Differences between pre-amp and head-amp?

[RawHit 0]

As the topic says, what are the differences between a pre-amp and headphone amp? If I have a decent headphone amp (but no separate pre outs, only a headphone jack) can I use it as a pre-amp?

Whats the difference between active and passive pre-amps?

I am total newbie when it comes to speaker systems

[cmk 0]

Headamps are meant to drive headphones, of course, ie with a range of impedences up to 600ohms maybe. While the preamp is designed to drive poweramps, which may have input impedences of much higher than those of headphones, because the poweramp is supposed to amplify the signal anyway.

 

For the above reason - diff impedences, its not a good idea to use a headphone amp to drive a poweramp.

 

Active pres have a small amplification stage in them. The gain can vary from 8db to 20+db. Passive pres don't have any amplification whatsoever, just vol, and an input selector(some don't even have this). Another diff is that for passive pres, you have to make sure that the source has sufficient drive to power the interconnects, vol control, 2nd interconnect before reaching the poweramp. Else you will find that the music is lifeless, no dynamics.

 

Nowadays there are a number of pres which are sufficiently transparent, such that passives are less appealing.

[fuwen 0]

preamp is the component within the hifi system for controlling volumn and selection of components. That are the main functions. Others may vary like: mute, phase selection, mono/stereo, etc etc some preamp comes with headphone jack. If using preamp you need a power amp to amplify the signal further to drive the speakers.

 

headamp is a component which receive signal from a source (CDP direct or preamp) and amplify the signal for the headphones. I will leave this part for the headamp experts to elaborate.

[RawHit 0]

Thanks for the info guys. What are the advantages in going for separate pre and power stages over an integrated amp?

 

cmk,

from what I understand in the standard Melos SHA-1 the preamp and headamp section is same but in Gold and Maestro versions these sections are different. Thats what made me wonder whether a headphone amp can be effectively used as a pre-amp.

[jtfoo 0]

Actually active preamp and head amp are very similar.. looking at some circuitry, head amp borrowed designs from preamp and vice versa. The idea of both is to provide a low output impedance so as it's 'easier' to drive the next stage which would be power amp or headphone respectively. The diff here is head amp has a gain stage, which amplify the signal. While preamp usually has unity gain becoz the power amp it's driving already has a high gain.

 

For example a cmoy with buffer or even meta42 can easily be converted to a preamp by making them unity or very low gain. There are exception of course, like the PPA which cannot be converted else you loose the benefit of the differential output.

Edited February 27, 2004 by jtfoo

[cmk 0]

RawHit

If you read HeadFi postings, especially fr Carlo(famous for his Maestrobator), you'll note that the pre section on the std SHA-1 was put in as an afterthought, whereas the Gold and Maestro versions have full preamp sections, plus other refinements. So the preamp and headamp, although have a lot in common, have diff objectives. If the gain for the headamp and preamp are diff, it could very easily mean that one would be better than the other for that specific application.

 

I did try out the Melos as a pre in my setup, and it sounded very noisy. Now it does do the function of a preamp, but without the proper preamp stage put in, it won't perform optimally in that application. I suspect the gain was also too high for my poweramp as well, but it was noisy.

 

Disclaimer : I'm not a techy, correct me if there's an error.

[jtfoo 0]

RawHit

If you read HeadFi postings, especially fr Carlo(famous for his Maestrobator), you'll note that the pre section on the std SHA-1 was put in as an afterthought, whereas the Gold and Maestro versions have full preamp sections, plus other refinements.  So the preamp and headamp, although have a lot in common, have diff objectives.  If the gain for the headamp and preamp are diff, it could very easily mean that one would be better than the other for that specific application.

 

I did try out the Melos as a pre in my setup, and it sounded very noisy.  Now it does do the function of a preamp, but without the proper preamp stage put in, it won't perform optimally in that application.  I suspect the gain was also too high for my poweramp as well, but it was noisy.

 

Disclaimer : I'm not a techy, correct me if there's an error.

cmk,

 

You're right, a headamp would not behave properly if it were to use as a preamp directly without some modification, becoz we'll have 2 gain stages. A little turn of a volume knob would result in huge increment of loudness. Need to do a little mod to convert to the head amp to unity gain. This can easily be implement on most head amp via a switch.

[Mackie 0]

What are the advantages in going for separate pre and power stages over an integrated amp?

 

Having dedicated power supplies for pre-amp and power amp stages may benefit from better headroom and lower noise floor. This often results in better dynamics and more detailed music owing to having 2 dedicated power supplies as opposed to one feeding all. However, recent integrated amps do come with dual-mono design ie. one transformer for 1 channel, which helps to relieve the strain of conventional one-transformer design. Last but not least, one can also mix and match pre-amp to power amp but not all audiophiles will agree with this approach for some hark on pre/power amp setup to be of the same maker and series.

[RawHit 0]

thanks to all again for the info. I am looking at setting up a speaker system in the coming months though havent done any auditioning yet.