Kirkus & Alpha_gt: Thank you both very much for the edifying clarification here. This has been a curiosity of mine for a little while now, but did not really know where to begin...I think some lights have begun to come on for me! Much appreciated. |
Thank you Kirkus for your thoughtful response on rail voltages, I kind of knew it, but could never have said it so eloquently. And let's not forget safety! A failed component on a 120v rail could start a fire! And a failed shunting cap could knock you into the next room! But I just wanted to add, and to answer Eno's post, that the reason this is in a pre and not the amp is because preamps are traditionally voltage amplifiers, while power amps are current amplifiers. And the voltage on the rails is not as important as the available current.
And based on what you were saying Krokus, upping the rail voltage sure sounds like a good way to increase the cost of a component, if that were your goal as well. Plus after all that high voltage is created, it must be reigned back in before leaving the device or as you say, it would be incompatible with most every known amp. I guess many great designs started by thinking outside the box, so even though I believe it's not a good idea, I will reserve judgement having never heard it. |
I've personally no evidence that the professional audio market is any less susceptible to changing vogue or irrational expressions of machismo than the high-end consumer market. This fashion of escalating rail voltages has been evolving over at least a decade, IIRC a big influence here was the design and marketing of Solid-State Logic consoles with high-voltage (+/- 90v?) rails.
While I have great respect for SSL and no specific opinions on the SPL gear you mention . . . here are some very specific reasons why I chose to optimize a recent discrete opamp design around +/- 24v rails:
- The requirement for higher voltage imposes some severe constraints on semiconductor manufacturing, and consequently the selection of small-signal parts available to circuit designers really plummets above the 40-60 volt range. For bipolars, lower gain and higher noise is a given to withstand voltages above this range, and there are virtually no matched precision pairs or small-signal JFETs of any type at all.
- The methods for using lower-voltage devices in higher-voltage circuits (i.e. variations on cascoding and bootstrapping) make up some extremely well-trodden ground, and in the best situations the only drawback is complexity. But frequently there are also penalties in noise performance or open-loop response (adding another response pole), the latter means increased distortion, reduced bandwidth, and/or reduced stability.
- Increasing the rail voltages is pretty inefficient at creating additional dynamic range (each doubling of the voltage gives you 6dB). On the other hand it's very effective at increasing heat dissipation, and with higher signal voltages the distortion mechanisms of passive components become much more significant.
- Maximum voltage output with +/- 24v rails can easily exceed 13VRMS, even without special attention to "rail-to-rail" circuit design. This is enough to b!tch-slap the input stage of most any piece of equipment that's likely to follow a preamp, ADC, DAC, EQ, or whatever . . . and that's assuming either an unbalanced, pseudo-balanced, or 1:1 transformer-balanced design. For active-balanced outputs (or a 1:2 transformer) the maximum output is doubled to 26VRMS . . . which for perspective would drive a 4-ohm speaker to 170 watts (if it had enough current of course). By my logic this is more than sufficient for any line-output stage, and if substantially more is required to keep something from clipping inside the equipment, then I need to re-think the equipment's internal gain structure.
- Speaking quite conservatively, a well-designed discrete-opamp line-level architecture with +/- 24v rails can achieve a -110dBu noise floor up to maximum output of 24.5dBu (13VRMS), meaning 134.5dB dynamic range. This exceeds that of a low-noise dynamic microphone (let's say 210 ohms and 1.8mV/Pa based on the industry-standard AKG D112 kick-drum mic) suddenly being moved from an extremely quiet room (15dBa) to a position 50 feet from a jet engine at takeoff thrust (150dBa).
In the end, I felt that setting by the rails at +/- 24V, I could design a simpler circuit that achieved better performance while drawing less power and producing less heat, with no real-world loss in usable headroom. Other designers may of course come to other conclusions for their applications . . . and if they happen to enjoy bragging about how high the rail voltages are on their designs, then they certainly win on that point. |
Ivan, I agree. I actually researched a little to find any power amps that had the 120v but I had little success. |
Wolf Garcia, it's funny you mention the first watt, because the amp I am using is First Watt J2
Princka, I use JBL 4425 which I did not get at first and then it hit me with proper placement and listening position. This speaker is what made me investigate pro gear for some of the areas in my systems chain. |
Sethlover you are on my wavelength!!! (or I'm on yours) I recently started using "affordable" Canare cables and they are awesome and reliable. I see you are using the Tascam in the same way I have been thinking about the SPL, which is inspiring. I feel that the pro gear manuf. wouldn't make a controller that changes the signal in any way or engineers would give them grief and not buy their gear. |
I am using a Tascam LM8-ST line mixer in one of my home systems because I need a lot of inputs and it is all balanced. It has 8 stereo in's and 2 stereo output busses. The versatility is awesome and sound quality is first rate. It sounds every bit as good as a Mark Levinson & PS Audio that I've used as well and it is DEAD quite. I've been a musician all my life (62 Y/O) and am well experienced with pro equipment. I have tried a few pro power amps but was not too happy with them so I stick to home audio for that. Oh I almost forgot, I am using an Ashley 7 channel parametric EQ in another home system and have not observed and degradation in sound. Also I have sold off all of my high end I/C's and spkr cables and am now using Mogami 2534 Neglex star quad I/C cable and Canare 4S11 speaker cable...make'm up myself. All this stuff is considered pro audio and I highly recommend giving it a try. |
Enobenetto, understood about the rail voltages. Looks intriguing to me too. But, if this were easy enough to arrange in a preamp (for the maker's stated advantages), then could this same idea not also be applied to amps...leading to a combo of high-headroom amp/pre in order to get the most from this approach - that would evidently be the logical conclusion, to me. What comes of their efforts seems to bear watching, I would think. |
I use JBL 4350A with JBL DX 1 active crossover and power them with FM Acoustics 600A and the preamplifiers are Dennesen JC80......pure fun! |
It's all about that first watt. |
Very cool insights.I think having an entire rig of pro gear for home listening is not the way to go, but some areas could be helpful. As stated before, if you are going passive that would be the obvious area to acquire pro gear for. I remember linkwitz for his speakers uses very ordinary pro amps and PMC has bryston in them. I feel that some speakers, like for instance Harbeth, feel that amplification is cheap and abundant and it is there to amplify, nothing more.
