Take two amps...

[ashevans09]

I've seen a couple of posts here recently talking about how "loud" valve amps are. I was kind of under the impression if you had, say, a solid state amp and a valve amp both rated at 300 watts or whatever that they would both put out more or less the same volume as they had the same wattage?

Am I completely wrong here?

Thanks for any help and (hopefully ) the lack of flaming

[Kiwi]

Loads of stuff written about this on the forum already thanks to Messers Claber and Fitzmaurice. Basic gist is loudness is subjective depending on the sensitivity of your speakers, the number of speakers, the efficiency of the cabinet, the differences in how valve amps and solid state handle transients etc.

300w RMS is 300w RMS however.

[Merton]

[quote name='ashevans09' post='102883' date='Dec 11 2007, 08:33 PM']I've seen a couple of posts here recently talking about how "loud" valve amps are. I was kind of under the impression if you had, say, a solid state amp and a valve amp both rated at 300 watts or whatever that they would both put out more or less the same volume as they had the same wattage?

Am I completely wrong here?

Thanks for any help and (hopefully ) the lack of flaming

[/quote]
Power output and volume are not linked exlcusively. Power output could be heat generated in the power amp, or generated in the speaker cables etc etc....

As Kiwi says, there's lots of other things which influence perceived volume level too, and several other peeps are better placed to explain them more clearly than me

[RIM Basses]

When I had my mesa 400+ at full power, I was told that to get the same power out of a solid state rig you would need around 1600w So basicly tube amps are four times louder? Ive been playing a Thunderfunk 550B and I dont really miss the Mesa anymore. So lets face it, there's lots of different amp and cab setups. Some will project better than others.

Cheers,

Robbie

Edited December 11, 2007 by RIM Basses

[Bill Fitzmaurice]

[quote name='RIM Basses' post='102939' date='Dec 11 2007, 04:54 PM']When I had my mesa 400+ at full power, I was told that to get the same power out of a solid state rig you would need around 1600w So basicly tube amps are four times louder? Ive been playing a Thunderfunk 550B and I dont really miss the Mesa anymore.

Cheers,

Robbie[/quote]
Tube amps have natural soft-knee compression. 6dB of compression can make the amp seem to be four times as powerful. You don't actually need four times as much SS power, but you do need a properly set high quality compressor.

[carlosfandango]

[quote name='Bill Fitzmaurice' post='102941' date='Dec 11 2007, 10:00 PM']Tube amps have natural soft-knee compression. 6dB of compression can make the amp seem to be four times as powerful. You don't actually need four times as much SS power, but you do need a properly set high quality compressor.[/quote]

Hmmmm that sounds interesting.....how does this work? Do you mean like you would use a compressor/limiter e.g when mastering a recording or in modern PA systems to create a "louder" mix?

[paul, the]

[url="http://basschat.co.uk/index.php?showtopic=294"]http://basschat.co.uk/index.php?showtopic=294[/url]

[Merton]

[quote name='RIM Basses' post='102939' date='Dec 11 2007, 09:54 PM']When I had my mesa 400+ at full power, I was told that to get the same [color="#2E8B57"]power[/color] out of a solid state rig you would need around 1600w So basicly tube amps are four times louder?[/quote]
Careful with the use of "power" instead of "volume" or even "perceived volume" That's where a lot of people's confusion comes in I think.

My old Trace head and current Nemesis head are both 300W (well, the Nemesis is 320W) but to get the same perceived volume, the Trace would be set on ~2-3 and the Nemesis on 5. I half wonder whether that's to do with input headroom (Trace had gain on about 9 with no clipping, Nemesis on 4 with a bit of soft clipping for the compressor), but that's another query for another thread...

[LukeFRC]

in my experience valve is a 'fuller' tone that sounds louder.

try this experiment-
get a Ashdown evo head or some other head with both solid state and valve pre-amps.
turn it to the ss pre amp, start playing as you do blend in the valve pre amp. It seems to get louder and the sound seems to be fuller and more permeating but at the same time it doesn't feel like it is louder- just different.

