Head-Fi.org › Forums › Equipment Forums › Headphone Amps (full-size) › Little Dot Tube Amps: Vacuum Tube Rolling Guide
New Posts  All Forums:Forum Nav:

Little Dot Tube Amps: Vacuum Tube Rolling Guide - Page 133

post #1981 of 7248

Siles 1991,

 

Sounds like you have  a badly recorded tune. We all have such recordings where something does not sound right or strange....
 

Inphu510n,

 

If the tube sounds all right I would not worry about the getter flash. I have seen some early tubes 6AK5 that did not have a visible getter flash and the top of the tube was completely clear. They worked just fine. The same goes for the heater. Sometimes it is visible in one tube and not in the other, but it only has to do with how it was assembled. If the tube works, all is well.

 

Also got the shopworn dirty 1680 tubes. Usually I just take my old little pen knife and do a cursory scraping of the pins. IMHO the contact areas for the pins are much smaller than the entire pin, and you need very a very small contact area for the tube to work. Just think of the tiny area the jumpers occupy. If the first cleaning does not help, I'll try harder the second time. BTW, I had a 6N6Pi power tube that I thought had stopped working. Luckily, I did not throw it away. A year later I thought of cleaning/scraping it and got it going. Despite all the hype about expensive chemicals, mechanical cleaning works the best.

post #1982 of 7248

Tracking down the origins of the various Siemens EH90 is proving to be an interesting puzzle. I have learned that at least some of Siemens EH90 with smooth plates and squarish holes were made by Mullard in their Blackburn factory. If you have a pair of these, check on the side of the glass, near the bottom, for a sequence of three or four alphanumeric characters, beginning with the letter B. For example, my smooth plate Siemens EH90 have the following code: B9F, which indicates the Blackburn factory, June, 1959. In the two samples I am aware of, these codes are very faint, so it may take some patience and a good magnifying glass to find them.

 

But I have also learned that smooth-plated Siemens EH90 with "Made in Germany" printed on the glass exist! .....So we still have much to learn before the mysteries of the Siemens EH90 are finally revealed to us.... :)

post #1983 of 7248

got the first pair of new tubes today, a RCA 6AK5 5654 SHARP CUT OFF PENTODE, not that i know a whole lot about them

other than they sound very good to me

i also have coming in a pair of RCA 5915 with black plates, multiple mica supports, upper ring getter, and i don't know to much what all that means, other than it was suggested .

post #1984 of 7248
Quote:
Originally Posted by Oskari View Post


That should be the case. Valvo was Philips Germany, so to speak.

The Belgian manufacturer was MBLE. Their own tube brand was Adzam. MBLE-made tubes should also have the Philips codes.

 

Quote:
Originally Posted by gibosi View Post

Tracking down the origins of the various Siemens EH90 is proving to be an interesting puzzle. I have learned that at least some of Siemens EH90 with smooth plates and squarish holes were made by Mullard in their Blackburn factory. If you have a pair of these, check on the side of the glass, near the bottom, for a sequence of three or four alphanumeric characters, beginning with the letter B. For example, my smooth plate Siemens EH90 have the following code: B9F, which indicates the Blackburn factory, June, 1959. In the two samples I am aware of, these codes are very faint, so it may take some patience and a good magnifying glass to find them.

 

But I have also learned that smooth-plated Siemens EH90 with "Made in Germany" printed on the glass exist! .....So we still have much to learn before the mysteries of the Siemens EH90 are finally revealed to us.... :)


OK, this Siemens puzzle is getting more and more complicated lol...

 

I just got my "Siemens" EH90 tubes, 3 tubes (playing it safe from now on), and also a pair of "Pope" "Made in Holland" EH90.

 

Let's start with the Siemens tubes. First, some pictures:

 

The two identical Siemens tubes, Siemens logo, 3-digit number on top, factory code LOA.

 

 

One of the two tubes above on the left, on the third Siemens on the right. They look identical, but they are not. The tube on the right is factory coded B4F3, and has grid 2 and 4 soldered to same pin at the base, whereas the tube on the left has g2 and g4 tied together by a metal plate at the top. Getter flash and nub are also different, and they are a few extra minute differences if you look closely. Oh, and of course, you can't miss the "Made in Germany" sign on the right tube.

