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Two Exquisite 12AX7s

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I have rolled a lot of 12AX7s. USA and European vintage tubes to new manufacture such as Genalex Golden Lion 12AX7. My amp is very clear and can hear micro details effortlessly. Two tubes that always had my attention and I always come back to are the Mullard 12AX7 long plate and the RCA 12AX7 long black plate.

These two brands reproduce audio with beautiful sound. The tubes do not have the slightness shrillness, any apparent distortion and provide the most open soundstage I heard with a lot of black around instruments & voices.

But, the tubes do sound a little different. And, this difference will likely vary as which is best in a particular amplifier. If your amp is vintage, you may not hear any difference at all due to the stock vintage coupling caps response may mask the differences (small details). Most new manufacture amplifiers have better coupling caps.

All my amps sound close to the same due to all use K40Y-9 paper in oil capacitors and the most clear sounding power tubes I can find.

I find it hard to describe in words the sound of tubes, but here we go.

The Mullard 12AX7 long plate is ever so slightly more open sounding vs the RCA with a crystal clear sound. It is not cold sounding, but not warm either. It easily provides that 'wow' factor.

The RCA 12AX7 produces a little more warmth and is also very clear. On chimes it kind of 'rings' a little vs the Mullard making for a wonderful sound. The extra warmth would be better in a 'cold' sounding amp vs the Mullard.

On my amps I ever so slightly prefer the Mullard, but could not exactly say the RCA is second best if that makes any since. Either tube is stunning.

Both tubes are expensive. I can buy NOS RCA 12AX7 black long plate for $90 each. NOS Mullard 12AX7 long plate are $175 each. Source is Brent Jessie.

I heard good things about the rare early 1950s Sylvania 12AX7 black ladder plate. I just bought a pair and will be here next week. If these Sylvania 12AX7 sounds as good as the RCA or Mullard I would be surprised.
 
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What he is trying to say is that he believes you to be someone looking to illicit an argument. He likely does not believe there is a “right place” for such feedback. Also, the plugging of specific vendors or manufacturers is considered uncouth.

This sort of subjective feedback is seen by those with a technical background as heavily misguided and this topic has been pretty beaten up in a number of other threads. They will say tubes have no sound just parameters. They will take offense at the suggestion of oil capacitors resulting in revealing of all “microdetail”.

You are using the language of art to describe science and suggests you don’t have a technical understanding of how these devices operate.

But you took quite a bit of time to put it together which is admirable and shows you are looking to be helpful.

However without a description of the circuit it’s in or the parameters of the tubes it doesn’t provide any useful information besides marketing for Brent Jessie and old stock tube dealers.

It’s likely you are just listening to minor variances in samples interacting with your circuit. You could also rewire your heaters and use 6N2P-EV and save a ton of money in the process.

Anyhow, you are not alone in this misunderstanding.

Search the forum for information and it will come up in spades.

Rather than chastise like the other poster I think it’s better to be compassionate.

I’ve made similar mistakes in my life in many areas and wasted a lot of $$$ in the process.

After all we are all a bit off-put by someone suggesting our perception is rather out of balance.

Just trying to save you a headache.

All the best.
 
Ok, I will ask moderator to remove my post. I did delete my posting. Why would my findings start an argument? I have not posted here until lately and do not exactly understand this forum apparent rules. However, interest in the tubes forum of my testing of EF86s were well received. I was not suggesting to buy from Brent Jessee, just showing cost of tubes from one supplier. BTW- like almost all preamps, the tubes were operating in Class A.
 
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Sorry there was no need to delete the original post. I was just skeptical about the intentions which is probably a prejudice move so I apologize. Name dropping a distributor of cork sniffing status audio tubes was what set me over the edge. I am interested in open loop testing of gain devices to which their linearity can be scrutinized but I didn't see this going that direction with such subjective descriptions.

If you are serious and not trying to incite engineers then please re-post your original thoughts.
 
Ok, I will ask moderator to remove my post. I did delete my posting. Why would my findings start an argument? I have not posted here until lately and do not exactly understand this forum apparent rules. However, interest in the tubes forum of my testing of EF86s were well received. I was not suggesting to buy from Brent Jessee, just showing cost of tubes from one supplier. BTW- like almost all preamps, the tubes were operating in Class A.



No no. I didn’t think you wanted to start an argument.

I have zero hostility. Was offering considerate guidance.

He was speaking tongue in cheek. Let it roll off you like a ducks back.

Let me break it down in terms I think you might be receptive to (ie my own dumb mistakes):

In my early 20s I had an Audio Research Dual 75-A (lots of tubes). I loved that thing. I joked that the 75 meant pounds, not watts per channel. It could heat a room in colder months. (And in its defense it did sound wonderful)

I subscribed to much of the same thinking you do. I was simply a lover of music and a weekend tinkerer / hobbyist. I enjoyed the process. I wanted that warm tube sound people spoke of in reverence. I spent untold sums on NOS tubes in a quest for divine sound. How could it be possible that all these people are wrong?

One day it needed service and I brought it in to this local fellow I was tipped off to as being the best (Rest in Peace John!).

He designed amplifiers for a living (mostly for guitar), had an engineering background and his stuff went for very high ticket prices. He was known as the best technician within a 100 mile radius of my home in a densely populated area.

He then proceeded to tell me all those NOS GE tubes were just folklore, explained the “magic tone” mentality, the marketing shtick, and so in interspersed with this vast history of tubes, solid state, audio, guitar etc. It was like a complete history class condensed into 35 minutes.

