OP Tx for signal tubes in Headphone amps

[M Gregg]

Just a quick question,

What Output Tx's have you used for small signal tubes like 12au7 or EF86 to drive Headphones?
Thinking single ended..

I have only seen line driver Tx's with 63k to 300 Ohm?
What primary impedance have you used..25K etc
Any ideas where can you get them?

Regards
M. Gregg

 

[45]

1/2 ECC40 SE per channel with 15K primary load at the max power rating (250V/6mA) as from datasheet. Works great with high sensitivity headphones.
Even better in PP.
For the ECC82 I would try 15-22K in SE.

 

[M Gregg]

Thank's for the info,

Trouble is the primary values are hard to find so where can you buy them?

Regards
M. Gregg

 

[45]

What secondary impedance do you need? 300R? Then you can try this: http://www.sowter.co.uk/specs/1160.html or ask for a custom OT. The Sowter 1160 will handle 0.7W RMS at 30Hz into 300R impedance. So you could make a 12AU7 PSE and use 5:1 connection to get 7.5K (i.e. 15K per valve).

 

[45]

The 8988 and 8969 could also be good for 12AU7 PSE or if you use a valve that works fine with 8-10K.
SOWTER HEADPHONE TRANSFORMERS
More expensive than the 1160 but they are true headphone OT's with several secondary impedances.

 

[M Gregg]

Thank's for the info..

I now have a few ideas....😀

Regards
M. Gregg