Tube rolling in Hagerman Trumpet MC


I have been doing some tube rolling in the Trumpet MC and am trying to be a sure as I can that I don't substitute a tube that could cause a problem.

It looks like from my very poor reading of the schematics that the V1 12ax7's are for initial gain pre RIAA, the second pair V2 are phase splitter post RIAA, and the 12au7's V3 are driver/output/cathode follower (not sure about that last one as the circuit doe not look like a typical cathode follower circuit and even looks like anode follower?).  Any enlightenment here would be helpful.  This is because even tubes that are considered "drop in" substitutes are not actually identical on the manufacturer spec sheets.  For instance the 5418 has a slightly higher heater current than and au7 and there might be another parameter that is different (Vhk?).  Even the 7316 is slightly different.  And of course the 5751 has lower gain than a ax7 as well as other differences.  Many of the differences are still within spec, and given what I can see from the online schematic of the Trumpet MC, look like no problem, but I just want to make sure.  I have emailed Jim Hagerman and he has been helpful when I have, but I hate to keep bugging him with my questions, so I will bug you guys instead.

Thanks for you help and the bandwidth.

oceanica

555 is a timer, probably used to delay application of plate voltage after filament voltage is first applied after turn on.

To those who recommend the Sbooster, I asked about this too. I noticed on looking over the schematics that Mr. Hagerman used a 555 “chip” as an internal power supply to get the voltage to the rails (at least that is what it looks like to me with my very limiter ability in that area). So, if there is no way to bypass the internal switching power supply,, how would and external LPS make any real difference? JH, basically had the same opinion and also said that some folks who tried it reported improvement.  

Given confirmation bias, etc., I would be happy to try an Sbooster if someone would loan one to me to try. I would cover shipping both ways if needed. Otherwise I am content to leave that out.

 

Well, speaking from my own experience, the difference from the switching power supply to the sbooster was not a subtle one at all. It was pretty transformative. As to why, I don't know enough to really answer authoritatively. I have a general understanding that switching power supplies are "noisier" and that good linear power supplies (like the sbooster) have a lot more power filtering. That being said, I highly recommend the power supply upgrade over a tube one any day of the week.

Yes, 555 is usually a clock function, looked like it was doing more than that to me, like it was somehow involved in getting higher dc voltage to the rails.  But, my ability to read the schematic is pretty poor, so…

When I asked, I saw another post a while back someone asked JH about it and he said it didn’t make much sense that LPS would make any difference.  But, I am open to trying it as long as I don’t need to put $500 into what might make no difference in my system.  I could see where if one had a mostly digital system, the noise from a switching power supply could cause some interference.  My chain is strictly analog.

There are such things as well designed SMPSs that don't add any more noise than a good linear supply, like in the Berning amplifiers for many years now. I would not fret about a well designed SMPS, and I feel confident Hagerman knows what he is doing.  They got a bad rap because often used in el cheapo gear, which the Hagerman is not.  On the other hand, if you have good evidence that the linear supply is better  in this particular unit, then I do understand your dilemma. Why not enjoy what you have for a while and then consider the upgrade at a later date?

@lewm 

chickenoregg, Regarding the E80CC, Jim Hagerman probably would not approve on the same grounds by which he did not approve of the FQ7, the excess heater current requirement. And the FQ7 is more like a 12AU7 than is the E80CC.  The fact that you got away with subbing the E80CC with a 12AU7, and I got away with subbing the FQ7 for the 12AU7 in my Quicksilver preamp (with audibly positive results) have no bearing on the question of the Trumpet.

Yes, I hadn't read back far enough in the thread to see that. Not that I needed to to know a manufacturer will always advise against any kind of risk that creates liability for them.

You asked about my statement, "Honestly, I think tube rolling is way over-rated and prone to expectation bias on the part of the listener." To which you responded, "I am genuinely curious to know what gear you rolled what tubes in to no or little effect?"

First, I did not and would not say there is NO effect, but I would say it has little effect, and here is what I mean when I say that:

There is no need to be defensive, it was a genuine question not an accusation. I have clients with certain pieces of gear that rolling tubes has zero effect on. Rare in my experience, but it does happen. Was curious if you also had had that experience so I could note it for future reference.

 (1) Tubes age; any beneficial effect you hear at first is probably not going to last forever for that reason. 