[Bill Fitzmaurice]

[quote name='carlosfandango' post='102945' date='Dec 11 2007, 05:04 PM']Hmmmm that sounds interesting.....how does this work? Do you mean like you would use a compressor/limiter e.g when mastering a recording or in modern PA systems to create a "louder" mix?[/quote]That's pretty much it. The power output of an amp is limited by its voltage swing. Compression allows one to increase the density of the signal within a given voltage swing, therefore sounding louder without actually being louder. The one thing that sets valves apart is that they can compress the signal in both the pre-amp and output stage, while SS can only do so in the pre-amp, so while valve sound can be emulated it can't quite be duplicated.

[jammie17]

[quote name='Crazykiwi' post='102898' date='Dec 11 2007, 08:54 PM']Loads of stuff written about this on the forum already thanks to Messers Claber and Fitzmaurice. Basic gist is loudness is subjective depending on the sensitivity of your speakers, the number of speakers, the efficiency of the cabinet, the differences in how valve amps and solid state handle transients etc.

[i][b]300w RMS is 300w RMS however.[/b][/i][/quote]

Well, that's not necessarily true. 300 watts with a lot of current vs voltage, or 300 watts with a lot of voltage vs current. There is an audible difference.

[stevebasshead]

[quote name='Merton' post='103151' date='Dec 12 2007, 11:35 AM']My old Trace head and current Nemesis head are both 300W (well, the Nemesis is 320W) but to get the same perceived volume, the Trace would be set on ~2-3 and the Nemesis on 5.[/quote]

That's more to do with the taper on the volume pot, they're not always linear all the way from min to max. Most of the output volume from a Trace is available in appoximately the first half a turn, thereafter it makes less and less difference. I'm not familiar with the Eden but at least some of the volume difference you hear at what look to be the same positions could be explained by that.

[Merton]

[quote name='stevebasshead' post='103946' date='Dec 13 2007, 04:36 PM']That's more to do with the taper on the volume pot, they're not always linear all the way from min to max. Most of the output volume from a Trace is available in appoximately the first half a turn, thereafter it makes less and less difference. I'm not familiar with the Eden but at least some of the volume difference you hear at what look to be the same positions could be explained by that.[/quote]
Thought that may well be the reason!

[Bill Fitzmaurice]

[quote name='jammie17' post='103682' date='Dec 12 2007, 09:16 PM']Well, that's not necessarily true. 300 watts with a lot of current vs voltage, or 300 watts with a lot of voltage vs current. [/quote]
It's always true. Ohm's Law. For a given wattage in order to alter either the current or voltage one must also alter the load impedance. For instance, 300 watts into 4 ohms is 34.6 volts at 8.7 amperes, period.

[jammie17]

[quote name='Bill Fitzmaurice' post='103956' date='Dec 13 2007, 04:48 PM']It's always true. Ohm's Law. For a given wattage in order to alter either the current or voltage one must also alter the load impedance. For instance, 300 watts into 4 ohms is 34.6 volts at 8.7 amperes, period.[/quote]

Ahh..thank you Bill...I did mis-state. Let me re-state. 300 watt amp with multipal taps on it. 2, 4, 8. Amplifier is claimed to deliver 300 watts into evey load, however, if you hook up the same load, say, 4 ohms, to the different taps, you get three different volume levels. Why? Three different Voltages delivered at those different outputs.

Voltage = volume...so in the ohms law it would be best to have more voltage with less current....but then speaker control would suffer.

[GreeneKing]

[quote]Voltage = volume[/quote]

Seems odd to me?

I'm an absolute Amplifier numpty but surely current and therefore power come into the volume equation?

Or do you mean Volume is proportional to voltage? That I can handle.

I'm getting confused and I'm vaughly (sp?) aware of how complex the maths around this stuff can get

[Bill Fitzmaurice]

[quote name='jammie17' post='104039' date='Dec 13 2007, 03:01 PM']Ahh..thank you Bill...I did mis-state. Let me re-state. 300 watt amp with multipal taps on it. 2, 4, 8. Amplifier is claimed to deliver 300 watts into evey load, however, if you hook up the same load, say, 4 ohms, to the different taps, you get three different volume levels. Why? Three different Voltages delivered at those different outputs.

