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Old 1st August 2006, 02:19 PM   #1
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Default Eco warrior thinking of jumping ship !!!

Hi there,
This subject is sort of an extension of an ealier thread about EEC legislation and class A amps.
Been a very Eco minded sort of a bod, it troubles me every time I switch on my Class A push pull valve amplifier. I am thinking eventually I may well go off the grid, and then a Class A amp becomes out of the question. So my question, is there anything out there that can come close to the shear quality of sound availble from a top notch class A valve amp ?

Last night I plugged in my best implementation of a LM3875 gainclone and had a listen. It sounded lovely and certainly I could live with it. However when I switched back to the Valve amp the difference was not subtle. Low level detail, stereo image and width, silky smooth midrange. It had it all in spades. I am certain that there are better versions of the Gainclone, but I am almost certain that there will still be a significant margin of difference.

So my question is - what options are open to me to build an amplifier which can compete/better my class A PP valve amp, whilst offering the efficiency that my principles will let me live with. As far as i'am concerned the gainclone rought is a dead end. I was thinking maybe something in the emerging field of class D.

Discuss.

Shoog
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Old 1st August 2006, 02:32 PM   #2
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Default Re: Eco warrior thinking of jumping ship !!!

Quote:
Originally posted by Shoog
Hi there,
This subject is sort of an extension of an ealier thread about EEC legislation and class A amps.
Been a very Eco minded sort of a bod, it troubles me every time I switch on my Class A push pull valve amplifier. I am thinking eventually I may well go off the grid, and then a Class A amp becomes out of the question. So my question, is there anything out there that can come close to the shear quality of sound availble from a top notch class A valve amp ?

Last night I plugged in my best implementation of a LM3875 gainclone and had a listen. It sounded lovely and certainly I could live with it. However when I switched back to the Valve amp the difference was not subtle. Low level detail, stereo image and width, silky smooth midrange. It had it all in spades. I am certain that there are better versions of the Gainclone, but I am almost certain that there will still be a significant margin of difference.

So my question is - what options are open to me to build an amplifier which can compete/better my class A PP valve amp, whilst offering the efficiency that my principles will let me live with. As far as i'am concerned the gainclone rought is a dead end. I was thinking maybe something in the emerging field of class D.

Discuss.

Shoog

You might want to speak to Hugh Dean about a LifeForce SS amp
module. I have tried his earlier amps (the AKSA 55) and it would
suit a tube enthusiast well.

Apparently the Lifeforce is better again. Well worth looking at.

Cheers

Terry
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Old 1st August 2006, 02:35 PM   #3
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I don't know whether I can address the quality questions, but I'm also looking at being off-grid either partially (cabin) or fully. I've started the process of moving to Class D amps, which IMHO are likely to be the only truly viable off-grid approach. Fortunately, many of the Class D implementations can sound very good, although it may take some searching to find the ones that you personally like. The high-end Tripath implementations for example are frequently described as having tube-like qualities, and may be a place to start looking.

IMHO Class-D amps running directly off batteries is the ideal way to approach an off-grid system. Having to run things off an inverter introduces losses that greatly undermine the efficiency of the approach. You may still need a sine-wave inverter for your signal source, but without the power amps this can be very small and hence much more efficient at low power draws.
In my prototype experiences battery power also sounds far better than garden-variety conventional power supplies. I'm currently running a Panasonic XR25 off a 24V battery supply, and get impressive run times out of even a pair of 7aH cells, and IMHO it sounds great.

Whether it's worth switching over if you don't go off grid is another question, though. I'm not entirely sure that the overall energy consumption of even a Class A amp is a significant factor in your overall household consumption. Obviously that depends on how much time your amps are on. Maybe get a Kill-A-Watt meter and see what your system draws in kWh over a typical day/week/month.

It goes without saying that efficient speakers are also part of the equation. Since you're already a tube guy, this may already be covered.
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Old 1st August 2006, 02:37 PM   #4
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...Has anybody tried to build something like Bob Carver's Sunfire amp? That would be something where the outputs are biased full Class A, but the rail voltage follows the input signal keeping just a couple of volts above and below the Collectors/Drains (for common emmiter) or Emmiter's/Sources (for current dumpers). There could always be high idle current, but low dissipation.
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Old 1st August 2006, 03:56 PM   #5
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i would say that for me there is really no alternative, i went from tubes to class-D and class-T and now i'm back with tubes again.
My suggestion: use the best of those two worlds, combine efficient class-T with a wonderful tube preamp, a tube preamp does not consume very much power, neither do class-T!

(at least give it a chance 8-)
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Old 1st August 2006, 04:56 PM   #6
Sheldon is offline Sheldon  United States
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Based on threads here, the Aussie's seem to have a corner on high quality DIY AB ss amps - Hugh Dean, Anthony Holton, and Greg Ball. Hugh intentionally trades vanishing distortion specs., to get the sound he wants.

