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New member Username: PlanetsutcliffePost Number: 1 Registered: Feb-08 | I recently got a Yaquin valve amp which will drive 4 and 8 Ohm speakers. I have some 8 Ohm speakers and I want to get some studio monitors at 4 Ohm. The speakers I am looking at are 4 Ohms and 150 watt, the amp is 52 watts per channel (at 8 Ohms) [Tech specs below] My question is: Will these speakers draw too much power from my amp? I think that if the impedance halves, then the power should (roughly) double, and they would be ok. Am I right? Thanks guys! Output Power : 52W x 2 "8 ohm" Lose true degree : 2% "40W" Frequency : 20Hz---60Hz "±1.5dB 10W" Signal/Noise Ratio : 85dB "A Weight" Load impedance : 8ohm or 4ohm Signal Inputs Level : 300mv Audio Input : 4 groups Audio Output : 2 groups with 2 x GND Input Consumption : 250w |
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Platinum Member Username: Jan_b_vigneDallas, TX Post Number: 12302 Registered: May-04 | . Tube amps don't operate in the same way solid state amps will when the load is changed. Since tubes are high impedance output devices they require an output transformer to step down their impedance in order to adequately drive a typical loudspeaker load. Higher cost tube amplifiers will have output transformers with multiple taps (2,4,8,16) for various impedance loads to provide the highest power, lowest distortion and broadest frequency response into any speaker. When only one tap is provided the manufacturer has chosen a specific tap/load and then chooses to advertise the amp has the ability to drive any load between such and such value. They are not necessarily lying but they are not telling you the truth either. When the load on a tube amplifier is mismatched by using the incorrect transformer tap, the amplifier will produce slightly more or slightly less power but the wattage will not increase as much as a transistor amplifier under the same conditions. (When multiple taps are provided a tube amplifier should produce the same output voltage at any tap; therefore, a well executed 40 watt transformer coupled tube amp should produce 40 watts at the 4,8 and 16 Ohm taps when the load is properly matched.) A 40 watt tube amp will produce, on average, no more than 45 watts and no less than 30 watts when the tap/load is severely mismatched. When the amplifier manufacturer doesn't provide adequate specifications and the speaker manufacturer just makes up numbers to fit a spec sheet, it is difficult to predict what will happen when the amplifier's load changes. I assume you know speakers are not typically eight or four Ohms throughout their response range. They vary broadly and any particular "four Ohm" (nominal load) speaker might dip to below two Ohms and rise above 30 ohms. Or it might be a very consistent four Ohms over most of its frequency response range. This variation in the impedance curve is important to know when pairing any loudspeaker to any tube amplifier. It is also important to know the electrical phase angle of the speaker at the lowest and highest impedance points in the speaker's range. Impedance and phase angle together determine how "tube friendly" the speakers will be. If you cannot determine these two measurements for any particular speaker (the manufacturer should be able to provide the information you require), you should pair a tube amplifier with a fairly high impedance load speaker. Remember "eight Ohm" speakers vary also and can still be four Ohms or lower at some frequencies. I don't have a clue what "lose true degree" could possibly mean in your amplifier's specifications. The frequency response you quote is quite unimpressive. I assume you meant 20Hz---60kHz, though this "±1.5dB 10W" is also confusing. I suspect the 52 watts quoted at "8 Ohm" means the amp is clipping at about 10% distortion by 52 watts output and 2% distortion at 40 watts. Most measurement techniques consider "clipping" to be no more than 1% distortion. That would put your amplifier at about 35 real watts before clipping becomes noticeable. That's just a guess on my part but you have one of the new generation of tube amplifiers that seem to be aimed at new tube owners who don't really understand tubes or specs. There are plenty of these coming out of China right now. The good news is 35 tube watts will probably sound more powerful than 35 transistor watts and the difference between 35 and 52 watts of clean power is rather insignificant anyway. It would just be nice if these manufacturers told you what was really happening with their products. Depending on the actual load of your speakers at various frequencies the amplifier will very likely produce slightly more power than it would into a purely resistive eight Ohm load, maybe a few watts more. However, it will also produce slightly more distortion than it would when driving an eight Ohm load and do it with slghtly less extension at the frequency extremes. As I've stated transformer coupled tube amplifiers have an inherently higher ouptut impedance than a direct coupled solid state amplifier. A typical direct coupled transistor amplifier can have an ouput impedance around 0.10 Ohm while a typical tube amplifier has an output impedance around 1.0 Ohm or higher. It would be nice to know the output impedance of the amplifier and the actual impedance curve of the speaker since they will interact and produce frequency response errors when paired together. More than likely these errors will be less than 2dB in the worst case scenario but that is enough to be somewhat audible as a deviation from flat response. (Your room probably introudces much more severe deviations from flat response so this 2dB is not all that terrible in the overall scheme of things.) I would suggest you forgo the four Ohm speakers (which will in any case only make the errors more egregious) and stick to a modest eight Ohm design. Look for a speaker that maintains a relatively high impedance at all frequencies and has a minimal phase angle at any point where the impedance dips below eight Ohms. This will give the smoothest response with the lowest distortion product from the amplifier. A single driver loudspeaker would be a good match for this amplifier. If you can't find such a design, then I would suggest you ask about the crossover design of the speakers you select. It should be a minimalist design with a first or second order crossover and few components in line with the drivers. If you are interested in high volume levels with this amplifier, choose a speaker with the highest sensitivity specification available. Klipsch speakers typically pair well with tube amplifiers and the new Infinity speakers have reasonably high sensitivity. At any rate I would suggest a speaker with approximately 90dB sensitivity with 1 watt input. Each additional 3dB of sensitivity you gain from the speaker will be the equivalent of doubling the power of the amplifier and each 3dB you give up in the speaker will be the same as halving the amplifier's output power. Keep the impedance and the sensitivity as high as possible in the speakers you choose and you should do well with this amplifier. . |
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Platinum Member Username: Jan_b_vigneDallas, TX Post Number: 12303 Registered: May-04 | . https://www.ecoustics.com/electronics/forum/home-audio/111344.html |
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New member Username: PlanetsutcliffePost Number: 2 Registered: Feb-08 | Hi, first, thanks for the in depth reply! The Yaquin does have 2 discrete outputs on the back for 4 and 8 Ohms, is this what you refer to as "taps" or is that something within the output transformer itself? I'm now looking at the options you suggested, higher impedance and sensitivity. Thanks, Robin |
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Platinum Member Username: Jan_b_vigneDallas, TX Post Number: 12305 Registered: May-04 | . Those are taps. |