I will once again attempt to make the case for 'open loop' operation. It appears to be entirely possible to make 'open loop' tube amps, that sound really good. I once heard the LAMM at a CES that really got my attention. I could have listened all day to it, even with a digital source. Why? Perhaps it is too smooth, but certainly listenable. I don't know why LAMM is so expensive. Perhaps, because they can get the price, but it did sound very, very good. Best of show that year.
Even with all the high order distortion, including your dreaded 7th and 9th order?
Had you thought about raising the output impedance of your amps, increasing the distortion and power compression, making the frequency response lumpy, decreasing the efficiency and reliability, and tacking an extra couple of zeros on the end of the price tag?
Let me make myself clear. I do not like tubes because I feel they colour the sound, no matter how pleasantly. Most of them, and I have heard a few units I did like.
But that actually means nothing, that's just my taste. It is no greater, much less universal, truth. Other people, like George and Fdegrove, lobe them - fine, no problem at all.
We should never lose sight of the prime prupose of this hobby, which is to make you happy. How it does that is really of no consequence to anyone but you.
Gear as such does not really make me happy, it can please me at best. But playing a CD with pop hits from say 1969 or 1978 will make me happy, not just pleased. All that gear has only one purpose, to let me hear what I want to hear with good resolution, or as good as the recording will permit. I honestly don't get a hard on from owning an integrated amp which costs € 6,000 or so abroad (Karan Acoustics KA-i180), it pleases me more because of the friendship of many years it reminds me of and of watching his son and daughter grow up right before my eyes.
Just as listening to old pop hits reminds me of the days gone by and the nice things well worth remembering, the people well worth remembering. This is not nostalgia, I know and do not expect all that to happen all over again, but it does fulfill me.
And, frankly, I am sick and tired of the tube vs. SS "debate". It somehow always goes south, I say I don't like tubes and somebody always feels obliged to convince me of the error of my ways. I've had it far too many times. I say I don't like them, and somebody always reads that I think tubes are horse dung. But I did NOT say that, I just said I don't like them, no more, no less, and I said why I feel that way. This coincided with Pavel's views, and wham! we have another bout of the age old discussion.
Do we REALLY need that?
But that actually means nothing, that's just my taste. It is no greater, much less universal, truth. Other people, like George and Fdegrove, lobe them - fine, no problem at all.
We should never lose sight of the prime prupose of this hobby, which is to make you happy. How it does that is really of no consequence to anyone but you.
Gear as such does not really make me happy, it can please me at best. But playing a CD with pop hits from say 1969 or 1978 will make me happy, not just pleased. All that gear has only one purpose, to let me hear what I want to hear with good resolution, or as good as the recording will permit. I honestly don't get a hard on from owning an integrated amp which costs € 6,000 or so abroad (Karan Acoustics KA-i180), it pleases me more because of the friendship of many years it reminds me of and of watching his son and daughter grow up right before my eyes.
Just as listening to old pop hits reminds me of the days gone by and the nice things well worth remembering, the people well worth remembering. This is not nostalgia, I know and do not expect all that to happen all over again, but it does fulfill me.
And, frankly, I am sick and tired of the tube vs. SS "debate". It somehow always goes south, I say I don't like tubes and somebody always feels obliged to convince me of the error of my ways. I've had it far too many times. I say I don't like them, and somebody always reads that I think tubes are horse dung. But I did NOT say that, I just said I don't like them, no more, no less, and I said why I feel that way. This coincided with Pavel's views, and wham! we have another bout of the age old discussion.
Do we REALLY need that?
One thing that keeps me 'on my toes' so to speak is the listening QUALITY of a number of tube playback systems. It just doesn't 'hurt my ears', it sounds in some ways, more musical, and yet, often, not quite as 'accurate' as the best solid state. It well could be the excess distortion, or low slew rate, or whatever, but it is something to be taken seriously, if I am going to stay ahead in audio design.
Many think it is all an intellectual exercise that is related to measured specs, and in some ways it is, but it is also, 'whatever works' that has to be taken into serious consideration.
