Craig Sawyers

Are both channels the same in this regard? If so, have you checked that the LED's are the right way round, and the 100V zener is the correct way round?

That is where your active diff probe comes in handy. But interestingly the really old generation Tek probes, I guess because of their physical size, can handle much higher voltages. http://www.reprise.com/host/tektronix/reference/voltage_probes.asp Although CMRR would not be as good as the current product, using two P6000's say, inverting one channel on the scope and adding might skin that cat. There are two NOS P6007 on eBay at the moment for about $70 each BIN/ONO, x100 and handles 1.5kV AC and 2.4kV DC.

^That, old son is good natured

OK - decent scope, but be careful what and where you probe. My tendency would be not to probe with the T2 turned on - one slip with the ground lead, probe tip or your finger could spoil your day big time. I would turn the T2 off, attache probe connections and turn on again. But bear in mind that any complex feedback amplifier can oscillate - IIRC there are the odd single figure pF capacitors in there to stabilise the amp. Also probe impedance can modify the effect - either stopping the oscillation, making it worse, or changing the frequency.

Now you're hitting my buttons. A Quad-like array of Neoliths.......

I'm speechless. Who would? Why? Back on planet earth, ML recently introduced the Neolith; the design brief was anything goes with the only requirement that it fits though a standard domestic door. At around $100k you could buy 50 of them for the solid gold microsystem above.

Yup - that'll do it. Nice probe. If you can cope with x100 and x1000 attenuation.

What scope, what probes? Highly specified Tektronix probes only handle 300V for a x1 and 450V for a x10 non-destructively. Generic probes can be much less, or poorly specified.

This is the reason that Krell went over to some sort of dynamic biassing scheme, because running flat out class A was just not reliable. I had a late model KSA100 that demonstrated that perfectly. Typical Krell battleship construction, with superb engineering, and two fan cooled heatsink chimneys. Power transistors were rebranded as KrellA and KrellAA. It blew up three times in my ownership - same symptom each time, power transistors going into second breakdown failure accompanied by lots of smoke. Lat time it happened was after I had sold it on eBay for quite a lot of money. The buyer was actually on his way to collect from about 150 miles away - and I thought I'd turn it on so he could listen to it. Major league failure with plumes of smoke; phoned him in the car, apologised profusely and he went back home. This time it had taken out the drivers too, and the associated driver load resistors had ignited and burned part way through the board. Replaced the sand, using generic high power transistors and NOS obsolete drivers. Dremelled out the char and coated with conformal coating before replacing the load resistors. Worked perfectly, and the guy honoured the sale, paid the money after auditioning and off he went leaving positive feedback. I've also seen the same generation of KSA50 ignite too. But it is all down to component stresses - high power class A puts a combination of high voltage and high current through the power devices all the time. Smoothing caps and power transformers likewise need to be carefully thought about, since they are running flat out all the time too. But non-linear distortions, including induction distortion are much lower than class B or AB, which is why high end users like it.

I just love you guys - I'm still laughing five minutes in

Let's hope those few days stretch on and on and ......

And Cantor spent years in a sanitorium, such were the rigors of contemplating infinities.

I'm with you on that. I'm very selective what I leave on. Low power solid state small signal gear: Preamp (solid state), yes. Active crossover, yes. DtoA yes. Power amps and anything with tubes (8-channel power amp, CD transport, T2, BH original), no. If I'm going to do any serious listening, I power up whatever the heat generators are and have a coffee and sandwich - and everything is on song by then. But even with a solid state electrostatic amp, I definitely would not leave it switched on - parts are stressed both in temperature and voltage - and I would not want to leave a set of expensive electrostatic phones with bias permanently applied. Made that mistake with a pair of ML Aerius speakers and the film eventually disconnected itself (later ML's only trigger bias when music was detected, so they knew they had a problem).

Weirdly late to this thread. I just put together a retro system - simply because I had the stuff kicking around collecting dust for an eternity since I am incapable of throwing stuff out or selling it, and I wanted to remind myself of what this kind of gear actually sounded like. Thorens TD150/M75ED with original signal cable, Quad 33, Quad 405 into Koss ESP-9. I even had to fix the 33 (one channel dead; edge connector) and 405 (power transistors blown on one channel and terminally noisy 071 op amp on the other) before I could listen! It is frankly amazing how far we have come in music reproduction - that set up sounded at best a resounding "OK-ish". Fatigue set in within one disc. But it left me reaching for my primary headphone systems (T2 clone/Stax, or Dyna-something and selection of dynamics) or main loudspeaker system (Transporter streamer, Tortuga LDR passive, and Linkwitz LX521) with massive relief.

^This!

Have a great day!

^That is bloody glorious - totally mad but glorious! But I'll take your marbles and up you a glass armonium, designed by Benjamin Franklin

I'm with you on that. The DT990 (old version) is streets ahead of the K701 in neutrality.

It does make you wonder STAX's move to PEEK film rather than their tried and trusted mylar is behind some of this erratic behaviour. Looking at the material properties alone, PEEK is higher performance in pretty much all areas, so I can see from an engineering perspective why the change; water absorption alone is 0.1% as compared with 16% for mylar, which might be thought rather important for a component in an electrostatic transducer. But there seems to be a few reports of degraded performance over time - either sticking to a stator, or a drop in sensitivity of one side. The only mechanism I can think of is that the film is not getting enough charge so the force drops, so maybe it is not the mechanical properties that are so important and it is down to the processing detail of applying a highly resistive film and making a reliable contact to it. I had a pair of Martin-Logan speakers that happened to - the connection to the film failed.

Have a great one!

I'm a firm believer in showing products who's boss.

Bloody hell. I've chanced on an accident shortly after it has happened too. And you know what - if you were a few minutes earlier.....is what it goes though my head. The only biggy I've been personally involved with was back in 1991. I braked into traffic on black ice, and slewed out of control into the rear wheel cluster of an oil tanker. Blew his rear wheels and buckled his wheel rims. Blocked the whole freeway (the A1, UK). Got away with front impact whiplash. So I went out that evening and had the biggest steak and most expensive bottle of wine in celebration of being alive.

Dublin, Ireland. When you visit the Book of Kells, you exit through this library. It is just as mind-boggling as this picture shows. Any of you who get to Ireland for whatever reason, this is a must visit. We were there early Feb.

For some weird reason I read that as "nipple simulation". OMG - that looks like something that I make. A keep-one-hand-in-your-pocket test fixture.

There is an old Orpheus on eBay Germany at the moment for Euro24k item 301907794353. And another for UKP17.5k item 141918737646. Don't all rush now. At least the old ones don't have the silliness of the knobs and tubes magically sliding out of the case of the new amp.