hirsch

It's a bit more problematical than that. You see, the extra current being drawn from the tubes has to go somewhere. What it does is turn into heat. When enough heat is generated, what appeared to be a near short in the transformer becomes a real short, and an expensive output transformer is now an expensive paperweight. Once a tube is operating into a dead short, it will burn out quickly enough. In some pro gear, there is a short across the output jack when nothing is plugged in, so that the tube is operating into a dead short immediately. The idea is to burn out the tube as quickly as possible, before it can kill the transformer. Tubes are cheap relative to output transformers, in most cases. While this only applies to transformer-coupled amps, I tend to advise people to always put a load on a tube amp. Even if the amp is safe without a load, it creates good habits. Plugging a headphone in when not necessary doesn't hurt anything. Forgetting to plug a headphone into a transformer-coupled amp can be disaster. Better to develop a good habit than learn from an expensive mistake.

I've read that some people have experienced that with Walker SST, which is not what I use. I do use XtremeAV Quicksilver, and have not had any issues in over two years so far. Silver itself does not stop conducting after a period of time. However, there could be issues with some vehicles for holding it in place. All academic to me. Tube pin conductance issues have gone away since I started using the Quicksilver. Even if I had to reapply it now and then, it would be worth it.

Actually, no. I haven't seen any tester manual that recommends tapping a tube when testing for shorts. A short is either there or it's not. Where you DO tap a tube is if you happen to have a tester that checks for microphonics (These are few and far between). Essentially, you plug in the tester's headphone, tap the tube (gently!), and listen. This is the same function performed by a headphone amp, so a tubed headphone amp can give you pretty much the same information that a tester checking for microphonics would give you. Also note that a gain stage is likely to be much more sensitive to microphonics than an output stage. It gets more complicated still (doesn't it always?). I just replaced a 2C51 in my SDS. The new tube was microphonic, but not offensively so if not tapped, so I left it in. After several hours of use, the microphonics have disappeared completely, even if the tube is tapped. The tube is now dead quiet (except when music is playing).

Tubes are pretty robust against cracking, but it can happen. If it does, the gettering (chrome-colored coating often at the top of the tube) will turn white (the barium oxidizes). If that happens, throw the tube out; it's done. If you've still got chrome-colored gettering, the vacuum is intact.

Thanks for the birthday wishes!!!

I'm not sure about much. All I can say is that I was lukewarm about my original OII, and that it sounded like another OII that I had significant use of (and that one was brand new at the time). About the only thing that I am sure of is that I have a strong preference for the OII that I have now.

Remember that impedance of many drivers changes with frequency. If that +/- 15% represents changes over the entire frequency response, it might actually be a pretty good spec. Alternatively, they could report an impedance at a particular frequency and get a much tighter, but less useful, spec. Finally, driver matching could simply be crap, but I wouldn't assume it without considering alternatives.

My original MK1 was smooth as silk almost all of the time. The problem came when the music that I was listening to wasn't supposed to be smooth as silk. I felt that the headphone was imposing a pleasant, but bland, coloration on what I was hearing. The MKI that I have now seems much more transparent than the last one. It's only polite if the music is polite. A big improvement to me.

I wouldn't call it just a more forward sound, although that's part of the issue. The bass, when driven by a BHSE wasn't just reduced, it was gone. As in, where did this system misplace it's balls? Further, the key to the music, the midrange, was muddled and confused relative to the Mark I. I heard about three or four of the Mk II's, and in each case first thought that the system was broken (it was that much worse than the Mk I to me). Only when I used my Mk I did I realize that in each case, the problem was the Mk II headphone. I'm curious to hear one with your mods someday, because as it stands, I'd have a hard time classifying the OII Mk II as a worthwhile headphone. I'm actually understating just how much I disliked it.

It surprises me that you found the combo non-resolving. I hear loads of detail (although the Tung Sol round plate is probably the champ in that department). What I miss is "slam". The combo doesn't really have enough punch and definition at the low end. I'm still searching for the right mix that maintains definition but gives me the bottom end I'm looking for. The Tung Sol's get close, but the top end gets congested with those.

The Lemo connectors used in the Qualia 010 can take a maximum of 28 gauge wire, which does limit the options a bit. I wound up using a solid silver cable that I got from Larry at Headphile, and did the termination myself. I had thought that this cable might be too bright (it was brutal on a CD3000 I had heard), but that didn't materialize. It's very clean and fast, but the high end is not out of line. So far, I haven't heard a better cable for the Qualia. On SDS-XLR, I like Ken-Rad VT-231's on the inputs, and Sylvania VT-231's as outputs. I've tried a lot of other tube combinations, but always find my way back to the 6SN7.

I can see that you haven't met Tyll yet Tyll, Happy Birthday! The pics were great (and also a great way to get rid of vestigial modem-users). Looks like you've been having a blast. Also looks like that bike was fast enough to get away after you robbed the liquor store (some people would just take the money). All the best (liquor) on your B-day.