Many think it is all an intellectual exercise that is related to measured specs, and in some ways it is, but it is also, 'whatever works' that has to be taken into serious consideration.
Exactly so, John.
A number of tube amps sound very pleasant, easy going, relaxed, but they simply lack the ultimate control of some of their equivalent price class solid state units.
To be fair, quite a lot of SS designs also lack that same control, for whatever reasons. And while not as seductive as tube designs, they do cost a lot less.
A number of tube amps sound very pleasant, easy going, relaxed, but they simply lack the ultimate control of some of their equivalent price class solid state units.
To be fair, quite a lot of SS designs also lack that same control, for whatever reasons. And while not as seductive as tube designs, they do cost a lot less.
Managing clipping will make a big difference in open loop vs. feedback amps. With feedback when the amp clips the feedback loop is going the wrong way. It can be managed in various ways but it will always be a sudden transition with feedback. Possibly the best was the McIntosh soft limiter, however it was slow. With an open loop design its possible, especially with transformers, to have the more gentile compression like magnetic overload on a tape recorder. This may be part of why a tube amp can sound louder than a much more powerful solid state amp.
Its also possible that the sudden onset of harmonics in a feedback design makes them more apparent that the continuous increase of an open loop design.
However in the product realm few here ever confront- the under $300 Bluetooth speaker, you will find active crossovers, multiple parametric eq's and most important, sophisticated multiband limiters. Most of these were fantasy ideas for high end products 20 years ago. The limiters work very well and when tuned correctly are almost inaudible beyond frequency balance changes. I have a goal for my free time (currently nonexistant) to map the transfer characteristic of a 2A3 or 300B SET to one of these 1 chip solutions. I believe it would be possible to get pretty close. BOM including power supply can be as little as $25 for 4X 20W.
I have heard one of these solutions generating continuous 100 dB with decent sound using about $4 worth of drivers. With decent drivers that have real magnets and better cones it could be interesting. Unfortunately $300 retail makes that almost impossible.
Its also possible that the sudden onset of harmonics in a feedback design makes them more apparent that the continuous increase of an open loop design.
However in the product realm few here ever confront- the under $300 Bluetooth speaker, you will find active crossovers, multiple parametric eq's and most important, sophisticated multiband limiters. Most of these were fantasy ideas for high end products 20 years ago. The limiters work very well and when tuned correctly are almost inaudible beyond frequency balance changes. I have a goal for my free time (currently nonexistant) to map the transfer characteristic of a 2A3 or 300B SET to one of these 1 chip solutions. I believe it would be possible to get pretty close. BOM including power supply can be as little as $25 for 4X 20W.
I have heard one of these solutions generating continuous 100 dB with decent sound using about $4 worth of drivers. With decent drivers that have real magnets and better cones it could be interesting. Unfortunately $300 retail makes that almost impossible.
Hi,
What makes you so sure valves colour the sound?
It's simply not true.
People should stop blaming valves for colouring the sound, you can build valve amps that are perfectly neutral and are very fast too.
To my mind, the problem sits more with uncommodating speaker designs with low efficiency and weird impedance curves (from a valve's perspective).
That plus the fact that decent OPTs just don't come cheap.
Cheers,
What makes you so sure valves colour the sound?
It's simply not true.
People should stop blaming valves for colouring the sound, you can build valve amps that are perfectly neutral and are very fast too.
To my mind, the problem sits more with uncommodating speaker designs with low efficiency and weird impedance curves (from a valve's perspective).
That plus the fact that decent OPTs just don't come cheap.
Cheers,
Hi,
What makes you so sure valves colour the sound?
It's simply not true.
People should stop blaming valves for colouring the sound, you can build valve amps that are perfectly neutral and are very fast too.
To my mind, the problem sits more with uncommodating speaker designs with low efficiency and weird impedance curves (from a valve's perspective).
That plus the fact that decent OPTs just don't come cheap.
