That's interesting. When. I got it it wouldn't get very loud unless I put a Sansamp or some kind of boost to the input signal. A tech assured me it was putting out 310 watts and asked me " waddya want ? Hehe. I was still puzzled but then the tech at another store pointed out it had to have plugs in something to do with the output jacks in the back ?? ( don't remember details.) Anyway , that did the trick it was a monster.
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That's interesting. When. I got it it wouldn't get very loud unless I put a Sansamp or some kind of boost to the input signal. A tech assured me it was putting out 310 watts and asked me " waddya want ? Hehe. I was still puzzled but then the tech at another store pointed out it had to have plugs in something to do with the output jacks in the back ?? ( don't remember details.) Anyway , that did the trick it was a monster.
agedhorse
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Anybody who described the output power of any amp without monitoring the THD of the incoming power and takes he results as gospel has no understanding of how a power amp really works. Output power (for a conventional PSU) doesn't care one bit about the RMS supply voltage because the DC voltages are based on the peak AC voltage not RMS. Flat topping of the AC supply is very common under high power testing with big amps due to peak charging currents, and this error can result in gross errors.
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Mr. Foxen
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Figuring where the controls are flat is a whole new complication. And on valve preamps, probably not a thing.
All 4 of them?
I did think about the lady designers but used “he” generically.
Women are grossly underrepresented in engineering in general but even more so in audio/amplifier design so "he" is safe bet in the vast majority of cases.
Our department has 20 engineers. Two of them are female. Considering the active old boys club misogynistic attitudes still kicking around the local engineering faculty (and engineering faculties in general from what I can see) it's no wonder more women aren't getting into the field.
Some companies specify how to set the controls when performing tests. As you say, they don't always provide this. Frequency scans can be performed to determine how to set the flattest response.
Often tone is set flat but it depends on the procedure. This is required if you are injecting a signal and taking readings to compare against voltage or oscilloscope references in the service manual.
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Women are grossly underrepresented in engineering in general but even more so in audio/amplifier design so "he" is safe bet in the vast majority of cases.
It's disheartening to see this still going on. People tend to always find a ways to give themselves an advantage and hold others back. If it isn't old boys, it's something else.
There are a lot of women on assembly lines doing excellent work building the amps that we use. They are valued employees.
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As the OP of this thread, I wanted to take a moment to express my appreciation to everyone who has taken their time to post in this thread and share information regarding why power output ratings of tube power sections vary with amps having the same type and number of power tubes.
Based on the posts, it seems that the variability in power output ratings of tube power sections having the same type and number of power tubes (which was my original question) is "primarily" a function of the amount of B+ voltage being fed to the power tubes, and also the THD level.
And based on the posts, it seems that the variability in "tone and feel" of tube power sections having the same type and number of power tubes is a function of a whole lotta different things all working together in the amp.
Based on the posts, it seems that the variability in power output ratings of tube power sections having the same type and number of power tubes (which was my original question) is "primarily" a function of the amount of B+ voltage being fed to the power tubes, and also the THD level.
And based on the posts, it seems that the variability in "tone and feel" of tube power sections having the same type and number of power tubes is a function of a whole lotta different things all working together in the amp.
agedhorse
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Well, except that the output transformer matching and circuit topology might make as much or more difference than B+.
This is from somebody who has a fair amount of experience actually designing some commercial tube power amps from the ground up, with the ability to design the parameters of the transformer rather than use off the shelf parts.
Did you guys know that the winding ratio for best matching varies with the design B+???
This is from somebody who has a fair amount of experience actually designing some commercial tube power amps from the ground up, with the ability to design the parameters of the transformer rather than use off the shelf parts.
Did you guys know that the winding ratio for best matching varies with the design B+???
I believe that a woman designed the Ampeg V4-B reissue. From all reports it sounds like she did a hell of a good job.
...And to boot, that winding ratio/B+ pairing is optimized based on class of operation (AB1/AB2)....Which hinges upon the capability of the driver stage/phase-inverter to drive a low-impedance load (the conducting control grid). To parrot-phrase from somewhere on AX84: "AB2 loadlines will generally be flatter (higher-impedance)"...Something about maximizing the available voltage swing...
