EAR HP4 Tube Rolling Thread - Page 2

Why not? What would you do if a tube wore out?
It's a good amp that can be made better. Some tubes are better than others. Why shouldn't I find the best ones?

Why do you thinks it's a Sennheiser amp? This amp is not OTL. It's got some pretty hefty transformers at the outputs. Note that one pair of jacks is for low impedance headphones, and the other is for high impendence headphones. It's designed to play headphones. The ones it works best with depends on how it's tubed.

Skipping over several experiments, which I'll try and post at some point, I'll skip over to the best of the short bottle tubes I've tried so far.

Sylvania 6SL7WGT Brown base. I've tried a bunch of these. The low end in particular is better with tubes made in the 50's, and gets lean as manufacture date hits the late 60's and 70's. Sylvania also made a black base version that appears identical to the Philips, and also was less than impressive sounding relative to some others. This is a very smooth tube, with great midrange, but lacking a bit in punch. Another version of the same tube was made by Tung Sol, also brown base. There is also a Westinghouse, which appears to be a rebranded Tung Sol. These are aggressive sounding tubes, with great highs and lows, but lack fullness in the midrange. So, the question became, could I get the midrange of the Sylvania's paired with the frequency extremes of the Westinghouse/Tung Sol types? The answer was yes. I used a pair of Sylvania's close to the inputs, and a pair of Westinghouse 6SL7WGT's as the drivers. This combination was the first that really let me see the potential of the HP4. It retained the midrange I wanted, with the in your face sound of the Westinghouse rebranded Tung Sol (which, to complete the chain, was probably manufactured by GE). The weakness of the tube set might be an almost overly clean type of sound. Not the best for high end "air". Still, this sounded better than almost anything else I'd heard to that point.

However, the best was yet to come (I had that case built for a reason). To be continued...

I’ve been slow updating this thread. Too busy listening…

The first set of tubes that I used that really showed what the HP4 could do was the Amperex 6SL7GT. This is a tall bottle tube, with chome plates. It’s got a clear top, with the getter on the side. My guess is that Amperex only marketed the tube, but that is was actually made by GE. There are a bunch of GE tubes that have the same construction, but most that I’ve run across are short-bottles…ideal for the HP4, and on my list of tubes to try.

This tube does it all. The headphone that I’m using to guage these tubes is the R10, my primary headphone on the EAR. I’ve often described the bass on the R10 as lean. Further, the R10 has a tendency to add a coloration to the sound, that I suspect is due to lack of dynamics. While it often sounds absolutely gorgeous on acoustical music, high powered electric music can be found wanting. Not with these tubes! The first thing you notice is impact. A drum sounds like a drum, with fundamentals that go deep. The speed of the R10 picks up piano notes better than any other headphone I’ve heard, if the amp will let it. This tube lets it. The laid back coloration that the R10 can exhibit is just not there with this tube. Clean, clear sound. Smooth tube delivery, but faster than almost any solid state amp I’ve heard. This would have been the end of my tube rolling in the EAR, I think, but the tube gods decided otherwise. One of my quad went noisy after being in use only a week. Tubes, particularly NOS, are at risk of this, particularly during the first month. So, one of my best tubes was no longer suitable for audio use, and I had to roll it to…

Sylvania VT-229. A classic. The matched quad of these I used was from 1943. Gray plates, with a bottom getter. The first thing I noticed was the detail. As clean and as clear as the Amperex was, the Sylvania did it better. Everything was laid out in front of you. But something wasn’t quite right. The bass response on this tube was not as good as the Amperex. Where I had been listening to bass lines, they started becoming indistinct on the R10…bad. The impact that the Amperex delivered wasn’t there. Imaging was another issue. As good as the detailing was, it didn’t seem to cohere into a soundstage. I finally realized I wasn’t enjoying music as much with this tube as with the Amperex. The differences were not large, and my description of them is making them sound bigger than they were. To put it in perspective, I would not be unhappy if I had to live with this tube on a permanent basis. But, having heard the Amperex, I knew it was possible to do better…

Valvo 6SL7GT. When you get into tubes, you learn about Telefunken and Siemens very quickly. But they weren’t the only German tube makers. Valvo was the third largest of the German manufacturers, but their tubes didn’t give up anything in quality. The Valvo 6SL7GT has grey plates and a bottom getter, in the tallest bottle I’ve seen in a 6SL7. These have only been in the EAR for two days, so impressions don’t have as much time on them as the other tubes, but…