Voltage = volume...so in the ohms law it would be best to have more voltage with less current....but then speaker control would suffer.[/quote]
Irrespective of the tap used if you don't change the impedance of the load. ie., the speaker, then you are not changing the output voltage of the amp if the same power output is maintained. What you are changing by using a different tap is the number of turns on the secondary of the output transformer being utilized, and yes, that will alter the volume level, because it changes the output voltage available. But it does not alter the current available, that is a constant with a tube amp, so if the volume goes down it is because the voltage swing is also down. Doing so is also begging for trouble, as an impedance mismatch between the output transformer and speaker can fry everything from the output transformer to the output tubes to the input transformer, and everything in between. Most amps are built to withstand abuse of this sort, but many have found out the hard way that amps will only take so much.

[tauzero]

[quote name='jammie17' post='104039' date='Dec 13 2007, 08:01 PM']Ahh..thank you Bill...I did mis-state. Let me re-state. 300 watt amp with multipal taps on it. 2, 4, 8. Amplifier is claimed to deliver 300 watts into evey load, however, if you hook up the same load, say, 4 ohms, to the different taps, you get three different volume levels. Why? Three different Voltages delivered at those different outputs.

Voltage = volume...so in the ohms law it would be best to have more voltage with less current....but then speaker control would suffer.[/quote]
Um, no. Valve output stages use transformers, unlike SS ones which are direct. When you're powering something via a transformer, you get maximum power transfer when the impedance of the transformer is equal to that of the load (if the load impedance was higher, the amount of current flowing in the circuit would decrease, and if the load impedance was lower, it would have a reduced proportion of the voltage). So if you hook up a 2 ohm load to the 2 ohm tap, you'll get the same volume as if you hook up an 8 ohm load to the 8 ohm tap (assuming speakers of identical efficiency).

An SS output stage is different - it is delivering a voltage swing which can be up to 0.6V away from the power supply rail voltage. The internal resistance of the amp is as low as possible, the voltage is a constant, so the lower the load impedance, the more volume you'll get. Due to the fact the amp does have some internal impedance, the available output voltage is split between the internal resistance and the load, so the lower the impedance of the load, the smaller the proportion of output voltage it will get, which is why an SS amp will deliver, say, 250W into 8 ohms and 350W into 4 ohms, rather than the 500W you might expect.

[jammie17]

[quote name='tauzero' post='104319' date='Dec 14 2007, 02:45 PM']Um, no. Valve output stages use transformers, [i][b]unlike SS ones which are direct[/b][/i]. When you're powering something via a transformer, you get maximum power transfer when the impedance of the transformer is equal to that of the load (if the load impedance was higher, the amount of current flowing in the circuit would decrease, and if the load impedance was lower, it would have a reduced proportion of the voltage). So if you hook up a 2 ohm load to the 2 ohm tap, you'll get the same volume as if you hook up an 8 ohm load to the 8 ohm tap (assuming speakers of identical efficiency).

An SS output stage is different - it is delivering a voltage swing which can be up to 0.6V away from the power supply rail voltage. The internal resistance of the amp is as low as possible, the voltage is a constant, so the lower the load impedance, the more volume you'll get. Due to the fact the amp does have some internal impedance, the available output voltage is split between the internal resistance and the load, so the lower the impedance of the load, the smaller the proportion of output voltage it will get, which is why an SS amp will deliver, say, 250W into 8 ohms and 350W into 4 ohms, rather than the 500W you might expect.[/quote]

Don't want to argue. Mc'Intosh uses output transformers called, "audioformers" with s/s power amps. As I tried to restate and Mr. Fitzmaurice eloquently pointed out to me, (thank you) my basic post was trying to state that volume is derived from voltage. My apologies to anyone if my lack of knowledge/interpretation confused anyone.

