Noob question - High current amplifiers

[Kasman]

Hoping the brains trust can impart some knowledge...

 

I keep hearing about certain amps being better for high current applications or hard to drive speakers. 
 

How can I tell from amp specs that it is capable of high current applications?

 

On the flip side, how do I tell if my amp will drive low impedance speakers ok?

 

For reference I have a Vincent SV-227. 
specs below. 
 

Im considering some Monitor Audio Gold100’s which I know drop to quite low impedance. 
 

obviously I would trial prior to purchasing any speakers, but interested in thoughts on this. Happy to read any links if you have them. 
ta!
 

Technical Specifications

• Frequency Response: 20 Hz – 20 kHz +/-0,5 dB; 20 Hz – 50 kHz +/-2 dB
• Nominal Output Power RMS/8 Ohm: 2 x 100 Watt
• Nominal Output Power RMS/4 Ohm: 2 x 196 Watt
• T.H.D.: < 0.1 % (1 kHz, 1 Watt)
• Input Sensitivity: 280 mV
• Signal-Noise-Ratio: > 90 dB
• Input Impedance: 47 kOhm
• Max. Power Consumption: 320 Watt
• Inputs: 4 x Stereo RCA, 1 x Optical, 1 x Coax
• Outputs: 1 x Stereo RCA Rec Out, 1 x Stereo RCA Pre Out, 2 x Power Control, 4 x 2 Speaker Terminals
• Playable Digital Formats: WAV, FLAC, APE, LPCM, MP3, ACC, AC3, WMA
• Tubes: 3 x 12AX7
• Colour: Black or Silver
• Weight: 20 kg
• Dimensions (WxHxD): 430x150x435 mm

 

[buddyev]

Better brains than mine will jump in but what you’re looking for in a high current amp is close to a doubling of watts as the impedance halves.
Ideally, though rarely in practice, something like:

100 watts into 8 ohms

200 watts into 4 ohms

400 watts into 2 ohms

The speakers have nominal impedance of 4 ohms and drop to 2.8. 

the amp doubles between 8 and 4 but doesn’t state what the amp outputs at 2 ohms, which I suppose is what you really want to know.

 

 

Edited March 10, 2021 by buddyev

[buddyev]

https://www.soundstagenetwork.com/index.php?option=com_content&view=article&id=2204:nrc-measurements-monitor-audio-gold-100-loudspeakers&catid=77&Itemid=153

[Deepthought]

30 minutes ago, Kasman said:

 

 

 

Im considering some Monitor Audio Gold100’s which I know drop to quite low impedance. 
 

obviously I would trial prior to purchasing any speakers, but interested in thoughts on this. Happy to read any links if you have them. 
ta!

 

https://www.soundstagenetwork.com/index.php?option=com_content&view=article&id=2204:nrc-measurements-monitor-audio-gold-100-loudspeakers&catid=77&Itemid=153

Looks to be about 3ohms in the 4khz region. There is a bit of Electrical phase shift above that. A low impedance at very  low and /or high frequencies might give an amp' bigger issues but a decent amp' should be able to handle this load. 

1 minute ago, buddyev said:

https://www.soundstagenetwork.com/index.php?option=com_content&view=article&id=2204:nrc-measurements-monitor-audio-gold-100-loudspeakers&catid=77&Itemid=153

Beat me by 10 seconds...

[MusicForever]

I think that it's further complicated by the ability for some amps to deliver high "peak" current for short bursts- usually via banks of capacitors.  I think that the figures quoted above usually refer to constant watts delivered into a impedance of 8 and 4 ohms.  

[davewantsmoore]

2 hours ago, Kasman said:

How can I tell from amp specs that it is capable of high current applications?

 

Most amplifier manufacturers do not really provide enough information for you to know.

 

Part of the reason for this, is that it's a very complex question.

 

 

Your speaker is nasty at ~4khz (low ohms, with a large negative phase angle) which will draw significant amounts of current (completely dependant on how loud you play).

 

 

So there are two questions.

 

Will the amp "fail" at such a load, most won't, some will  (eg. shutdown, or protection mode, etc)..... and when the amplifier clips, what is its performance like  (this is very varied).

 

The simplistic answer is you need an amplifier which can operate safely with 2ohm, and if you want to play loud, significant amounts of power.  (eg. >>> 100w)

[mattd2308]

denon-pma-2500ne-hifi-news-2016.pdf (novial.sk)

 

This test swayed me to the 2500 as, 1. Always admired the premium gear, 2. Engineered and Made in Japan. 3. Build quality, and 4. Sounds terrific paired with my Legend speakers(which dip into 4ohm or lower) and that HIFi News are a credible magazine to obtain info.

