[OctavianH]

I want to end my 4654 chapter, but I have 2 things more to do. One is to check if Valvo 4654 sounds similar with Philips 4654 and then to try a pair of Tesla 4654. The problem with these tubes with P8A base is that they are not easy to compare if you do not have a dedicated pair of adapters for each of them. Because removing and inserting into adapters is a pain. And you are always afraid not to damage adapters and why not tubes. Prices are still decent for these if you have a little bit of patience, but they are very old and an idea unstable when used. I observed that some of them start with a lot of current in the first hours and then, randomly currents decrease 4-5mA. One of my pairs measured 18mA and 20mA in the first 30 minutes and after 4-5 hours of usage I measured 14mA and 20mA. One of them decreased from 18mA to 14mA while the other remained at 20mA. Why? Hell knows. Here I have manual grid bias, fixed and meters to check, but I wonder if these would work nicely on auto bias or amps where you cannot check anything on bias. I have no idea, I would be very curious to understand more about this. Anyway, picky as they are, I can use them and I like them a lot, soundwise.

So let's start. Valvo 4654.

Boxes were some simple military boxes, not very well preserved. Nothing to see. Tubes instead are new.

Different type of markings than the Philips red paint on base. Even those side contacts are somehow rounded while on Philips had different form, more "rectagonal".
I cannot see too much inside and I do not want to clean these too much. But I tried to make a better photo of the upper side.

Does not seem very different than the Philips ones. On amp, well am idea noisy in the first minutes and then the glass was crackling for a time, but I guess that's normal.

I tried them for a few hours on the amp with Brimar 6SL7 and I think these are close sounding to the red painted Philips. Very good sounds, I was not able to decypher drastically differences in sound from those. Same style, transparent, creamy, holographic. If for example on EL42 a Philips sounds totally different than a Valvo, here it's not like that so I start to think that all of these ST shaped 4654 are similar sounding. But as I said it's hard to compare these without a lot of pairs of adapters and months. I'll do this but you will be old when I'll finish and you'll not care anymore about them. Until now, I cannot say I have a preference soundwise, but I like more those red painted round logo Philips and that pair is 15% matched so I prefer to use it. Only because of comfort, not because of something else.

Will follow Tesla and I'll shut up forever about 4654. I'll continue to use those red painted and keep these as a backup pair.

 

[OctavianH]

And now a post regarding a very interesting tube. Visseaux 6L6. Found this by mistake at a seller where I wanted a pair of Tesla 4654 (or at least 1 piece) at a decent price. Was auctioned as Neotron 6L6 and got no interest. No problem, when people do not want such a tube I am always here to help. Because this is a VERY interesting tube. I'll show you.

It's relatively ugly compared with the beautiful red painted EL50, but I like it. And this pair measured very high. I put it at -21.2V on my fixed bias setting I use for KT66! And on that setting both sit at 22mA. Incredibly strong, I was expecting to bias it at 807 levels around -18.5V. But no, this one goes much higher with currents at that value.

On the amp, well brighter than RCA 807, quite linear but I do not want to say more. I'll make a separate chapter with 6L6 one day, I have a few pairs here and never had time for them because I was too excited by 807. I'll stop one day and spend some time with 6L6. Good catch this pair, really cool tube.

 

[triod750]

I saw this pair too and liked what I saw. Tubes with personality!

 

[triod750]

I observed that some of them start with a lot of current in the first hours and then, randomly currents decrease 4-5mA. One of my pairs measured 18mA and 20mA in the first 30 minutes and after 4-5 hours of usage I measured 14mA and 20mA. One of them decreased from 18mA to 14mA while the other remained at 20mA. Why? Hell knows.

Someone told me the other day that back in the days they revived picture tubes by feeding them higher heater voltage for a while and this made them work again. Then someone came up with the idea to try the same with misbehaving power tubes. They got good results with pretty many of those by raising heater voltage by ~ 20% for five minutes and then emission went up considerably for quite some time. They used a lot of tricks back then...

 

[OctavianH]

I saw this pair too and liked what I saw. Tubes with personality!

It's a very sturdy and good sounding tube. Visseaux is brighter but the 6L6 type is muscular. Combining brand type with tube type goes into something cool. I like it and I will come with more and more about it. What a surprise was this. European 6L6 are cool, rare and I want to look more into them, if budget allows, of course. I stick to my rules and plans. I like this for sure more than Sylvania 6L6GAY I have here (both clear and grey glass versions).

 

[OctavianH]

A cool blog with some cool pictures.

 

[OctavianH]

I wanted to read what others think about Visseaux 6L6 and found this guy who describes perfectly what I hear.

