Do tubes do anything well in circuits?

[mhardy6647]

Not to mention everyone used to have a massive one in their loungeroom... monitors, anything that still uses a CRT.
View attachment 151030

Please clarify...



JSmith

"used to" . . .

Even I retired our 1983 vintage Toshiba CRT TV... albeit just a couple of months ago.

 

[gags11]

Overall the cost-per-watt is MUCH lower with solid state. And there aren't a lot of high-power tube amps. It's easy to find 1000W (or more) solid state amps but I don't know if I've seen a 500W tube amp,

https://www.vtl.com/products/power-...iers/siegfried-series-ii-reference-monoblock/

VTL Siegfrieds are rated at 650watts, but cost north of $60,000 and have relatively high distortion.

 

[JSmith]

I was suggesting that intentional manipulation is done with 2 ch to Mch matrixing.

Ok, so you're not talking about real multi-channel content, just faux surround... to be clear.



JSmith

 

[GXAlan]

Ok, so you're not talking about real multi-channel content, just faux surround... to be clear.

It's super confusing, but the main point was that the "intentional manipulation" of audio isn't always bad.

Dolby Surround is part of "the Atmos bundle of technologies." It will also convert real 5.1 or 7.1 multichannel content into the flexible speaker layout available through "discrete Atmos" with object+bed based audio. So you can get Atmos processing on non-Atmos surround sources and Dolby Surround processing on 2ch sources.

Meet the New Dolby Surround | Sound & Vision (soundandvision.com)

https://www.dolby.com/siteassets/te...atmos-installation-guidelines-121318_r3.1.pdf

 

[JSmith]

the main point was that the "intentional manipulation" of audio isn't always bad.

I assumed as much... I don't think anyone here will disagree, however most here will prefer said manipulation to be user variable and not baked into a product.

So you can get Atmos processing on non-Atmos surround sources and Dolby Surround processing on 2ch sources.

Thanks, I'm quite aware of how 2 channel sources and converted into faux multi-channel. The point was to clarify that previous statement which implied multi-channel sources are modified somehow, which isn't the case and wasn't what you meant.



JSmith

 

[xaviescacs]

I know very little about electronics but I wanted to add something as an example of tube use in amplifiers. I don't know how useful or interesting is it going to be for the audience in here.

Several years ago I bought an amplifier from this italian brand pathos that has an hybrid topology, combining tubes and mosfets with no feedback. I haven't found a topology scheme of this one, but here I found some good pictures and some other explanation of its components and topology. I've also found this video by someone of Upscale Audio in California commenting something about the topology and components.

I then investigated a little and found that for the most expensive designs they use a topology they call inpol, which is also hybrid. They state the following in their website:

The early theory influencing the whole INPOL project comes out to avoid any kind of general “output-input” back-feedback. It is claimed that, despite a fine developed back-feedback implies important benefits, it is considered always something "artificial", which influences the sonic outcome and causes a loss of naturalness and “spikiness”.
A good project not including the use of back-feedback implies – on the other hand – a higher rate of conversion and a slightly poorer damping factor, to put up with naturalness and harmony of the actual signal.

INPOL was born from this design theory: developing a power stage without any back-feedback, featuring a limited distortion, and a satisfactory damping factor. For this purpose it has been used a single solid-state component in follower configuration, with hypothetical voltage gain = 1 and with high current gain. Polarization is in pure Class A to avoid crossover distortions, typical of Class AB stages.

Only solid-state NPNs are used, which are totally different from PNP ones; this difference could only be solved by back feedback. INPOL makes use of a big inducer as energy supply, which is driven by a transistor as a “controlled current generator”. In so doing the theoretical efficiency is doubled – from 25% to 50% – and low impedance is achieved, necessary to get a correct damping factor.

INPOL features an amplification factor of 1 when current is provided, so it "copies" the signal received from the input, without changing the harmonic content and keeping the signal naturalness unchanged.

The only task of INPOL is therefore supplying the necessary current for driving the loudspeakers perfectly. INPOL is a worldwide patent.

From what I've been reading in this forum, it seems they proposed (that was in the 90s) a solution to solve a problem with other amplification topologies that doens't exist anymore.

They say it's a worldwide patent but I've found this guy's website were he explains how it works and proposes a DIY amplifier using this topology, or at least what he thinks it is, I guess. The specs he gets though are worst, in particular the THD.

 

[Phorize]

Around here, my impression is that tubes are considered distortion generators and little else. In my time with tube amplifiers I remember reading that there were certain things that tubes do better than solid state components. I know nothing about electronics but am interested in whether there is any truth to that, and if so, could whatever that is be incorporated in circuit design.

There’s nothing inherent to tubes that prevents transparency. Tube amplifier design achieved audible transparency in the 1940s. As far as I can tell high distortion designs only became popular well after tubes became obsolete, especially in the 80’s sections of the audiophile community lost interest in good engineering, favouring a more mystical approach.

Maybe one of the experienced tube amp designers here could chip in on whether there are advantages from a designers point of view. @SIY @tomchr

 

[pma]

Not everything is so bad with tubes. We may ask if speed is necessary with the same validity as of showing distortion plots at inaudible level. Everyone is free to make the choice.

