Valve sound?
 

I have heard it said mainly by musicians that valves amps have a better sound than transistors but to be honest I can't hear any difference up to the point of overload where valves distort more gradually due to the transformer smoothing out to some extent the severe instant clipping that occurs with direct driven transformerless output stages, does valve sound actually exist or is it some form of nostalgia for a bygone age ?

Re: valve sound
 

I'm sure this will be a contentious thread! Its very subjective, but in my view It certainly exists for guitar amplifiers. They distort in a very smooth and pleasant way that doesn't seem possible to replicate with transistors. Many guitar players like distortion, myself included and there's really nothing like it.

I feel the hifi side of things is overrated, and perhaps because any distortion from valves is more pleasant to the ear its gained a better reputation. I'd imagine either technology could achieve excellent results with the right engineering

Re: valve sound
 

... and you'd be right.

I can't speak for guitar amps - distortion is a complex thing. But if you want to make a valve audio amp with minimal distortion and noise, broad and flat audio (and ultrasonic, and infrasonic) bandwidth, good transient response and perfectly adequate output impedance (i.e. adequately low) then you can. What it won't be is cheap, light in weight (depending on the power required), capable of extreme power (100-200W/ch is straightforwardly do-able though) or able to run for years/decades without any attention whatsoever. Nor will the design exercise, particularly of the output transformer, be easy. You might also struggle to make a gain stage capable of directly amplifying the sub-millivolt signals from a moving coil cartridge without any audible background noise, although once the stylus is put onto a record the noise from the vinyl surface should be greater.

Cheers,

GJ

Re: Valve sound?
 

As a fully paid-up audiophile (don’t shoot me!!), I would agree with the above. I’ve heard good and bad valve amplifiers, and good and bad solid state ones - in fact, if asked to name the two best amps I have ever heard, one is solid state and one is valve. Then again, I have personally heard far more bad valve amplifiers than bad solid state ones, so my preference is generally for SS.

In my experience, when people outside the Audio industry talk about the “valve sound” they mean something warm, soft and woolly it, in other words, a bad valve amplifier!

Re: Valve sound?
 

I used to chat to a writer (can't remember his name or books) on 2 metres, he lived in Brixham I think and he tried to explain it to me. It's apparently to do with harmonics, valve amps are rich in even ones and transistor in odd ones.

Anyone who plays an electronic organ/keyboard will probably be aware of the sound difference between settings which introduce even or odd harmonics. The even ones give a smooth sound and odd ones a sharper sound.

Peter

Re: Valve sound?
 

As someone who plays guitar and has tried various solid state technologies, I can confirm that for electric guitar, a valve amp provides the full fat sound.

It's smoother, warmer, juicier, fuller.

In overdrive it's just so silky full of tone.

Solid state amps tend to sound a lot flatter, tinnier and compressed.

I've tried all sorts and valve cannot be beaten.

Re: Valve sound?
 

When people ask for 'valve sound' they are usually asking for a particular type of low order distortion and limited bandwidth, which can be delivered by valves in a poorly designed circuit (in some cases deliberately so!).

Valves and semiconductors both have a transfer characteristic which means that second-order distortion dominates. However, circuit design may allow some of this to cancel so then third dominates. You can do this with valves or semiconductors.

The 'instant clipping' of an SS amp comes from the usually large amount of negative feedback, which is needed because a BJT is less linear than a valve.

Re: Valve sound?
 

The small amount of colouration introduced by a typical valve hifi amp actually sounds pleasant to most people. In a sense they sound subjectively better than even very good SS designs because they're less not more accurate.

Of course, there's a huge amount of audiophoolery and snobbery involved too.

Re: Valve sound?
 

In a nutshell:

Engineering is what matters - the devices are a means towards meeting the specification.

Assuming competent design, the differences between amplifiers run within their limits are small.

Audible differences can be accounted for by measurement, once you have found the right parameter to measure.

Amplifiers in musical instruments are a different matter, as they are habitually run into overload. At this point, all bets are off and it's then a question of which distortion you prefer.

Re: Valve sound?
 

Much of the difference comes from the great majority of valve amplifiers being transformer coupled to the load. This limits the practical damping factor which can be achieved to around unity. It also limits how much negative feedback can be applied to the amplifier as a whole, as a result of phase shifts in the transformer. It was said on here a while ago by someone that the main skill in designing a valve amplifier is to come up with an output transformer which allows enough negative feedback to be applied to keep distortion down to reasonable levels. I can't disagree with any of that.

I've been experimenting with a valve amplifier at home, normally I use big solid state stuff (Hitachi HA-7700, Beomaster 8000 etc) for any serious listening. The negligible damping factor produces big, fat bass lines and the distortion harmonics seem to artificially sharpen up the top end, giving the impression of vivid treble despite the premature roll-off given in the specifications. The combination of these two effects is quite pleasant and I can see why people like them, but it isn't hi-fi. "nice-fi" is the term I use.

The best thing about old valve amplifiers is that they are fun. Fun to get working and fun to see how well they do work in spite of their age. This is especially true with modern sources (CD etc) and modern loudspeakers. I can't understand the appeal of new ones though, they just look like fakes to me.

Re: Valve sound?
 

I see parallels, in this discussion, with the debate about if records are better than CD. Pro's and cons. for both.

