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I want to design a headphone amp for Sennheiser HD-600 cans (300 ohm). I own a pair of LL1660 10ma transformers. Is there a way to make these two play together?
I am open to any tube...
Thanks, Clyde
Follow Ups:
"a tube that will run happily at 10mA with a 3K plate impedance and a mu of 18"
How about the AVVT or EML AV-20? It's a DHT, a nice bonus too:
http://www.elektronenroehren.de/avvt/datashts/av20b.htm
I think I will work this problem from a different angle.
I'll go to Kevin's pushpull headphone amp with 6h30 and or maybe 6n6p, a direct coupled, two stage
.
Maybe a triode connected 4p1l in some other configuration...
Thanks for kicking this around.
Clyde
Let's do the math...
With a 4.5:1 step down the 300 ohm impedance "looks" like 6K as a tube load. I'd be hard pressed to recommend a tube with an Rp of more than 3K for good bass damping under those circumstances. You also have to consider having enough gain to drive the 'phones from the usual sources. I can drive my HD-600s nicely from a CD player plugged into my preamp with a gain of 11dB. So 4.5 x 4 = 18 for a mu. The problem that remains is finding a tube that will run happily at 10mA with a 3K plate impedance and a mu of 18. Unfortunately, the list is so short that I can't think of one. If you relax the Rp requirement, you could use, for example, a 12BH7, but I'm not sure that the bass will be satisfyingly tight with 5K.
Anybody else have a candidate that fits the prescription?
Kevin Carter
K&K Audio
www.kandkaudio.com
triode connected E180F
paralleled 5670/396A/2C51
paralleled 5687 at low current
paralleled or single 6922
??
OK, 6cb5 triode connected. I'm guessing the output won't be enough to make the HD600 go...
http://frank.pocnet.net/sheets/106/6/6BC5.pdf
http://frank.pocnet.net/sheets/106/6/6BC5.pdf
It'd go... just not very low. What you're needing is low plate resistance (Rp).
E180F as triode, 10mA, 200V plate, bias -2.5V or so. Cost you $5 NOS each, gold pin SQ 10,000hr tube. Rp ~2000ohms, plenty of gain. Linear too.
For kicks, I'd parallel a 5687 at 4mA per section, 100V plate, 8mA total for ~1k drive Rp. For the $10 you might even like it. Fancy Japanese manufacturer ran single section like that in a well received linestage. You got nothing to lose.
Have Fun!!
Shane
that should be 6bc5 sorry
Would a 6n7 be of any use?
Clyde
Not much. Highish Rp.
Kevin Carter
K&K Audio
www.kandkaudio.com
You might try ECC99.
Same parameters as 5687/6N6P, etc. Thinnish sound at 10mA.
Kevin Carter
K&K Audio
www.kandkaudio.com
Ecc99 srpp running 18-22 ma, parafeed the transformer might work.
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