gasolin

what is and which amps are a high current amp ?

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Super Wammer
Posted (edited)
32 minutes ago, ChemMan said:

I would say your question has not been sufficiently answered.  I'm waiting for the same answer.  Where is @rabski?

My VTL amp is just 60 W, but gets stupid loud.  I'd like to know how or why this is the case compared to my 125W Arcam and 100W McIntosh.

One thing the McIntosh MA252 isn’t is high current. Into two ohms it produces the same 150 watts as it does into 8 ohms. In the real world that is unlikely to matter, but it shows it isn’t a bottomless pit of current. 

At home, I’m sure the differences between your three are not down to maximum power or current. 

Edited by Nopiano
Extra clarification
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Posted (edited)
6 minutes ago, Nopiano said:

One thing the McIntosh MA252 isn’t is high current. Into two ohms it produces the same 150 watts as it does into 8 ohms. In the real world that is unlikely to matter, but it shows it isn’t a bottomless pit of current. 

OK. So why do those measley 60W of the VTL do so much?  High Current? What's the spec, Output impedance? Something else? Or just what happens in to 4 and 2 ohms?   https://www.stereophile.com/content/vtl-it-85-integrated-amplifier-specifications

https://www.hifinews.com/content/mcintosh-ma252-integrated-amplifier-lab-report

Edited by ChemMan

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Super Wammer
Just now, ChemMan said:

OK. So why do those measley 60W of the VTL do so much?  High Current?

It’s hard to say. It may have a more sensitive input or the volume control action is quicker, giving the impression of more power. It may sound sweeter so is easier to enjoy at higher volumes.  But although I’ve not seen measured specs it’s very rare for tubed amps to double power as impedance halves - they just don’t deliver in that way.  It doesn’t mean they lack anything, just that they will sound different to a SS equivalent, mainly due to high output impedance reacting with the speaker. 

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1 minute ago, Nopiano said:

It’s hard to say. It may have a more sensitive input or the volume control action is quicker, giving the impression of more power. It may sound sweeter so is easier to enjoy at higher volumes.  But although I’ve not seen measured specs it’s very rare for tubed amps to double power as impedance halves - they just don’t deliver in that way.  It doesn’t mean they lack anything, just that they will sound different to a SS equivalent, mainly due to high output impedance reacting with the speaker. 

I posted the specs and lab reports for both amps for you above while you were typing your response.  What do you think?

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10 minutes ago, ChemMan said:

So why do those measley 60W of the VTL do so much?  High Current?

The Stereophile review specifies 60W into 8 Ohms and 80 W into 4 Ohms, so the latter is hitting the current limit of the amp (at about 4.5 A). Not particularly high current capability.

As I think I said above how much current anyone actually needs will be determined by desired listening level and the speakers.

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Super Wammer
7 minutes ago, ChemMan said:

I posted the specs and lab reports for both amps for you above while you were typing your response.  What do you think?

Well the Mac wins hands down technically because of the SS power amp.  The VTL output is summarised in the review thus:-

“With just one channel driven (fig.9), considerably more power was available at the 1% THD point (magenta line): 78.3W into 8 ohms (18.9dBW, black trace) and 123W into 4 ohms (17.9dBW, red). But the distortion rose quickly enough to limit the 2 ohm power to 15W (blue) and the 1 ohm power to just 3.5W (green).“

Over 100 watts from a tube amp into 4 ohms is very impressive and doubtless is way more than you need, even in your large room. But you can see the output plummets thereafter, so speakers that drop down into 2 to 3ohm territory might work less well.  Sensibly designed Spendors won’t cause any problem.   

I would therefore suggest the volume sensitivity and tonal balance as I mentioned above is what make you subjectively identify it as powerful on music programme (rather than sine waves)! 
 

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1 minute ago, Nopiano said:

Over 100 watts from a tube amp into 4 ohms is very impressive and doubtless is way more than you need, even in your large room. But you can see the output plummets thereafter, so speakers that drop down into 2 to 3ohm territory might work less well.  Sensibly designed Spendors won’t cause any problem.

Atkinson said there should be no problems for the VTL with speakers that don't drop below 4 homs.   D7 has a minimum impedance of 4.5 ohms. Equals good sound.  Nice Music. :)

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Super Wammer

As I understand it - high current delivery is down to the power supply which allows the amp to draw much more current on peaks and transients.  The overall current delivery to the loudspeakers is just the normal calculation  for 2x 25W RMS, speaker impedance 8 ohms; thus the theoretical maximum current given by P = I^2 / R is sqrt(25 W / 8 ohm) = 1.77 A.    The bigger the amp the bigger the available current delivery but most of the time the amp is working down in the tens of watts so the only time you will see that big current delivery is on transients when it may need many tens of watts for a few milliseconds.  No doubt the techies in here will correct me if I am wrong

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Super Wammer
1 minute ago, ChemMan said:

Atkinson said there should be no problems for the VTL with speakers that don't drop below 4 homs.   D7 has a minimum impedance of 4.5 ohms. Equals good sound.  Nice Music. :)

I have no experience of the VTL all I can say is I have a considerable experience of EAR 509s - friends of mine are still using theirs 40 years on .. they are tough and reliable sound great and would be top of my list if I wanted a high power valve amplifier 

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Super Wammer

A snippet from HiFi News about high power and current, featuring Marantz, Musical Fidelity, Perreaux and Krell.  
 

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Super Wammer
1 minute ago, gasolin said:

high current is like a diesel engine compared to a patrol engine ?

Not a good analogy in my book - the difference between a diesel and petrol engine is torque .. when music has a transient it needs to be able to go faster .. so it is a bit like having an engine that is capable of far higher revs (which will not restrict the overall speed) or having another gear lol ,.... now if you were comparing an amp that can deliver its output into difficult loads then IMO the analogy of diesel versus petrol is better.  

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