Different tubes age differently, some die a slow tedious death, others stay fully with you until one day they die in their seep. But also, let's be real here, most NOS tubes will sound great for thousands of hours. Many over 10,000 hours. And not through some miracle, but because they were designed to.  If the #1 reason you cannot hear a substantive difference from one tube to the next is old tubes, you should take better care of your kit. Also, a tube may lose gain over time, but it doesn't go from having personality to sounding generic, it just won't work as well.

(2) There is a lot of fraud these days in vacuum tube sales in that vendors know what audiophiles want and the market is replete with fake copies of TFK, Mullard, Amperex, etc, branded tubes.  That would deter me from making new purchases of rare NOS tubes for fear that they are copies. I do have a stash of all the named brands that I purchased NOS back in the 1970ss in their original boxes, mostly 12AX7, AT7, and AU7.  As well as 5687 and its congeners, and yadayada. I trust my stash but not some other guy’s recently purchased samples. 

With all due respect, this kind of exaggerated fear mongering is dangerous and frankly irresponsible. How is it that you are the bona fide expert on market conditions in 2025 when you cite the 1970s as the last time you were really engaged in the market as a buyer.  That was fifty some years ago. You even clearly state that your distrust (and thus behavior) is rooted in anxiety and fear, not in fact. The market is not in fact "replete with fake copies" nor is it an organized criminal conspiracy. 

I sell tubes, and in order t0 sell tubes, I buy tubes. Close to $1,000,000 worth over the past three years, and I buy everything from a single tube to a $50K+ collection. I have done and do business with a staggering large cross section of sellers. And I have been deliberately ripped off exactly one time. I can count the number of fake tubes I've come across on a single hand — and I have hundreds of thousands of tubes.

There are certainly those with a wayward moral compass and a casual relationship with truth— there isn't a market in the world that does't have that, but the idea that not getting ripped off is the exception is absurd. In a way, this kind of thinking and behavior is in part responsible for the increase tube prices, because it not only kills trust, it creates a market place where every buyer is a scared, nervous, often confused mess trying to navigate a world they don't really understand, so they jump at every noise and shadow they think might be the tube boogeyman coming for them, and because they don't trust anyone, they won't ask for help because they are afraid of exposing themselves as an easy mark. This leads to more returns, which means time and money. It also means sellers feel constantly accused and attacked, and then, often in misguided ways, try to find ways to protect themselves and their business in ways that just perpetuate the problem.

(3) My prior experience tube rolling suggested to me that the expensive rare brands, even authentic ones, do not always sound as good as some of the modern tubes made in the far East or in Eastern Europe, let alone do they sound any better.  I will not make any generalizations, but when I compared a slew of different NOS 12AT7s at the input of my Atma-sphere amplifiers, probably about 20 years ago, the best sounding without any doubt were tubes made in China and purchased from Billington in the UK.  Problem with them was a short lifespan. 

Unclear how having a 20 year old preference for cheap Chinese tubes supports your position that there is little effect in tube rolling. Sounds like you actually thought they were significantly different, in fact.

(4) Tubes depend upon the contact points between the pins and the tube socket.  Tube sockets do not always age well or maintain a tight fit on the pins.  This alone can cause the sensation that performance is fading.  Few of us pay attention to that and even fewer of us clean tube pins and tube sockets periodically to assure good contact. (I do pins with Q tips and sockets with tiny wire brushes made for the job,) When you pull one tube and replace it with another, you are per se cleaning the tube socket by friction and by the fact that some dirt comes out with the pins of the old tube. That is one cause of a false positive sense of achievement. 

I don't want to speak for everyone, but I think that is safe to assume that if you are reading or participating in this thread you know what a socket is. This also doesn't support your position that there is little effect in tube rolling. If your sockets are so old, dirty and  oxidized that they are impacting the sound quality of your kit so much that you think the most likely difference between a Telefunken and a Mullard tube is confirmation bias, you're doing it wrong.

(5) Expectation bias is a real thing and every one of us is susceptible to it.

Your preconceived notions about the state of the tube market is a text book example of expectation bias if there ever was one.

There may be those that convince themselves something is better when it's not because in some way for some reason they need to believe that to be true. But I can tell you with great certainty I don't get up and go to work everyday so I can play make believe with all of my tubes. 

Truth is, I don't have the time. I'm too busy making enough fake tubes to keep the market flooded with them. And when I'm not doing that, I'm counting and sorting my dirty tube blood money into nicely manicured G-Stacks, which I have to be sure to have finished before our daily tube seller global conspiracy scrum. If I am lucky, that meeting will break early and I'll have hour or two to really rip some folks off before dinner. Nothing like a few nicely executed pre-dinner cons to get my appetite worked up.