I have a pretty nice tube preamp which uses a pair of 6SN7s in the final stage. See below:
How could I rig this to produce headphone output? Switching between line and headphone would be OK....
Thanks!!
An externally hosted image should be here but it was not working when we last tested it.
How could I rig this to produce headphone output? Switching between line and headphone would be OK....
Thanks!!
Yes, it looks like it might be meant to be an SRPP. A suitable SRPP could perhaps drive headphones, although a cathode follower (possibly a compound type) would be better.
Does this look better?
Thanks!
An externally hosted image should be here but it was not working when we last tested it.
Thanks!
I went through a bunch of research on designing a tube headphone amp, and concluded that I'd want to use something like a single ended class A 6BQ5 and output transformer, for the output driver. Higher source (output) impedances are going to have either huge efficiency loss, high distortion or the bass will all get rolled off, unless the headphones have a very high impedance. The 6SN7 is one of the best tubes out there for a line level preamp, but can't drive 32ohm headphones worth a darn, even set up as a follower, IMO.
Yes, it is now an SRPP. The maximum current it can produce is a little less than twice the DC quiescent current. It might just work with fairly high impedance and high sensitivity headphones.Rodango said:
Please tell me how and what to connect where to get a headphone output. From additional tubes, transformers, components - whatever. And i see the additional circuitry being either switched in or out...
Thanks!
I'd recommend a transformer, too. You'd simply put it after your 3.3uf cap.
Which transformer, depends on your headphones. It would be a parafeed style transformer, so should be relatively inexpensive.
You're going to have to do some research on transformers. Magnequest will certainly wind you some. I recently got their b7-15k's for a linestage, and have been plugging headphones in to it for testing.. It sounds GREAT! Mine aren't quite rite for headphones at 600ohms, but he will make some that are for headphones. Electraprint is another option.
There are other less custom, less expensive options, too.
It's not that simple. The transformer divides the preamp's gain by 5 or more. That means there will not be enough gain left to drive headphones.
What would be the perfect input impedance for a transformer to be matched to this circuit? I'd want a 300 ohm output for the Sennheiser HD650
Oh, sorry! I know there are plenty of 6sn7 parafeed headphone amps out there, but not set up like his starting point, I guess.
My best advice would be to search google and headfi, etc, for 6sn7 headphone amp, and find a schematic you like 🙂.
I remember seeing a similar project here a few weeks ago.........
here: http://www.diyaudio.com/forums/tubes-valves/250317-6sn7-srpp.html
So are we saying that any way you cut it, a 6SN7 SRPP is not going to have what it takes to drive a headphone output transformer?
How about if I was to add an SE 6BQ5/EL84 driver and a transformer as its load to my circuit? What would be the best way to set that up?
Thank you!!
That appears to be exactly what I am looking for...
My only question is should I modify my 6SN7 SRPP to look exactly like the schematic in the article or will what I have work well enough?
6SL7 is a great tube for a front end, but has a much higher plate resistance than a 6SN7, which has a much higher plate resistance than a 6BQ5, so would be less able to drive the low impedance of headphones.
I never finished designing the circuit using the 6BQ5 and a transformer, but I'd go class A, and use the appropriate single ended output tranny for a 5 watt amplifier (I hear good things about Edcore brand trannies - being a cheapskate I use Hammond and they seem fine), even though I'd only need less than a watt for headphones. I'd use a transformer that would deliver an 8 ohm output impedance, to minimize any issues that could arise with headphone impedance variations over frequency.
I never finished designing the circuit using the 6BQ5 and a transformer, but I'd go class A, and use the appropriate single ended output tranny for a 5 watt amplifier (I hear good things about Edcore brand trannies - being a cheapskate I use Hammond and they seem fine), even though I'd only need less than a watt for headphones. I'd use a transformer that would deliver an 8 ohm output impedance, to minimize any issues that could arise with headphone impedance variations over frequency.
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