I have a p/p tube amp running a pair of 6Ca7's for about 30 watts per channel . I have read here that p/p tube amps sound their best when they have to work a bit harder , as opposed to a SET amp that sounds best near idle . My present speakers are claimed to be 92 db. eff. If this amp is driving a pair of speakers rated at 85 db. efficiency , should it sound a bit better due to working a little harder or closer to its optimum level ? Conversely , would the same amp sound a bit worse driving a more efficient speaker of 99 db. due to it working less hard or further away from its optimum level ?
Yes the input stage is class A as are nearly all input /preamplifier sections in amplifiers (power or integrated). I was referencing the KT 88 "output stage" which is class AB. Pentodes can be wired to function in triode mode. Charles
@saki70 it might be awhile before I get my Magnapan 0.7's More than likely another 6 weeks : ( But I will post my findings for what it's worth : ) I found this on my VAC PA 80 80 manual, I had to sent it in and the UPS guy might of been mad at me as it weighs over 70 lbs They also did an over all upgrade caps etc It still has the original KT 88 Golden Dragon Tubes
Ultra-linear or Triode? The input amplifier, phase splitter, and driver stages are triode tubes operated in ClassA with no cut-off or grid current. The output stage is connected for partial-triode, well known for low distortion, good damping factor, and high efficiency. This technique was invented by Alan Blumlein of EMI in England, and was popularized in the US as "ultra-linear." VAC can convert amplifiers to triode connection for a small charge.
"...I forgot , in the post that you responded to , to add that the volume levels would be adjusted to be the same for both speaker tests .
Does that change your thinking ?"
What I stated was how the efficiency values are interpreted. If you compensate for the efficiency by increasing the volume, then you're basically asking the amplifier to work "harder" which in case of most tube amplifiers, particularly low powered SET designs, means more distortion. Aside from the speaker efficiency, another important criteria is the speaker's impedance and how it varies as a function of the frequency. Typically, the higher the impedance the less demand from the partnering amplifier which also translates to less distortion.
I don’t believe that the VAC amplifier switches between SET and push pull (PP) operation. Rather it switches between PP triode versus PP ultra linear output. This particular VAC amplifier is a class AB circuit. SET amplifiers are by default pure class A exclusively. Technically speaking the KT 88 if used to run single ended would be a SEP class A (single ended pentode) as opposed to SET (single ended triode) which are DHT (directly heated triode). Such as 300b,2A3, 845,, 211 etc. Charles
Before I convert my VAC from triode to PP l will use the same speaker tap ( 4 ohm) and listen to the speakers with the same volume setting using a sound meter
"If I use this 30 watt p/p tube amp with two different speakers , one with 99db. efficiency and one with 86db. efficiency and all other characteristics being equal , would the amp have a different sound with each ? If so , how ?"
If the listed dB specifications are at 1watt/1meter, then the 99dB speaker will sound louder than the 85dB rated speaker at the same listening distance when fed the same power. This applies to any amplifier regardless of its power rating.
I wanted to add , in the above supposition , that the volume for each speaker would be the same . This would mean that the amp would be barely idling on the 99db. speaker and turned up for the 85 db. speaker .
Would the resulting sound change due to how hard the amp is working or would the sound be the same regardless of how hard the amp has to work ?
Maybe I can have some input on this as I'll be added a pair of Maganapan 0.7 speakers in a few weeks to my system. Currently I'm using a VAC PA 80 80 set in triode mode with a ARC LS15 pre amp that drive my Definitive technology Mythos ST speakers that are rated at 91 db efficiency The speakers do double duty for me as I also use them for HT. The VAC at 35 watts has no problem driving the Mythos ST's
I'm very sceptical that the VAC with have enough juice in triode Mode for the Maganpan 0.7's but will give it a try and a good listen. More that likely I'll have to convert the VAC to PP and see if that has the power required. It does have 2,4&8 ohm taps and weights a ton! It should be interesting to listen for any changes in sound quality when it's in PP mode
@lowrider57's repost of my quote has made me realize that I should clarify: when I said "the higher the speaker impedance, the lower the distortion", the distortion I was speaking of is that produced by the amplifier, not the loudspeaker.
