[firev1]

 
Are we talking tube vs transistor or about impedance issues, I really don't know where this is going. Anyways I'm not answering as I can't verify any of those claims made, nor trust the word of a single company who sells tube amps without any watermarked graphs or proof. 
 
On another note

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And as for you..........LOL.............are you also an EE student, sir?

I'm glad I got your back, Jack.
Excuse my dry sense of humour please.

I've read Self's "Power Amp Design Handbook", the movie wasn't as good as the book.
If you would like one or two or a whole bunch of Otala's papers, send me a PM.
I'll be glad to send them to anyone who asks.
Hs work was very groundbreaking, if nothing else he got everyone talking and thinking about TIM and high output current.
For only that, all modern power amp designers at least owe him a "tip of the hat".
 

Not at all, I'm a aeronautics student. I do study laplace and impulse response and other stuff like that in my course of study(I have a advance module aptly named Physics for Engineers). I also have a grasp of electrical fundamentals and IC logic. I do read books on analog design as part of hobby and research for a group project though.
 
 

 

[germanium]

Quote:

 
Are we talking tube vs transistor or about impedance issues, I really don't know where this is going. Anyways I'm not answering as I can't verify any of those claims made, nor trust the word of a single company who sells tube amps without any watermarked graphs or proof. 
 
On another note
Not at all, I'm a aeronautics student. I do study laplace and impulse response and other stuff like that in my course of study(I have a advance module aptly named Physics for Engineers). I also have a grasp of electrical fundamentals and IC logic. I do read books on analog design as part of hobby and research for a group project though.
 
 

Tubes were brought up compared to transistors to show largely that low output impedance is not always nessessary to get great sound, In fact many times works against great sound. Tubes even with feedback generally don't have super low output impedance. If you have a damping factor of more than 30 on a tube amp then you are the exception wheras with transistors that would be a very low damping factor. Some speaker drive systems just don't like to be choked which is what happens when they are fed with an amp with a high damping factor.
 
This includes most horns & especially full range electrostats. Feed an electrostat with a high damping factor amp & you will experience some of the worst sound imaginable. No bass & sizzling top end. Put a low to zero feedback tube amp on them & they will sound balanced. They can even have quite substantial bass as they did with my friends zero feedback tube amp. Enough to activate the protection circuit on the speakers with only 25watts available yet the transtor amp that was normally used with them would not activate the protection circuits even with 300 watts & believe me this guy was using them 300 watts when we arrived with my friends tube amp. However the transistor amp required a subwoofer to get any bass at all & my friends tube amp sounded balanced without the use of a subwoofer on those same speakers. These were Quad ESL speakers I are talking of, not known for exceptional bass because of the amps they are nomally paired with.
 
 Many of the lower end Martin Logan speakers sound sick with the tipical amps used with them. Unfortunately I don't think that my friends tube amp would help them much as there is way too much discontinuity between the woofer & the electrostat panel with these. The lower end Martin Logans have builtin dynamic woofers & to my ears sound horrible at best with any amp driving them it seems. They look nice but to me that is where the nice ends.
 
High damping factors also waste power as power is used in the proccess of choking (braking) the driver This power comes from somewhere & that somewhere is the power supply of the amp. Zero feed back tube amps don't waste power trying to brake the speaker hence they play louder for a given wattage rating. Whie this does work against them with cirtain speaker designs that were designed with high damping factors in mind (acoustic suspension speakers in particularwith total Q's greater than .707 which most are) it works very well with most other speaker designs Horns, electrostats, many ported speaker designs & ribbons all benefit from low to zero feedback tube designs which have low damping factors.

 

[xnor]

Quote:

Tubes were brought up compared to transistors to show largely that low output impedance is not always nessessary to get great sound, In fact many times works against great sound.

Nope.
 
 
Quote:

Tubes even with feedback generally don't have super low output impedance.

Which is a limitation.
 
 
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High damping factors also waste power as power is used in the proccess of choking (braking) the driver Zero feed back tube amps don't waste power trying to brake the speaker hence they play louder for a given wattage rating.

