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PostPosted: 01 Sep 2017, 19:00 
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Joined: 30 Aug 2017, 09:49
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I am Old School. I have been doing this for 40+ years now. I hope some one can enlighten me on very low power audio amps why? I have always built used and sold HiFi tube amp with 50 watts of more. For my own use O have 2 813 P-P that put out over 120 watts a channel. The main reason is head room. I get fantastic bass at even very low volume settings. Plain and simple they sound great! I also over the years have had 304TL amps they also sounded great with a lot of head room.I do not under stand the whole low power amp thing.I had a SE 300B stereo amp with some Westeten Eleteric in it.yes it sounded good but there was no head room and the low end was not that great..So can some one let me know what I am missing.

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PostPosted: 01 Sep 2017, 20:53 
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Hi, It all depends on what you are using for speakers IMO. Right now I am using ones that are 95 db/w. I have my choice of amps from 5 watts to 45 watts each (all are tube mono blocks). All class A push-pull of extremely high quality. All easily extend past both ends of the audio band at full power. So which am I using? The 5 watters work great and will drive you out of the room before they distort. Even when playing loud, I suspect the average power level to be below 100 milliwatts. If my math is right (always in doubt at my age) I can get peaks at about 102 db (per channel) before stressing the amps. Since I value my ears I don't allow for that level. 80-90 db is fine. With other less sensitive speakers, I naturally use the larger amps necesary to get similar levels. I see a few reasons to agree with you and a few against. On the plus side is as you mentioned headroom, plus at low output levels they may have their lowest distortion levels. That would depend on the design and not necessarily be true of all power amps. On the down side I find that smaller amps will tend to have less residual hum and noise. I particularly hate both. They are generally less costly to build and normally require fewer stages. IMO every time a component is added to an amp it will in some way, perhaps very small, reduce the purity of the signal. Thus fewer stages will be less prone to altering the sound. YMMV.

Good listening
Bruce

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PostPosted: 02 Sep 2017, 00:37 
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I don't like many SE 300B's for that reason either. Most designs are **very** in-the-box thinking and people are very pigheaded about innovation.

Each tube has a different sound. So for the same power level, you can have say a SE 300B, SE trioded EL34, low voltage SE trioded KT88 or 6550. If you like good low end, the trioded pentodes will blow the 300B out of the water every time in a traditional circuit. BUT... parallel some 2A3's and you'll have a piece of heaven no others can touch :D

But this is subjective. Bruce is "da man" for your answers and he's given them ;)

Cheers!

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PostPosted: 02 Sep 2017, 04:35 
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This is an interesting discussion,

I have never liked any 300B amplifier I have listened to and prefer PP in some situations.

There are many reasons for low power amps, some a practical rather than HIFI audio based.
In days gone by 1970's it was common to see big power tube amps at HIFI conventions with big speakers hammering out loud music.
However the "HIFI" sound is different to different people.
To me Audiophile sound is close your eyes and you can't tell if the listening room exists you can hear people breathe and the sound of the floor under peoples feet as they cross the room on a recording. In all my years of listening to very expensive equipment at HIFI shows this magic sound has happened about a dozen times.

Now we are past the year 2000 guess what HIFI conventions are not so prominent vinyl records / CD players / cassette tapes and even some digital formats are "Old school" domestic electrical power is going wind farm and solar.
Its difficult to justify 211 tubes 845 etc heating up the room to desert levels and running air con to be able to sit in comfort.

There is a debate now is SE really HIFI, is PP better, is triode the only way forward, is tube equipment obsolete, is there actually an information loss on a phase splitter, is there an information loss on heavy speaker cones and air pressure resistance.
I could drone on for days about these kind of things. Some people say it almost became a religious belief about what is or was good HIFI or audiophile reproduction.

Lets just think for a moment,
How loud is loud enough? Is magnetisation current and sensitivity an issue, should we use OTL..
In a nutshell each of these topics and there are hundreds I haven't mentioned are relevant.

Here is the argument for low power amps:
Low power consumption.
Low room heating.
Possibly SE where the output transformer is always magnetised and there is no phase splitter.
Triode or pentode or true triode or ES or UL etc
Using high sensitivity speakers that move with very low signal and information levels.
Possibly with no cross over full range..
Then there is the same argument using low power PP or triode variants.

It gets a bit same old after that on high power, taking on the ideas of transient recovery and high power PSU situations, but there is always SMPS.

I used to build high power amps in the 70's because we tend to believe the hype, if you need a tannoy type power level system great.
I tend to use SE low power most of the time these days. Its quite interesting.
I like tube equipment but I have to question the long term viability as times change.
Simple question do you used CRT tv or flat screen?

I don't believe that the old school amplifiers were the best that could be built, but some people will argue that Mullard made tubes they had circuits that cannot be improved on. I think we need a reality check as time moves on.

Regards
M. Gregg

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PostPosted: 02 Sep 2017, 06:45 
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On the subject of headroom,

If you have to run 600W of power to get a reasonable 5 watt low level listening experience, then you need to ask why..
In most cases its current delivery and damping factor and or core saturation in the output Tx.

However there is one of the bones of contention>>magnetisation current and detail/information.
Then the ideas of feedback and information cancelation :sleep:

Regards
M. Gregg

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PostPosted: 02 Sep 2017, 08:48 
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In regards to what M. Gregg said . About using a CRT TV or a Flat screen. Also using 600W to get a good 5W out. As said I am old School. That being said. I use a Flat screen tv LED lights and also have 2.5KW in solar panels on my roof witch are not grid tied. My speakers are also 98db. The thing is my amps sound great at only a few watts and just as good at full power. I can turn them up all the way and leave them there all day with no prolbems. Also at full power they do not distort at all. The only issue at full power is 4 813 tubes give off a lot of heat. That being said I do live in the North East US. The extra heat in the winter is welcome. Besides my Wife loves the sound of the amp. She listens to Enya and states its like her in the room.

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PostPosted: 26 Sep 2017, 01:03 
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When I think low power I'm thinking 2W (tube SE UL amps). At this Level you need speakers of very high sensitivity. My 15" concentric drivers are 99db sensitive and 2W provides plenty of volume. Not sure about head room at this level but there appears to be plenty of dynamics so I'm assuming head room is fine.

I've also run 250W Class D amps on the same speakers. It all sounds good in fact extremely good. I'm amazed how close the two very different amps sound. I swing toward the tuber though.

In the end is what sounds good to you. If your not happy with the sound fix it.

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