Edited December 14, 2007 by jammie17

[GreeneKing]

I'm aware that my knowledge of electronics isn't what I'd like it to be so I've set myelf some learning targets for 'fun'. I was trained to work with 3 phase generators and suchlike and even that knowledge is pretty rusty.

Ultimately I'm hoping to understand amplifiers and such stuff and maybe I'll build myself something useful.

[Bill Fitzmaurice]

[quote name='jammie17' post='104359' date='Dec 14 2007, 11:11 AM']Don't want to argue. Mc'Intosh uses output transformers called, "audioformers" with s/s power amps.[/quote]Once upon a time, before the invention of transistors capable of being direct coupled, all SS amps used output transformers. For the last 40 odd years direct coupled outputs have been preferred.

[jammie17]

[quote name='Bill Fitzmaurice' post='104387' date='Dec 14 2007, 04:53 PM']Once upon a time, before the invention of transistors capable of being direct coupled, all SS amps used output transformers. For the last 40 odd years direct coupled outputs have been preferred.[/quote]

Autoformers
All solid state power amplifier output circuits work best
into what is called an optimum load. This optimum load
may vary considerably from what a loudspeaker requires.
In the case of more than one loudspeaker connected in parallel,
the load to the power amplifier may drop to two ohms
or even less. A power amplifier connected to a load that is
lower than optimum, causes more output current to flow,
which results in extra heat being generated in the power
output stage. This increase in temperature will result in a
reduced life expectancy for the amplifier.
The Autoformer creates an ideal match between the
power amplifier output stage and the loudspeaker. Refer to
figure 15. There is absolutely no performance limitation
with an Autoformer. Its frequency response exceeds that of
the output circuit itself, and extends well beyond the audible
range. Its distortion level is so low it is virtually impossible
to measure. In the rare event of a power amplifier
output circuit failure, the McIntosh Autoformer provides
absolute protection from possible damage to your valuable
loudspeakers.

[url="http://www.mcintoshlabs.com/mcprod/..%5Cdata%5Cmanuals%5CMC252om.pdf"]http://www.mcintoshlabs.com/mcprod/..%5Cda...s%5CMC252om.pdf[/url]

Thanks for your explanation Bill, but they are being used today by a leading Audio Company. This is where my initial experience came into play. These amps have /had a individual voltage under the output taps. I used a 4ohm speaker on the 8 ohm tap and then 4 ohm tap one day as an experiment. There was a significant volume difference. That's why I asked about the voltage question. Anyway, thank you for your explanation, and as usual, you cleared it up for me.

[Bill Fitzmaurice]

[quote name='jammie17' post='104392' date='Dec 14 2007, 12:03 PM']The Autoformer creates an ideal match between the
power amplifier output stage and the loudspeaker.[/quote]Autoformers are nothing new, they've been used for decades. They're only necessary if the impedance load is lower than the output stage can handle in a normal direct coupled configuration. While acting like transformers they have only one winding, so they are not preferred for use in audio, as there is no separation between a primary and secondary. Their advantage is that since they have only one winding they are cheaper to produce than a transformer.

[jammie17]

[quote name='Bill Fitzmaurice' post='104456' date='Dec 14 2007, 06:59 PM']Autoformers are nothing new, they've been used for decades. They're only necessary if the impedance load is lower than the output stage can handle in a normal direct coupled configuration. While acting like transformers they have only one winding, so they are not preferred for use in audio, as there is no separation between a primary and secondary. Their advantage is that since they have only one winding they are cheaper to produce than a transformer.[/quote]

Ahhh, you see I did not know that about them. So, an an amplifier that has say, three different outputs...say 2,4,8, ohms, has three Autoformers?

[Gazm]

[quote name='jammie17' post='104467' date='Dec 14 2007, 07:32 PM']Ahhh, you see I did not know that about them. So, an an amplifier that has say, three different outputs...say 2,4,8, ohms, has three Autoformers?[/quote]


Only one, with two (possibly three) taps.

Pete.