dsavitsk

The K&K is differential. For use as a preamp, you need to use a pair of input transformers (Kevin suggests the LL1690's -- same core as the 1674's, but 1+1:1+1 instead of 1+1:4+4). Due to the input transformers, it will accept balanced or single ended input. If you leave out the IPTs, then you need to feed it with a balanced source. Here is the simplified schematic (no cascodes). However, for a pot, you can use a 2 gang Alps in a differential shunting configuration ("B"). This effectively removes the pot from the signal path making the quality not much of an issue. (The TKDs don't work in this configuration, b/t/w/) Here's some background on the linestage: http://www.raleighau...m/chapter_4.htm

K&K Linestage : Foreplay 3 :: Acura NSX : Honda Accord I think the K&K is probably hard to beat. The only thing I might suggest is that for output duty, I prefer the LL1930's in this topology to the LL1674's. Kevin disagrees with me on this, but while I think the 1674's are unequivocally the best input transformers available, for output duty they sound a little cold to me. The 1930's are slightly warmer, and are slightly more forgiving. And they cost quite a bit less (due to using mu-metal cores instead of amorphous, and not being shielded, which is not necessary in this application). Not sure if Kevin's board will accommodate them, but if not, it is pretty easy to mount them off board.

Makes sense. That's horrible. A LM334 in the tail would work wonders ...

Am I the only one that thinks this can't be right? Maybe it is late, and I am tired, but R12, R13, and R14 don't make any sense, unless R14 is tied to a negative rail and not ground. And were does C7 go? Shouldn't it connect to U3 instead of C5?

I think the best way to learn is to get your hands dirty. It is hard to just read about circuits in the abstract. To that end, Tangent's CMoy article is a pretty good starting point. http://tangentsoft.net/audio/cmoy-tutorial/ This is tube specific, but it was written for teaching people who did not know anything about electronics http://electriciantraining.tpub.com/14178/ And, this thread has links to lots of similar articles: http://www.diyaudio.com/forums/tubes-valves/38278-line-tube-learning-newbies.html Linked from here: http://www.ecpaudio.com/

I emailed you a response. Let me know if it does not get through. Thanks

Maybe Apple could license Beats Audio for the IPod ...

You can easily get regulated 250VDC out of the Triad vpt230 series of toroids from Mouser. These will fit inside the chassis, not get to hot, and not have an issue with stray fields.

Fair enough -- my interest, agreeing with Wayne in the first place I think, is not civility, it is boringness.

Bingo. Maybe someone should start a slower political forum thread that the rest of us can not look at ...

Indeed. As close as you can. Each board has a servo that should keep the output very close to ground. In a pinch, the servo opamps can have their offset trimmed, so you can solder in a trimmer across two of the pins (I think Colin left them unused) to zero this out. It probably won't be necessary. But, the transformers really do not like any offset.

1 as well, but it surely doesn't matter here. Since it is balanced, any induced ground noise will be cancelled. And, the preamp this is feeding has input transformers, and the circuit is truly differential and has no ground reference. What matters more is keeping the offset between the + and - pins to absolutely 0. Even a mV will interfere with the amorphous cores.

Hard to believe that the anodizing could build up so much as to make the sides no longer mate, or the PCB not fit. I think the best bet is to probably sand it down -- use a dremmel on the built up parts. These anodizing and powder coating shops are largely slop shops. They work on volume, and don't care so much about quality. I ran into the same issue when building my prototypes. Most places I called said they wouldn't do runs of under 100,000 parts. I eventually found a friendly local anodizer who said he's be happy to drop my stuff in with another run for a small fee. I spent hours sanding the aluminum only to have him smack it around, and then deny he'd done it (and get really nasty when I suggested he be more gentle). Fortunately, I got it back before it went in the bath so the scratches and dings were not permamently etched in. But, in the end I have discovered that to get case parts finished the way I want that they need to go to a specialist metal finisher who understands "high end audio" and who will work with small volumes. Such places are few and far between, and their work on this case would likely cost as much as the whole kit. As for a replacement -- it might not be as easy as you'd hope. It would leave us with an extra pcb and transfomer set. However, you could order a blank one from Context (not sure of the cost, or I have a blank from a different manufacturer that will work -- IIRC it was about $40) and send it to FPE to have it machined. Probably run about $50-60 for the machining. Not sure the one-off cost at Context to do that.

Hey, I grew up at Purdue -- dad was a prof there. Home of McCord Candies -- try the olive and nut sandwich. Indianapolis airport is a lot closer, but has the downside of not being in Chicago

The HD-800 is a very well damped headphone. If you drive them with an amplifier with a very low output impedance, they will be over damped and sound bright and a bit thin. On the other hand, if you drive them with an amplifier that has some output impedance, the damping factor will be less, and they will sound fuller, warmer, and bloomier. Contrarilly, something like the HD-650 is less well damped and thus does much better with an amplifier with a very low impedance. This, however, has little to do with tubes vs. solid state. It is true that most tube amplifiers have a higher output impedanace than most solid state amplifiers. There are a variety of semi-inherent reasons for this -- for instance, tubes generally have lower transconductance. But, when comparing something like the Eddie Current amps vs. say a B22, it has more to do with amplifier topology than anything else. However, it is not the case that tubes amplify different frequencies, or sound much different than transistors, or anything like that. Indeed, the differences are really overblown by many people. Instead, it is that tubes tend to be used in certain ways, and transistors tend to be used in different ways, leading to many gross generalizations about how tubes sound like this, and transistors sound like that. So, what I am trying to say is that I think you are ascribing traits to tubes and transistors that are actually traits of topologies, and not the devices themselves.

This ^^^

Happy Birthday, John! Have a great day in the snow.

Wow! I bet it sounds awesome.

It's a thing in as much as things my brother invented* are things -- he is a psychology professor if that gives him any authority (it probably shouldn't) *Looking around, I don't think the term is unique to him.

Post Christmas Letdown (PCD). Happy Birthday!

NYE and Halloween are my least favorites for the above reason, and for the enforced fun aspect ... ... and from the year that a kid, after eating too much candy, vomited all over our front porch. Then his mother, after getting some candy from us, showed us the vomit but didn't stick around to help clean it up.

In the U.S., too http://en.wikipedia.org/wiki/Implied_warranty

Happy Birthday!