dsavitsk

Poor pups

It appears that someone cut and pasted a different web page and just didn't edit a few of the values. That stuff is clearly from a power amp page. Anyway, I don't see any untold riches to be found here, but to each his own.

12AX7 cathode followers are worthless, even paralleled. They just don't have enough current across them or Gm to drive anything. Generally, for lowest distortion, a tube wants to see a load several times higher than its rp (even when the load is on the cathode). rp on an AX7 is ~80K, both sides ||, 40K. That means that if your next stage has an input Z of lower than 250K, distortion will be high. Maybe it will sound toobey. What's with the Ultra Linear class AB, 1W into 8 ohms, and the 240W power requirement? Just a sloppy cut and paste job?

Looks like I mistyped -- I meant that I wanted an android device to be an X terminal, a thin client that does the display part of programs running on the terminal server. So, not an "Xterm". So, what I really want is an interface on a tablet that looks like the Winamp media library and play list that controls the actual application running on the FreeBSD box across the room. RDP and VNC are both cumbersome ways to accomplish this, but it seems like making X do what X was designed to do in the first place should not be so hard ...

I am generally opposed to anything Apple (though I do enjoy Olympic Decathlon on the old ][+), but if that works, I could definitely see having an iPad as a Xterm to control a FreeBDS box. I'd prefer an Android, though. VNC is worse than RDP.

Used to be that Apple was a hardware company that created an OS to sell the physical units. Now, Apple is actually a memory company that makes all sorts of loss leading products to sell it. One question -- anyone have any insight into running Xterm on an Android tablet? I was thinking that a *BSD music server/player with a remote interface would be just the sort of music system I have been looking for, and not finding, for years. Best I've come up with is an RDP client on a laptop to control an XP box, but it's not ideal and is way too cumbersome ... and I hate the squeezeserver, so that has ceased to be an option.

An orange, and a banana, and a chocolate chip cookie dipped in ganache.

I was thinking that you were zeroing offset between the two plates, in which case R7 would need to be in a different place. But, yes, as you have it, you can zero it w/r/t/ ground, though you can't do it for both sides. But, why does that matter? The headphones appear to be differential, don't connect to ground, and thus have no zero reference? Instead, they just need to sit some voltage below the bias. So, you'd either simply increase the bias to some voltage above the plates, or you could tie the B+ to ground and consider it a negative rail only. Something like the LL1668 as a plate choke will drop ~7V in this setup, which seems pretty incidental, and will keep the offset from bias pretty close to what you want.

As someone who has never built a stat amp, here's my contribution Basically, LTP input and output stages. Choke loads on the output, and while chokes are not free, I think the savings of not needing a bipolar supply would make up for it.

I think R7 is out of place, too. Have you compared the driver + cathodyne to just using the first tube as a LTP splitter? I don't have enough experience with either topology to form much of an opinion so I am curious if you tried both. One thought, though, is that LTP front end might enable DC coupling and eliminating the negative rail (to keep the cathode load high (though, does it really matter?), use a choke, or use a single CCS bypassed by a high value resistor to give some slop)?

Should the grid of V4 be connected to that side of R3?

I have a scsi raid card and 3 scsi HDDs that are yours for the shipping if you want them. Otherwise, I'd buy a used thinkpad X61 and call it a day

Pffft. Real DIYers have MAPP gas torches ...

Some people argue that the perceived big sound of DHTs is basically reverb from the DH filaments. Any correlation between people who like the LCD2 and people who like 300b/2a3/307a/etc headphone amps?

I took a differential geometry class once, and I'm pretty sure it was all made up as the professor went along. all the way with gauss bonnet

That sounds like no fun at all. Best wishes for a speedy recovery.

No, not dead, just delayed. We have, in hand, what we hope to be the final revision of the PCB -- it is now 14" long. We are waiting on a prototype of the final case, which we thought would have arrived already. Probably in the next week -- other cases ordered at the same time from the same vendor are in transit, so this one can't be far behind. There were only two of the final prototype boards made. Tom is building one, but if anyone (HiGHFLYiN9) wants to do the other, I also have a set of the transformers and a blank 14" case. Whomever wants it can have it for cost.

Thanks Marc -- I'd appreciate it.

Thanks everyone! I spent most of my birthday driving from Ithaca to Chicago. Didnt quite make it, so I am spending the rest in a dumpy hotel in fremont Indiana home tomorrow ...

Maybe they mean Australian winter

Does anyone have a 1uF, 250V or higher electrolytic cap (on 2.5mm pins)?

I don't get the appeal -- I don't listen to headphones because I can't afford speakers, I listen to them because I like them better. Why would I want to ruin that experience?

There is this weird belief at HF that a 10W amp is really different from a 1W amp when putting out 1/10W. I heard a pair of these at the NYC meet, and they sounded like PA speakers in a gym. All resonance and awful. Maybe the felt had fallen out, or maybe the amp was a bad match, or maybe I was just not in the mood, but it was not good. Very odd. I am itching to hear another pair now that are known good on a system I am familiar with as something definitely felt wrong.

The auditory neuroscience community uses Etymotic, if that means anything.

The Wolfson WM8741 DAC chips have a voltage output of 2Vrms with a full scale digital signal. 2Vrms is about 5.7Vp-p. The DAC chips can only handle a PS of up to 5.5V, and are really recommended to run at 5V (actually, they can take 7V, but Wolfson will tell you never to actually run them over 5.5V). Anyhow, suffice it to say that the chips clip. They have an option to cut the signal by 2dB which results in 4.5Vp-p (~1.59Vrms) which they do just fine with. Different headphones perform differently with different amplifiers. Full stop. The notion that one perfect amp can perfectly drive everything is simply nonsense. For instance, with a traditional voltage amplifier, I think Grados do best with 10-15 ohms of Zout, balanced or SE. With an amp with near 0 Zout, they sound terrible. And this is a large part of the reason for the "Grados work well with tubes" myth in that tube amps tend to have a non-0 Zout. However, I also think they really shine with a Gm amp with a Zout in the hundreds, if not thousands, of ohms. Those same amps may not do well on other brands/designs. So, finding just the right synergistic combo would be a lot easier if we started matching gear in reasonable ways, rather than treating every headphone as a black box to be driven the same as every other one. Nobody expects a 45 amp to drive their B&W 801's, and nobody expects their Krell monstrosity to drive Loethers, so why do we expect this in the headphone world? Anyhow, this is a great thread so far