Head-Fi.org › Forums › Equipment Forums › Sound Science › Differences between tube amps and solid-state amps - How do I know which one to get?
New Posts  All Forums:Forum Nav:

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

post #31 of 44

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 44
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 44

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 44

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 44
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 44
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 44

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 44
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 44

which?

post #40 of 44

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 44

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 44
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 44

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 44
New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Sound Science
Head-Fi.org › Forums › Equipment Forums › Sound Science › Differences between tube amps and solid-state amps - How do I know which one to get?