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Old 24th June 2007, 10:31 AM   #1
jarthel is offline jarthel  Australia
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Default rock music and SE?

I have read several replies that goes like "PP for rock music".

1. Is this because most SE amps have lower power than PP?

2. if "yes" to no. 1, would I avoid the problem if the SE amp has 18W and above power?

3. If "no" to no.1, what could be the possible reason why people would say such?

Thank you for the replies.

ps. I asked as I listened to both rock, techno, classical, jazz and anything in between.
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Old 24th June 2007, 11:05 AM   #2
bigwill is offline bigwill  United Kingdom
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If you have big efficient speakers with big efficient woofers, then rock will probably sound excellent with single ended amplifiers
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Old 24th June 2007, 11:18 AM   #3
disco is offline disco  Netherlands
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Why do you expect the power of an amplifier to be of importance to enjoy the music?
> It was the early seventies that commerce made us buy heavier stacks because they would sound superior to everything made before. Nowadays we know better.

I can enjoy every type of music coming from my 35 year old transistor radio (1.0 watt 100-12.000Hz reproduction) on much less than half volume. If I connect a good loudspeaker (3W, 97dB, 50-18.000Hz) there's no need for much more. I'm talking mono here, so a 2W+2W amp on good speakers should rock your house -and your neighbours.

Of cause not every combination of speaker and amplifier works great and in general it's not wise to use insensitive (=bad) loudspeakers on any tube amp, whatever the output power.
Even small (1-4W) output power amplifiers can establish a rich, rock-steady reproduction on good speakers. Try for example the 2x0.7watt Darling amp on a pair of Goodmans or Altec speakers. You'll probably love it.
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Old 24th June 2007, 11:54 AM   #4
jarthel is offline jarthel  Australia
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the idea that I am getting (based on the 2 replies above) is that it all comes down to amp power output (of course you would nice higher power amp for lower efficiency speakers) and speaker's efficiency. Is this right?
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Old 24th June 2007, 12:50 PM   #5
disco is offline disco  Netherlands
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Quote:
Originally posted by jarthel
the idea that I am getting is that it all comes down to amp power output... Is this right?
Why do you expect the power of an amplifier to be of importance to enjoy the music? There's no scientific evidence for this understanding, neither for the amount or size of speakers involved.
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Old 24th June 2007, 01:07 PM   #6
jarthel is offline jarthel  Australia
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Quote:
Originally posted by disco


Why do you expect the power of an amplifier to be of importance to enjoy the music? There's no scientific evidence for this understanding, neither for the amount or size of speakers involved.
because if I have a 4W amp and the speakers I have are something like 84db efficiency, I may not be able to hear the music at all. It's hard to enjoy the music if you can't hear it. yes?

Also, I was never talking about size. I have said efficiency.
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Old 24th June 2007, 01:15 PM   #7
isaacc7 is offline isaacc7  United States
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One of my best "rocking" systems I had was with a pair of Golden tube audio SE-40 amps and a pair of KEF speakers (86db efficient?) I had 6 SE 6l6 per side. It had most of the things I like about SE but with enough power to get nice and loud...

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Old 24th June 2007, 01:41 PM   #8
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A lot of rock music has some serious bass, extreme dynamics, and the propensity to find intermodulation distortion in your system. Many users tend to play rock music louder than other music on the same system. It is not uncommon for rock to have musical peaks that are 10 to 20 db above the average power level.

Most SE amplifiers have a few disadvantages to overcome when playing rock, techno, or other highly dynamic music.

The OPT must be air gapped to handle the DC bias current. This reduces the primary inductance. A lot of primary inductance is required to allow big bass without phase shifts. Phase shifts in the bass region will cause the fundamental and its harmonics (from the bass guitar) to be out of phase with each other destroying the definition of the bass. A lot of core area is required to allow big bass without saturation (sounds gross). This means a physically large OPT which means an expensive OPT.

The average SE amp has an output impedance in the 1 ohm + region. Many speakers need a very low (milliohms) output impedance to control cone motion and improve bass definition. The output impedance can be improved when the amplifier is designed by choosing a tube with a low plate resistance, running it at a relatively high plate current, choosing a higher than "traditional" load impedance, and applying some feedback.

The average SE amp has a fairly low output power rating. The OPT is often the limiting factor. This forces a high speaker efficiency, or the amplifier is operated close to its power rating using up headroom for transients and dynamics.

