[analogsurviver]

 
The short answer - YES, it will make a great headphone amp.  Better than most "headphone amps" and trust Skylab and I, we kid you not.

+1.

 

[micmacmo]

  I just found this thread and searched for info on my amp, but didn't see anything. So here goes.
 
I bought a Yamaha "Natural Sound" A-450 integrated amp in highschool as part of my first system. I've used it to power my living/bedroom speakers until I bought an NAD D3020 a little over a year ago, at which time I put it in a cupboard. It only just occurred to me that I could use it as a headphone amp.
 
 

I'm using a restored Yamaha A-550 to drive headphones. The caps haven't broken in but I'd have to say it's a nice combination with my orthos off the speaker taps. Definitely on the warm side and never fatiguing.   

 

[gixxerwimp]

 

micmacmo /img/forum/go_quote.gif
  I'm using a restored Yamaha A-550 to drive headphones. The caps haven't broken in but I'd have to say it's a nice combination with my orthos off the speaker taps. Definitely on the warm side and never fatiguing.   

 
Cool! Big brother to my barebones, bottom-of-the-line A-450. Bought it at A&B Sound in Vancouver on Boxing Day with money I saved from my part-time job flipping burgers at McDonald's.
 
Not thinking about using the speaker taps (I see you've got HE-6). You've also got some modded T50RPs which would be similar to the ZMFs I'm getting. Speaker taps would be overkill for those, no?
 
Can you tell me anything about the headphone section?

 

[gixxerwimp]

 

KeithEmo /img/forum/go_quote.gif

gixxerwimp /img/forum/go_quote.gif
  I bought a Yamaha "Natural Sound" A-450 integrated amp in highschool as part of my first system. I've used it to power my living/bedroom speakers until I bought an NAD D3020 a little over a year ago, at which time I put it in a cupboard. It only just occurred to me that I could use it as a headphone amp.
 
Can anyone tell me if it would be any good as a headphone amp? For the price ($150 in 1981), it did a pretty good job driving bookshelf speakers. Pots have gotten a bit noisy, and I had to replace some of the indicator bulbs. But it was a pretty nice unit and worked reliably for over 30 years.

  There are a couple of important factors that determine the answer to that question.....
 
1) If you have low-efficiency planar headphones ...

Spoiler: cont'd

that actually require a speaker amplifier to drive them well, then the only thing that matters is how good the main amplifiers in that receiver actually are (because you'll be using them directly). Other than the way it actually sounds, the only real issue there is that some speaker amplifiers may be too noisy to make great headphone amps. (Even though low-efficiency planars aren't going to be much fussier about the noise floor than speakers, they're still headphones, and they're attached directly to your ears, so background noise that you might not notice with speakers might be audible.)

2) In "the old days" the most common way of "making" a headphone output was to simply run the output of the speaker amplifier through a voltage divider (a pair of resistors) to drop the level. This is NOT a great way to run normal headphones for several reasons. For one thing, many speaker amps of this vintage and quality aren't especially quiet, and this becomes more obvious with headphones. For another, since the resistors are in series between the output and your headphones, they raise the output impedance seen by the headphones. (If they used a voltage DIVIDER, then the output impedance at the output end of the divider will be the parallel combination of the two resistors - so, if they used a 100 ohm resistor and a 10 ohm resistor, the output impedance will work out to about 9 ohms, which is not great but still OK. However, if they did it the really cheesy way and just put one resistor in series with the output, then the output impedance is pretty much simply the value of this resistor - so, if they used a 100 ohm resistor, the output impedance is 100 ohms. This means that you have almost no damping factor, which means that the output will interact with your particular headphones (so it may sound very different with different headphones), and simply won't sound very good with many headphones.
 
3) If you're lucky, then an old receiver will have an actual dedicated amplifier on its headphone....

Spoiler: cont'd

It is also true that most older receivers would have used separate transistors for this, but that isn't really important (both IC amplifiers and amplifiers made out of separate transistors can be good or bad - and neither is especially likely to be better than the other). The simple reality is that, until recently, the sound quality of the headphone output wasn't considered to be terribly important - so they range from "really awful" to "quite good". The problem is that, unless you know specifically that the headphone amp in a given model and brand is good, the only way to tell is to try it (you sometimes find lousy headphone outputs in otherwise excellent units, and you sometimes find really excellent headphone outputs in receivers that aren't otherwise especially good).
 