OP asked this question in the thread title:
Do tubes do anything well in circuits?

so my reply is in the plot below

Tube preamp large signal square response with 1us rise time. Not every opamp can do it (not too many in fact), but almost any tube can.

 

[sergeauckland]

Low distortion valve amplifiers, at least, low enough for transparency, are perfectly possible, just pointless. They're bigger, heavier, less reliable and consume a lot more power, and if transparent, won't sound any different to a SS amp. Apart from looks, that's why I think valve amplifiers are still used, because they're mostly not transparent, and some like that sound.

S

 

[restorer-john]

We may ask if speed is necessary with the same validity as of showing distortion plots at inaudible level. Everyone is free to make the choice.

I agree.

 

[SIY]

Maybe one of the experienced tube amp designers here could chip in on whether there are advantages from a designers point of view. @SIY @tomchr

HV swing for the few application which require this. Otherwise, the advantages are all non-auditory.

 

[Grumpish]

They'll stand a nuclear EM pulse much better than most SS device, so after WW3, you'll be able to use your Dynaco amp when all the others are burnt out.

Vacuum devices are still of use in very high power transmitters, and in generating microwaves, but for home HiFi, there's nothing I can think of where vacuum devices are better, except possibly looking great.


S

Off topic, but when the US got their hands on a MIG-25 in the mid-70's, they were amazed to find that most of the avionics was miniature valves - which they then realised was actually an advantage because of the resistance to an EM pulse.

 

[AnalogSteph]

Tube preamp large signal square response with 1us rise time. Not every opamp can do it (not too many in fact), but almost any tube can.

So that's about 40 V/µs worth of slew rate. Somewhat high by the standards of audio opamps, yes (it's not like it would be impossible, it would just make them harder to use), but then you have to keep in mind that the permissible voltage swing is higher than usual as well, as is the input voltage noise level... basically, tubes are higher-impedance devices than solid state, you want to run them at higher voltages and lower currents. A fair comparison would have to be based on equal dynamic range, not equal voltage.

Interestingly, measured input noise seems to be less severe than I remember it being, with numerous devices in the 6-10 nV/√(Hz) equivalent region (we're obviously talking 1/f dominated noise). So that's maybe a factor of 3-5 in voltage to be on equal footing with "sand" (well, JFETs anyway)? That would reduce our equivalent required slew rate to 8-13 V/µs, which - surprise! - is within reach of typical audio opamps. (I could be mean and do a comparison to low-noise BJTs, which would yield a factor of more like 8-10.)

These days, you wouldn't be designing with vacuum bulbs unless you really had to... their bulk, added heater power consumption, sample-to-sample performance consistency or lack thereof, need for uncomfortably high / lethal supply voltages (and often impedance transformers to interface with the world out there), potential suceptibility to microphony, cost and propensity to wear are a real turnoff for a majority of applications and restricting circuit complexity severely. Even in the realm of Stax electrostatic headphone drivers with their hundreds of volts of output voltage, their best solid-state models perform better than the tube-based ones...

 

[pma]

So that's about 40 V/µs worth of slew rate.

I know you know that the tube is not slew rate limited. What you see is rise time, not the slew rate. The rise time is limited by composed output impedance and composed load capacitance, nothing else. And the swing can be considerably higher than shown, still keeping the rise time and not introducing TIM and SID.

I am not routinely designing with vacuum tubes, I only try to answer questions like "do they do anything well in circuits", which is exactly what was asked in this thread - anyone can read the title. The tubes do what they do according to laws of physics and electrical circuits. Same applies to solid state components.

 

[jeff57]

Hi,

I used to have an Accuphase amplifier (E-270).
I now have a valve amplifier from LAB12 company.
Same range, same price.

The sound of LAB12 valve amplifier is way better than my Accuphase !
KT150 tubes are powerful and magic.

replying to "Do tubes do anything well" ?
my obvious reply is ... MUSIC.

Jeff

 

[restorer-john]

HV swing for the few application which require this. Otherwise, the advantages are all non-auditory.

At what specific point/value would you regard HV swing (slew rate) shifting from "non-auditory" to clearly audible or identifiably audible? You've made the claim, what evidence do you have?

 

[JSmith]

KT150 tubes are powerful and magic

Thanks for this information and your 3rd ever post... I needed a good laugh.



JSmith

 

[thefsb]

Question should be, have tubes any bennefit in audio frequence amplifier design?

https://www.sweetwater.com/c623--Tube_Guitar_Amp_Heads

And if, which are this?

That is very much debated. Personally, I like the old Fender amps (Bassman for humbuckers and Twin for SC) but there is simply no arguing with how Jimi played the Marshalls.

 

[tomtoo]

https://www.sweetwater.com/c623--Tube_Guitar_Amp_Heads



That is very much debated. Personally, I like the old Fender amps (Bassman for humbuckers and Twin for SC) but there is simply no arguing with how Jimi played the Marshalls.

Ok, my foult i missed the hifi. No diskussion about instrument amplification. You are absolutly right, i change that.

 

[FrantzM]

Hi

This needs to be put to rest. in Audio there is nothing that tubes do better than SS. Nothing.
Any sound effect that can be done with tube can replicated and then more , with SS and software. One could debate of the performance vs cost of software effects box.
To repeat: In Audio Reproduction, there is no need for Tubes today.