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What is the difference between a preamp and a headamp?

post #1 of 15
10/31/04 at 11:34pm
Thread Starter 
Other than the fact that the output is a 1/4 (or 1/8 I guess) instead of RCA's - is there a difference?

Could a PPA for example, be modded to be a preamp for an amp and speakers?

mark in Canada
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post #2 of 15
11/1/04 at 5:36am
Yes, there's a difference: Compared to the input of a poweramp, headphones are low impedance loads that need quite a bit more current. Thus the output sections of preamp don't necessarily have to be as powerful and stable - some of the really good ones still are, though. In addition, preamps usually have quite a few more inputs to select from.

Greetings from Hannover!

Manfred / lini

P.S.: I'm not too familiar with the PPA, but yes, I'd think it could be modded to work as a preamp as well.
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post #3 of 15
11/1/04 at 5:43am
I asked Mikhail to put pre-outs on my Mpx(and he did), so I guess it wouldnt be hard to put them on other amps.
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post #4 of 15
11/3/04 at 7:55am
why would one want to add another link to the component chain (the pre-amp) . Unless of course one wants some particular coloring.
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post #5 of 15
11/3/04 at 11:11am
Quote:
Originally Posted by marios_mar
why would one want to add another link to the component chain (the pre-amp) . Unless of course one wants some particular coloring.
A power amp has one input (some have more). Some integrated amplifiers and all receivers have several inputs, and recording ouputs.

But a power amp usually just has 1 input. And unless you don't want a volume control, the ability to select among many inputs, and in some cases Dolby processing, you'll want a preamp.
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post #6 of 15
11/3/04 at 3:14pm
It's not only about switching capabilities. Some power amps need higher gain signals to drive its output devices then what it receives from your source. The role of the preamp is to amplifiy the source signal so it is usuable by the amp's driver and output stages. Some amps can receieve digital source signals directly and use them. No amp I'm aware of can use phono source signals directly.

Also, most power amps do not have volume control. Pre amps usually provide this function.
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post #7 of 15
11/3/04 at 4:49pm
hey mark
my sha is a preamp-headamp combo.

i would say that those who own just headamps look for the simplefied chain to provide better quality.
lots of headamps are preamps tho.

don't know much about circuitry just passing along what i was told.
fwiw apparently the ppa would make a bad preamp due to its layout (heard it from mister x)

cheers
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post #8 of 15
11/3/04 at 7:32pm
Quote:
Originally Posted by JeffL
A power amp has one input (some have more). Some integrated amplifiers and all receivers have several inputs, and recording ouputs.

But a power amp usually just has 1 input. And unless you don't want a volume control, the ability to select among many inputs, and in some cases Dolby processing, you'll want a preamp.
Basicaly its the active part that I dont understand. I know what a preamp normally is for.
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post #9 of 15
11/3/04 at 8:20pm
Aside from some amps needing the added gain from an active preamp, the other main benefit is that an active preamp is more "stable" then a passive one. It's specified high input and low output impedances are buffered and less susceptible to promblematic interactions between components (including cables). When using a passive preamp, you have to make sure your amp doesn't need more gain and also to match impedances carefully by taking into account all components in the signal's chain of custody, including cables.

Generally, I find active preamps more tonally accurate in a wider range of applications, and most sound more "exciting" to my ears. Passive preamps are more "transparent" and the purity of sound (when used with carefully selected associated equipment) is really its strongest selling point. Active preamps are certainly easier to use.
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post #10 of 15
11/3/04 at 9:36pm
most headphone amps will work well as a preamp if the gain amount is what you need to drive your amp/speakers to a suitable level but not all preamps make for good headphone amps due to output current drive and impedance.
In one of my systems i use a simple class A high current follower after my preamp to drive cans because the line stage itself is not up to it but as a gain stage for driving the power amp sounds just fine .The headphone "buffer" takes the place of the power amp for driving duties.
another preamp needs transformer matching to accomplish this while another performs double duty (headphone out/power amp out)

A shame the current delivery and "real world" impedance into various loads is not something found in the manufacturers specs so you could know this before purchasing
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post #11 of 15
11/4/04 at 10:12am
The PPA has a ground channel to deal with return currents from the headphone, but that's not good for a preamp; in order to make it one, the preamp output's ground needs to be tied to the input ground instead. You can't just plug a 1/4"-to-RCA cable into the headphone jack, but all it takes is an extra switch and plugs. It's very easy to do.
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post #12 of 15
11/4/04 at 9:53pm
Thread Starter 
Thanks for the answers all, I watched this thread in the beginning, but then it stalled for a day or two... But now I come back and find all this - cool!

I was asking, since I see some really cool custom built headamps here, that seem affordable - I don't even use 'phones (can I say that here ) but am interested in a good pre, and love modded gear, so a custom built unit seemed to line up for me, in theory, but I have no idea if such a headamp, could even BE used as a preamp.

Thanks to these answers, I see that, as with most things audio, the answer is maybe...

Mark in Canada
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post #13 of 15
11/5/04 at 2:46pm
The best reason for using a quality headamp as a preamp is that it gives you an excuse to pick up some good headphones, of course
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post #14 of 15
11/5/04 at 4:15pm
Thread Starter 
Right, forgot about that headphone part - my current setup is an older set of (brace yourselves headphone folks...) Sony DJ500's, that I used to use, on the job in clubs.

Mark in Canada
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post #15 of 15
11/6/04 at 1:59pm
don't forget the original jung AD744/AD811 multiloop stage.Even though i use all discretes and/or tubes in my signal chain I have in the past (and still have one around somewhere ) used this ciscuit as a line stage/headphone amp and it is pretty darn good at both.

All it needs is a line out (RCA jack)/headphone out (stereo phone jack) switch.Having the line outs attached when listening to headphones causes the amp output to be loaded down by whatever follows the stage which would be in parallel with the headphone output (both impedances in parallel).Plus it allows for ameans to turn the speakers off (line out mute) when listening to cans.
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