how to choose an amplifier

[TSK]

Newbie here. Setting up a home system using two vintage 6ohm 275 watt ESS speakers. Will use an unpowered mixer to manage turntable, TV, karaoke, and drunk jam sessions. How do I choose an amp for all this? I see $100 amps that advertise a thousand watts, and $1000 amps that advertise 50 or 60 watts. What can I get for a couple hundred dollars?

 

[oceansize]

You need to be a lot more specific about what you're looking for. What size room are you trying to fill with sound? Your turntable - does it include a phono preamp? If not, you'll either need a seperate phono preamp or an amp with phono input. And what sort of cartridge are you using? Moving Magnet (MM) or Moving Coil (MC)? I'm going to guess MM is the more likely, but you need to be aware of the difference. And what do you mean by drunk jam sessions? 6 Ohm speakers shouldn't be difficult to drive, so you have a wide choice of amps to use. Have you considered second hand? What's available locally?

 

[Joe Smith]

Good candidate is probably a Hypex Class D amp from one of the US builders (Buckeye/VSV), but expect to pay more like $700-800 for enough power w/ headroom for your speakers.

The alternative would be restored vintage class AB amps, but with proper restoration, probably in that same ballpark.

If you aren't going to run them super loud and in a large room, there might be some 100 -150 wpc integrated amps or AV amps that could be used...

 

[Mr. Widget]

Newbie here. Setting up a home system using two vintage 6ohm 275 watt ESS speakers. Will use an unpowered mixer to manage turntable, TV, karaoke, and drunk jam sessions. How do I choose an amp for all this? I see $100 amps that advertise a thousand watts, and $1000 amps that advertise 50 or 60 watts. What can I get for a couple hundred dollars?

A roll of the dice on the used market.

I would think you need a 200wpc min if you want to play loudly. You may also have the wrong speakers for your intended application, but since you have them give them a go.

Currently on eBay there are a number of "lightly used" Crown amps that would probably work and are closer to your price point. Many have a fair amount of extra power... we call that headroom, and it is never a bad thing. Just realize if you buy a 1000 wpc amp to use with most residential speakers, it will be fine as long as you don't bake the speakers by using sustained power levels above 100-200 watts.

 

[dlaloum]

Working out how much. and what sort of power you need can be tricky - but ultimately it depends mostly on your speakers.

Firstly for an order of magnitude determination of how much power you need.... find out your speakers specifications for "Sound Pressure Level" efficiency...

This will be quoted as XXdb/w or XXdb @ 2.83V - it amounts to the loudness of an individual speaker at a distance of 1m from the speaker, for an input power of 1 W

Get a rough idea of the average Sound Level at which you listen to things (typically between 75db and 85db) - this will be the average/continuous loudness level you need to spec your amp for...

For each additional speaker you add, you add 3db - so stereo, you would add 3db to the base speaker efficiency

Then you adjust for distance from the speaker - each doubling of distance drops the loudness 6db... so at 1m it is as per spec, at 2m spec-6db, at 4m spec -12db - larger room usually means greater distance from speaker, and greater db loss due to distance.

then each doubling of power, boosts your SPL by 3db

Here is an example:

My speakers have spec 86db/w @ 1m

Stereo setup so +3db = 89db/w @ 1m

Listen at roughly 2m from the speakers (near field-ish) - so -6db = 83db/w @ 2m

For each doubling of power, +3db

1W 83db
2W 86db
4W 89db
8W 92db
16W 95db
32W 98db
64W 101db
128W 104db

Note: here you are calculating CONTINUOUS capability...

With linear ClassAB (or A, or B) amps, you will typically have substantial "peak" power above and beyond the base power
With Class D amps it can be highly variable, and you should check what the peak capability is, but many ClassD designs have only limited peaking ability...

For your peak output, you will want around 15db above your continuous... (some people aim for 20db, just to be sure)

As you can see in my example - a target continuous of 85db is achieved with around 2W
For peak abilities (and both music and movies have substantial momentary peaks!) - you would be looking at either 100db (15db peak) or 105db (20db peak)

So looking at it roughly - with my 86db SPL/W speakers, I need circa 130W peak, but only 2W continuous

This is without discussing speaker impedances and power ratings at different impedances...

P.S. actual monitoring of the LED power indicators on my power amps, has never indicated any more than a slight flicker on the -20db LED (which calculates out to circa 3.5W)

 

[dlaloum]

Having said all that about power requirements and determining what loudness you need, and therefore your power needs...