Aub

Re: Valve sound?
 

The OPT does not limit damping factor to around unity, unless it is a SET with no feedback - but then that has been deliberately designed not to pursue high quality sound reproduction.

Yes, the OPT is a limiting factor on the amount of feedback which can be applied yet a high quality OPT will allow sufficient feedback for a good result. 20-30dB of feedback is usually possible, and is sufficient. A typical SS amp may have little more feedback than this at higher frequencies, although it will have lots more at low frequencies.

Re: Valve sound?
 

Valve amps date to a time when power was limited by cost and as a result the more forgiving distortion close to full power was considered a good thing.
I have run valve amps as a main hifi and have found that there is no difference until you turn the wick up a bit. This is not practical in my case as all the decorative items get shaken off there display shelves.
For playing guitars a lot of musicians add a valve "fuzzbox" in order to introduce such distortion in a controlled way when recording or playing a small venue.

Re: Valve sound?
 

Belatedly- I see that much of my comment here has been said already but I'll leave it up to show agreement. I notice that Peter N [p5*] might have been talking to someone who wrote the article that I can't recall:shrug:

It's a half century old question now and there have been other threads. An explanation that made the most sense to me was that driving or overloading the circuits hard tended to manifest itself in in "odd" harmonically related waveforms in valve equipment-so that it is more pleasing to human "beans" who tend to like intervals of a third, fifth, sevenths etc and that instruments are primarily tuned to facilitate that. The suggestion was that solid state amps have a chopper effect in "evens" ie 4ths/8ths/10ths and this sounds harsher.
Bagpipes are tuned in 9ths [apparently] and that may not be seen as all that smooth by some but it's a wide interval once you get up there anyway!

I'm in no position to give [or understand] supporting evidence for this theory but the chap who wrote the article seemed sufficiently clued up in both music and electronics to be convincing. Of course there may be no apparent difference to many of us [depending on the content and context] but that's within the subjective arena like people insisting on certain types of food or clothing etc. Very few people have anything close to perfect pitch for example! Personally I think there is a "warm sound" but much of that and
especially in live guitar performance, may well relate to pick-ups and playing techniques as well.

Dave

Re: Valve sound?
 

I worked on a Radford STA 100 amplifier once. It had started life in a recording studio. I measured the output impedance into a 12.9ohm load to be 0.23ohm (1kHz) rising to 0.39ohm (7.1kHz) and 0.47ohm (50Hz). The measurements were taken at 3W output or so, but until the amp starts to distort significantly the output impedance won't vary much with power. Those measurements represent amp damping factors of between 28 and 56, although they're of no real consequence because the secondary circuit resistance will be overwhelmingly dominated by the resistance of the speakers, just as it will for a solid-state amp.

The reason for the odd load resistance was that the original STA100 is really a 100W, 100V-line amp, so the optimum load impedance is nominally 100ohm. However the output transformer's three secondary sections, which are normally wired in series, can be strapped in parallel instead to match 11ohms. 12.9ohms was the nearest resistor I had that could be relied upon not to introduce significant distortion itself at up to 100W dissipation. So I wasn't really testing the amp under the conditions for which it had been optimised.

By the way, the THD was 0.03% at 20W continuous output, made up entirely of the second and third harmonics.

If your valve amp gives poor damping and adds harmonic distortion then I'm afraid the only solution is to swap it for one that doesn't.

Cheers,

GJ

Re: Valve sound?
 

I fear you're mixing up musical intervals with harmonic numbers Dave. 2nd harmonic is a musical interval of an octave, 3rd harmonic is an octave and a fifth, 4th harmonic is two octaves, 5th is two octaves and a major third, 6th is two octaves and a fifth. So far all of them, both odd and even, are euphonious. The 7th, however, isn't. So much for 'odds good, evens bad' I'm afraid ;).

Cheers,

GJ

Re: Valve sound?
 

Broadly speaking, that's always been my understanding. too.

Al.

Re: Valve sound?
 

Symmetric clipping gives odd-order distortion; asymmetric clipping gives even-order too. Which type of active device you overdrive to get the clipping is of less importance. I think it would be more accurate to say that valve amps tend to clip more smoothly (due to less feedback) and so generate less high-order distortion than a transistor amp; both will generate mainly odd or even depending on whether the clipping is symmetric. It is the difference between 'little high order distortion' and 'more high order distortion' which most people can hear; the distinction between even and odd order is less of an issue and partly a matter of preference, but few people like high order distortion!

Re: Valve sound?
 

That would have been Gordon King, per this thread:

https://vintage-radio.net/forum/showthread.php?t=54437

Re: Valve sound?
 

My feeling, in general terms is to agree with what has been said, but, in my opinion, there has been a lot of variation over time. Igrew up when there were still a lot of valve amplifiers about. Most sounded pleasant. When the first transistor amplifiers became commonplace, and got beyond the low power Germanium types, I noticed a lot of solid state amplifiers that sounded really nasty. Maybe it was his setup, but one setup using the Sinclair modules, I noticed, a prime example. Cheap Silicon! In time things got better (maybe with lots of money they always were), and transistor amps sounded Ok. Now we are pretty much there with them 'digital' has come along with it's nasty sound.

I suppose the main things to take from this is that things go in cycles and (emphasis) a good sum of money well spent, gets a good sound.