This is referring to whether the power stage is running in AB1 or AB2. Been trying to draw up an AB2 power stage using an old Plush-4000G OT (23.8:1 @ 525VDC). I'd like to see how much power I could flog from a pair of triode-strapped KT88.
Unless I'm mistaken, biasing into cold AB2 can allow for huge current swings in the class-B region of the loadline. Keeping quiescent dissipation at <50% rated power ("cold bias") seems to allow for peak power to (briefly) reach beyond 100% rated plate dissipation in AB2 amps. Something about duty cycle and integrals....
I believe some of those 160PS/400PS models ran in AB2 via interstage coupling transformers....The SVT uses grid-current capable cathode follower drivers, but hamstrings AB2 capability with large grid stoppers on the power tubes. Seems they were employed solely to adequately drive the low-value grid-ground resistors shared by each 3 tubes.
TL;DR: Most push-pull amps run in AB1, which, as demonstrated by rock 'n roll, can be optimized to be quite loud and powerful. At additional expense to the designer/manufacturer, the design can be optimized to run in AB2, which can allow for slightly power output. Current tube manufacturers don't care to provide detailed data (or consistent manufacturing!) w/r/t grid-current handling for their products, which makes it a riskier avenue for the modern designer to try to gain a few extra watts. The sonic benefits of a robust driver stage may still outweigh the modest increase in rated power. Your SVT is loud.
The Ashdown 427 is UL and definitely gives the perception of weight and mass regardless of volume. My description of the amp is it always feels like you're playing an arena gig
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Mr. Foxen
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The Ashdown 427 is UL and definitely gives the perception of weight and mass regardless of volume. My description of the amp is it always feels like you're playing an arena gig
Not heard those are UL, would not expect that., and especially wouldn't expect it being kept low key.
Ultralinear operation typically produces less output power than AB. The negative feedback to the screens from the transformer taps creates some degeneration.
Ultralinear is complex. In this link, part of the UL patent is presented.
ultra-linear
Some amps that appear to be ultralinear because they have screen taps do not strictly conform to the impedance/turns definition. Fender “UL” amps apparently are in this group. I’ve never measured one of these transformers to confirm this. They use the taps to set the screen voltages where they want them.
Not to nitpick terminology, but Triode/pentode/Ultralinear is a different parameter than operating class. My single-ended KT88 amp runs in A2, switchable between UL/pentode mode. Global feedback greatly reduces the sensitivity in pentode mode, but it's still far more sensitive than UL mode.However, "less sensitive" does not inherently mean "less powerful", given a properly robust preamp/driver
...In some UL amps, perhaps the perception of "authority" as seemingly increased power output can perhaps be attributed to two sources:
1: Lower output impedance of the UL power amp resulting in greater damping factor (tighter control over the speaker cone)
2: Decreased input sensitivity of the power amplifier (Larger input voltage swing required to drive amplifier to full output). [edit: this may play out as increased dynamic range, allowing one to run the preamp at higher gain]
To be fair, global feedback applied to a pentode output stage accomplishes similar ends....
...beans-on-toast, yearp: "Ultra-linear" is such a snazzy buzzword though. Makes me wanna sell myself another amp. "Distributed Load" makes me think of seedy hotel rooms....
[edit: addition to #2]
But the operating class is, in part, tied to the UL circuit.
I haven’t met an ultra-linear musical instrument amp that I liked. Missing that rawness and harmonics. I had a 135W Twin Reverb that had it’s uses with it’s bell like tones. With a Telecaster you could also peel paint off the walls.
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agedhorse
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Note that UL is not global feedback, it's quite local in fact (though it does derive it's source from the transformer primary taps). If the signal source for the feedback came from the secondary, a better argument could be made for "global feedback" but that term is usually reserved for the feedback around more than a single amplifier stage.
A UL amp will still distort if over driven just that the distortion will be more controllable.