I have my favorites though and usually go w/ Tung Sol 6550 Black Plates or Amperex EL-34 Double D Getter. However, I am always impressed when a few times a year I plug in some Visseuax 6L6 straight bottles! WOW!!! Incredible punchy bass that is very fast and articulate and I swear sometimes I think the top end is more natural and detailed than my Amperex EL-34, which happens to be about the best top end tube I have as a general rule w/ the TS 6550 being more robust and soundstage MONSTERS! The top end of the Visseaux though are more than just detailed, it is the way cymbals become VERY brassy and natural sounding that just drop your jaw! The midrange is not TS 6550 BP special, but what is? They maybe lack just a little of the soundstage magic of the Amperex EL-34, TS 6550 BP and Sylvania 8417 but it sure ain't by much!

And he also does not like Sylvania. Cool, I'll have to read more about these. And listen more to them.

 

[OctavianH]

I always considered these grey glass input tubes, regardless of the tube type, as veiled somehow. That smoky atmosphere, loosing some detail and focus. For certain genres and some amps this might be good. For Elise/Euforia users those 6SN7 VT-231 grey glass were on top of the preference. I had at the time some Ken-Rad and RCA. Sold them a long time ago. Those were smoothening the grainy sound of the amplifier. But well, Eternity has already low distortion, a clean low distorted sound and there are not quite making the trick here. So I rarely use some grey glass on input. An exception was Psvane CV181T2 which was clean enough sounding but well, not quite tubey and too much towards neutral and dry. In the meantime I stopped using non-NOS tubes so I do not have that one anymore. But why I'm writing this, because with Visseaux 6L6 I was able to enjoy a few of them after a long time.

For example this Tung-Sol 6SL7. I have a few of these 6SL7 or 6SU7 tubes from Tung Sol and I appreciate them. One of the best 6SL7 available on the market. This grey glass one was not often used because of the "veil" but here sounds quite good on top of the Visseaux signature. Bass remains punchy and extremely fast, while mids are an idea smoothened. Yet, Tung-Sol is fairly linear and does not force anything. Good pairing and a surprise.

Another good example was RCA 6N7 grey glass and I guess also my Tung Sol 6N7 black glass might work well with these. I have to try this later.

 

[Isaacc7]

I am finally trying out a tube that I got interested in almost 2 decades ago. I read the story about how Sylvania made a 6b4 replacement out of a triode wired 6av5. A 6b4 is a directly heated, 6v equivalent of a 2a3. The 6av5 is a run of the mill TV sweep tube so I was immediately intrigued by the possibility. Later testing revealed that certain 6av5 tubes could be driven to much higher levels than a 6b4 could. And while they sound very good, they apparently don't quite measure up to the best 2a3 or 6b4 tubes sound-wise.

I'm using some Sylvania 12av5, the ones that Tubelab found to be the most rugged. By the time these rolled out tubes had stopped looking good lol.



Like most sweep tubes the screen grids on these have a really low maximum voltage so they won't work in every amp. I'm running them pretty conservatively 300v 40ma in triode. George said that these particular Sylvania tubes should be fine at those settings but other versions of the tube won't be.

Anyway, how do they sound? Amazing. With b36 drivers, these tubes are giving me a smooth, full, detailed sound. It is giving similar vibes to DHT amps I have listened to in the past. Voices in particular are really nice. I was a bit worried because they have a reputation for being prone to oscillation. When Tomas was building my amp I had asked for grid stoppers to be installed to help mitigate against that. He rebuffed me and said his ams are really stable and didn't need them. Turns out he was right.

I think I have some RCA or maybe some GE 12av5 around here as well. I'll probably run those around 275v. In addition to the 6 and 12 volt versions there are also 17 and 25 volt versions as well. I'll keep these in for the next week or so, possibly trying out other inout tubes.

 

[OctavianH]

I am finally trying out a tube that I got interested in almost 2 decades ago.

Well, you are at least 15 years ahead of me in tube understanding. I found about tubes 6 years ago. No problem, we will discuss in 2038 mister when I'll do what you now are doing. Reading your posts and also other info about these I realize more and more that Eternity is limited at trying optimally several tube types because of the relatively low operating point it has. At least for output. I would love to be able to compare the same tube at different Vplate and see how this changes. Of course besides that I need to understand more about feedback and amplifiers design and so on. You speak about several amplifiers you heard during the time and that you worked somehow in the industry selling some equipment (if I remember correctly). Well, that's a huge advantage over folks here to be able to see the bigger picture and understand more.

 

[OctavianH]

Another blog with interesting stuff is here, a Direct Heating Triode blog. Or here, ElectraVolt. For example this article, Famous Direct Heated Triodes (DHT's) and the Unknown, is addictive. This guy knows how to tell a story.