 

 

The same tubes, different angle, still different. See that metal plate that ties g2 and g4 towards the top on the left tube, and lack thereof on the right tube?

 

 

The tube boxes. The two left ones are from the LOA codes tubes, the last one on the right is from the B4F3 coded tube. That last box has a different tag on it; you can't see it here, but it says "hexode" where the others say "heptode". Because the two screen grids aren't tied the same way? Who knows...

 

 

Same order, different angle. Last box looks like it has a slightly different "shine" to it, but it just doesn't seem that relevant at this point.

 

 

Basically, the "L" coded pair is a M.B.L.E Mazda, Brussels Belgium, manufactured pair, and the "B" coded tube is a typical Mullard Blackburn manufactured tube (come on, you saw that coming, right? Those tubes screamed Mullard the second I saw them. The Mazda Belgium are a bit a of surprise though).

 

So, essentially Siemens labeled but Philips group production. The plot thickens yet again. I think I saw a "B" on at least one of Hypnos' tubes as well -and no metal sheet at the top- so I'm curious whether anyone else ended up getting the same Mazda Belgium tubes I got (which you could probably find labeled Adzam much more easily btw).

 

From the 5 minutes I took to test the Belgian tubes, I can say they sound dramatically different from the supposedly genuine Siemens EK90 I have. If I were to grade them on the Euro-Tubiness Continuum (copyright gibosi and me lol), I would put them way over towards the UK-Mullard end. These are warm and tubey all right, but not in the usual Mullard way. It's weird, I need some more testing to get better impressions, obviously. What I can say is that these tubes immediately transported me in what seemed like a separate musical dimension the second I lit them up and put my headphones on. You like ambiance? You'd find these interesting. I'll wait a few hours to give more objective impressions; after all you know the saying: all heptodes sound good. (except the Brimar perhaps)

 

Next, and yet untested, the Pope EH90. OK, I'll cut to the chase: these are not "Made in Holland"... The Mullard Blackburn factory codes kind of leap at you really, it's almost sad... At least, I'll be able to compare these, Mullards, to the, M.B.L.E. Mazda, Siemens.

 

 

The standard boxes these came in, labeled with the same shameless lie that is written on the tubes.

 

 

There is one element that strikes me here; it is that three out of five of these tubes claim to be made somewhere but are evidently not! Now, I do have to ask myself if it really is a bold lie in each case, or if the factory codes only show where a part of the manufacturing process was conducted, and not where the tubes were necessarily assembled (if I recall, Philips codes, and perhaps all codes, only tell you where the "pumping process" occurred; so tube A and B could both have Blackburn codes, but one could have been assembled in factory XYZ and "pumped" in Blackburn, while the other could have been assembled and pumped out in Blackburn...? Or not. But I'd be curious to know.).

 

Interestingly, I could swear I'd read something about Pope tubes being Philips Holland; and I found this, quoted below:

 

"Very unusual label I found on a tube in Holland. Pope means "Productie Overschot Philips Eindhoven" = surplus production from Eindhoven."

post #1985 of 7248

 

Received EF95 T0 EF91-92 socket adaptors today unfortunatly duds again they dont work you figure they'd figure out a way to test them before shipping them out but they haven't let me down yet so patience patience.

post #1986 of 7248

As some of you might remember, I initially received a mismatched pair of Siemens EH90, one with ribbed plates and the other with smooth plates. I contacted the vendor and he offered to send me the mates to these tubes such that I would have two pairs. Well, I received the package today, and now it seems that I have four Siemens EH90 and none of them match!! lol It seems obvious to me that the vendor realized he had sold out of tubes that matched mine, because he also sent, free of charge, an extra Telefunken EH90 and a matching pair of Valvo EH90, so I still recommend him. He tried to make things right.

 

A nice pair of Valvo EH90, Mullard/Blackburn codes, 1967

 

 

And here is my Siemens EH90 "Collection" to date:

 

A "slightly" mismatched pair of Siemens EH90, Mullard/Blackburn codes, 1959 (B9F) and 1964 (B4K5). And the lie, "Made in Germany" is written on the 1964 tube. 

 

 

And a completely mismatched pair. Note that the design of the getter attachment to the support rod is different, as well as the ribs, holes and getter splash.

 

 

Also note the metal strap tying g2 and g4 just below the getter, left side, on the right tube. Whereas, there is no such strap on the left tube as g2 and g4 are soldered to the same pin at the base.