Hi Grinnell … yes I am still enjoying my Di Capo's .
Let's try this question a different way with this supposition ...
If I use this 30 watt p/p tube amp with two different speakers , one with 99db. efficiency and one with 86db. efficiency and all other characteristics being equal , would the amp have a different sound with each ? If so , how ?
Also true is that the higher the speaker impedance, the lower the distortion.
Your speakers have 92dB sensitivity. That's good but more importantly is what is the nominal impedance? And no way to know how your amp will perform with 85dB speakers without knowing the impedance. And the impedance curve will help determine how the amp will respond to the load of said speakers.
Not angry. Not bitter. Not even all that insulting. Read it again: "overthinking, shooting own foot, not seeing forest for the trees" These are all symptoms of a lack of perspective.
A pretty common fault, when you think about it. Alex Honnold, the only man to free solo El Capitan, when his fiancee asks about furniture looks at the bare floor and says, "I could sleep right there." Paul Krugman, Nobel Prize in Economics, says breaking windows adds to the economy. Its just awful hard to get real close to one subject and yet still maintain a healthy broad perspective.
That being the case, to the extent you draw attention to it, how's that anything but good?
tube amp designers know that good sound is the result of a well-balanced design, not distortion specs alone.
It is my understanding (correct me if I’m mistaken ;-) that ALL tubes produce less distortion as power output decreases (at least, above say a watt). What IS true is that tubes have to be run at their optimum plate and heater voltages, etc. to perform their best. Also true is that the higher the speaker impedance, the lower the distortion.
And yes, lower distortion = better sound. Ultra-low distortion figures got a bad name in solid state amps in the 1970’s, with good reason. The means employed to achieve lower measured static distortion specs (excessive negative feedback, etc.) resulted in worse sound. That is not the necessarily and automatically the case in well-designed tube amps., as tube amp designers know that good sound is the result of a well-balanced design, not distortion specs alone.
Yeah, you will hear a lot of stuff like that. Consider the source: audiophiles. No greater propensity for overthinking, shooting own foot, not seeing forest for the trees, etc, exists. Anywhere.
What is with the recent spate of anti-audiophile rhetoric on this site? In another thread, we’re called "morons" and "fanatics."
Why the anger and bitterness?
Who is served by this? If we’re such morons, why are these apparent adversaries so inclined to post here?
Still using the de Capos? im using mine with a 4 watt decware mini torii and don't think im losing anything from when i used my PL2 with EL34s. Now there are very different amps the PL2 is not as detailed at the Decware and the Decware has a fuller richer sound. Can i rock out as much NO but Im getting up there in years lol
I have read here that p/p tube amps sound their best when they have to work a bit harder , as opposed to a SET amp that sounds best near idle .
Yeah, you will hear a lot of stuff like that. Consider the source: audiophiles. No greater propensity for overthinking, shooting own foot, not seeing forest for the trees, etc, exists.
Anywhere.
So what happens is some guy hears some system sound really good, and... WHY? Can't just be that its a good combination. Has to be some technical reason for it. And being audiophiles, the more technical the better! Even if it makes absolutely no sense whatsoever!
The craziest thing I could think of is to get rid of speakers you like because they're too damn efficient. Now if there's something else you don't like about them, fine then. If you find speakers you like more that are less efficient, fine then too. But to change speakers only to make your amp "work harder" is nonsense on stilts.
Which, again: audiophiles! Bet you five hundred quatloos before the day is out we have at least one saying I'm nuts and yeah you should get some low efficiency speakers, and maybe even tell you drive them with a SET. Because: Audiophiles!
If you like the way your amp sounds with your speakers, great. If you don't, fine. Figure out which you like better- speakers or amp- work on finding ones that sound better. SOP.
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