EAR HP4 Tube Rolling Thread - Page 4

Just tried some Tung Sol VT-229's in the HP4. Weird tube. On initial listening, it had a lot of promise. However, as the tubes burned in, the highs went away, and the bass got bloated. They never recovered. So, I'd say avoid this one. I tested with HP-1, and simply cannot find any redeeming features to that tube.

ALERT: older tubes wearing too fast

In preparing my HP4 for shipment to its new home, I tested several sets of tubes that are going with it. To my surprise, I found that some of the tubes showed signs of major wear, even though they did not have a lot of hours on them. These turned out to be older tubes used as the output tubes (closest to the transformers). Tubes that showed significant wear included the Sylvania VT-229, Raytheon VT-229, and Valvo 6SL7GT. Some of these tubes were brand spanking new. After only a few weeks of use, they test as though they had thousands of hours on them.

There was no significant wear in the other pair of the quad, used as the drivers. The one thing that these have in common is that they are older tubes. I suspect that construction of the 6SL7GT changed somewhere around the late '50s. The stock Sovteks show no sign of wear in the output position, nor do the Amperex (GE) 6SL7GT, or any of the 6SL7WGT's that I tested. My guess is that the older tubes would last 6 months to a year in regular use (maybe less), based on the change in Gm I saw.

Recommendation: If you're going to use vintage 6SL7GT's, use them as the driver tube. That has the most influence on the sound, IMO. For outputs, use the stock Sovteks, a pair of 6SL7WGT's, an Amperex or other tube vintage 60's or later. That's all I've checked so far. An alternative strategy would be to buy a LOT of your favorite older 6SL7GT. If my measurements are correct, you'll need them. If anyone else has checked vintage tubes for wear after they've been in the HP4, please post.

Nik,

I just found this out when I packed the amp, so I haven't tried different pairs. Amperex and GE are the same tube (if there's a wire between the two filaments), and it's a very good tube. If I was keeping the EAR, my next move would likely be Raytheon VT-229's as drivers, with Amperex as outputs. If I'm right, that should give you most of the benefits of the Raytheon without wearing tubes out too fast. If it adds some of the punch of the Amperex to the midrange of the Raytheon, it could even turn out to sound better than a quad of the same tube.

If you like the Sylvania VT-229's, they should be safe as the first tube in each channel (toward the rear of the amp). The output tubes (close to the transformers in front) are the ones that showed wear.

Hi Nik,

I had the Sylvania's and the Raytheon's in the HP4 in different systems, with different cabling and different sources. There's no real way to compare them. FWIW, I really loved the Sylvania VT-229 with the HP-1. It got a clarity out of the HP-1 that I hadn't heard before.

Yes,

The Raytheons I've seen are short-bottle tubes that fit in the original case easily. That's one of the reasons I like them