Response to Piezo from SWD. *** I think you're right on pulling one of two output tubes on class A. I think only class AB would work since it's the class B operation that makes the distortion. *** And true, you can't beat a seperate power line, especially if the washing machine cycle is washing out those bass peak cycles too! *** Happy Listening, Steve Desper |
Hi Steve, thanks for the detailed jnfo on the variac and other approaches to getting good stage tone. Eddie Van Halen has used the variac trick for years but i never thought of using it as you suggested to keep the voltage where it needs to be for the home rig. I'm going to run a dedicated line first and see if that does the trick but the effect the furnace (or my stereo) has on the lights in the rest of the house tells me i may need to resort to more drastic measures. I have used the pull a pair of tubes approach to taming amps like a fender twin (class AB) but does that work in a class A tube amp?. I currently have a Dr. Z prescription that runs 4 el 84 in class A and has two of the biggest transformers i have ever had to lug around. Talk about midrange spank. As to the mega system I've played a small size auditorium that was kind of fun but i always wanted to do a gig through a monster system like you describe. I saw Kiss's farewell tour (it was free and i had to do it for old times sake) and I both my brother and I swear that stanley was not going through the mains...the stage volume from about 12 full marshall stacks was carrying auditorium (actually it was about killing me). Imagine being onstage in front of that much power, thanks again, JOhn Hartley |
Response to Mr.Piezo from swd (Steve Desper). *** Suggest you get a variac autoformer (variable step-up autoformer) from electronic surplus or your big electronic parts store. You will need a 2000 watt unit or so. These devices are made with a big dial on top that lets you over-volt the output. So if the voltage should drop to 100 or so, just turn the autoformer up to over-volt and get back to 120 volts at the output. I've done this for years to get that extra power needed for realism. *** What is really going on is the extra power (Voltage X Current) is allowing the caps in the amplifiers to charge faster. It's the capacitors that deliver the power within the amplifier, and re-charging them after they have been hit by a demand from a guitar chord, or drum slap enables (or should I say empowers) the transistors or tubes to give full power the next time it is required. In music that can be two or three time a second (the beat goes on...). So try the autoformer. *** Since you are using a tube-head for your instrument here is a trick to try with the autoformer. If you want that saturation sound, that almost distortion sound, that pushed to the limit sound -- but to get it you are too loud for the band, try the autoformer. Hook your (must be) tube amp power cable to the autoformer and LOWER the voltage to around 90 volts or so. Use your own judgement based on the sound you want. You can't hurt the amp. Lowering the voltage will lower the B+ supply voltage inside the amplifier circuit, in effect making the amplifier "think" it is straining to deliver that distorted sound (discribed above), but at a much lower sound level. You see the ear, when hearing slightly distorted or strained sound amplification, interperates this as being a "loud" sound. In fact the distorted sound may measure just as loud (SPL-dB) as a "clean" sound, but the ear hears the distorted sound as if it were louder. That is why folks using amplified guitars like to push it up to high SPL's -- the distortion makes it seem even louder! So use the autoformer to lower the operational voltage of the amplifier and it will distort at a lower sound level, but it will sound louder to the conditioned ear. When miked over a sound-reinforcement-system, you will get the "sound" you want but not washout the singer's microphones or overpower the band. *** Here is a second trick to try if you are using TUBE amplification for your guitar. Go into the amp and remove one of the two output tubes. Yes that's right. If it is a push-pull tube amplifier design, as most are, removing one of the output tubes will give you a distorted sound at reduced levels. Again, only you can judge if this is the sound you want, but sometimes it has done the job for me. *** BTW I'm a mixer *** Here's another trick to try next time you find yourself in a studio session. Take the output of your amp or instrument and split it. That is to say, run two amps from your guitar. One amp you listen to in the studio for monitoring. The second amp will be the one you record. It should be a lttle practice amp with a small 5" or so speaker and a small cabinet. Put a high-quality condenser mic in front of this amp and use its sound for the recording. This works very well if you are playing/recording a bass guitar. The reason is harmonic distribution. The little amp will certainly produce (not reproduce -- that's what we record to do later) the low frequencies of a bass guitar, just that they will be at a low volume. Run the little amp at low volume and isolate it from the band -- put it in an isolation room. You will be amazed at the sound you get on playback in the control room. The high-quality condenser mic (larger diaphram works best) will give you plenty of bottom end, but the beautiful thing is that because you are using a small 5" speaker to begin with, the upper harmonics will be very rich and full. When you RE-PRODUCE your bass over a small radio or car system, because you recorded a 5" speaker to begin with, the 5" speakers in your car system or table radio system will have big, beautiful, full, rich bass. The smaller REPRODUCTION speakers will not be trying to reproduce the sound of a big bass speaker or direct box -- a sound very difficult for a small speaker to reproduce. The smaller REPRODUCTION speaker will be reproducing your small 5" bass PRODUCTION speaker -- not a problem. And the stressing of the upper harmonics (where the beauty of the instrument is) will make the smaller speaker sound as if it is reproducing a deeper bass sound. Also when you reproduce the recorded smaller bass speaker on a big system with genuine deep low end, it will be there because of the quality of the microphone you used. If you doubt me, just play your bass guitar through a small speaker at a low volume and put your ear next to the speaker -- you'll hear deep bass, just as the mic will. *** Since this thread is about POWER -- the most powerful gig I ever mixed produced 200,000 RMS Watts per side. It was a big outdoor event with mega stars. WOW talk about ego, moving those sliders on the mixing console made your heart miss a beat once in a while -- like playing god. What a rush!!! Happy Listening, Steve Desper |
