Little Dot Tube Amps: Vacuum Tube Rolling Guide

[Acapella11]

nkoulban, good to hear that the psvane 12AT7 tubes are a great find for the LD MK VIIISE.
 
Now, considering this forum is generally read by LD MKIII and MKIV users, are the 12AT7 compatible?
 

 

[Categg]

A quick google gave me this: 
 
 

[size=1.09em] 12AT7 / ECC81

[/size]

[size=small]12AT7's have a lower voltage gain than 12AX7's.  They have a higher plate current and transconductance, making it popular for guitarists who want cleaner headroom, and lower the gain in their amp. 12AT7's are also great for hi-fi applications that need a quieter tube in their circuit.  ECC81 is the European equivalent.

[size=small]12AT7's can replace your 12AX7 or 5751 for lower gain.
12AT7's can replace 12AY7 if more gain is desired.[/size]

 

 

[size=small]So i'm guessing most likely its not usable in Mk III & IV.[/size]

[/size]

 

[Acapella11]

After listening a bit to the Mullard CV4010 (M8100), I remember there are also small and large shield versions.
Which one is considered to be the best of these and why?

 

[Acapella11]

Thanks for checking that Categg, that's what I thought.
 
In this official LD forum post http://www.littledot.net/forum/viewtopic.php?f=5&t=2195
 
it says: "...only 6H30 or 6H6PI type power tubes are compatible."
 
This was for LD MKIV SE and is from version 2 on also true for LD MKIII.

 

[mordy]

Hi AC11,
 
I believe that small and large shield describes the size of the logo printed on the glass envelope of the tube,  and that it has nothing to do with the construction of the tube. IMHO it is just another piece of marketing hype to sell the tubes for more money.

 

[viking59]

thank you for this fantastic work.
 
do you go on , with the power tubes; they are many différents super tube, but nobody explain the différences beetwen  old supertube and new, after 1990.
thanks again !

 

[mordy]

Dear Viking59,
 
From what I have read vacuum tubes made in Russia after the fall of the Soviet Union were not made with the same quality standards as earlier ones. Some people seem to think that the tubes made in the 70's were of the highest quality.
 
Since the DR supertubes get such high prices it is possible that there are some fake ones as well.
 

 

[Acapella11]

Respective Mullard M8100
 
Dear Mordy,
 
1.) Apparently, I already ordered the Mullard M8100 KB/Q with logo and small name before you typed your answer:
 
http://www.ebay.co.uk/itm/M8100-MULLARD-6AK5-EF95-E-MATCH-PAIR-NEW-VALVE-TUBE-/390429216735?pt=UK_Sound_Vision_Valves_Vacuum_Tubes&hash=item5ae7650fdf
 
2.) Before, I got the Mullard CV4010 KQDD/K without Mullard or M8100 label:
 
http://www.ebay.co.uk/itm/M8100-CV4010-6AK5W-MULLARD-NOS-MATCHED-PAIR-/310282214423?pt=UK_Sound_Vision_Valves_Vacuum_Tubes&hash=item483e42dc17
 
Actually, both types are not the exactly same tube. The first one with logo has a square getter, whereas the second without logo has a halo (or O-) getter.
 
Both sound great and not very different but I think the one with logo is airier, has more sizzle in the treble. Personally, I prefer this. The tube sounds somewhat more exciting. Now, it is on the best way to become my favourite tube . I probably gonna update this later. 

 

[mordy]

Hi AC11,
 
I have several pairs of the Mullard tubes, and as you notice, different production runs use different parts. I have not been able to find any information if the various getter types have an effect on the sound. Some are square, others rectangular, some are thinner metal, some thicker, some of the rectangular getters are bent (like the electric takeoff on a tram), and some are round or D shaped. Some Russian getters  look like a little bowl on legs.
There is even a Tung Sol tube that has a clear top, and the getter flash (silver) is on the side of the glass, with a half moon shaped getter facing it in the middle of the tube.
 
Another mystery area is how the Mullard tubes are coded, with the various letters and numbers. If you need a brain exercise, google the Mullard codes and try to decipher the factory codes and manufacturing months and years. Here is an example (but and educated guess):R1A4 means Made in the Mitcham factory on Jan 4, 1961. (Some letters are silk screened, others etched, and you may need a good light to see them).
 
All these variations add to the fun of tube rolling.
Then you have Mullard 8100 equivalents made by Mullard such EF95 and CV850....
 
You have to try different tubes and see what you like the best, and then enjoy the music! Good luck!
 

 

[hwy61]

trying to date a pair of russian 6n6p otk rhombus 5 gold grid tubes .........numbers shown are  8808.........not 2008 is it ?                                                            
 
has anyone tried rolling voskhod  6j1p's from the year 1967 ?.............

 

[mordy]

Hi hwy61,
 
An "educated" guess would be August 1988. If you google Russian tubes you will easily find a chart with pictures of the logos on the tubes from the various factories. There is also information if they still are in business - most of them are closed.
 

 

[hwy61]

thanks mordy,......that's kinda what i thought ........what thru me off was the voskhod 6zh1p driver tubes show a 06-83 date, which seems to be a more logical dating
system....
as for the 6j1p's same deal 111- 67 (11-1-67)..... i decided to not only roll these tubes....  but also roll the dice sound-wise .....(the old yellow shipping box with the rocket logo was pretty cool too)   

 

[Acapella11]

Thanks for the info Mordy.
Very interesting how much Mullard altered the manufacturing process. Sounds like a lot to roll =). Although, I am very happy with these Mullard M8100s (square getter, small name logo) I got now, and then there is also the Sylvania JAN 5654W, which I might pop in. I think the driver tubes are sorted for me now - I am still on the power tubes for the fun of it and enjoying the music .
 
hwy61,
The labeling could be plant specific. I have got some Novosibirsk 6N6P with the print 1182, which I presume is Novermber 1982. These were stamped with the pentagonal symbol from the old Novosibirsk factory. The other 6N6P I have are from the new Novosibirsk plant with the wound snake like symbol. The label says 9804, which I suppose is April 1998. To top that, these newer tubes have even two stamps on it 9504 and 9508.
Here are the logos and explanations of Russian tube factories:
http://www.gstube.com/factories/ (in Russian) and transliterate here: http://www.convertcyrillic.com/Convert.aspx
If you find a tube, the logo is explained. For example here for 6N6P tubes sold:
http://www.gstube.com/catalog/?key=6n6p&submit=Find

 

[mordy]

Dear AC11,Here is a link to Russian tube logos. It is a simple and short list that will aid in identifying the tube manufacturers and it has proved useful to me.
 
http://www.ominous-valve.com/russtube.html

 

[Acapella11]

Thanks for this link mordy.
 
Found coincidently something for the real Mullard fans between us: http://www.tubedepot.com/sw-ts-003.html