Amps that can drive the HiFiMan HE-6 planar headphones

[wuwhere]

I don't. I use a high quality 10 ohm non-inducting resistor in parallel with the HE-6's 50 ohms
to bring down the impedance to about 8 ohms at the amp's 8 ohm terminals.
 
HiFiman's adapter box also uses a 10 ohm resistor in parallel and a 25 ohm 1/4 watt resistor in series for protection.

 

[grokit]

If the tube amp is OTL or high wattage (>90 wpc), then you want to use the box or come up with your own resistor setup, but if the amp is transformer coupled and modestly powered it's not necessary.
 
Having said that, I have a 10 ohm resistors in parallel on my modestly-powered SS speaker amp, as equalizing the impedance makes me feel better

 

[wuwhere]

Got my Copland 504 tube amp today. This amp is very non-fatiguing. Detailed yet non-offensive.
 
This amp is for pure listening pleasure, vocals in particular, its magic is in the mids.
 
This is my end of the line amp for my HE-6.
 
Right now it has 4 EH KT88 reissues. I'll swap them with GE 6550 later.

 

[Happy Camper]

I always felt a high wattage tube amp (more than 80 watts) would pair well with the HE-6. Something like you have there. The tube bloom must be magic in the mids.

 

[wuwhere]

Yes, no SS amp has this mids regardless of price, you only get this with very good tube amps. It beats my audio research d70 hands down.
 
Also, this amp has upgrades and the previous owner used Raytheon 12au7 instead of 12ax7. As you all know, 12au7 is pin compatible with 12ax7 except it has lower gain.
 
I need to add this, its relevance with the HE-6.
 
The HE-6 is like a messenger, don't blame the messenger.

 

[Face]

If you add a tube pre to a SS amp, it too can have euphoric mids.

 

[wuwhere]

Which tube pre and which SS amp? I'd like to try it if I can afford it.
At one time I had a tube pre, a VTL Ultimate, and solid state amps, a pair of Krell KMA-160 monos. It was nice powering my Apogee Scintillas ribbon speakers at the time.

 

[Happy Camper]

I use a tube output dac with my ss speaker amps. It used a 12ax7 and I rolled several without much difference. Then someone recommended a GE Command 5 star 12AY7. I like better than any of the 12ax7.

 

[wuwhere]

The different gain factor is:
 
12ax7 - 100
  5751 - 70
 12at7 - 60
12ay7 - 45
 12av7 - 41
 12au7 - 19
 
The following is from the tubestore.
 
"The gain factor of a tube simply measures how much it amplifies the input signal.  For example, the common 12AX7 type has a gain factor of 100, while a 5751 (which is often used in place of a 12AX7) has a gain factor of 70. This means that if you plug a 5751 into a socket that expects a 12AX7, the pre-amp will have about 30% less gain. Not only will this make the amp quieter, but it can also alter the sound by making the power section work harder when you turn it up. Many guitar amp users (particularly harmonica players) like to reduce the gain to get a different sound or calm the amp down to prevent feedback."

 

[wuwhere]

So I rolled another set of output tubes in my Copland 504 from my stash, Russian SED Winged C 6550s. Not as good and sweet as the US GE 6550s. Next are Russian TS 6550 reissues.

 

[Rossliew]

What's the minimum power output for tubed amps sufficient to comfortably drive the HE-6 with bottom end reproduction similar to an SS amp?

 

[wuwhere]

I have a small 10wpc @ 8ohm tube amp. It can drive the HE6. It uses 4 Russian 6P1P output tubes.
 

 

[wuwhere]

Quote:

The different gain factor is:
 
12ax7 - 100
  5751 - 70
 12at7 - 60
12ay7 - 45
 12av7 - 41
 12au7 - 19
 
The following is from the tubestore.
 
"The gain factor of a tube simply measures how much it amplifies the input signal.  For example, the common 12AX7 type has a gain factor of 100, while a 5751 (which is often used in place of a 12AX7) has a gain factor of 70. This means that if you plug a 5751 into a socket that expects a 12AX7, the pre-amp will have about 30% less gain. Not only will this make the amp quieter, but it can also alter the sound by making the power section work harder when you turn it up. Many guitar amp users (particularly harmonica players) like to reduce the gain to get a different sound or calm the amp down to prevent feedback."

 
Quoting my own post.

 
I think I'm beginning to understand this gain factor but I can be wrong. I was checking the bias of my Copland.
 
My amp is designed for 12AX7 with 6550s, bias should be set at 45mv. The previous owner swapped the 12AX7 with 12AU7. The 12AU7 has a gain factor of only 19% relative to the 12AX7. When I measured the bias voltage on each tube, they were very high, like 230mv and higher. It didn't make sense to me. When I brought it down to 45mv, the sound became flat and thin. Again, it didn't make sense to me.
 
Then it hit me. I have to adjust for the gain factor. I should set the bias at 45mv/0.19 = 236.8mv. After I adjusted each one, the magic returned.
 
Edit: I was told that my setup is not good cause it overdrives the 12AU7. But it sounds good so I'll stick with it for now.
 
There must be a moral here somewhere.

 

[Rossliew]

Thanks for the reply. Do we always need to connect through the 8ohm speaker taps or can it be via 4ohms as well? I suppose any decently made Chinese tube amp should do?

 

[wuwhere]

Quote:

Thanks for the reply. Do we always need to connect through the 8ohm speaker taps or can it be via 4ohms as well? I suppose any decently made Chinese tube amp should do?

 
If you use the 4ohm tap from the tube amp, you need to parallel a 5 ohm resistor instead of 10 ohm. The resistor must be non-inducting.