This comment plays off of the comment from swd above.. Coming at this from a different perspective the outcome is the same. more is better I am a part time working musician as well as an audio enthusiast. For my stage rig i have a hand built 45 w class A tube amp driven by 4 el84s that will rip your head off at a stage volume of 3 (louder than the soundman lets me get away with in a 150 seat room) I always am thinking that a smaller amp that could be turned up to get tube saturation without all the volume would be great. Well i recently heard a band using just that type of set up and man what anemic sound...and that was with the soundman doubling up channels and processing like hell to get some body inot the guitars. Long story short: you need an amp with sufficient headroom to cope with the dynamics of the music or there will be no life in the music. My stage sound has a much bigger and better tone than the little amps because, even though the preamp and input signal is rolled back the power section has all the breathing room it needs. I recently moved my home stereo to a house with out dedicated power lines and it simply runs out of gas, the amps can't make the power they are supposed to (185 w per side)...no power no dynamics...no life...no good |
My experience as a thirty year professional recording engineer and studio designer has been that both Solid-State and Tube Amplifiers sound the same if running at well below their respective maximum power ratings. That is a 100 watt SS and 100 watt Tube amp delivering five or even ten watts will have the same "sound." It's that even-order verses odd-order distortion production difference that makes the two amps sound different. If you stay away from distortion being generated because you are operating the amp near its non-linear region, both are going to give you a linear amplification. After all, the signal doesn't know thermal from switching amplifiying schemes until non-linear slopes on the amplifiying scale are reached. It's not the fact that tube amps use thermal devices to amplifiy that makes them sound the way they do, its the topology of the amplifiying scheme. MOSFET's and Tubes are the same topology and have very simular "sound," not because of temperature but because of topology. Push both types into distortion or near-distortion and both begin to sound alike -- when compared to doing the same with tube verses any non-MOSFET SS amplifier, you get that "transistor sounding amp." I would also comment on this: I'm not certain as to why, but I have noticed that when you are converting one form of energy to another, tubes are generally the better sounding interface. Energy conversion such as: phono (mechanical) to electrical, microphone (acoustic) to electrical, electrical to acoustical (loudspeaker). However in all conversions, again, if you operate the converter (preamp or amplifier) in its linear area, that is, at very low voltage or power ranges, both tube and solid-state "sound" the same. In other words, once the conversion is made, what you do in the electrical area with the signal (EQ, Filter, Dynamic compression or expansion, etc.) tube or SS makes little difference. Conversion of energy forms is where the difference is made and is heard. I would further comment that good quality transformers (such as Jensen Transformers) placed near the energy converter will eliminate distortion due to common-mode-rejection, i.e., getting ride of noise and letting only the sound signal through for further amplification. This may be one BIG reason many people prefer the sound of tube amplifiers. It's not the tubes, it's the transformers that make that sound so sweet. Placing a good Jensen Transformer closer to the source of program material will do wonders to clean-up the signal for amplification further down the signal line. Comments Please ... |
YES!! If you choose Classe, go for the higher end models -CA 400 OR CA401 OR even the new monoblocks |
I have 2 systems in my den. (28ft x 14ft 9ft ceiling. One consist of 2 CERVIN-VEGA 3 way 15" with a 450W solid state amp. The other is 2 BOZAK B310 speakers each have 2 12" lo freq drivers, 2 6" mids abd 16 3" tweeters. The amp is MaCINTOSH 2-70 tube amps. Both systems have been voiced with passive EQs. ie LC nets. The sound is noticably diff. as to be expected. At low levels 75dB spl the Bozak MAC system sounds much more realistic. At higher levels the CV system is better. Swapping amps makes a diff. With the higher pwr. amps the BOZAKS have more punch from transits. The CVs with the 70W tube amp sound totaly diff. Probably dur to the higher output Z of the tube amp. You can get a tube like sound from a solid state amp by putting a resistor in series with the speaker (1 or 2 OHMS 50W. This reduces the damping of the lo freq. drivers and rounds off the sharp edges of transits. This diff. sound is very noticable and sounds better to some people. It also lets you play at higher levels without causing the lo freq. driver bottom out. |
You can never have too much (amplifier) power, RAM, wit, compassion, intelligence or horsepower. Contrary to popular belief, however, it is quite possible to be too rich and/or too thin. |
