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In Reply to: RE: Tube amp clipping is akin to compression...... posted by viridian on September 10, 2016 at 10:52:26
Yes, I did make that point. However, even an SE DHT amp does "eventually" clip hard, and I could detect no deformation of those peaks in quite a long time staring at the scope.
The compression part is more subjective - I don't detect it. More powerful amps don't sound more dynamic. Of course, if I tried 110 dB at the listening seat, there would be a huge difference. Why would I do that?
Sanders' numbers aren't legit, even for solid-state amps where you must avoid clipping at all costs.
(Again, he provides no support for his 500W-for-90 dB/W-speakers requirement.)
What I should do next is my five-watt First Watt F2J - a solid-state amp (one stage, no feedback, single-ended) that sounds better than most DHSET amps I've had.
Follow Ups:
It's not necessary to determine by eye whether the waveforms are being rounded or flattened while playing music. In fact, I'm not sure that's even possible, except in extreme circumstances. Instead, just calibrate the scope to the amp with a sine wave and note where the amplifier clips on the screen. With music playing, no signals should reach that level.
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Buy Chinese. Bury freedom.
First, my intent was to duplicate the experiment as suggested by Mr. Sanders.
(I think is IS possible to spot clipping if it's hard and regular.)
Second, your suggestion presumes that speaker impedance is known at all frequencies, more or less, does it not? Does not one "calibrate" to a voltage? If not, please explain. Thanks.
You're right, speaker Z will affect the amplitude where clipping occurs. That's due to the changing load reflected back to the tube(s), power supply sag, etc. However, if the clipping point is found on the scope using a sine wave at 1 kHz, intermittent peaks in musical material will clip at roughly the same amplitude. It's not exact science, but there's no other way to do this with inexpensive equipment. The point is to determine whether your listening level is likely to be causing momentary clipping that you might not otherwise notice.
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Buy Chinese. Bury freedom.
Ok, but certainly going by specs will be close enough, eh? The 45 SET will produce ~2W at 3-5% THD ("clipping"). Into my 16 ohm speakers by P=V^2/R we have ~5.7V.
I will run such a test some time soon. I'm curious.
"3-5% "clipping" ". Deformed signal, not necessarily clipped maybe? JH
Well, you are right, that is inaccurate. 3-5% THD is usually considered around the power limit for an SE amp (and what S-file will call "clipping") but obviously 3% THD doesn't look anything like a square wave. However, the SE amp that is at 5% THD is indeed going to be at far higher levels with just a bit more power, generally. There is still a knee in the curve.
Even if you could output a true square wave whilst trying to deliver a sine, you'd not even get to 50% distortion.
There is all sorts of things that deliver distortion around max power. Grid current discharging coupling caps, or for stages capable of delivering power, the radical change in load when the grid goes positive.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
He's a guy making a really powerful amp, what do you think he will say?
If you ask him what speakers are the best, what do you think he'll say, horns? He makes stats, he says stats are best. Duh.
As for how much power, I have really liked 20 watts into my 100db/watt speaker. I've liked 170 watts better. So, what do I NEED? Well, I have the money to easily pay for the big one, so I own it.
If I could not afford the big one, I could happily live with the 20 watter.
So, it's not about need, necessarily, it's about desire and what you are willing to pay to satisfy your desire.
One thing to remember, it's a LOT more expensive to find a great high powered amp. There are few great amps, so even fewer high powered great amps.
There's no 170W amp that sounds as good as the best 20W amps.
Duh.
That's what the guy who does not have the big tiodes with single transmitter tubes will always say.
You don't know what's better, or what it will sound like, until you hear it.
If you owned a bunch of small AND big ones you would not have the agenda you do. I have many of small and big ones. I have no agenda. The big ones, if they are really good, will show you what your small ones don't do.
So much of audio is "if I don't own it then it can't be as good as what I do own".
Agenda? Please elaborate, oh mind reader.
I've owned at least 50 SET amps. Probably more. At least 15 of the 211/845/805 variety.
What's your 170W SET?
Why do you think you need that much power? What kind of volumes do you listen at, in what size room, and how's your hearing these days?
I did not say I or anyone NEEDS large power, but I am saying that with a really good sounding SET amplifier that is also more powerful than the typical SET there can be advantages. Big room, but I sit from 4 to 11 feet from the speakers depending on my mood. Typically 82 db peaks, once in a great while I'll boost it to 100 for a minute, but the advantages in dynamics and bass control, as well as in unstrained and unrestrained sound of the mids, is evident at 82db.