The SPL calculated are at the Nominal impedance of your speaker (which you mentioned was 6ohm)

The impedance of a speaker is NOT fixed with frequency, it rises and falls - which is why speaker reviews plot the impedance to frequency on a graph.

Basically you need the amp to be able to handle the toughest impedance (and phase variation) -that your speaker can throw at it...

With a 6 ohm speaker, you need the amp to be able to cater to circa 4 ohm typically (and sometimes a touch lower)
8ohm speakers are easier to drive.

And power specs as well as current load tend to be quoted at different impedance levels... indicatively, whatever power your amp puts out at 4ohm, it will put out half as much at 8ohm, and twice as much at 4ohm - so when doing your SPL calculations you need to know at what impedance you are calculating.

An alternate approach (and one often taken for obvious reasons) - is to approach it with dramatic overkill....

I run a pair of Crown XLS2500 amps, capable of 440W @ 8ohm and 1200W @ 2ohm - they do the job. (and are available on the used market at bargain prices!)

I also have Quad 606 power amps capable of 135W @ 8ohm but only 90W @ 2ohm.... they also do the job (based on my subjective auditions)

I have difficult speakers with impedance dropping down to 1.6ohm - so I tend to use the 2 ohm specifications as my benchmark.

The Quad amps with only 90W @ 2ohm.... are providing the equivalent of 45W @ 4ohm... and with my speakers being specced nominally at 4 ohm, that is the impedance at which I calculated the SPL requirements.... and yes they can provide the required loudness without stress.

NOTE: both these power amps, can drive 2 ohm loads without instability or other issues

To give a negative example - my 100W @ 8ohm 2 channel, AVR, sounds terrible with my speakers. - in theory you would think it has enough power @ 100W.... but it is not specified for 2 ohm loads - and it ends up sounding like rubbish. (basically, various distortions increase at lower impedance if it has not been designed for it!)

If you are somewhere where the Crown amps are readily available, you should be able to pick up something like an XLS1500 - which would provide ample power for almost any circumstance, and is built very rugged, for pro band/dj/pa use.
(I picked up my XLS2500's for only US$250!!)
Early generation Drivecore XLS amps would be XLS1500/2000/2500, current generation is XLS1502/2002/2502

Obviously there are many options in the used market, which would suit your budget, but a robust reliable amp is key if buying used....
Availability of different brands differs substantially by country.... Quad amps are readily available in the UK, not so much in the USA, and vice versa for Crown.

 

[DVDdoug]

and drunk jam sessions.

If you are serious about that, be careful with amplifier power. Speakers are SUPPOSED to be safe with an amplifier rated power equal to the speaker's maximum rating with the amplifier hitting it's maximum power on the peaks without clipping. That is, you should be safe with a 275W amplifier that's not clipping. But it's sort-of "statistical" because it depends on the musical dynamics of the particular program material and they are counting on the high frequencies being weaker than the lows (which they usually are) and tweeters can't handle as much power as woofers.

When you push an amplifier into clipping/distortion it puts-out more average power, even though the peaks are clipped and that puts more heat into the voice coils and you are more likely to burn-out the speaker. And clipping generates more harmonics which go to the tweeter so it's doubly dangerous. (There is a myth that a clipped low power amplifier is more dangerous than an unclipped higher-power amplifier but that's not true and you shouldn't over-power a speaker in any case.)

For "sane" home listening I'm not too concerned with using an "over-powered" amplifier. Speakers are usually blown when drunks or teenagers are in charge of the volume control.

How do I choose an amp for all this? I see $100 amps that advertise a thousand watts, and $1000 amps that advertise 50 or 60 watts. What can I get for a couple hundred dollars?

Yeah... You can't really trust the manufacturer's specs. Of course you CAN trust the independent measurements published here at ASR. You can get pro amplifiers for less than $1 USD per watt and a the good pro brands (like Crown) are usually CLOSE to their specs. Home and "audiophile" amps are usually more expensive per-watt. Usually pro amps are fine for sound quality (noise, distortion, and frequency response) but many of them have a cooling fan that makes acoustic noise and that can be a problem for everyday home listening. It's not a problem for loud parties!

