 100:1. And since transformers transform impedance by the square of the turns ratio, we need a turns ratio of 10:1 (10 being the square root of 100). So if we have 10,000 turns of wire on the primary, we'll need 1,000 turns on the secondary. Now with a 50 ohm load on the secondary, the tube will see 5,000 ohms at the primary. As well, the output impedance of the tube will be reduced by a factor of 100 so the headphones see a much lower impedance than they would without the transformer.

But as was said, transformers also transform voltage by the turns ratio. So in order to achieve a given voltage at the output, the tube will have to deliver 10 times that voltage at the primary. In other words, to get 1 volt out, you have to put 10 volts in.

This is all a consequence of transformers being passive devices so due to that nasty law of conservation, power out can never be greater than power in (and in real world devices where there will always be some losses, power out will always be slightly less than power in). One volt into 50 ohms is 20 milliwatts. 10 volts into 5,000 ohms is also 20 milliwatts.

Hopefully this will take some of the mystery out of transformers.

se
Edited by Steve Eddy - 3/14/14 at 9:35am
post #36 of 77
Quote:

Originally Posted by firev1 View Post

 

Probably the knowledge, especially with regards to which distortions weigh more on the human hearing, even now its not really known. Soundstage IME is a very real thing though, imo phase and harmonic distribution has the most to do with it along with other factors.

 

I know from personal experience that equalization of the high frequencies results in better soundstage which I consider being able to hear the placements of instruments in space. I have also read in some tube rolling forms I have read that the right tube can improve soundstage with the placement of instruments explicitly stated as the improvement the writer recommending, said tube, was talking about.

 

 

Consequently I assume the recommended tube was affecting the harmonic distribution the above respondent was talking about. So what about the two together high-frequency equalization plus the proper tube for good soundstage, will the two only probably complement each other or is this some probability they will detract from one another? Or will one make the other superfluous?

post #37 of 77

Phase and harmonic distribution are a hundred times worse on speakers than headphones, yet speakers have soundstage that is a hundred times clearer than headphones.

 

Soundstage requires space for the sound to inhabit.

post #38 of 77
Quote:
Originally Posted by bigshot View Post
 

Phase and harmonic distribution are a hundred times worse on speakers than headphones, yet speakers have soundstage that is a hundred times clearer than headphones.

 

Soundstage requires space for the sound to inhabit.

That has not been my experience.

post #39 of 77

which?

post #40 of 77

Are we even certain soundstage is related to phase and harmonic distortion?

 

Since still no one can't figure out what's soundstage. Stuffs like very uneven freq response can create soundstage (i.e KEF M500) but there is little we know about soundstage in general.

post #41 of 77

Soundstage is very well known in speakers. There are specific things you can do to create a clear soundstage, none of which apply to headphones.

post #42 of 77
Quote:
Originally Posted by bigshot View Post
 

Soundstage is very well known in speakers. There are specific things you can do to create a clear soundstage, none of which apply to headphones.

Quote:
Originally Posted by Nirmalanow View Post
 

There are ways to create a more realistic soundstage ranging from software to hardware:

 

http://www.head-fi.org/t/642013/noozxoide-for-android#

 

http://www.head-fi.org/t/361251/the-holy-grail-of-true-sound-stage-cross-feed-the-next-generation

 

http://www.head-fi.org/t/648968/a-headphone-shootout-from-a-speaker-listener-testing-eight-headphones-from-80-to-1-200/75#post_9210326 (This headphone review features a new amp called the iCAN that has a 3D feature built in. I just got a loaner of this amp that I am going to review)

 
post #43 of 77

DSPs can only do so much for headphones. A big part of soundstage perception is based on moving your head as you listen to locate sound sources. The only way to do that on headphones is with head tracking software. You can add cross feed, adjust phase and add reverb using DSPs, but it just alters the "open -ness" of the sound, it doesn't place it in three dimensional space like soundstage does.

 

DSPs can do amazing things with 5:1 systems though.

post #44 of 77
post #45 of 77
Quote:
Originally Posted by Citan View Post
 

Amps should be as transparent as possible, that is, all they should do is amplify the signal.  They shouldn't sound like anything, if it does, the amp is distorting the signal.  Tube amps will almost always add more distortion than a decent solid state amp.  There really is no reason to go with a tube amp if you are looking for the highest possible fidelity.    

 

This is ridiculous. All amplified waveforms are distorted it's impossible to avoid. In fact there are 6 primary types of distortion and each represents a different effect on a waveform. The two primary factors that control an amps accuracy are deflection and efficiency. It's for this reason that anything other than a Class A amp is inferior. Without 360 degree deflection your amp will not be outputting all of the signal that was inputted. Can a Solid-State amp be biased into Class A... Yes. Are electronic transistors more efficient than vacuum tubes? Yes... Until they heat up. Then a solid-state amplifier will begin to waste power as heat and the efficiency goes down. 

 

Tubes are not Green, but they are in every way better at reproducing sound than an IC. As tubes heat up the cathode becomes more efficient at emitting electrons. The exception to all of this may (I say may because I can't get Nelson to send me one) be the Pass SIT-2... Which he custom engineered to mimic a tube. It is the only one the even comes close to the bench performance of a tube.

 

An amplifier should not produce a perceivable effect on your waveform. It should be, and typically always is FLAT in it's response from 20 to 20. If you hear something from the amp, then it is a POS or you have a bad ground. If it is even average it will have a Flat response. "But I have listened to..." Irrelevant. Why? Because personal audio amplification is the byproduct of amplified audio recording. You can not replicate what was heard in the control room without first trying to replicate the equipment that was used when they made the album. Why do you think the Telefunken, Fairchild and Harmony are all LEGENDS that cost 50k+ to find in working order?

 

"Lots of PRO studios use..." Irrelevant! If you want to listen to poorly recorded music then grab a SS and get busy. But I am 100% certain that if Rick Rubin were here he'd agree that a studio without tubes is a dead zone. I know engineers that turn the studio on 12 hours before the session starts just to get the heat balanced out and everythign nice and hot... You literally sweat your ass in those studios.

 

What you should really spend your cash on is the flattest set of headphones you can afford. Why? Monitors and headphones in a studio are calibrated to be as flat as possible. My friends at Sonarworks can take any speaker or set of cans and make them perform like any other driver in the world. It requires a 16000 band EQ (Taps) and a computer. But flat is how the drivers should perform if you want to experience what the recording artist did when they recorded the album.

 

Audio is about Physics. There is no science in our reality that will allow a rapid switching device (gate) to produce a smoother continuous waveform than a Class A Tube amplifier with a properly designed linear power supply. Tubes are about power. Low-power and high-power and not comparable to the performance of one another.

 

If you are wondering who this crazy one-hit wonder is that's crapping all over your parade... My name is Jason and I grew up behind the API Legacy 48+48 in the historic RCA studios. I have watched 16 Grammy albums be recorded, was a certified Audio Engineer by the time I was 16 and currently own Tubecore Audio and design robotic tube audio systems with embedded computers.

 

How I got here I can't even remember, but after reading this entire thread I just couldn't stand it. What are you talking about? Why are you feeding a newbie all this forum trash? Wiki physics and read... 

 

Quote:
Originally Posted by miceblue View Post
 


Ooh, that's a cool test. I'll be sure to cast my vote when I get the chance. :)

 

 

Psychoacoustics is pseudo-science for the unenlightened. 

 

Flat response and driver efficiency are all that matter. Everything else is POWER and how you wield it.

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