Wow! The Valvo may be the most complete of the 6SL7’s I’ve heard so far. It’s got the detail of the Sylvania beaten, with the impact and fast sound of the Amperex. I had looked at the bass response of the R10 when the VT-229’s were in place, and got nothing below 30 Hz. Switching to the Valvo produced output down at 25 Hz. This was felt, rather than heard, but it was there. The soundstage has snapped back into focus. Much clearer than the VT-229’s. Every instrument has its place. Nothing sounds crowded or smeared. You can clearly hear background instruments being recorded at low volume underneath the leads, if you want. The sound of this tube with the R10 is extremely seductive. This is as close to transparent as I’ve heard in a headphone system. It’s difficult to describe a sonic signature, because it’s difficult to hear one. What you hear are instruments playing music, not the audio equipment. So far, this is the best of the tubes I’ve heard in the EAR…but the real test will be what it sounds like in a week or two…

The Valvo has brought my tuberolling the EAR to an abrupt stop. This is a subtle tube. At first listen nothing stands out. As you listen further, you realize that it's doing what it's supposed to do. Everything is there, just nothing stands out because the music itself is presented as a coherent whole. The tube addresses IMO the weak area of the R10 (bass) nicely. It doesn't make the bass loud, but controls it perfectly. So, a double bass sounds like a double bass. You can hear what the player is doing to the strings. The level of detail is immense. You can hear every nuance of a singer's voice...and yet you only hear it if you listen for it. It doesn't jump out and scream "look at how detailed I am!". It just presents it. Background noise...what background noise? The extreme quiet of the amp allows presentation of a lot of very low-level information that is part of what makes the presentation work. I was just able to order a couple more quads of this tube for backup, and am very happy about it. Unless something weird happens, tuberolling that amp is done. It's now handling every headphone I throw at it beautifully. Why mess with success?

It’s time to add a few more tubes here. I’ve switched the R10 over to the Supra SET amp, so I’m now trying to optimize the HP4 to the Grado HP-1 headphone. My long-term impression of the Valvo’s is that they’re as close as I’ve come to getting the EAR to drive the R10 properly. The imaging is as good as I’ve heard, detail is excellent, and both frequency extremes are well represented. However, the more I listen, the more I realize that there’s a coloration present. It doesn’t obscure anything, but it’s like looking through a tinted glass. You may not even notice it. I certainly didn't at first, but it pervades everything. The more I listen, the more it bothers me. This coloration is not present on the Supra amp, which is OTL. So, using the HP4 with HP-1’s this time…

RCA 6SL7GT: An overall steady performer. Coloration is less than Valvo’s. Imaging good. Detail good. Does not seem to get a lot of detail at the low end, even though lows are well represented. I’m not sure that it’s got the entire upper spectrum either. I’m probably being more critical of this tube than I really need to be. It greatly reduces the coloration I was hearing (my suspicion is that the coloration will always be present to some extent, as I suspect the source is the HP4’s transformers.) I could live with this tube. However, there’s a sense that I could do better.

Tung Sol 6SU7 GTY. This is a 6SL7 variant with shaded glass. NOS quad manufactured in 1951. The feeling you get with this tube is clarity. There’s more detail than the RCA’s. Bass is better integrated and very detailed. For female vocals, it’s heavenly. Soooo smooth!!! And that’s the rub. Put on some aggressive rock, and it stays smooth. The tube simply won’t hit the dynamics needed to play rock music convincingly. The apparent polish is an artifact produced by lack of dynamics. For some types of music, this tube could be someone’s answer, but it’s not mine.

GE 6SL7GT. Looking at the GE tube, you know who made the tubes marketed by Amperex. These come in tall and short bottles. Most have the distinctive chrome plates, and an odd wire that goes between the two posts at the top, which glows along with the posts. It’s a unique construction. The short bottle sounds close to how I remember the Amperex tubes. Very good highs and lows. Little coloration. Great detail. It’s a signature GE sound. However, it has the main drawback of most GE tubes I’ve heard. I have no idea why this is, but GE tubes are bright. True so far of 12AT7, 6SN7, and now 6SL7. Perhaps over time the brightness might eventually burn-in. Who knows? The sound has been completely stable for three days, so whatever’s going to happen isn’t going to happen fast.

Got my Sylvania VT-229’s warming up now…

Sylvania VT-229 dated 1944. Tall bottle, black plates. The most detailed 6SL7 I've heard. Immense increase in depth of image. Slightly dark sound, minimizes transformer coloration. Very smooth. This tube is a superb driver for the HP-1. There may be a slight loss in dynamics compared to the GE or Valvo tubes, but it's not a problem with HP-1 (although it's a bigger problem with R10). This could be my favorite tube for the HP4 so far.

The short answer is yes, although it might be awhile. I want to live with the Sylvania's for awhile. I've got two boxes of 6SL7's. I've started with the ones I thought most likely to be good, but there may be some surprizes left.