I haven't any experience with those, but I did build Symasym's from a thread here. Pretty darn good. Users claim better sound with higher bias currents, but it would be easy to make that switchable, so one setting for background, another for serious listening. The low setting would be under 10 watts at idle for a stereo amp. Significantly better sound than the chip amps I built (both with input buffers and regulated supplies), even at that setting.

Real life power consumption for some of the AB amps is not much more than it would be for class D. For instance, I looked up digital amps and came up with a company called Spectron. Their digital amps range from about 100 watts to 500 watts. Power consumption at idle is anywhere from 20-40 watts. Yes, the efficiency is better than 90% for the music signal, but unless you listen at high levels you won't save much.

Maybe a good AB sand amp for regular listening, tubes for sessions where you really concentrate on the music.

Maybe a good pair of cans with a little tube or Fet amp is part of the mix.

Sheldon

edit: BTW I'm not arguing against class D amps. Just pointing out that the energy savings may not be much in your home.
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Old 1st August 2006, 05:33 PM   #7
Sheldon is offline Sheldon  United States
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Or as DWK said, high eff. speakers and something like this: http://www.hornet.hr/SM/Brian.htm

With SS rectification, not much more than 20- 30 watts per channel power consumption. Maybe even a little more power output with low consumption with a spud PP amp.

Or go active. Class A on the mid and tweeter, AB or D on the woofer.

On opportunity to get creative here.

Sheldon
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Old 1st August 2006, 05:44 PM   #8
kevinkr is offline kevinkr  United States
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Before you jump ship take a look at how much power other things in your household are using and figure out their contribution to your overall usage relative to your amplifier - you may find that the amp does not consume a meaningful amount of energy overall.

Offset hifi power consumption against more efficient lighting, heating and cooling - this is the strategy I am taking.

First get some efficient speakers. Small folded back horns based on Lowthers or similar..

Design a tube amplifier with high efficiency in mind.
Here are some pointers:

Design the amplifier to produce no more power than required for your pk spl + say 3dB margin for safety.

If pushpull run class AB1 with fixed bias, no energy wasted as heat in cathode bias resistors, lower overall B+ needed means less wasted power.

If SE build an amplifier based on lower power dht or idht and only enough power to do the job. Again use fixed bias.

Select moderately high perveance tubes with relatively low filament currents. Consider the 6BQ5/EL84, 6L6, 45, 2A3 and other types with relatively modest drive requirements met with one or no more than two stages.

Use solid state rectifiers and choke input, peak currents in the secondary will be greatly reduced and your power factor will closer to unity.

Heat filaments with AC only and choose driver tubes with relatively low filament currents like the 6CG7.

Choose higher quality power transformers and run them well below their ratings.

You can design a tube amp to be pretty eco friendly particularly when you take into consideration how little it is used relative to something like your fridge..

My latest SE amplifier design uses about 85W in operation and was not designed to be that energy efficient. With some thought and the above guidelines I could probably have gotten it down to about 50W.
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Old 1st August 2006, 06:59 PM   #9
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Great ideas everyone.
My current setup is using very efficient speakers and my current amp is pumping about 7watts per channel of pure class A. Takes about 120W of power overall (I think). However we tend to switch it on when I get up in the morning and switch it off again when we go to bed at about midnight, the thought of it sitting ticking over when the wife is listening to womens hour is a bit painful.
So there are a number of options.
Have a switching box to switch from Valve to Gainclone without having to fiddle with leads all the time. I suppose this would be the easiest thing initially. Still wouldn't be adequate for an off the grid situation though.
Look seriously at some type of low power class D or class T (Class T been pure digital I take it).
I like the sound of the variable rail class A design - but it sounds complex to build.

Shoog
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Old 1st August 2006, 07:18 PM   #10
phn is offline phn  Sweden
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I don't have a Class A amp. But I still have too many reasons to hate my tube amp. It's big, heavy and gets hot. I just got a plasma screen. I didn't read the manual (duh), but did flip through the 200-300 page beast, printed in numerous languages, and noted it consumes 220 Watts. You can almost fry eggs on it. The heat hits you when you walk by it at a metre distance. My PC is always on. I have a fixed electrical bill of €15 a month here, so economically it doesn’t matter. But I'm not a jerk just because I can be.

I solve some of that by using a Sonic Impact (just got a 41Hz AMP3 kit) for CD playback. My PlayStation and SI consume 20 Watts, tops. 12 of those are consumed by the PlayStation. The tube amp I only use when I listen to vinyl. I still hate on the tube amp and seriously consider selling it.

A modest 2A3 should be nice. EL84 could be another alternative.

As for SS, the only "alternative" to tubes that I can see is a vintage SS amp that uses output transformers, like Altec theatre amps and McIntosh. I couldn't see myself go that route. Should I decide to sell my tube amp, I will go bi-amping using two AMP3s (or the coming AMP4) and use a chip-based active crossover. While the amps may mean a trade-down, the active crossover should compensate for some of it.
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