Nope, tubes waste a lot of power.
 
 
Quote:

Whie this does work against them with cirtain speaker designs that were designed with high damping factors in mind (acoustic suspension speakers in particularwith total Q's greater than .707 which most are) it works very well with most other speaker designs Horns, electrostats, many ported speaker designs & ribbons all benefit from low to zero feedback tube designs which have low damping factors.

(Emphasis by me.)
Nope, has nothing to do with tubes. You don't need tubes for low feedback, nor for high output impedance.
 
Also, besides being inefficient, tubes are bigger, less rugged, require periodic replacement ...

 
 

 

[Chris J]

Quote:

 
Are we talking tube vs transistor or about impedance issues, I really don't know where this is going. Anyways I'm not answering as I can't verify any of those claims made, nor trust the word of a single company who sells tube amps without any watermarked graphs or proof. 
 

This thread was originally started by Germanium to discuss (I think):
 - Output Transformerless Vacuum Tube power amps
 - low damping factors
 - high output impedances
 - zero feedback
 - Class A operation
 - mechanically damped loudspeakers (I think)
 
I agree, the Atma-sphere link is mostly unsubstantiated marketing fluff.  The designers (like Jack) really seem to know what they are doing. Lik most audiophile marketing groups, they cloud the issue with obscurant  articles.
 
Quote:

 
 
Many of the lower end Martin Logan speakers sound sick with the tipical amps used with them. Unfortunately I don't think that my friends tube amp would help them much as there is way too much discontinuity between the woofer & the electrostat panel with these. The lower end Martin Logans have builtin dynamic woofers & to my ears sound horrible at best with any amp driving them it seems. They look nice but to me that is where the nice ends.
 
High damping factors also waste power as power is used in the proccess of choking (braking) the driver This power comes from somewhere & that somewhere is the power supply of the amp. Zero feed back tube amps don't waste power trying to brake the speaker hence they play louder for a given wattage rating. Whie this does work against them with cirtain speaker designs that were designed with high damping factors in mind (acoustic suspension speakers in particularwith total Q's greater than .707 which most are) it works very well with most other speaker designs Horns, electrostats, many ported speaker designs & ribbons all benefit from low to zero feedback tube designs which have low damping factors.

Thanks for the tip, on garbage day I will throwing out my lower end Martin Logans.
BTW, I my opinion, they sound better with a solid state amp.
I used to use an Output Transformer Coupled vacuum tube power amp with a cascode differential pair input stage, I thought that amp and the MLs sounded sick.   Just my opinion.
 
Mathematically, a high output impedance power amp is less electrically efficient than a low output impedance amp.
Quote:

Nope.
 
 
Which is a limitation.
 
 
Nope, tubes waste a lot of power.
 
 
(Emphasis by me.)
Nope, has nothing to do with tubes. You don't need tubes for low feedback, nor for high output impedance.
 
Also, besides being inefficient, tubes are bigger, less rugged, require periodic replacement ...
 

I gotta agree with all of what you say except the part about rugged.
Not too sure if I have ever seen a tube power amp with short circuit protection, but I have seen a lot of solid state power amps with circuit limiting protection. 
Generally speaking most tube power amps can withstand a momentary short circuit. I'm not sure, but I suspect this only holds true for Output Transformer Coupled tube amps.
If you are saying that tube are less rugged mechanically, well then, I agree.
 
 

 

[firev1]

Quote:

Originally Posted by germanium /img/forum/go_quote.gif
 
This includes most horns & especially full range electrostats. Feed an electrostat with a high damping factor amp & you will experience some of the worst sound imaginable. No bass & sizzling top end. Put a low to zero feedback tube amp on them & they will sound balanced. They can even have quite substantial bass as they did with my friends zero feedback tube amp. Enough to activate the protection circuit on the speakers with only 25watts available yet the transtor amp that was normally used with them would not activate the protection circuits even with 300 watts & believe me this guy was using them 300 watts when we arrived with my friends tube amp. However the transistor amp required a subwoofer to get any bass at all & my friends tube amp sounded balanced without the use of a subwoofer on those same speakers. These were Quad ESL speakers I are talking of, not known for exceptional bass because of the amps they are nomally paired with.
 