 

[OctavianH]

I returned to this combo after a few months, more to check if it still remains on the table. It's true it cannot dethrone 4689 or EL50 but it has its own place. A very special tube is this GEC ATS25 and I still enjoy it a lot. One of a kind.

 

[OctavianH]

I wanted to play with some Mazda smooth sound on top of GEC ATS25 and my only choice was Mazda 6BM5 pentode. So I made again this crazyness of putting my 6AQ5/EL90 -> 6V6 on top of 6V6 -> 6J5 adapters. Sounds quite ok, but gain is low. I am past 12 o'clock with the volume and I almost never do that.

These 6V6 -> 6J5 adapters are useful to me, because can turn into input amost everything can be biased and works in output without using adapters created for input. But of course, I do NOT advise this. I checked all of them in detail and understood exactly what is happening and even in this case might be problematic. One more thing I can do is to use 6J5 adapters on the 6V6 slots, that can also be a trick to save some adapters, but of course, many input tubes are not suitable because of ratings to the output duty.

Hmm, something is missing in that picture right? Some color. This is the best direct heater triode available. Heated by nearby tubes and specially made for audiophiles as Vint-Elec is advising. Some say it enhances euphony and musical enjoyment when used.

 

[OctavianH]

Let's add an artistic picture. I doubt I'll use too often pentodes on input on this kind of adapter on adapter so why not, let's celebrate the moment.

While I consider this an interesting sound I do not really feel it will be an option for the future, it was an experiment. I bought these 6BM5 because they were cheap and I wanted a pair of EL86 from the same seller. Definitely not bad but I start to remember what Tomas said, in short words "You'll have plenty of options to choose, why to use a low gain pentode in input". Well, I guess he was right. The only example where I can contradict him is EL3N with EL50. There is a magic synergy there, which cannot be explained. But what is happening there is magic.

 

[Isaacc7]

Well, you are at least 15 years ahead of me in tube understanding. I found about tubes 6 years ago. No problem, we will discuss in 2038 mister when I'll do what you now are doing. Reading your posts and also other info about these I realize more and more that Eternity is limited at trying optimally several tube types because of the relatively low operating point it has. At least for output. I would love to be able to compare the same tube at different Vplate and see how this changes. Of course besides that I need to understand more about feedback and amplifiers design and so on. You speak about several amplifiers you heard during the time and that you worked somehow in the industry selling some equipment (if I remember correctly). Well, that's a huge advantage over folks here to be able to see the bigger picture and understand more.

This is wildly OT… I was smitten by the audiophile bug while I was in college in the early 90s. Went to a high end dealer and heard actual imaging from speakers and it blew my mind. First job out of college was selling audio gear. Mostly sold Denon but also Parasound, Rotel, and McIntosh. I got to go to a lot of people’s houses and hear a lot of different systems. I had always been enamored by tubes since I was a kid. We had a really old DuMont TV that used tubes. Watched dad fix it by yanking tubes, going to the hardware store, using the tube tester, and getting replacement tubes. Heard my first tube system at the job. Customer had a McIntosh 240 and a pair of Spendor speakers. It was love at first listen.

Later on I moved near Washington DC and discovered a dealer that only sold tube gear. No home theater, no TVs anywhere. He had all sorts of amps, speakers, you name it. Here’s a picture I took 6 or 7 years ago.

That’s a pair of Atmosphere OTL amps driving a pair of Omni directional speakers. Probably about 30k worth of a system. Some random Conrad Johnson amp and Italian gear on the back table. Check out all the albums to test out gear! There were another 3 rooms like that filled with LPs. Turning to my left I saw

That’s a custom line preamp using top cap tubes, several vintage amps, a field coil speaker from the 40s I think. Oh, and a 2 chassis Jadis preamp that probably costs upwards of 20k just sitting there. There are 9 or 10 different listening rooms there just stuffed to the gills with gear. It’s a real wonderland for tube lovers. Here’s a shot from some years before that:

That’s an actual Western Electric Voice of the Theater horn with a vintage WE amp. Oh, and some custom made amps strewn around. It’s just absurd what he gets through there.

I hung out there regularly for multiple years listening to all sorts of amps and speakers. Also got to go listen to some of the custom systems he had made for clients.

At the same time I started reading Audio Asylum religiously. Years later I hung out on DIYaudio absorbing more technical information. Was able to connect some dots and figure out what I liked and what probably caused what I liked. It was quite the education and tons of fun of course. I drifted away from audio for a while when I moved overseas but came back to it with a vengeance over the past 4 years. I’m still learning about the technicalities about amp design but I known just enough to be dangerous lol.

Now back to our usual tube rolling…