HOWEVER, the headphone amplifier is a really tiny portion of the electronic circuitry in a typical receiver or integrated amp - literally a few dollars worth of parts at most. Therefore, unless you're using the speaker outputs (and so the main amps) to run low-efficiency planars, using the headphone output on an integrated amp for a headphone amp makes about as much sense as keeping your old car around so you can use the radio. (It's doubtful if the headphone amp in the most expensive receiver or integrated amp around is anywhere near as good as the little $99 one from Schiit audio, and you're running a lot of other junk just to use tat one little corner of it). So, by all means, try the headphone amp on the one you have and see if you like the way it sounds, and, if you're buying a receiver or integrated amp anyway, you might as well check around for a model that's known for having a decent headphone output, but don't even consider BUYING a receiver or integrated amp just to use its headphone amp to run ordinary headphones; it's just not worth it. 

 
Thanks to micmacmo's post about his A-550, I found a service manual for his amp (which I figured would basically be the same as mine). The block diagram shows that the headphone out uses the "cheesy method" with a resistor in series. The schematic shows that it's a pair of 220Ω resistors.
 

 

 
I popped the lid and found the headphone-out board. The L/R positive speaker outputs go from the main board to either side of the headphone socket. The speaker signals then come out at the R-hand side of the headphone-out board and then back to the speaker taps. The resistors are marked "red, red, brown, gold", and measure 221Ω and 219Ω.
 

 
So it looks like the output impedance of my headphone jack is 220Ω + the output impedance of the amp itself. Is this necessarily a bad thing? It seems not necessarily.
http://www.innerfidelity.com/content/musings-headphone-amplifier-output-impedance
 
Plus, the ZMFs I'm getting have a T50RP driver which has a very flat impedance curve. So the "cheesy method" won't have an adverse effect. I think it'll be the hiss that might be my major problem using this amp for headphones, as I seem to remember it being quite significant.

 

[Skylab]

Right, that's part of my objection to the whole argument - it's FAR from a given that the high output impedance of the headphone out of vintage amps is a bad thing, it's also FAR from a given that vintage amps will be noisy...especially for those of us who have recapped/restored ours.

Coming into an enthusiast thread and spouting a bunch of tired dogma as a reason why the enthusiasts are wrong...well I don't get why that seemed like a good idea. The proof, indeed, is in the listening, and I for one have heard some of the best headphone amps ever made, and I'm perfectly happy listening to the headphone out of my Pioneer SX-1980. Call me kooky

 

[BGRoberts]

Right, that's part of my objection to the whole argument - it's FAR from a given that the high output impedance of the headphone out of vintage amps is a bad thing, it's also FAR from a given that vintage amps will be noisy...especially for those of us who have recapped/restored ours.

Coming into an enthusiast thread and spouting a bunch of tired dogma as a reason why the enthusiasts are wrong...well I don't get why that seemed like a good idea. The proof, indeed, is in the listening, and I for one have heard some of the best headphone amps ever made, and I'm perfectly happy listening to the headphone out of my Pioneer SX-1980. Call me kooky

 
 
Nawwww
Kooky was on 77 Sunset Strip. 

 

[Oregonian]

Right, that's part of my objection to the whole argument - it's FAR from a given that the high output impedance of the headphone out of vintage amps is a bad thing, it's also FAR from a given that vintage amps will be noisy...especially for those of us who have recapped/restored ours.

Coming into an enthusiast thread and spouting a bunch of tired dogma as a reason why the enthusiasts are wrong...well I don't get why that seemed like a good idea. The proof, indeed, is in the listening, and I for one have heard some of the best headphone amps ever made, and I'm perfectly happy listening to the headphone out of my Pioneer SX-1980. Call me kooky

+1000
 
I own 8 systems, ALL in use, and have never had this hiss issue with any headphone I've tried on them - and I've tried over 50 now, from HE-6 from the taps to a M Audio Q40 and a lot in between. 
 