 

[TSK]

Thanks for all the responses, I'll do some research on new and used amps. For more background, I have the two ESS 2 way speakers with 10 inch woofers, Technics turntable and Technics integrated amp, and I bought all of it brand new in 1976. Don't think the turntable has a preamp but I know the receiver does. Am building a 300 s/f basement man cave, rectangular open space with 7 foot ceilings and heavily insulated walls to be sheet rocked. Bare concrete floor, sofa, recliner, upholstered bar, etc. Trying to determine my specific needs for gear so I can plan all the AV cordage and run it behind the walls before they go up. So mic cords, line level instrument cords, RCA cords and hdmi from two TV's, main speakers out plus two pairs of bulk speaker wire for future expansion. All cords will run through accessible conduit and go to a mixer. I plan to use powered PA speakers for loud parties to prevent abuse of the vintage gear. I have not found a "sound pressure level" for the speakers but but I did find a "sensitivity level" spec of 90db, if that helps.

 

[Steven Holt]

Don't overthink this, it will make your head hurt. The Yamaha AS701 is a fine unit, a little over yr budget. I have the Topping PA3s, within yr budget buy probably underpowered. I have no experience with it, but many on this forum like the Topping PA5 (but read the cautions on this forum b4 u buy).

 

[restorer-john]

P.S. actual monitoring of the LED power indicators on my power amps, has never indicated any more than a slight flicker on the -20db LED (which calculates out to circa 3.5W)

That's really sad for you. You really need to blow the cobwebs out of your amps and speakers now and then.

I regularly swing my meters well over 200wpc (really 400wpc as the speakers are nominal 4R dropping to 2.7R)

The OP should forget the Hypex/Purifi units unless they are properly heatsinked, especially for "drunk jam sessions". I'd be using some big ol' class AB professional amp like some of the big Yamahas- they can picked up for very little money and will run a small rockband or half a nightclub.

 

[rationaltime]

Newbie here. Setting up a home system using two vintage 6ohm 275 watt ESS speakers. Will use an unpowered mixer to manage turntable, TV, karaoke, and drunk jam sessions. How do I choose an amp for all this? I see $100 amps that advertise a thousand watts, and $1000 amps that advertise 50 or 60 watts. What can I get for a couple hundred dollars?

In my opinion you do not need to match the amp carefully to the speakers.
In your price range I would browse craigslist under "musical instruments"
for a used Crown amplifier or the lower priced QSC brand. Speakon connectors
on the back for the outputs will show the amp is not too old. An amp labeled
"70 V" near the outputs is set up for public announcement systems. You do not
want one of those. You want an amp with low impedance output. These are not
rare. They are out there.

Yes, these amplifiers have fans. Under normal continuous operation when standing
next to the amp you can feel the fan blowing some air, but you don't hear it.

Start browsing craigslist. You want to be ready for some tunes when your friends
come over to help finish the basement. Also you don't need to be finished to jam.
Have fun.

 

[TonyJZX]

ideally you need to know the characteristics of the speaker but if its an average speaker with no crazy ohm dips of good sensitivity of say 86dB and above then pretty much anything of a reasonable reputation will do

i'm running 7.5" standmounts at 8 ohm and 87dB and really, you can get away with a 35w amp as long as you dont expect to hit over 100dB (and why would you in normal circumstances)

so any of the chinese digital amps up to a yamaha 701/801 would be fine

i think its pretty clear what should be avoided... there's absolute shit on ebay called Pyle, Technical Pro and those kinds of white van electronics that its obvious you should avoid

i would tend to avoid pro or PA type amps like Crown unless you truly know WTF you're doing

i would tend to avoid any Chinese amp unless you know WTF you're getting into

its always better to have too much amp than too little amp

stick with classic mid spec famous brand integrateds or stereo recievers and you're good to go

but even then there are misses like that infamous Sony STR-190 that famously shit the bed

 

[delta76]

A roll of the dice on the used market.

I would think you need a 200wpc min if you want to play loudly. You may also have the wrong speakers for your intended application, but since you have them give them a go.

Currently on eBay there are a number of "lightly used" Crown amps that would probably work and are closer to your price point. Many have a fair amount of extra power... we call that headroom, and it is never a bad thing. Just realize if you buy a 1000 wpc amp to use with most residential speakers, it will be fine as long as you don't bake the speakers by using sustained power levels above 100-200 watts.

unless he has some very inefficient speakers, that's not true. from 100w to 200w (2x power) you gain 3dB and that's not a lot

 

[ZolaIII]

You don't really need very strong amplifier if you don't want to listen on mind blowing levels. Think good old AB class Yamahas (both as new) as some already mentioned rated at 100 W @ 8 ohm's while feed unbalanced with 500 mV (you will feed it with 2V and use volume trim - 6 dB) will do fine. They will give you about 60 W clean and up to 140 W without clipping. You really won't drive them even at 60 W but you do need headroom for things like normalisation. In the end remember W*2=+3 dB.
In the end to suggest Yamaha R-N803/D if you still can find it and like the stuff it has (phono input, streaming, radio's, sub out and menagement...) and how it looks.

