Hifi, why bother?

[Nick]

On about small speakers, I really like the Fostex FF85WKs for near-field use...

I've made several sets of µFonkens- design is free from http://www.planet10-hifi.com/fonken.html

There's a thread about my initial attempt (which came out quite nicely) on Audio-Talk... http://www.audio-talk.co.uk/phpBB3/viewtopic.php?f=4&t=5997

[Diabolical Artificer]

Thanks kallee for trying to get at the nub of the thread, though it's fragmented as all discussions do, though in essence it seems to be "what is good hifi" I'd say that in a nutshell a good hifi is one that brings enjoyment, that reproduces music in a way that's pleasing. We've seen from Marks excellent informative posts how the sound a band records gets manipulated, the result is completely different to a live sound, which with Classical music is what they're trying to capture, both are trying to capture an event, an emotional interplay between musicians and audience if there is one and then mix it so it sounds nice on the various devices it's played back on.

Originally sound engineers and electrical engineers designed mixing desks, microphones etc to capture a performance without adding distortion or other artifacts but then the waters got muddied, The Beatles upsetting recording engineers by shoving the faders up, increasing gain so a track was distorted, Ray Davies slashing his speaker cone on his amp to get distortion on You Really Got Me and Phil Spector building his wall of sound so singles sounded good on tinny transistor radio's.

So already we have a divided approach to sound recording & reproduction, the audience or listeners are further divided into purists who want to listen to that recording as it came out of the studio without any added artifacts, the hifi camp and those who couldn't give a toss. The hifi camp is further divided as they can't agree what the best way is to achieve this, which is complicated further by us all living in different sized boxes, having less than optimal and non standard transducers on the outside of our heads, non standard interfaces between said ears and whoever/whatever it is that is us/I. Then all this is complicated further still by folk who believe the shinny bits of metal and coloured pieces of paper that reside in other folks pockets should be theirs, who then think of clever & dubious ways to part said aformentioned folks from it.

After writing all that I'm not sure it makes anything any clearer and I can't remember what my original point was, perhaps a better title for the thread would be "Hifi is complicated : ) Not really, as long as it brings pleasure that's all that matters, a chef can work assiduously to prepare a meal, to design it to have the optimal taste, only to have the eater put Daddies sauce all over it. Perhaps like the chef a designer of an amplifier or speaker we can engineer it to have low distortion, the best taste as far as we are concerned but include a bottle of Daddies or Tomato Sauce as part of the package.

Andy.

[Doodlebug]

    Look before you buy !

[Crackle]

I have always understood that pop and rock records are mastered according to the wishes of the producer and the wishes of the band are often overridden for commercial reasons.
Live performances can be different, the band have more opportunity to produce the sound THEY want the listener to hear.

Compare. Deep Purple's "Smoke on the Water", from their original 1972 live Made in Japan album and the more recent remixes.
Mike

[ppppenguin]

At 63 I can no longer really hear 15625Hz line whistle. I can sort of sense it, just about. 10125Hz for 405 is still LOUD.

I get occasional tinnitus which sounds distressingly like line whistle.

[Mark Hennessy]

Studio techniques - no matter how dramatic - are part of the original performance. If a band overdrive equipment to get a grungy sound, it's because that was their artistic intent. If that sound was put together with a certain demographic and context in mind, then that again is part of the artistic intent. OK, as Mike says, the record company will have an input to that. I wouldn't go so far as to say "overridden", but their input is significant nonetheless.

So what might end up on the disc might be grotty, or it might be amazing. But in my mind, the media delivered by the record company is the "demarcation point". Everything up to that point is "artistic intent", and everything the consumer does to alter that sound is "personal preference".

Like I mentioned earlier, it's a shame that tone controls are so rare today. Many recordings benefit from some gentle correction, and that's perfectly valid. But the great thing about tone controls is that you can bypass them.

Similarly, some recordings might benefit from some added distortion. Some recordings are very "dry" and clean, and some people might prefer these recordings to sound a bit warmer and possibly even grungier. And that's where a valve amp with high distortion is so great.

But the trouble with a distorting valve amp is that you can't bypass the distortion.

And that is where we came in. Wouldn't it be great if the "nice" distortion could be added to taste, and completely removed when not needed? Then, you have the ability to choose between "artistic intent" and "personal preference" - all on a simple control knob, just like you do with bass and treble.

To be clear, I have never wanted to diminish the notion of personal preference, but did want to raise awareness of the big picture in the recording and hi-fi industries, so we now know that by making the choice to add euphonic distortion, we are (a) deviating from the artistic intent, and (b) likely to need deep pockets and are at risk of being sucked into a big, scary machine (the esoteric hi-fi industry).

Of course, Andy - like many of us here - has the advantage that he can build these amplifiers without handing over a single penny to these companies. I also think he has learnt a really valuable lesson about audio here - and so have all of us following along. As I've said already, building low-distortion solid-state amplifiers is really simple. Building valve amplifiers with good distortion performance is harder in many ways, but he's mastered that. The next step is to build amplifiers with "high-but-nice" distortion. That's much harder, but he's done it!

I could probably come up with a solid-state amplifier with 8% distortion. But I guarantee it will sound horrible. So, Andy has done something that I can't do. And if Andy and I were running hi-fi amplifier companies, he'd be able to sell amps for huge sums, whereas I'd be selling at much more modest prices - his amplifiers will stand out as being different and interesting, but mine will be merely "ordinary". That will cause me great pain because I know my amplifiers are better by any technical description, but he'll have the luxury company car and I'll still be struggling to put food on the table. Joking aside, you might actually be onto something with this!

