Valve power - feel the force!

[Steve Toy]

it should be reserved for seriously important things like the correct use of the apostrophe.

Agreed.

[anthonyTD]

right folks,
i am going to stick my neck out here, and try and explain why i think valve amplifiers seem to have much more power and effortless transient response, compared to solid state amplifiers of similar power output.
i think its all to do with the rail voltages, i will explain, transistor/mosfet amps run on relitively low voltage rails compared to valves, around 50v + - where as an average valve amp consisting for eg, lets use KT88's would run on closer to 500v! now the only easy way i can relate why the two diffrent voltage realms could make such a diffrence is this, , imagine you have two cars, both are capable of 60 miles per hour, [we will call the speed the transient response] now, the first car is a nissan micra which although will do a top speed of around 90 miles an hour, its going to take a while to get there. the second car is a 911 porsche which has a top speed of around 170mph. they are both set off on their 60mph target speed, [transient] here is where the comparison should make sense, the nissan micra will take in excess of 12 seconds to reach its 60 mph target but the porsche will do it in 5 seconds or less, the reason being is because the porsche allready has a much higher top speed capability to start with so my point is, if you have a device that runs on a lot more voltage to start with, it should be capable of delivering a transient response of a given amplitude much quicker. obviously there is a lot more to it than that, but its a start. gentlemen, its over to you!!!
anthony...

[lurcher]

But, just to continue the analogy, the porsche is (maybe) 15 times further away from the watcher than the micra, so even though its faster, wtih a faster top speed, it will have to travel much further to appear to cover the same apparent distance.

[anthonyTD]

But, just to continue the analogy, the porsche is (maybe) 15 times further away from the watcher than the micra, so even though its faster, wtih a faster top speed, it will have to travel much further to appear to cover the same apparent distance.

not sure if thats relivent with the analogy i have used for the comparison, but please, elaborate further if you think it may help....
anthony...

[Iain Sinclair]

But, just to continue the analogy, the porsche is (maybe) 15 times further away from the watcher than the micra, so even though its faster, wtih a faster top speed, it will have to travel much further to appear to cover the same apparent distance.

Plus the insurance on the Porsche will be a shocker compared to the Micra.

[jcbrum]

so my point is, if you have a device that runs on a lot more voltage to start with, it should be capable of delivering a transient response of a given amplitude much quicker. obviously there is a lot more to it than that, but its a start. gentlemen, its over to you!!!
anthony...

It's a crap anology for two reasons.

1. You've got the cars the wrong way round.

2. Transients RESPONSES are current driven, and current is generated by a SUSTAINED potential difference.

What happens in a valve amp is that the output valves saturate and won't put more current into the load, and consequently the voltage droops because of the internal resistance of the valve. This is called "clipping" and because the rise time is slow the harmonics are limited and "musical" (Steve and Marco pay attention at the back.)

In a high power ss bipolar amp the internal resistance is very low indeed and so MASSIVE current can flow, (enough to self destruct sometimes).

This causes very fast rise times and if clipping is allowed to occur it generates an almost perfect square wave with horrible harmonics.

This is why ss amps should not clip and therefore need to be able to generate 300w or more to sound really good. most don't.

As far as the correct use of the apostrophe is concerned, one or two commentators on this thread simply have no understanding whatsoever of these matters, and are actually prone to talking f'ing bollocks. not you Anthony

[Marco]

This is called "clipping" and because the rise time is slow the harmonics are limited and "musical" (Steve and Marco pay attention at the back.)

I don't hear any "clipping", and so don't need to "pay attention", JC. The bottom line is my valve amps sound simply wonderful - better to my ears than any solid-state designs at any price I've owned or heard, and this is all that matters to me. I really couldn’t give a monkey’s about anything else!

Marco.

[lurcher]

not sure if thats relivent with the analogy i have used for the comparison, but please, elaborate further if you think it may help....
anthony...

Just pointing out that the presense of the output transformer does slight alter the equivilance your analogy requires.

Though I wonder if the transformer is responsible for valve amps having seemingly effortless dynamics, the transformer itself is a store of energy (in its flux), so its a simpiler process for that to be dumped into the speaker. The output stage of a SS amp contains no sources of stored energy, and merely allow the energy stored in the power supply caps to flow towards the speakers. And then of course the flow of that current is restricted by the ESR and other problems that plague large caps.

And that another difference, to store the same energy the size of a cap in valve amplifier the cap can be smaller, as the stored energy is proportional to the square of the voltage, but directly proportional to the capacitance.

Hmm, maybe that was what you were trying to show with your anaolgy, I will get my coat...

[Mike Reed]

; it should be reserved for seriously important things like the correct use of the apostrophe.

I cannot believe there is another person out there who cares about the apostrophe sufficiently to mention it in despatches, so to speak.

Of all the grammatical rules in English, ( and some are admittedly arcane ), the rules for the use of the apostrophe are straightforward, simple and easy to understand.

WHY do so many people (it seems) get it wrong?

Damn, wrong forum: back to valve amps and apologies for digressing.

Due acknowledgement to the semantic Scot (????)

[Iain Sinclair]

Due acknowledgement to the semantic Scot (????)

Thank you. Though of mixed Scottish and Irish descent, I am actually English by birth.

I have to bow out of discussions when valve and ss afficionados start throwing techy terms around. My knowledge of physics is, shall we say, limited.