[mariospeedwagon]

If your tape out is really only putting out 500mV or so (presumably for the sensitive tube input stages of contemporaneous open-reel decks), this will barely be enough to drive a desktop headphone amp properly. An iPod puts out more than that. Modern “tape outs” are effectively line outputs (@ 2V).

If you insist on using the tape out, you may need an additional gain stage. There may also be an impedance mismatch.

I think you are right. Seems like most modern headphone amps are going to be looking for 2V. Back in 1961, the HK was sending out tape signals to devices that are quite different from what we are talking about today.

@tomb is also right because voltage can mean different things.

You and @pbui44 are likely right that I'll need another gain stage. Some of the options mentioned earlier (Magnius, Liquid Platinum), Lyr seem to have plenty of power at 150 ohms, but if it is expecting 2V and only gets 0.5V..........who knows. Impedance mismatch might also be a factor but I'm not sure what I should do about that (sorry).

I think I will shop for something on Amazon with decent power that I use solely for testing purposes that can be returned easily. If I get decent results with whatever I find on Amazon (open to suggestions), I'll send it back and get shopping for some good Schiit or a used/open-box Liquid Platinum ($419 right now).

If the Amazon test fails, I'll just send the Senns back and forget this whole mess ever happened. Or just get a headphone amp that I can plug into my Black Ice DAC and be a digital only headphone listener. I guess I should have put some more thought into this before impulsively late-night-buying the Senns. I really appreciate everyone's help.

Which generation of Fortes are you using?

Forte I with the Crites upgrades (new crossovers/caps/tweeter diaphragms). I listen to lots of different types of music and they do a great job with them all.

 

[mariospeedwagon]

Or just get a headphone amp that I can plug into my Black Ice DAC

de-railing my own thread here, but I just plugged the Senn HD660s into the Black Ice's 1/8" headphone jack for the first time. The specs for that DAC say the headphone impedance is 30 ohms so I thought there was no way it would be able to get good results out of the 150 ohm Senns. Surprised to find out that it sounds decent and I only need to turn the volume up to about 11 o'clock to get it plenty loud.

FWIW I've got an Eitr in the path before the DAC.

Is this just the HD660s being efficient and easy to drive, or am I just an idiot who doesn't understand impedance and voltage? Both?

 

[CJG888]

Here’s a thought: the Senns should sound excellent out of the Bottlehead Crack. If you don’t mind a little self-assembly, you could ask BH to do you a “special” with a higher input sensitivity...

 

[mariospeedwagon]

Here’s a thought: the Senns should sound excellent out of the Bottlehead Crack. If you don’t mind a little self-assembly, you could ask BH to do you a “special” with a higher input sensitivity...

funny you should mention that. I just agreed to purchase a used one located nearby for a fair price on USAudioMart.

If I don't have much success with it, I should have no problem selling it for what I just paid.

 

[CJG888]

Sounds good. Now you can contact Bottlehead about the necessary (minor) modifications to increase the input sensitivity to match the 0.5V tape output.

 

[mariospeedwagon]

I just spoke to someone at Bottlehead on the phone. He said 0.5V should be fine. The Crack would expect to see voltage like that from a phono preamp and that seems to works fine.

He was more concerned with the 150 ohms of 660S and said thats right about the border of what they recommend. The higher impedance headphones in the 600 line might have better bass. We shall see.

 

[mariospeedwagon]

Update for anyone who might care:
Tape Out to the Bottlehead is sounding glorious.

Going to exchange the 660S for 650 to give the Bottlehead what it wants (high impedance), but I think this confirms that 0.5V from Tape Out is enough juice. Thanks to everyone for your help.

 

[CJG888]

STOOOOOOP!!!!!!!!

You want the HD600!!!!

 

[mariospeedwagon]

Check back with me in a month and I'll let you know what I think about the 650's. You might be right.....you might not be. I haven't heard either of them so I can't tell you yet.