Had considered Musical Fidelity M6si and Rega Elicit R. 

Others know more than me on this forum, however i took into account its "dynamic" power at low impedance, instead of dropping off, it increases. Also its maximum current is reasonably impressive.

Granted it wont likely go as loud as a Musical Fidelity, Rotel Michi, Parasound, to name a few, or separates.

For me, depending on the production of a recording, i rarely go past 10 o'clock on the volume when i want to crank it up. Also having recently acquired new speaker cable (Purist Audio Design Musaeus), the signal is getting to the speakers far more efficiently than my previous cable.

Others here will give good advice.

my 2c

 

Edited March 10, 2021 by mattd2308
grammar

[andyr]

3 hours ago, Kasman said:

 

I keep hearing about certain amps being better for high current applications or hard to drive speakers. 
 

How can I tell from amp specs that it is capable of high current applications?

 

On the flip side, how do I tell if my amp will drive low impedance speakers ok?

 

 

4 minutes ago, davewantsmoore said:

 

The simplistic answer is you need an amplifier which can operate safely with 2ohm, and if you want to play loud, significant amounts of power.  (eg. >>> 100w)

 

 

^  ^  ^ what the man said ... so your Vincent SV-227 may not do them justice.  

 

Unless:

a. you ears are only a couple of metres from your spkrs, or

b. you don't listen very loudly.

 

Andy

 

[sir sanders zingmore]

 

Monitor audio claim these as being 86dB, the measurements show them almost 3dB less efficient.

 

3dB Doesn't sound like a lot but it actually requires double the power

[rantan]

1 minute ago, sir sanders zingmore said:

 

Monitor audio claim these as being 86dB, the measurements show them almost 3dB less efficient.

 

3dB Doesn't sound like a lot but it actually requires double the power

Indeed.

It is a really big and widespread problem with almost all speaker manufacturers significantly over stating the sensitivity of their speakers when compared to actual and properly conducted measurements.

[Hifiplus]

Choose other speakers.

 

 

[Guest DrSK]

15 minutes ago, sir sanders zingmore said:

 

Monitor audio claim these as being 86dB, the measurements show them almost 3dB less efficient.

 

3dB Doesn't sound like a lot but it actually requires double the power

 

Although in the scheme of things you need around 10 times the power to get twice as loud. 

 

So being 3dB quieter may not be as bigger issue, about a 20% difference. 

[allthumbs]

18 minutes ago, sir sanders zingmore said:

Monitor audio claim these as being 86dB, the measurements show them almost 3dB less efficient.

 

Why isn't that fraud and prosecutable under consumer protection laws as misleading advertising?

[pwstereo]

On 10/03/2021 at 5:16 PM, DrSK said:

 

Although in the scheme of things you need around 10 times the power to get twice as loud. 

 

So being 3dB quieter may not be as bigger issue, about a 20% difference. 

3 dB sound increase or decrease is twice as loud or half as loud.

10 dB electrical increase or decrease is twice as loud or half as loud.

 

Please note, this is incorrect, I confused the issue and I apologise.

Edited March 12, 2021 by pwstereo
I was wrong

[sir sanders zingmore]

25 minutes ago, DrSK said:

 

Although in the scheme of things you need around 10 times the power to get twice as loud. 

 

So being 3dB quieter may not be as bigger issue, about a 20% difference. 

 

I get what you're saying but I think it still matters.

As an example of why I think this

 

Let's say you usually listen at 86db but sometimes crank it up to twice as loud (~96db)

Let's say you require 50w of power to 86db (due to listening room/distance from speakers etc) 

You'll need 500w to get to 96db (ten times the power as you say)

 

But now you plug in your monitor audio speakers that claim to be 86db but are only 83db

Suddenly you need 100w of power to get your 86dB and 1kw when you want to crank it up

 

So that 3dB misstatement actually means that to get "like for like" volume, you need double the power at all listening levels

 

EDIT: Just saw @pwstereo's reply, so maybe I'm talking out of my hat as usual (although I thibnk I end up at the same spot which is the 3dB difference means you need double the power)

Edited March 10, 2021 by sir sanders zingmore

[Kasman]

Thanks for all your comments. Yes most of what your all saying is what I suspected. 

1 hour ago, davewantsmoore said:

Most amplifier manufacturers do not really provide enough information for you to know.

I suspect this is why I was a little confused. 