 

[tomtoo]

Newbie here. Setting up a home system using two vintage 6ohm 275 watt ESS speakers. Will use an unpowered mixer to manage turntable, TV, karaoke, and drunk jam sessions. How do I choose an amp for all this? I see $100 amps that advertise a thousand watts, and $1000 amps that advertise 50 or 60 watts. What can I get for a couple hundred dollars?

Get a https://www.thomann.de/de/the_tamp_e400.htm. Absolutly ok for your tasks.

 

[Keith_W]

I see $100 amps that advertise a thousand watts, and $1000 amps that advertise 50 or 60 watts. What can I get for a couple hundred dollars?

I agree with all that has been said so far about amplifier power, especially @dlaloum about calculating how much power you need based on your speaker's sensitivity and your listening distance. I should also re-emphasize the point that an underpowered amp which is overdriven is more likely to damage your speaker than a powerful amp operating within its envelope. That is because when an amplifier clips, the top of the sine wave is sheared off and it produces an approximate square wave. If you Fourier transform a square wave, you will see a lot of high order harmonics which will usually burn out the voice coil of the tweeter.

As for why a $100 amp might put out a thousand watts - the answer is marketing. A reputable amp manufacturer quotes power in RMS (Root Mean Square) at a certain amount of THD (Total Harmonic Distortion). As mentioned above, when an amplifier is overdriven, it will clip and start to produce more distortion. The manufacturer will quote the amplifier's power output prior to clipping. A less reputable manufacturer might quote the power output as "PMPO", or "Peak Music Power Output", which is the maximum the amplifier can produce regardless of distortion. This was a popular marketing ploy in the 80's and 90's when I was starting to get into the hobby. A "1000W PMPO" amplifier might produce 20W RMS, if that. Those are marketing Watts, and not real Watts.

Having said that, there are amplifiers that are inexpensive, small, and can produce a lot of power. These are usually Class D designs and might have a cooling fan to dissipate heat. These are meant for public address or nightclub applications and may not be suitable for your home given the amount of noise these fans generate.

 

[Mr. Widget]

unless he has some very inefficient speakers, that's not true. from 100w to 200w (2x power) you gain 3dB and that's not a lot

Same is true between 100w and 50w... so what's your point?

From decades of experience of abusing speakers and my ears you simply can't have too much power. Ideally you should have 10dB of headroom... so that 200wpc amp will be playing at around 20 watts... for speakers with say 90dB sensitivity, that stereo 20 watts will give you around 100dB in a modest room.

 

[fpitas]

Crown Audio - Professional Power Amplifiers | English (US)

www.crownaudio.com

Feed in the pertinent data, allowing reasonable headroom for peaks (like, 20dB or more). Voila!

 

[delta76]

Same is true between 100w and 50w... so what's your point?

From decades of experience of abusing speakers and my ears you simply can't have too much power. Ideally you should have 10dB of headroom... so that 200wpc amp will be playing at around 20 watts... for speakers with say 90dB sensitivity, that stereo 20 watts will give you around 100dB in a modest room.

Many amplifiers have output between 50 and 100w

 

[Mr. Widget]

Many amplifiers have output between 50 and 100w

Yes, and in my youth I was able to blast the hell out of a modest room with a 40wpc Kenwood and a pair of 103dB 1watt/1m speakers... I rarely used more than a couple of watts when it was crazy loud and milliwatts for sane playback levels. With speakers that are 13dB less sensitive one would need 800wpc to match that output. Of course most domestic speakers will have massive dynamic compression at those power levels if they don't simply fail.

I'm not exactly sure what the drunk jam sessions are, but I doubt they are the same as listening to a pair of Quad ESLs with a tiny Quad amp.

Will use an unpowered mixer to manage turntable, TV, karaoke, and drunk jam sessions.

Perhaps @TSK can give us a better idea of what he will be asking from his system? Cocktail party background music levels? Dance club music levels? Stadium rock concert levels?