The thing is - we vintage fans KNOW what we have and it's like lightning in a bottle.  It's only a bit sad that more of the thousands of Head Fi members DON'T know about vintage speaker amps.  They think headphone amps are the ONLY way to go.  Or, for us who sometimes think there's a reduced inventory in the free world (true) maybe we're better off not sharing our discovery.  Either way, we are the proud old school owners of what we love.    
 
Skylab was the impetus for my vintage addiction - and for that I'm eternally grateful!
 
Another reminder of the other benefit of vintage - they look pretty darn good.  Not that men are visual creatures but.............
 

 

[PhoenixG]

 
+1000
 
I own 8 systems, ALL in use, and have never had this hiss issue with any headphone I've tried on them - and I've tried over 50 now, from HE-6 from the taps to a M Audio Q40 and a lot in between. 
 
The thing is - we vintage fans KNOW what we have and it's like lightning in a bottle.  It's only a bit sad that more of the thousands of Head Fi members DON'T know about vintage speaker amps.  They think headphone amps are the ONLY way to go.  Or, for us who sometimes think there's a reduced inventory in the free world (true) maybe we're better off not sharing our discovery.  Either way, we are the proud old school owners of what we love.    
 
Skylab was the impetus for my vintage addiction - and for that I'm eternally grateful!
 
Another reminder of the other benefit of vintage - they look pretty darn good.  Not that men are visual creatures but.............
 

They sure do look good, but they can also have a bit of "character" as well. Quick story - I just got the sx-1980 back from a full recap a few weeks ago and I've been troubleshooting a few very minor gremlins ever since. First, it was dropping channels. Resoldered the volume pot and we're back in business. Now it's surging volume on the phono input. I suspect a cracked solder on a cap. Either way, I'm going to feel like a genius when I figure it out...

 

[Oregonian]

  They sure do look good, but they can also have a bit of "character" as well. Quick story - I just got the sx-1980 back from a full recap a few weeks ago and I've been troubleshooting a few very minor gremlins ever since. First, it was dropping channels. Resoldered the volume pot and we're back in business. Now it's surging volume on the phono input. I suspect a cracked solder on a cap. Either way, I'm going to feel like a genius when I figure it out...

Dang, you have a 1980?!  :bows down:

 

[PhoenixG]

 
Dang, you have a 1980?!  :bows down:

Haha, sometimes I feel like half of this thread has one or something just as good. You have some good stuff too!

 

[claybum]

Here's my headphone amp. It's all I need

 !!!
 

 

[moodyrn]

Well I thought I would show off some internal goodies that I've restored recently. Every since posting a restored amp on cl a while back I keep getting calls to do others for some reason lol.
 
 
.
 

 


 

 

 

 
I did own one that was partially restored by Terry Dewick. But the only boards that were recapped were the amp boards and stabilizer board. So I finally got to hear one completely restored including the power supply board, preamp/phono boards, filter board, eq board and flat amp board. And wow! After owning a couple of others that were stock, I never thought the sx1280 sounded good as it looked on paper and also given how well the build and internals looked. But a restored one sounds every bit as good as I originally hoped and then some.
 
 
Next up is the sansui au20000. Although it has a few plug in boards, it's one very complicated beast. There are a few hidden boards, and boards even hiding behind those lol. But the work was well worth it. It gave the mcintosh rig a really good fight, but not quiet besting it. But it was really close. My wife actually preferred the looks and sound of this beautiful marvel. It's by far the best vintage intergrated I've heard besting the mcintosh ma6200 by a good bit. It's on my very short list. But man do these things fetch a good penny, so it may be a while. But now I understand why. The only thing that wasn't done on this one were the two main filter caps, but all other electrolytics were replaced.
 
 

 

 

 

 

 

 

[moodyrn]

   
There are a couple of important factors that determine the answer to that question.....
 

 
 
So after almost 1000 pages, over 14,000 posts, and over 1,000,000 views, you just proved we all are tone deaf. Lol, priceless. 

 

[Skylab]

Brother Moody, WOW!!! Those restorations are awesome!!!! Great stuff, buddy!!!!

 

[moodyrn]

Thanks Sky!