I'm sorry to say I'm not really knowledgeable on the topic of Electrostats and horns although I'm aware that the statement on high damping factor for electrostats may be false if the example I give is in context. Just look at the Kevin Gilmore SS electrostatic amp. It has a low output impedance(with corresponding high damping factor) and is reported to sound very good with better extension on the top end. 
 
Also, having the speaker's protection circuits activated is a sign of poor power control?

 

[germanium]

Quote:

I'm sorry to say I'm not really knowledgeable on the topic of Electrostats and horns although I'm aware that the statement on high damping factor for electrostats may be false if the example I give is in context. Just look at the Kevin Gilmore SS electrostatic amp. It has a low output impedance(with corresponding high damping factor) and is reported to sound very good with better extension on the top end. 
 
Also, having the speaker's protection circuits activated is a sign of poor power control?

The bass was very smooth & controlled. It was just more than the driver could handle so the protection cut in on them. Into the capacitative load the amp that my friend built would put out the equivolent voltage that if it were to be driving a normal speaker at that voltage it would have been delivering 100 watts in the bass frequencies.Due to the high speaker impedance of the electrostat at low frequencies the actual power is much less, probably as low as 10 watts. however a 100watt per channel transistor amp driving these speakers in the bass frequencies would deliver tha same wattage as the my friends 25 watt amp but would have delivered as 400 wats at the high frequencies assuming stable power supply at that load (Appox 1-2 ohms fepending on the design) making them sound thin & shrill. My friends amp would have only delivered a little under it's rated power. Probably about 20watts. This is more in keeping with getting a good balance on an electrostat speaker.
 
 The amp that you are talking of may have EQ built in to compensate for the charateristics of electrostats. As you pointed out they were designed to drive electrostats. Most transistor amps are not designed to do so & performance suffers as a result.
 
Without feedback the low damping factor allowed the amp to rise to the occasion when faced with a capacitative load delivering more voltage in the bass to maintain a more constant power than a high damping factor amp would have delivered. You really need to read up on electrostats before commenting. Electrostats are an almost pure capacitative load & transistor amp have problems with that kind of load as at high frequencies they look like almost a dead short & at low frequencies they have a very high impedance & as a result the amp needs to deliver more voltage in the bass in order to maintain proper balance. Martin logan full range electrostats were known to be quite ear piercing with high damping factor transistor gear. Note that while some transistor amps are stable into a capacitative load that is no guarantee of good sound with electrostats. Mark Levinson amps are stable into a capacitative load but still sound bad with electrostats I heard hooked to them. Yes it was Mark Levinson amps that were originally hooked to the Quad electrostats & my friends a tube amp did sound considerably better driving them, A fact that even the owner of the Mark Levinson amp acknowledged after hearing the tube amp hooked to them.
 
Here is a review of the Martin Logan CLS full range speakers I was talking about as sounding not good with solid state gear http://www.stereophile.com/content/martinlogan-cls-loudspeaker-page-3

 

[xnor]

Quote:

You really need to read up on electrostats before commenting. Electrostats are an almost pure capacitative load & transistor amp have problems with that kind of load as at high frequencies they look like almost a dead short & at low frequencies they have a very high impedance & as a result the amp needs to deliver more voltage in the bass in order to maintain proper balance.

From the review you linked:
 
Quote:

Looking at the amplifier load factor, the impedance curve (fig.1) is typically "electrostatic." Low at low frequencies, and with no visible signs of the 50Hz diaphragm resonance, it climbs steeply to a harmless 33 ohms by 1kHz. Above this level, the load is almost purely capacitive, falling with frequency at 6dB/octave, reaching 2.5 ohms at 10kHz, and finally bottoming out at a value of 1.6 ohms at 20kHz.

 
Emphasis by me. No further comment.

 

[Chris J]

 
Quote:

From the review you linked:
 
 
Emphasis by me. No further comment.

 
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