adding tube amp applicable for me? - Home Theater Forum and Systems -

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post #1 of 5 Old 09-29-07, 09:50 AM Thread Starter
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adding tube amp applicable for me?

I was pondering the idea of maybe adding an eastern electric minimax amp for my setup but dont know enough about tubes to make an inteligent decision.I have a rotel rsx1056 powering System Audio speakers(sa17500,sa720,sa505's).also have a minimax cdp which i really like alot,maybe it's the tube effect regardless love this impressed that i'm actually seeking advice regarding the tube amp.I use my sytem for everything via the receiver(HT,TV,2ch and multi music,Lexicon rt10 sacd/dvda).But the minimax i understand is only 8 watts,not knowing enough about tubes i've seen or read somethings about the low wattage of tubes being as good or better than ss amps.Would i benefit anything with a tube amp or is it out of the question for me knowing what i have and my use of my system.Any recomendations,opinions and advice would be whole heartedly appreciated.thanks

I wanted to add that i suggested the eastern electric but am not necessarily set on it any tube suggestion would be appreciated.All the tubes i've seen advertised have be up to about 50 watts,just dont understand the low wattage compared to ss amps

Last edited by enrique; 09-29-07 at 10:03 AM.
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post #2 of 5 Old 09-29-07, 03:05 PM
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Re: adding tube amp applicable for me?

As with so many things in audio, there is a huge Tube v. Solid State debate. What I'm about to post is simply my current beliefs based on the readings I've done..

stick with solid state

I'll assume that you know the basic issues with tubes and solid state (even order vs odd order harmonics, clipping vs rolling off, etc).

Where I think tubes would be the way to go would be with very VERY effecient speakers (e.g., horns), but for your typical cone/dome speaker, I'd stick with solid state. Someone from whom I've got a lot of respect for was even more specific -- he'd only use a SET tube amp, which are only going to get up to about 5-7 watts of power for his HF duties (he's also a HUGE proponent of active crossovers). He also went on to say that he'd use a solid state amp for a less efficient speaker (e.g., efficeincy of 90db included).

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post #3 of 5 Old 09-29-07, 03:09 PM
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Re: adding tube amp applicable for me?

To give the "other" side of the arguement, this is copied from another forum that copied it from somewhere else.. anyway, the author is OBVIOUSLY pro-tubes and some of his arguements are pretty whacky (at least to me), but he also gives some good info..

Vacuum Tubes and Transistors Compared

Vacuum Tubes: Advantages

1. Superior sound quality.
2. Highly linear without negative feedback, especially small-signal types.
3. Smooth clipping is widely considered more musical than transistors.
4. Tolerant of large overloads and voltage spikes.
5. Characteristics highly independent of temperature, greatly simplifying biasing.
6. Wider dynamic range than transistors circuits, due to higher operating voltages and overload tolerance.
7. Device capacitances vary only slightly with signal voltages (Miller effect).
8. Capacitive coupling can be done with small, high-quality film capacitors, due to inherently high-impedances of tube circuits.
9. Circuit designs tend to be simpler than transistorized equivalents, which are greatly complicated by the need to linearize intrinsically non-linear transistors.
10. Operation is usually in Class A or Class AB, minimizing crossover notch distortion.
11. Output transformer in power amp protects speaker from DC voltage due to malfunction and protects tubes from shorts and blunts back-emf spikes from speaker.
12. Tubes can be relatively easily replaced by user.

Vacuum Tubes: Disadvantages

1. Bulky, hence less suitable for portable products. Milbert mobile tube equipment is portable and battery powered. It's not particularly small but not particularly bulky: the TC crossovers put tubes in the dashboard, and the BaM-235ab is a 60watt shoebox sized amp that delivers the best sound you've ever heard.
2. Higher operating voltages generally required.
3. High power consumption; needs heater supply that generates waste heat and yields lower efficiency, notably for small-signal circuits.
4. Glass tubes are fragile, compared to metal transistors.
5. Sometimes more prone to microphonics than transistors, depending upon circuit and device. (Does not apply to patented Milbert BaM-235ab, impervious to audible microphonics.)
6. Cathode electron-emitting materials are used up in operation. (Does not apply to patented Milbert BaM-235ab, which has operating currents (and thus, operating lifetimes) two orders of magnitude below conventional tube designs (milliamps, not hundreds of milliamps, of bias current).
7. High-impedance devices that need impedance matching transformer for low-impedance loads, like speakers; however, the magnetic cushion provided by an output transformer prevents the output tubes from blowing up. In dramatic contrast to transistorized amps, the Milbert BaM-235ab will never blow up, even if you play it at full power into a directly shorted or completely open output! This advantage is difficult to overstate, especially in car audio where transistorized-amp faults are common but servicing is inconvenient.
8. Sometimes higher cost than equivalently powered transistors.

