I decided to start a new thread so I did not hack the other one up. Basically I have a couple questions for Joel or whoever else what to join in. I noticed on the schematic that you have a 220uf cap before the output. Why don't you have a switch so you can switch between the 220uf cap for headphones and maybe a .22uf paper in oil for preamp use. I have built a similar preamp/headphone amp that did this. Work great for that circuit. Maybe you could experiment with this.
Have you tried negative feedback? The headphones may get some help.
Just a couple thing to consider and discuss if you want.
Thanks
Guiness
Have you tried negative feedback? The headphones may get some help.
Just a couple thing to consider and discuss if you want.
Thanks
Guiness
Le Preamp.
Hi,
You could do that but you'll need the load R to a much higher value too.
Help in doing what?
A CF is a full feedback circuit already and the only thing a NFB loop will achieve is reduced gain.
Actually quite a lot of preamps are capable of driving headphones really, all you need is a jack and a bigger coupling cap and a switch as suggested...done.
Cheers,
EDIT: use a dual triode and things look even better.
Hi,
You could do that but you'll need the load R to a much higher value too.
Help in doing what?
A CF is a full feedback circuit already and the only thing a NFB loop will achieve is reduced gain.
Actually quite a lot of preamps are capable of driving headphones really, all you need is a jack and a bigger coupling cap and a switch as suggested...done.
Cheers,
EDIT: use a dual triode and things look even better.
Yeah I just realized that, thanks for watching out for me. Sometime the brain works alittle slower. Wish I was young again!
I might try the switch on this preamp design. See what happens. Increase R is really not that hard too do. I will build it the proper way first (for BurnedFingers) and then start the experimentions!
Thanks
Guiness said:
From the cathode junction of the 6SN7's run the 220u to a 6.5mm phone jack, and a small film etc to the RCA that goes to your poweramp, sized for the LF point you want. Unplug the one that's not in use, or use a DPDT switch to disconnect them that way. Either way is up to you and they'll both work fine.
I agree with Frank - the point is not to mimic a Mark Levinson preamp!
The switch idea is a good one. I won't bother, since I don't need a true preamp for anything, but it's a good idea.
As a side note, I'm actually rebuilding this circuit into a nicer box, and using 12BH7's on the outputs, and I'll be happy to post my results of that - although a certain forum member will still probably think I fantasized the whole thing.
The switch idea is a good one. I won't bother, since I don't need a true preamp for anything, but it's a good idea.
As a side note, I'm actually rebuilding this circuit into a nicer box, and using 12BH7's on the outputs, and I'll be happy to post my results of that - although a certain forum member will still probably think I fantasized the whole thing.
burnedfingers said:
I already included all the needed voltages in my descriptions of the circuit. And this does "actually work/measure as it was intended to", even if you refuse to believe that.
As I said in the other post, I think you need to do some reading.
Guinness: No need to change any values, I'm just thinking of using 12BH7's in the "new" version because I lived with the 6SN7 version for a year, and I'd like to try something different.
Try it !
Valves with larger innards to me sound better and in my view look better . I would much prefer to avoid these 9 pin types if I have a suitable octal or a loctal valve . I have far more teflon loctal and ceramic octal sockets than I have decent B9a's so you can also guess which types I would plump for ! In fact I would think most folks would prefer say a 6SL7 to a 5751 or a 6SN7 to a 6CG7 , 12BH7 or horror upon horrors a 12AU7 . Why not build using octal sockets and valves then try building an adapter for the 9 pinners to find out ? Just an opinion , others are entitled to theirs (apart from a few 'snake oilers' on this forum who only value their own).
316a
Valves with larger innards to me sound better and in my view look better . I would much prefer to avoid these 9 pin types if I have a suitable octal or a loctal valve . I have far more teflon loctal and ceramic octal sockets than I have decent B9a's so you can also guess which types I would plump for ! In fact I would think most folks would prefer say a 6SL7 to a 5751 or a 6SN7 to a 6CG7 , 12BH7 or horror upon horrors a 12AU7 . Why not build using octal sockets and valves then try building an adapter for the 9 pinners to find out ? Just an opinion , others are entitled to theirs (apart from a few 'snake oilers' on this forum who only value their own).
316a
OCTALS.
Hi,
What possible reason could there be?
Octals: exposed to airborne vibrations are : likely to be more microphonic.
May sound better because "radio nostalgia" tells us they're older than most novals, pico 7s, subminiatures and nuvistors.
Next they're going to broadcast that you better use single triodes etc, etc.
Cheers,
Hi,
What possible reason could there be?
Octals: exposed to airborne vibrations are : likely to be more microphonic.
May sound better because "radio nostalgia" tells us they're older than most novals, pico 7s, subminiatures and nuvistors.
Next they're going to broadcast that you better use single triodes etc, etc.
Cheers,
316a,
I'm not trying to pick on you - I just would like to see the forum move away from that type of generalization. (which I think it has been)
Saying "I like the looks of the old octals" is very different from saying "all octals sound better than all miniatures". The first one does not need any justification, the other definitely does.
Joel
I'm not trying to pick on you - I just would like to see the forum move away from that type of generalization. (which I think it has been)
Saying "I like the looks of the old octals" is very different from saying "all octals sound better than all miniatures". The first one does not need any justification, the other definitely does.
Joel
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