How much does an amp affect SQ?

Here are some traits of a bad amp:

- small usable volume control range / touchy volume control

- channel imbalance

- rolled off sub bass

- frequency response deviations due to high output impedance

- hiss (constant noise instead of total silence)

- distortion at higher volume

- limited power (low volume)

...

If any of these points is bugging you, you might consider to upgrade. :)

It can a lot and it can a little depends on the headphones. What are you using those with?  If I recall the HD650 does like a good amp. 

IIRC the HD650 is one of the headphones that need an amp. I tried searching but I could find anything. I don't think they're the easiest to drive if I remember correctly so in this case an amp would probably make a noticeable difference. 

Technically, every headphone needs amplification. All that changes is the amount of power needed.

The sensitivity of the headphone will tell you how much power is needed for a given sound pressure level.

HD650s are 103 dB SPL with 1 V of input. That's crazy loud.

But some laptops have very limited output, like ~0.3 V.

Quote:

Originally Posted by rt310 

I just received my new Sennheiser HD650's and i'm enjoying the sound alot; however, was wondering if buying an amp would be worth it, as i'm not sure how much the SQ will improve. 

Hi

I think this is a good question. Sometimes people don't understand very well the benefits of good amplification over poor amplification.

I will put this in two categories: capability and quality.

Capability

The amplifier must be well suited to your headphones. It must be powerful enough to drive them. With solid state amplifiers you can fulfil this criteria of "capability" easily and cheaply. It might be that your current amplifier is completely capable.

Quality

The next thing to consider is the quality of the amplification. There are several areas in the audio chain where signal is lost or distortion is introduced and the amplification is, I think, the second biggest in most of today's setups. The biggest area of loss is the headphones themselves, the actual transducer in the headphone and the acoustic design of the headphones.

In an audio amplifier there is the input signal (coming from the source) and the output signal (going to the headphones). These are separate circuits, the output circuit being much more powerful than the input circuit. The objective of the good amplifier designer is to try and get the output circuit as close as possible to the input circuit.

With good quality amplification you will be hearing what is on your CD, digital file or LP more accurately. Many people believe that a good amplifier will "make bass stronger" or something like this, that it will manifest itself in some way. However the good amplifier will "make bass stronger" only if the bass really is stronger in the recording.

Listening to a good amplifier can initially be an underwhelming experience. However after a while you might start to notice details which you had not seen before. Harmonies might start to make more sense. Very delicate parts of the music might be rendered even more delicately.

What to Avoid

Generally speaking I would tend to avoid amplifiers that "do stuff". By this I mean things like "warm up the sound" (most common thing to see reported). If an amplifier applies a lot of distortion you will get tired of it. After all you can't turn that off, it will be there in every piece of music you play.

Hi Fi isn't supposed to "do things". Good Hi Fi is about getting out of the way, letting you hear the recordings. Let the musicians make the music, that is their role, and they will do it better than your Hi Fi.

Different Types of Amp

There are many different types of amplifier and they can all be excellent (or crap). Solid state amplifiers, Valve amps ("Tube amps" in US) and hybrid amplifiers can all be extremely good or bad. You will see people describe amplifiers as "Class A" or "Class B" or "Class A/B". As headphones are much easier to drive than loudspeakers the more expensive amplifiers are most often Class A.

There you are!

A value for money posting from moi 

FWIW my HD580 I find completely unlistenable unamped... mushy, muddy and sluggish dynamically.  Cloudy attack and decay on just about any kind/type of instrumentation.  Very un-interesting to say the least.  Turning the volume up on the under-achieving circuit only makes things worse.  When I plug it into my Pimeta, larocco PPA or earmax OTL its a night and day transformation.  I would expect your HD650 (an even harder can to drive) would behave similarly.  I have heard them dozens of times at meets but I have never owned one... so take this commentary for what its worth.

The poster above makes some interesting commentary regarding amp circuits that do stuff to the sound.  I have always "thought" I preferred amps that color the sound, but looking back I have always had my PPA which I go back and forth on so it more or less does the "wire with gain" routine, which I always enjoy along side my more colored amps.

Quote:

Originally Posted by rt310 

Thanks for the detailed and informative post! Are there any particular amps you would recommend for the HD650's?

On that I'm afraid I can't advise because I have only heard the HD650s for fairly brief periods. There are many many users of these headphones and soon you will get suggestions from them.

I will mention that I really like the products from Meier Audio.

http://www.meier-audio.homepage.t-online.de

Click on "Phones and Amps" and scroll down. You will see amps amps amps :)

I think you'll want a DAC as well. An amp simply amplifies the signal at the end of the day. If the source signal isn't great due to the the internal amplifier, you won't be too impressed. $300 is plenty for a first DAC and amp. You could get the O2+ODAC combo if you're fine with a USB DAC. The O2 can easily drive the HD 650s. There are plenty of reviews here on them.

Eh, just get magni and modi for your first set up ;) You really can't go wrong at that price, and they are fantastic value.

Quote:

Originally Posted by spaark 

I think you'll want a DAC as well. An amp simply amplifies the signal at the end of the day. If the source signal isn't great due to the the internal amplifier, you won't be too impressed. $300 is plenty for a first DAC and amp. You could get the O2+ODAC combo if you're fine with a USB DAC. The O2 can easily drive the HD 650s. There are plenty of reviews here on them.

This is a good point. We don't know what the OP is using as a source at present.

I think the DAC in my MacBook Pro is really rather good, for example, and so when travelling I just use an amplifier from that and I get very good sound quality.

I have not tried built in DACs in other computer because I have used Macs since 1984 :)

If OP has an under performing DAC then a DAC/amp will be very valuable.