[idletime1213]

Some old headphones had very very high impedance.

 

[CervAnteZ]

Looks like you figured out why i was looking for an amp and not an ipod shuffle. Rest assured though that it will be done just for the fun of it, and i will report back with the results.

 

[Currawong]

http://www.head-fi.org/t/183272/elusive-very-toshiba-back-electret-electrostatics
 
wualta owns or owned a pair. He might have an idea what they work with.

 

[CervAnteZ]

thx for the hint, i just pm'd him on that matter.

 

[nihaz]

Do let us know how it goes...
 
I am quite interested about these cans... pics when you receive it? hahah
 
All the best with your headfi journey

 

[CervAnteZ]

Will do!
 
As soon as they're here, i'll document the hell out of them, i promise

 

[wualta]

The fat plug has step-up transformers in it, but the 'phone was designed to operate from the headphone jacks of the day, which is to say, the '70s, so no telling how loud it will get with modern portable gear without actually trying it. It will be fun to see what happens. 
 
Here's a photo of Rotel's gussied-up version of the HR-810 and the step-up transformers in the plug:
 

 

[Adda]

So the 104dB at 100v must be for the headphone without the transformer, 100v is quite high even for a poweramp.
 
My guess is that a good vintage receiver would do well with these, or an Aragon 18k, 28k or Aurum preamp, they drive 600 ohms with ease and will drive impedance's way in to the kohm range just the same.

 

[wualta]

 
Quote:

So the 104dB at 100v must be for the headphone without the transformer, 100v is quite high even for a poweramp.
 
My guess is that a good vintage receiver would do well with these...

 
Yes, they're giving you the raw performance of the headset itself. To put it in perspective, a 50w speaker amp theoretically delivers 20v max to an 8-ohm load. It doesn't take a large transformer to bump this up to 100v. When buying vintage, try to hit just below top-of-the-line where collector frenzy is less. That will usually get you more than 50w/ch, sometimes much more, and of course better parts, a more versatile preamp section (if any), and so on. If you're on a budget, just shoot for the neighborhood of 50 real watts per channel into 8 ohms. That'd be anything from 25 watts (only 3 dB less) on up.
 
And yes, anything capable of driving a 600-ohm load will drive a higher impedance easily. But the transformer knocks the effective impedance down to normal headphone-range impedances, so that's not at issue here.
 
 

 

[Anarchy]

From my experience what happens is that when you use high impedance headphones on an underpowered amp you get sound out of your headphones. However you only get the higher range. You can literally hear the fact that their isn't enough voltage on them.

 

[Adda]

When buying vintage receivers, try to see if you can get the service manual for it before you decide to buy, it might come in handy.
Nikko is great if you are on a budget.

 

[CervAnteZ]

While i havent really settled for anything, there are 3 vintage receivers currently on offer in my region, i'm unsure about the performance of those, anyone know about or even heard one of them?
 
technics sa-5150 (50W)
saba 9241 (70W)
kenwood kr-7200 (70W)
 
would these do for what i'm trying to accomplish?

 

[Adda]

I can't find a free service manual for any of those models.
Vintage gear will almost always need to have DC-offset and bias current reset, having the service manual will make it much more easy.
 
You can find a lot of service manuals here:
http://www.hifiengine.com/
 
When you find a receiver you like, go search their site for the service manual.
 
Brands I recommend includes: Sansui, Nikko, Mitsubishi, Pioneer, Kenwood, Yamaha, Hitachi, Marantz and Harman/Kardon.
 
Edit: This thread might also be of assistance:
http://www.head-fi.org/t/537704/calling-all-vintage-integrated-receiver-owners

 

[martykaiser]

What do you mean "low cost."  Where can  buy them

 

[bada bing]

Just winging a WAG, the two lower impedance settings are different taps on the transformer and the 1000 ohm setting is direct drive with the transformer bypassed. That would explain the comment about the 1000 ohm setting sounding better. 1000 ohms is an *easier* load for an amp than a lower impedance, not harder. If the sensitivity is 104dB for 100v, then you should still get 94dB for 10v. Quite a few headphone amps are capable of that. When you run out of voltage, you clip, which is quite audible, and the amp performance should be very good until just before clipping while driving a 1000ohm load. Considering how much compression most modern pop stuff is, 94dB isn't that much of a limitation unless you like your music loud.
 
If you're a tinkerer, I would think the best amp for the phones would be a headphone amp, not a receiver, with the power supply voltage jacked up to the limit of the weakest parts.
On a class A amp, you would want to dial the class A bias down because the current demands for driving 1000 ohms would be low. Even a Cmoy built with higher voltage parts and
a stack of 9 volt batteries would give you an idea what the phones sound like.