Also, I think the 120v rails is confusing, because I think it is different running of 120v AC. Look at the Innerfidelity video on the Phonitor 2 at Newport, and the rep explains it. To paraphrase he says that most gear runs on 36v rails and that 120v rails gives you more head room and dynamic range. Sounds interesting.
Would the wide use of balanced connections and power conditioners be two areas where the pro side influenced the hifi side? |
I use a Crown Xti 1002 to drive my woofers with the built in X/O at 320Hz....works great for tight pounding bass. |
A few years back I acquired a pair of Legacy Focus speakers, HUGE! At 200 lbs each and 5 feet tall, they are awesome to behold. But, I found them hard to drive. The specs say you should be able to drive them with any 200wpc amp. And you can, but, I found it lacking, not reaching their potential. So, I took my hi-fi amp. A Forte' 200wpc, and I drive the top half with that, and I bought a used Crown XLS2500, which is about 475wpc, to drive the bottoms. And am very pleased with the results! Now it has slam! But still remains so smooth on top even at higher volumes. I only paid $400 for the used Crown in like new condition, and it saved me from spending $5,000 on a Krell or Levenson monster amp. I may still get a Krell or Levenson monster one day, but for now I'm very happy with this Pro audio amp in my system. |
I'm tri-amping with Crown XTi 1002's and a 2002 and going preamp-less (using the gain input control on the Crowns). While I would tend to agree that high-end usually sounds better, I've also have been steadily acquiring a lot ($10k+ and counting) of some Alan Maher Designs electronic noise reduction gear...all that has collectively raised the level of their performance, under my roof anyway, just into high-end territory (I'm sure nicer hifi amps would've been improved by all that even more, of course). I suppose these Crowns may not have the utmost degree of sheer "magic" of timbre that the best amps can have, but it's easily good enough for me and, with AMD, all the attendant qualities like tonal purity, pitch accuracy, resolution, textures and harmonics are so good that I never have the feeling that anything is missing. It's nothing for me to get wrapped up in the performance and the music. What drew me to the XTi's were the pro tools: EQ, Crossovers, digital gain, delay...that way I could ditch my passive crossovers which has been a great step toward better sound here. And, from the beginning for myself, no worries about trying to win the "passive crossover parts" sweepstakes and that let me save a nifty buck or two. Normally, going digital there might sound worse because of the noise, but that as well is what all the AMD is for and it's all sounding rather gorgeous right now to me. The system itself costs well less than all the AMD, but everything here is working together well. If asked, I'm more likely to rave about AMD than the amps in particular, but these pro amps have certainly found a home here. They're not going anywhere anytime soon. The one DIY mod I had to do was to hardwire bypass the Speakon connectors...rather good for allowing buckets of currents through, but detail?...not so much. |
I'm a pro gear pro
I've been paid to use this stuff (mix mostly jazz shows these
days) for decades both as a musician and sound tech and I can say without
question that home gear sounds generally better in the home. I don't like amps
with fans even in my home recording rig, or need horn loaded high spl speakers
to listen to things from 8 feet away
but use anything that isn't heavy duty for
live sound reinforcement and you will fail. New pro stuff can sound better than
ever though (as long as the operator is paying attention and isn't an idiot), so
that's good news. Note that most audiophiles would be horrified to hear what
major recording studio's playback systems have sounded like over the years, but
often the studio engineers and mastering techs make the end results come out
OK anyway
amazing. |
As far as I know most gear for use in the US runs on 120V rails unless I am missing something. When I worked in the recording studio most of my stuff at home was so called pro gear. My current system which is not called pro gear but High End Audio gear is much better. The major advantage of pro gear is it is designed to play 24hours 7days a week without ever failing. Also most pro gear does not look very appealing
Alan |