I thought: This man clearly is a good engineer and knows a lot however he must just have poor hearing and just doesn’t get out much. I had experienced this differences for myself! Plus, I had so much stock in the choices I had made. I did not want to feel foolish, or that I had been duped. I considered myself better than that. I wrote a twelve page paper that year on cognitive bias for crying out loud!

He could see I didn’t believe him and just kind of beckoned me over to the bench. He then proceeded to explain to me with a scope and his shelf of test gear what was happening.

He was very patient with me and went into painstaking detail about how everything worked. I think he was just excited to see a kid showing up with a 50lb tube amp.... most of his customers were in their 40s and above. He said to me usually he doesn’t contest customers who have these kinds of views because it can be really upsetting to them and bad for business, but he wanted me to know so I wasn’t blowing cash I didn’t have for something he knew was backwards.

He also showed me the array of resistors that had gone way out of spec, the electrolytics that were pretty neat up, etc. and the effect these were having on the circuit performance.

Essentially what I was doing was much like listening to hi-fi a guitar amp with some of the tone controls turned up.

What I imagined as the sound of tubes was really just the different tube parameters behaving differently under unique stresses brought about by the design mixed with part deterioration.

After he swapped out all the aging parts in the amp and brought it back to full spec I came by again he put in all my super coveted NOS tubes, showed me everything again on the scope.

He then swapped in electroharmonix tubes, which I cringed for a moment looking at (those are guitar tubes for god sake!) and proceeded to do the same.

Each electroharmonix tested and performed at the same level or better than my NOS tube compliment at a small fraction of the cost.

Also the NOS Bugle Boy 12ax7a was beat to death and performing poorly. When the amp was repaired it was evident that I’d been listening to an amp with a bad tube for some time with absolutely no awareness.

It sounded great to me! But I was listening to distorted sound, completely oblivious.

It was evident to me I had made a mistake. I felt dumb. My ego was hurt. But a valuable lesson was learned.

If he had just yelled at me and exclaimed “Tubes don’t matter at all you foolish kid!” I’d have discounted him as a crazy old man hard of hearing. It was his patience and compassion that won me over to a more science based approach.

I made a nice chunk of change unloading NOS tubes that summer..

There’s nothing inherently wrong with NOS tubes, some NOS were manufactured to higher standards than today’s new production and can be considered “better”. However, the costs are outlandish for many of the classic tubes as NOS now and the differences can be easily mitigated by careful design and attention to technical details.

This stuff about tube attributes came from guitar culture in which they felt certain tubes had that “certain something” which gave their tone an edge. They largely weren’t engineers, just musicians doing their best to describe what they were experiencing in the way they knew how - the expressive language of art. They didn’t alter these “classic” amps - who would do that and ruin resale value!!? So, they used tubes and their inherent variances to get the tone they were after.

To me now this sounds much like exclaiming the new oil capacitors in my microwave oven reveal new layers of flavonoids hitherto untasted in my microwaveable burrito.

Unfortunately many are too entrenched in their beliefs to exchange in civilized dialogue.

Let me be clear:

Without a shadow of a doubt I am clear that the thousands of audiophiles that extoll any virtue of a tube using language like “airy” or what-have-you are simply optimistic and misguided folks doing their best to make sense of a complex technical occurrence using the language which is familiar to them. (And yes that includes much of the professional reviewing community.)

I know because I was one of them.

They often spend much money in this pursuit, aided by those who are happy to relieve them of their excess cashflow and may have similar misguided beliefs.

Some may be perfectly happy doing this... I’m not making a moral call here.

I personally had to be willing to accept the blow that I was quite wrong, and had wasted a lot of money for quite a while.

The solution is to either trust only seasoned engineers who lack a profit motive (many of them here; with very little patience for this kind of thinking anymore because it’s at epidemic levels) or begin learn yourself.

Of course you can also do both.

Not relevant to the topic but I had no idea John the engineer had terminal cancer when he did this for me. Even long time customers apparently were unaware.... I guess he thought it would be bad for business as people would think twice before dropping off their prized kit to a guy with stage 4 cancer. This guy somehow worked until just before they put him in the ground. Saw him a few times after this experience and then poof he was gone. I’ll be forever grateful for the time he took to guide me compassionately in a much more fruitful direction. So, in the same spirit I wanted to express my thanks to those out there who have given so much to idiots like me.
 
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Sony, feel free to revert your post. It will be there for others to find and make up their own minds.

Also, feel free to continue in this discussion.

Just because you got off on the wrong foot doesn’t mean you can’t learn.

I will make you a bet: for much less than the cost of those two pricey tubes this thing can sound even better than you think if you can stay open minded, ask for the guidance of others, and be willing to get your hands dirty.

You have the KA-95 by Knight?

Here is the schematic:

Page 1: http://oldtech.net/Knight/KA-95/schem2.gif
Page 2: http://oldtech.net/Knight/KA-95/schem1.gif

Have you replaced anything but the tubes?

Do you own a multimeter that can handle 600V?

Do you have the service manual?
 
We all love a good tube review but this crowd needs more meat and potatoes. We want circuit specifics and other specific quantitive test data along with your listening review.
He can come around.

Not everyone has your caliber of comprehension. You can’t expect a forum filled only with those more seasoned than you or at some predetermined level of baseline comprehension. It’s the internet... you’re screwed. Let’s move on.

My hunch is at some point in your life you found yourself making the less than ideal move in the room full of experts and veterans.

Why not be helpful to him and speak to him like a capable human being? He just might be more reasonable than you think.
 
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