 

 

With some luck and patience I hope to find suitable mates for my two ribbed Siemens. And the search for a pair of "real" Siemens EH90 continues.... lol :)

post #1987 of 7248

Here is an excellent film from the 50's showing how vacuum tubes are being made in the Mullard Blackburn factory. After the 22 min mark the film shows how tubes are pumped etc. Based on the complex manufacturing process it seems unlikely to me, IMHO, that partially assembled tubes would be shipped for final processing somewhere else. Thus the plot further thickens about the origin of the Siemens tubes and the labeling of country of origin.

 

This film is a new and very recent post on Youtube and has only been watched by a handful of people so far.

 

http://www.youtube.com/watch?v=5WCWejeRR_s
 

post #1988 of 7248

here's what's in the little dot now, while i wait on the rca 5915's

post #1989 of 7248
Quote:
Originally Posted by mordy View Post

Here is an excellent film from the 50's showing how vacuum tubes are being made in the Mullard Blackburn factory. After the 22 min mark the film shows how tubes are pumped etc. Based on the complex manufacturing process it seems unlikely to me, IMHO, that partially assembled tubes would be shipped for final processing somewhere else. Thus the plot further thickens about the origin of the Siemens tubes and the labeling of country of origin.

 

This film is a new and very recent post on Youtube and has only been watched by a handful of people so far.

 

http://www.youtube.com/watch?v=5WCWejeRR_s
 

Great watch and very interesting, I bet that was a nice safe plant to work in...

post #1990 of 7248

No information as to from where but what for is visible on my Siemens EK90 (here): A little eagle with 933 written in between the wings indicates that these tubes were produced for the German Army.

post #1991 of 7248

I have SPC cable with only 7-8 strands would that suffice for the jumper?

post #1992 of 7248
Quote:
Originally Posted by siles1991 View Post

I have SPC cable with only 7-8 strands would that suffice for the jumper?

 

The smaller the better, so this should work splendidly!

post #1993 of 7248
Quote:
Originally Posted by Acapella11 View Post

Just a quick info with respect to Svetlana 6A2P and Siemens EK90 (black bottom, saucer getter): They do not sound the same. Hence, one would not be a substitute for the other.

 

Otherwise, I changed something on my system and have to now go through tubes again. Also, I am suffering from heptoditis (= the choice of many good sounds), so I decided to not rush it but rather get used to them and come a bit delayed with a "more definitive" opinion.

 

I agree that focussing on one mode of operation (unstrapped that is probably) will make reviewing tubes easier. Every reviewer has anyways the option to try different modes "in secret" if he/she wishes and include information about them, if useful.

 

Good luck rolling everyone!

 

Hi A11.

 

Thanks for putting me right on this matter - are your Svetlanas IDENTICAL to the Siemens in appearance? It is a strange coincidence that, from what I saw on the web photos, the black-bottomed tubes should have the same slight ribbing and plain grey plates; the clear- bottomed smooth, silver/grey plates. Weird! Ah well, these Siemens tubes really are giving us the runaround, ya?!! Thankfully, my Siemens EH90s have usurped them anyway...more on those later (to add to the already escalating confusion).

 

The saga continues...

post #1994 of 7248

Maybe I am not using the highest quality jumper wires, but it looks to me that little fragments break off and end up inside the pin holes. A little piece broke off when I pulled out the tube and ended up lying on top of the tube socket. At first I thought I could pick it up with a magnet but that did not work.   Was able to pick up the little strand with tweezers.

 

The jumper will work fine even with just very few little strands.
 

post #1995 of 7248

Hi A11,

 

 

From post 1858:

 

"I have saved the Russian 6A2P pictures and a surprise for later."

 

Did not hear about the surprise yet - did I miss something?

 

BTW, on your excellent chart, which I refer to every day, why don't you add the EF95 + 6/7 socket wire modification = EF92 setting for those of us who hate to change the jumpers underneath the LD MKIII?

 

Also, if you could change the spacing between the columns so that the first three columns have more space between them for clarity. (Or could it be my computer that bunches the three first columns too close?)
 

New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Headphone Amps (full-size)
Head-Fi.org › Forums › Equipment Forums › Headphone Amps (full-size) › Little Dot Tube Amps: Vacuum Tube Rolling Guide