After 30 years of building both home and studio playback systems, I have concluded this. The way to approach the reproduction of sonic realism is by having tons of power at your disposal. I'll use my own system as an example, but this is how I set-up studio monitoring systems in the Hollywood area and high-end home theater systems too. I am currently running a three-way low-level crossover system (tri-amplified). Each of the six woofers has its own 400 Watt amplifier (speaker-fused at 150 Watts). Each large midrange is driven by a 400 Watt amplifier (spk-fused at 75 Watts). Each tweeter is powered by a 250 Watt amplifier (spk-fused at 25 Watts). All amplifiers are Bryston models and the crossovers are Bryston too. This may seem like over-kill power, but the resulting sound says it all. Two audible things result. First because the Brystons are generally operating in the bottom 10% of their power range, the distortion and frequency response is clean and flat. Second, when realistic peaks are required of the amplifier, these powerful units have no problem providing steep peaks instantly, meanwhile the speakers are protected from heat burn-out by the fuses. I have never lost a driver unit using this method -- lost a few fuses along the way, but no speakers. The big advantage is the realistic dynamic range this system provides. It's not about being able to play it loud, although it certainly can be, it's about having the effortless ability to reach those peaks when demended of the source material. A drum, cymbal crash, bell clang, are obvious examples of going from zero power to max power in nanoseconds. This translates into realism. Of course this system is adjusted and measures in-the-room within one dB from 25Hz out to 20k and has inadable noise even a full volume -- that goes without saying these days. But, no matter how good a fidelity a system has, if it does not have power and lots of it, it sounds compressed to me. Think of it this way, suppose you have a 125 Horsepower/2000 pound car going down the highway at 50 mph and you want to pass someone. You can certainly pass them without problems. No suppose you have a 850 Housepower/2000 pound car going at 50 mph. Do you not believe the second car would pass with very little effort as compaired to the first car? Of course. What is really going on is the amplifier is trying to control the speaker cone so as to make the cone the mechanical equivilent to the electrical signal provided by the source. A strong ampllifier will control the speaker cone with little strain whereas the smaller amp will strain to control the cone. This is heard as "amplitude compression" and the ear is very sensitive to compression of peaks. I can alway be certain the first comment people make when hearing one of my monitor designs or my current home system is "it sounds so real, so immediate." The immediate sound they notice is the fact that (even with the fuse) the midrange (for example) is under complete control by the amplifier at all times. By measurement, the fuse will let peaks of 200 watts go to the speaker (which is rated at 50 watts) for short periods of time -- the initial peak. Those peakes are usually so short that little heat is produced, but the impact of the wave front from the speaker is there to hear. It's like being held and shaken by a 10 year old child compared to being held and shaken by a 300 pound body-builder. Both can shake you, but one is definately going to put your body where they want it. Power = Control = Realism. ~HAPPY LISTENING, Steve Desper |
hi alun, i tink class-a amps *do* sound more powerful than comparably-rated non-class-a amps - prolly because they put out more current. the proacs would definitely like more power, tho what ya got should be sufficient in a smaller room. the least expensive way for you to increase the power would be to get another matching classe amp & bi-wire - put the biggest amp on the mid-woofs of the proac; or if ya got another classe 70, ewe could try biamping vertically. proac uses the audio research ls-16 & ls-25 preamp w/the a-r 100.2 amps, fwiw.... doug ps - i have an electrocompaniet aw100 amp f/s on audiogon - class-a, 100wpc into 8 ohms, 190 into 4 ohm, >80amps current output... :>) |
Alun...I had a similar experience. I bought a pair of Proac Studio 150's and felt my Arcam 9/9P pre/power combo (70 watts per channel)wasn't getting the best out of them. I consulted my local dealer and he recommended a class A amp....a Sugden A21a...I must admit I was sceptical that this single 25 watts per channel amp would easily replace two amps bi-amping at 70 watts per channel. I was wrong and a home demo proved that the theory behind Class A to me....(see other threads for the details of why this is so)....anyway I got more control,more detail and a clearer sound at exactly the same price as my Arcam combo (£900)-traded those guys in and the Sugden now happily drives my Proacs. I would recommend searching out a Class A amp(s) of your choice and trying a home demo before buying..... Regards, Ben |
i don't own proac and i do use tube amps. i have a pair of very effiecent speakers (jm labs mezzo utopias) that can run on anything from 50-200 watts. when i first bought them, i ran them through a 45-50 watt tube amp (cj's mv55). they sounded great. shortly thereafter, i replaced the amp with cj's permier 12 monoblocks wich produce about 140 watts per channel. the difference was, as many audiogon audiophiles would expect, incredible. better bottom end (the increased power helped the woofers move in and out more completely and accurately) and sharper detail through out. some of the improvements can probably be chalked up to the amp itself, however, i wholeheartedly beleive that the added power enabled my speakers to perform better. in terms of how much power, what is the manufacturer's suggested range, what type of music do you listen to and at what volumes? i think a safe (and hopefully affordable) bet would be to try and buy an amp (or amps) that deliver enough power to put you right in the middle or 60-65% range of proac's suggested range. although i own cj, i very much like some of vtl and ar's offerings. in my experience, today's tube amps are pretty reliable. they may or may not be for you, but don't cross them off your list without listening--don't worry about their reliability. like anything else, if you buy quality you should be okay. all of that said, be mindful of the fact that searching out and purchasing nos tubes is a fun, but expensive, habbit. good luck. |