The probability of finding good OPT's at a reasonable price goes down quickly as the power level goes up. There are several decent choices at the 10 or 15 watt level. I have tried several different "25 watt" SE OPT's and found them all less than perfect, but some do rock quite well. I have given up on finding a decent 50+ watt SE OPT that I can afford.

Many speaker systems have an impedance peak in the bass region. It is not uncommon for an "8 ohm" speaker to go to 20 ohms in the 70 to 100 Hz region (my Yamahas do). Even if your amplifier can put out 10 watts into 8 ohms, it will run out of voltage headroom and barely put 2 watts into these speakers at 80 to 100Hz. This frequency range sits right in guitar and bass guitar territory. The amp will clip as it runs out of voltage. A well designed SE amp exhibits fairly benign clipping, but as the bass line pushes the amp into clipping all other musical information is silenced during the transient. This is obvious if there is a strong bass line playing over a vocalist. Fleetwood Mac and Metallica comes to mind. The situation may sound ugly if the amp has poor overload recovery characteristics. The bass line may intermodulate the vocals.

Even with these drawbacks it is still possible to make a great sounding system with an SE amplifier. I have several SE amplifiers and I use some of them for rock, often LOUD rock. If you like loud, then you need to evaluate your speakers, and their true efficiency in the bass region.

I have a set of Yamaha NS-10M studio monitors. These were never meant for tube amps (very un flat impedance curve and 87db efficiency) but I have managed to make an SE amp thet works well with them in my small work room. It takes a 15 WPC UL amp with cathode feedback, and you still can't get real loud. I use the same amp in triode with the feedback turned off to listen to simpler music like Norah Jones or Diana Krall. The 45 DHT amp doesn't get much use here. I usually run the "8 ohm" speakers on the 8 ohm OPT tap to maximize power output and minimize the voltage clipping effect, as these speakers are always over 10 ohms below 200 Hz. Average listening level is about 5 watts. Clipping can be seen on the scope, and often heard if I get carried away with the volume knob.

I also have a set of DIY Open Baffle speakers in the living room. These have 15 inch woofers with a 96 db efficiency rating. The same amp will blow you out of the room if left set up in the same manner as before. If I use the same amp, I use the 4 ohm output tap with the "8 ohm" speakers, to increase the damping factor at the expense of output power. I usually operate the amp in triode mode without any feednack. This gives about 5 watts which is sufficient for most music. The average listening level is under 1 watt and some random clipping on transients can be seen on the scope but not heard. The 45 amp sounds real nice with these speakers, and I use it a lot, but it just doesn't have enough grunt to ROCK!

I have created an amplifier just for use with these speakers. It uses Hammond 1628SEA transformers, which have the best bass by far (at the expense of a little highs) and run EH KT88's at 480 volts and 80 mA for low output impedance and great dynamics. I usually operate it in triode mode, but if the neighbors need taming, I can always resort to UL with CFB, and play Dark Side of the Moon! The bass can move the walls in the house across the street.

I took 2 of my amps to a friends house who has 106db speakers with Lowther drivers and active subs. Here the big amp demanded to be played in triode mode with no feedback. Anything else just sounded gross. The 45 amp has more than enough power for ANY music with these speakers. It also sounded real nice. If I had these speakers, I would not build anything bigger than a 45. The average listening level was probably 1/4 of a watt or less.
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Old 24th June 2007, 04:24 PM   #9
disco is offline disco  Netherlands
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Quote:
Originally posted by tubelab.com
A lot of rock music has some serious bass, extreme dynamics, and the propensity to find intermodulation distortion in your system...

Hiya Tubelab, elaborate answer

Can't shake any walls here with my 110dB SE but I assure you it's loud enough for the police to stop by after 8PM. Built me some 1M horns on 96dB Fostex, powered by these babies (at the moment).

Outputs are 40W SE, wound on request by AE Europe (Dutch only). 12cm cubic, about 15lbs each Normally they're on a pair of KR300B @130mA monoblocks, good for 18W each.
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Old 24th June 2007, 04:46 PM   #10
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Jarthel,

You can offload some of the bass duty by using a subwoofer plate amp and subwoofer. Depending on the sub amp, if you use the speaker-level inputs, the amp will roll off the main speakers below 80-100 HZ and use the plate amp for the needed power.

You can also run the plate amp parallel to the main speakers, laeving them to run full range as well. The high input impedance of the plate amp in parallel won't affect the impedance interaction much at the OPT.

For a low-wattage tube amp, a decent 70-100 watt plate amp should be adaquate. You can get pretty decent volume from a couple watts this way, even with less-than-efficient speakers.
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