Transistors: Advantages

1. Usually lower cost and smaller than tubes, especially in small-signal circuits.
2. Can be combined in the millions on one cheap die to make an integrated circuit, whereas tubes are limited to at most three functional units per glass bulb.
3. Lower power consumption, less waste heat, and high efficiency than equivalent tubes, especially in small-signal circuits.
4. Can operate on lower-voltage supplies for greater safety, lower costs, tighter clearances.
5. Matching transformers not required for low-impedance loads.
6. Usually more physical ruggedness than tubes (depends upon construction).

Transistors: Disadvantages

1. Tendency toward higher distortion than equivalent tubed circuits.
2. Complex circuits and considerable negative feedback required for low distortion.
3. Sharp clipping, in a manner widely considered non-musical, due to considerable negative feedback commonly used. Does not gracefully roll-off or gently compress; instead, cuts off sharply, suddenly and abruptly with extremely hard edge.
4. Device capacitances tend to vary wildly with applied voltages (Miller effect).
5. Large unit-to-unit manufacturing tolerances and unreliable variations in key parameters, such as gain and threshold voltage.
6. Stored-charge effects add signal delay, which complicates high-frequency and feedback design.
7. Device parameters vary considerably with temperature, complicating biasing and increasing likelihood of thermal runaway, hotspots and unreproducible behavior.
8. Cooling is less efficient than with tubes, because lower operating temperature is required for reliability. Tubes prefer hot; transistors do not. Massive, expensive and unwieldy heat sinks are always required for power transistors, yet they are not always effective (power output transistors still blow up; whereas, tubes fade down gracefully over time with warning and usually without catatrophic results).
9. Power MOSFETs have high input capacitances that vary with voltage, complicating driver circuitry.
10. Class B totem-pole circuits are common, which cause severe crossover distortion, or else necessitate huge amounts of negative feedback to correct. This "measures well" for steady-state signals, but it completely "sucks the life out of" dynamic and transient signals such as music.
11. Less tolerant of overloads and voltage spikes than tubes. Except for their robust and forgiving heater filaments, it is very difficult, bordering on impossible, to blow out a tube with overvoltage; whereas, most transistors can be destroyed with as little as six volts, and every transistor can be destroyed by some voltage. Tubes are much harder to "zap."
12. Nearly all transistor power amps have directly-coupled outputs that can damage speakers, even with active protection.
13. Capacitive coupling usually requires high-value electrolytic capacitors, which give audibly and measurably inferior performance at audio frequency extremes.
14. Greater tendency to pick up radio frequency interference and self-oscillate to the point of self-destruction, due to rectification by low-voltage diode junctions or slew-rate effects.
15. Maintenance more difficult; devices are not easily replaced by user.
16. Biasing more difficult, as temperature effects and device variations complicate circuitry and degrade performance.
17. Older transistors and ICs often become unavailable after only 20 years, and sometimes much less, making replacement difficult or impossible. Tubes have a staying power, proven over many decades.
18. Hardly scientific or objective, but whereas transistors operate on an invisibly microscopic, quantum scale, tubes exist and operate on an intuitive, human scale. You can see the heaters lit up, you can sometimes see a glowing plasma, and you can feel and hear the warmth. Everything about tubes exists in a more human realm than hard, cold transistors. Measure away, but it's the sound that matters.

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post #4 of 5 Old 10-01-07, 12:16 PM
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Re: adding tube amp applicable for me?

Although tube amps "can" make the sound warmer and are generally cleaner than solid state amps the cost per watt is more than dubble what solid state amps cost.

The "coolness factor" of Tube amps is high but Tube amps draw a fair bit of power even when not in use. Warm up time is also a consideration plus they run much hotter and require some sort of cooling of the room.

Home theater:
Onkyo 805, Yamaha YDP2006EQ, Samson Servo 600 amp
3 EV Sentry 500 monitors across the front, 4 Mission 762i's Surrounds, SVS PB13U sub, Panasonic BDT220, Harmony 1100, Nintendo WiiU
Panasonic PT-AE8000 on a 120" 2,35:1 fixed screen

Living room system:
Sherwood/Newcastle R972, Mission 765's, SVS SBS02's, A/D/S MS3u sub, Yamaha YDG2030EQ
Yamaha KX-393 Tape deck, CDC 805 CD changer, Panasonic BD60, Sony turntable PS-T20
Panasonic TC-P50ST60, HD-PVR & WDTV Live, Harmony 900

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post #5 of 5 Old 10-30-07, 09:00 PM
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Re: adding tube amp applicable for me?

Hello, In a near future, I am going to use bi-amplification on my Yamaha NS-1000 speakers. I want to use a Mcintosh 275 tube amp for Mid and Tweeter. I will use a Rotel "solid state" to drive the woofers. But before that, I got to finish my sub-woofer project !

Does someone use bi-amp with a match fo tube and solid state amplifiers ?
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