Single tube GM100 and single tube QB5 are the configurations I'm talking about for the high powered amps. Other SET amps on hand use 845 (several amps), 45, 300b, 211, 2a3 .......way too many amps, really.
PaulF70 & others,
My 106+db horn system REQUIRES 20++ watts to sound "live"....Let me explain.
About 10yrs. ago I was bitten by the Lowther bug. After speaking to Jon Ver Halen on a speaker system, I wound up with a Medallion 2 cabinets and Dx-4 drivers. I thought had had this high end audio thing licked. I also had a pair of Cary 300b mono block amps, Cary SLP-05 preamp, Sony / Modwright cd/sacd player and all was well. Also in the mix was Medallion 3 cabinets with PM6a and Pm2a drivers to try. On simple music, these systems sounded very good but on large scale classical music, something was missing. It turns out several things were missing, low frequencies, mid bass snap, dynamics, clean, extended high end. I have attended almost all the audio shows like CES, Rocky mountain audiofest in search of answers. I listened to the big Sound labs, Maggies, Wilson and many others and realized I needed a bigger speaker system. At one of the CES shows I wandered into Dr. Bruce Edgar's room when he was showing his full Titan system and that was it. I have never heard such dynamics, clarity etc. and knew that is the type of system I wanted. IIRC Dr. Bruce was using a 30 watt tube amp from Cy Brenneman. I have visited Dr. Bruce's home and listened to his field coil version of the Titan system and was even more impressed so I asked him to design a mid bass horn using a pair of Altec 515b's and he did.
A few years ago I put together the following system:
1. Tweeter ---- TAD ET-703 with 107db sensitivity
2. Mid Range--- Field coil converted JBL 2441 with beryllium diaphragms connected to a Sierra Brooks solid wood tractrix horn measuring 25.5" at the mouth and 24" long. Should be about 110db sensitivity.
3. Mid Bass horn--- 2 Altec 515b's connected in parallel in a hypex horn measuring 32" x 45" at the mouth and 47" deep. should be at least 106db sensitivity. The horns in room are flat to 58hz and crossed at 400hz. The crossover is Dr. Bruce designed 6db.
4. Subwoofer's--- Pair of sealed 9 cubic foot using a pair of TC Sounds LMS 5400 18" drivers in dual opposed configuration. Powered by a pair of Crown I-Tech 5000hd amplifiers strapped to mono. The amps have built in DSP and crossover and go from 14hz to 60hz with 48db roll off.
Now, you would think that a horn system with a sensitivity of 106+db would get by with a flea powered SET amplifier---not so. I sit 17' away from the voice coils in a medium sized room 16' wide x 23' long with 10' ceiling. I have 2A3 mono blocks, Type 50 tube mono blocks, 300b mono blocks, 211 mono blocks, 845 mono blocks and none of them have enough power to convey the power and dynamics of large orchestral pieces such as The Rite of Spring or Mahler symphonies for example. You can also forget about the Joe Morello DMP drum cd and most of the Sheffield cd's. It takes a pair of Art Audio ( un cataloged ) mono blocks using a single KR T100 tube for 26 watts SET to make this system swing !! I expect 100db+ peaks at my sitting position when called for and if the an amp can't do it--it is out !! Perhaps I am spoiled by the mid bass power and clarity this system has but once you hear it,there is no going back. Flea power does not cut it for me. I don't like solid state amps on this system.
I conceptualise like this:
> Power & Efficiency (plus a few other factors) determine volume
> The sense of dynamics and vitality (within volume limitations) are down to other design factors... though increasing power can sometimes partially compensate.
Thankfully, I don't enjoy listening to music in my home at live levels, so I can compromise on power while saving my hearing to enjoy the occasional live gig. Still, I like a sense of vitality in music - the system still needs to be designed to achieve this.
Cheers,
91.
"Confusion of goals and perfection of means seems to characterise our age." Albert Einstein
I'm not surprised at all you need that kind of power. It's your passive crossover. I've had full horn setups as well (DIY & AV Trios) and noted they need some power despite the ~105 dB/W+ sensitivity.
No speaker is perfect, however, the Beauhorns have coherence that no front horn system ever will. I prefer them for jazz, which is what I listen to.
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