 

22 minutes ago, Hifiplus said:

Choose other speakers.

Yes it’s feeling a little this way, hence why I posed the initial question I suppose. 
I don’t however want to end up with a combo that’ll struggle if I want to turn things up a little. 

[sir sanders zingmore]

6 minutes ago, Kasman said:

Thanks for all your comments. Yes most of what your all saying is what I suspected. 

I suspect this is why I was a little confused. 

 

Yes it’s feeling a little this way, hence why I posed the initial question I suppose. 
I don’t however want to end up with a combo that’ll struggle if I want to turn things up a little. 

 

It's a balance. I've always felt you should first choose the speakers you love and then choose an amp to drive them.

Of course, if your speaker choice puts suitable amps out of your price range then you need to rethink

[Guest DrSK]

4 minutes ago, sir sanders zingmore said:

 

I get what you're saying but I think it still matters.

As an example of why I think this

 

Let's say you usually listen at 86db but sometimes crank it up to twice as loud (~96db)

Let's say you require 50w of power to 86db (due to listening room/distance from speakers etc) 

You'll need 500w to get to 96db (ten times the power as you say)

 

But now you plug in your monitor audio speakers that claim to be 86db but are only 83db

Suddenly you need 100w of power to get your 86dB and 1kw when you want to crank it up

 

So that 3dB misstatement actually means that to get "like for like" volume, you need double the power at all listening levels

Yep, you'd get 93dB instead of 96dB out of 500W.

 

The difference is always around 20% and 3dB.  Whether that makes a significant difference, guess it depends. 

 

Although I'm fairly certain the rating is at 1W at 1m. So 100W goes a long way if its RMS. 

 

I normally keep an eye on peak power and current and how quickly it can deliver it. Not all 100W RMS amps are equal. 

[Luc]

Turn things up a bit?  How loud do you need to go to get that 'loudness' hit?

If you believe that oodles of power on tap is what you want then you'll be worshipping at the alter of Roger Sanders and his Magtech amps.

Plenty of fanboi's here have them and swear by them. They have difficult systems (apparently) that need to have instant grunt when a track requires it and their speaker selection requires it.  Not many amps can do what the Magtech's do when they are called upon to use all their grunt to keep a hold of a speaker dropping down into 4 ohm purgatory or worse 2 ohm hell.

 

How deeps your wallet btw?

[Guest DrSK]

16 minutes ago, pwstereo said:

3 dB sound increase or decrease is twice as loud or half as loud.

10 dB electrical increase or decrease is twice as loud or half as loud.

 

No it most definitely isn't. 

 

Our hearing doesn't respond that way. 

 

3dB doubles power and sound pressure level, but only a small increase in loudness. 

 

I'm an acoustic engineer with 20 years experience, which includes research and development of algorithms in hearing perception. 

 

10dBA for doubling is a rule of thumb that holds reasonably well. Actual doubling of loudness really requires Phon instead of SPL. 

Edited March 10, 2021 by DrSK

[pwstereo]

2 minutes ago, DrSK said:

 

No it most definitely isn't. 

 

Our hearing doesn't respond that way. 

 

3dB doubles power and sound pressure level, but only a small increase in loudness.

That's my misunderstanding then, I think I'd equated a doubling of SPL with a doubling of loudness. Sorry for the goof.

[pwstereo]

19 minutes ago, sir sanders zingmore said:

EDIT: Just saw @pwstereo's reply, so maybe I'm talking out of my hat as usual (although I thibnk I end up at the same spot which is the 3dB difference means you need double the power)

And I may have confused a doubling of SPL with a doubling of loudness apparently

[Guest DrSK]

Just now, pwstereo said:

That's my misunderstanding then, I think I'd equated a doubling of SPL with a doubling of loudness. Sorry for the goof.

 

All good, doubling of SPL is usually just 3dB as with doubling of power. Not loudness. 

 

It gets a bit more fun if you have coherent addition of SPL, interaction between waves of similar frequency say. You might then get 6dB.

[Guest DrSK]

1 minute ago, pwstereo said:

And I may have confused a doubling of SPL with a doubling of loudness apparently

Sorry, my response was a bit abrupt! 

 

Just gave up on working for the day after a 4am start to catch up on reports and analysis, a bit grumpy.

[pwstereo]

6 minutes ago, DrSK said:

Sorry, my response was a bit abrupt! 

 

Just gave up on working for the day after a 4am start to catch up on reports and analysis, a bit grumpy.

Not at all, you were just correcting a factual error. I'm sure we're all grateful to have it quickly corrected and from a credible source.