Cheers,
Measurement of speaker distortion
Speaker distortion is lower than valve distortion. It is very easy to hear SE valve power amp distortion as sameness of the sound, regardless original quality. In fact valve amplifier is the only component that distorts more than the speaker.
Take care,
Pavel
Fdgrove, they colour the sound as I percieve it. Since I would be the one who would have to live with that, I think it's only fair that I have my say in it. You may, as you appearently do, feel differently, which is just fine, you hear it like you hear it.
And please read again, I did quite unequivocally say that I have also heard some tube which I did like, some of it quite a lot, too. Tube gear is just like any other gear, there are the good and the not so good samples.
As for the speakers, it is odd that AFAIK few new models suitable for tubes, meaning having elevated efficiency, have turned up. I find it a bit odd, given the newly gained popularity of tube designs.
As for the impedance curves, I believe, right or wrong, that this does not HAVE to be so in technical terms, but is so for purely commercial reasons. Development costs time, resources and money, and inevitably ends up being more expensive.
And please read again, I did quite unequivocally say that I have also heard some tube which I did like, some of it quite a lot, too. Tube gear is just like any other gear, there are the good and the not so good samples.
As for the speakers, it is odd that AFAIK few new models suitable for tubes, meaning having elevated efficiency, have turned up. I find it a bit odd, given the newly gained popularity of tube designs.
As for the impedance curves, I believe, right or wrong, that this does not HAVE to be so in technical terms, but is so for purely commercial reasons. Development costs time, resources and money, and inevitably ends up being more expensive.
Hi,
Pavel, I said it before, why stick to SE topology and blame the valves for the design drawbacks?
It's the topology that can't keep up in the context of inefficient speakers.
Prior to PP designs all you had were hugely efficient speakers (with their own shortcomings) that were happy to make your ears bleed using half a Watt.
Trust me, there's a hell of a lot more you can do with valves than building SE amps.
So, please, stop hammering the valves but blame global digititis for the resurrection of an ancient topology that is, in most cases, no more or less than a pleasant effect box to counteract the digital glare we all too often hear.
Cheers,
Pavel, I said it before, why stick to SE topology and blame the valves for the design drawbacks?
It's the topology that can't keep up in the context of inefficient speakers.
Prior to PP designs all you had were hugely efficient speakers (with their own shortcomings) that were happy to make your ears bleed using half a Watt.
Trust me, there's a hell of a lot more you can do with valves than building SE amps.
So, please, stop hammering the valves but blame global digititis for the resurrection of an ancient topology that is, in most cases, no more or less than a pleasant effect box to counteract the digital glare we all too often hear.
Cheers,
Demian, just one thing I'd like to clear up: in your first paragraph, you connect clipping with NFB. Does this connection vary with the amount of global NFB, and does it have anything to do with full power open loop bandwidth?
All Class A systems have predictable distortion level changes and this should be essentially the same with both open loop amps and loudspeakers. Therefore, as speakers reduce in level, Class A amps should get more and more linear as well. It should be relatively easy that Class A tube amps could measure better than most loudspeakers.
Hi,
Dejan, the above reply wasn't addressed to you but nonetheless....
I can assure you that designing a tube preamp or amp with THD well down to 0.001% is perfectly doable.
The preamps can even be designed without resorting to a global feedback loop.
No distortion, no colouration or am I wrong?
But of course, everyone is free to his or her personal preferences. I'm not defending valves per se, it's just that I know it's not the valves that are to blame.
Best,
Dejan, the above reply wasn't addressed to you but nonetheless....
I can assure you that designing a tube preamp or amp with THD well down to 0.001% is perfectly doable.
The preamps can even be designed without resorting to a global feedback loop.
No distortion, no colouration or am I wrong?
But of course, everyone is free to his or her personal preferences. I'm not defending valves per se, it's just that I know it's not the valves that are to blame.
Best,
Correct. Frank opted for quality sound reproduction
jan
PS Mailed your buddy BA, dropped your name shamelessly.
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