Something's not kosher about that.

Hmmm...can the Floats be driven by a Stax amp?

I just ran into someone last weekend who is trying to sell two NOS Jecklin Floats. He's only got one transformer, and wants to sell it with both headphones as a package. I'm contemplating making an offer, but have absolutely no idea what those things should sell for. In fact, I can't remember actually seeing a set sold. Any advice?

I was at UI (Psychology Dept) between 1978 and 1984. I went back for visits a couple of times since, but most of the people I knew have moved away, and I think it's been about 15 years since I was last there.

Wait a minute, wasn't that me?

Ah, Champaign in August. I've got six years of memories from there when I was in grad school. Particularly of note was the smell when a wind from the south came in over the experimental pig farms in summer...an experience that still causes me to shudder.

I've owned, and sold, HP-1, HP-2, PS-1, MS-Pro, SR-325, HF-1, SR-200, and GS-1000. The RS-1 appears to be the sweet spot in the Grado line for me. The only Grado's I still own are a single-ended and a balanced RS-1 (oh, and an iGrado). That said, I think the first RS-1 I bought sounded awful. It was new-in-box, and I returned it. For me, the key to the RS-1 is flat pads, particularly running single-ended. Balanced, the bowl pads can be used. Time can change tastes. There was a period when I swore by the HP-1000 series. Now, I can take them or leave them. At current pricing, I can simply leave them. The RS-1 has proven to be a keeper in the long haul. There are only three other headphones I can say that about: HD-600, K-1000, and R10. (I've only been using electrostatic cans for about 3-4 years or so, and it will be a couple more years before I can consider any of them to be long-term keepers.)

I've heard the 508.24 a lot. I own the G08, and would not downgrade. Not everyone agrees with the current round of G08 bashing.

There are several R10's living in the area. I've got two of them (one SE, one balanced) but they do have a different driver than Stevio's, which leads to bigger image but less bass response. I like the higher resolution of the "bass light" version myself. I had a pair of the heavier bass R10's, but the staging felt compressed and I didn't enjoy them as much, so they got sold.

Cracking and hissing are not normal sounds from good tubes. If you're lucky, it can be due to gas buildup that can dissipate when the tube is heated. Or, it could be some excess material deposited in the gap that simply burns off. Or, you could have a tube pin that is not making a good connection to the amp (clean your tube pins!). More often, it is a symptom of a tube with issues. The cracking sound is usually arcing between the grid and the plate, and you don't want it. At best it is annoying, at worst it can indicate that a full short is about to happen. If it doesn't disappear completely, in a fairly short time, and you know the tube is making a good connection at the pins, the tube is probably junk. The adaption to slow changes is why I didn't allow myself to adapt. Short sessions well-spaced don't cause adaptation in the same way that continuous listening does. Try a short listening session with brand new tubes. Listen again at about ten hours, but only for a short time. Then try again at 100 hours (no cheating). You can't adapt if you're not listening. Results might surprise you.

Huh? Way back when on the other forum I posted impressions of a bunch of 12AT7 types for the MicroZOTL. I was moving as fast as I could to get a bunch of impressions up, but did wait on each tube set until I felt the sound had "stabilized" and I couldn't hear differences in brief listening sessions separated by at least an hour. None of the tubes had settled at five hours. Some started settling at 8-12 hours, and some took a day or two. It would not shock me if subtle changes occurred over longer periods, but that was not what I was listening for. I'm only citing periods where changes in sound were obvious and unmistakable. When did the absence of tube burn-in become some sort of orthodoxy?

The best I found were Japanese tubes with a short "box" style plate. They are easily recognizable, as the plates only seem to fill half of the bottle. Some of these were rebranded by Raytheon, but not manufactured by them. I think the actual manufacturer was Toshiba, but it's possible that Toshiba also rebranded them from someone else. US-made Raytheons have a full-size plate, and are sonically uninspired, IMO.

There is some misinformation on that sheet. For example, although the 5692 is usually compatible with a 6SN7 circuit, it is NOT a 6SN7. It cannot dissipate as much power as even the earliest of the 6SN7's, and an amp that drives the 6SN7 hard will fry a 5692. The pics appear down, but the first step would be to identify the markings on the tube. Generally 6SN7GTB's are the latest version of the tube, but have the least value (and, in many cases, the worst sound). 6SN7 GTA's are more desireable, but the premium tubes are usually the 6SN7W and 6SN7GT. Value is dependent on brand and "coolness" factor. For example, the Ken-Rad VT-231 (military designation for 6SN7GT) has both a clear and black glass version. They sound identical, but guess which one usually costs more... If you've got a short-bottle 6SN7W in there, it's worth more than $50, if it tests well. Only a few of the 6SN7GTB's would be worth more than $10 (although I'll admit it's been awhile since I priced that tube).