Andy, I've just remembered that some valve amps have a triode/pentode switch, where you can choose your prefered distortion level, and that is getting close to what I was discussing above. I reckon that should be your next thing to investigate

[Mike Watterson]

I "repaired" one modern valve amp that had an EL84 and a similar Octal valve (forget which KTxx Beam Tetrode) and what looked like a too small audio transformer. An EL84 is described as Pentode, but actually it also is a beam tetrode. The g3 isn't a grid like on an EF80, it's beam forming plates.
"Do not operate valve changeover switch while power is on."
I explained that either valve could sound like the other just with slight adjustment of the cathode resistor. That it was a gimmick.

One ECC82 or ECC82 grid was earthed via the output transducer on the springline reverb. Putting a 470k at the valve base grid to 0V fixed the hum.
Additional problem was it was a painted chassis and the earths on most of the input sockets were not actually earthing due to clearance and thickness of paint. Unused earth tags were wired.

[Kalee20]

But the trouble with a distorting valve amp is that you can't bypass the distortion.

 
Why not? I'm thinking (consider something like the Mullard 3-3 which has been mentioned in this thread), a 2-position switch. One position is as-Mullard; the other position removes the negative feedback, and also introduces an input attenuator to bring sensitivity down to the with-feedback level.


Distortion isn't bypassed, it's cancelled - but you get the same thing.

I "repaired" one modern valve amp that had an EL84 and a similar Octal valve (forget which KTxx Beam Tetrode) and what looked like a too small audio transformer. An EL84 is described as Pentode, but actually it also is a beam tetrode. The g3 isn't a grid like on an EF80, it's beam forming plates.

I doubt that - so I had a look in an EL84 (luckily to hand right now!) and doubt it even more.

The g3 support rods can be seen through a couple of apertures in the anode, and there definitely is a spiral grid wound on them.

Mullard / Philips denied the beam tetrode (Not Invented Here) and did describe a few of their valves as pentodes for marketing purposes, eg DL92 which definitely is a BT. But not the EL84.

[Mark Hennessy]

But the trouble with a distorting valve amp is that you can't bypass the distortion.

 
Why not? I'm thinking (consider something like the Mullard 3-3 which has been mentioned in this thread), a 2-position switch. One position is as-Mullard; the other position removes the negative feedback, and also introduces an input attenuator to bring sensitivity down to the with-feedback level.


Distortion isn't bypassed, it's cancelled - but you get the same thing.

I mentioned in passing that some amps have a triode/pentode mode switch - they achieve a similar thing.

These are all interesting thoughts, but even when in "low distortion" mode, the distortion is still going to be orders of magnitude higher than a half-decent solid state amplifier. And the output impedance will also be considerably higher, so the frequency response will be affected by the impedance curve of the loudspeakers (I think I mentioned this earlier in the thread, but we've mostly concentrated on distortion so far). It might be better to sneak a solid-state amp in there, and switch between that and the valve amp. Just a couple of TDA2030s would do the job

Checking now, I see the Mullard 3-3 is around 0.5-1% THD (measurement conditions and measurement bandwidth unknown). On a pure 1kHz sine wave, 1% THD is readily audible if there's plenty of 3rd harmonic, such as you'd get with clipping, as we're especially acute at 3kHz. But it's surprising how much higher it needs to be if it's 2nd-order, as 2kHz is masked to a higher degree by the presence of 1kHz.

Until now, we haven't really touched on the audibility of distortion. It's a very complicated subject - one of those that gets worse the more you dig. As a starter, the nature of typical programme material needs to be investigated. I've done this sort of thing in the past, but a lot of it is hidden away on a forum that you need to join to read (that wasn't the case at the time) - suffice to say, it opened a lot of people's eyes, including the designer of a well-known UK brand of speakers. One day I'll put a shortened version of it on my website.

So while Andy reports a THD of 8%, I'd be interested to know how that varies with power output. A plot like that found on the [url=http://www.r-type.org/articles/art-003h.htm]Mullard 3-3 page[/quote] would be ideal, but perhaps a bit time-consuming to produce. If nothing else, results at 10dB and 20dB below maximum power would be telling.

If I ever manage to clear the workshop bench, I might experiment with a Hacker Mayflower. That's literally the only valve amplifier I have any experience of, having restored a load of them over the years. One time, I did a repair diary where I measured the THD with each set of component changes. The challenge would be finding the scrap of paper with all my measurements on!

[Mike Watterson]

I doubt that - so I had a look in an EL84 (luckily to hand right now!) and doubt it even more.

The g3 support rods can be seen through a couple of apertures in the anode, and there definitely is a spiral grid wound on them.

Mullard / Philips denied the beam tetrode (Not Invented Here) and did describe a few of their valves as pentodes for marketing purposes, eg DL92 which definitely is a BT. But not the EL84.

Obviously then I'm thinking of something else and confused.
Either old age, lack of fresh air, food, coffee ...

Though I'd have to break one. I can't see inside it, so I'll take your word for it. Either I've misremembered, been misinformed or confusing it with some other valves.

I have a box of dead valves and mean to dismember them like this:
https://www.radiomuseum.org/forum/ef89_anatomy.html#1

An interesting article on the Beam Tetrode.
https://www.radiomuseum.org/forum/beam_p...guage_id=5

Will a KT61 or KT63 sound much different to an EL33 or EL34 or EL84? Same drive, HT and audio transformer.
I'm sure it wasn't a KT66 as those are big.