[abman]

As far as I know GE was the inventor of the gold grid, but they never made any effort to use it in advertising. The amounts are minuscule.
My impression of the OTK stamp, which is always followed by a number, is that it a quality control stamp followed by an inspector number.

from my post at diyAudio forum:

"As I know:
"OTK" - sign of QC department, means that standard quality control passed. In the Soviet times ANY PRODUCT of ANY factory or other production MUST BE checked by "OTK" department - it was guaranty to civil buyers/users that this device is good and safe for use. It is "civil" sign.

"<>" empty rhombus or rhombus with only digits inside (since last '60-s - till present), also letters "ВП" and some two digits between them and inside rhombus - like "<В 171 П>" (before last '60-s) means that device passed Military quality control .
As I can find, digits inside rhombus does not mean any special concerning tube parameters - it's just personal provisory number of person who control QC process for military.

Rhombus signs also used and uses now for any other electronic components and devices which pass QC for military uses.

Sign like star and "CCCP" inside pentagone - is "Sign of Highest Quality USSR" - civil sign.
Words "Сделано в СССР" - means "Made in USSR"......."
Also I have one tube from '60-s which have very old Military Q control sign - letters "ВП" + digits (military QC inspector personal number) inside the star - I need to find it, will make photo and then post here.

 

[mordy]

from my post at diyAudio forum:

"As I know:
"OTK" - sign of QC department, means that standard quality control passed. In the Soviet times ANY PRODUCT of ANY factory or other production MUST BE checked by "OTK" department - it was guaranty to civil buyers/users that this device is good and safe for use. It is "civil" sign.

"<>" empty rhombus or rhombus with only digits inside (since last '60-s - till present), also letters "ВП" and some two digits between them and inside rhombus - like "<В 171 П>" (before last '60-s) means that device passed Military quality control .
As I can find, digits inside rhombus does not mean any special concerning tube parameters - it's just personal provisory number of person who control QC process for military.

Rhombus signs also used and uses now for any other electronic components and devices which pass QC for military uses.

Sign like star and "CCCP" inside pentagone - is "Sign of Highest Quality USSR" - civil sign.
Words "Сделано в СССР" - means "Made in USSR"......."
Also I have one tube from '60-s which have very old Military Q control sign - letters "ВП" + digits (military QC inspector personal number) inside the star - I need to find it, will make photo and then post here.

Hi abman,
Somehow I thought that all Russian tubes were military production.....

 

[abman]

Hi abman,
Somehow I thought that all Russian tubes were military production.....

Hi Mordy,

You can easily find out some Russian tubes with OTK sign, but without <> rhombus sign - this is the tubes made for civil purposes only, or maybe the tubes which did not pass hard parameters military QC.


This does not mean that they are "bad" or "worse" than the diamond tubes, maybe they just have a slightly larger variation of parameters than military requirements allow (maybe the tube did not fit into military requirements of only 1 milliampere, by ear you will never hear it, but the controller
cannot miss it according to indications of devices),
And it certainly does not say that they sound "worse" than a diamond tube.

 

[mordy]

Thanks for the information.
Did they use different designations for the same tube for military vs civilian tubes?
6H13C vs 6N5P?

 

[abman]

Thanks for the information.
Did they use different designations for the same tube for military vs civilian tubes?

As I know, not. the presence of a rhombus sign indicates military suitability.

6H13C vs 6N5P?

I'm not a big tubeworm, as I can see 6H13C is the Russian and 6N5P - Chines made
What is the question?

 

[Datun Walnut]

Over the past few weeks I've been trying all sorts out in my MkII.
Finally settled on a pair of CV4014s and a pair of 1959s Sylvania 6SN7GTs with adaptors. My cans are quite old Beyer DT44Os (600ohm 1980s vintage). Now they've fully warmed up, I feel the gain on the power tubes is a bit lower. That being said, the bass is really detailed and crisp. And the sound in general had opened up in a way, I don't really understand. Highs are not overpowering and vocals sound gorgeous.

 

[sghound]

Over the past few weeks I've been trying all sorts out in my MkII.
Finally settled on a pair of CV4014s and a pair of 1959s Sylvania 6SN7GTs with adaptors. My cans are quite old Beyer DT44Os (600ohm 1980s vintage). Now they've fully warmed up, I feel the gain on the power tubes is a bit lower. That being said, the bass is really detailed and crisp. And the sound in general had opened up in a way, I don't really understand. Highs are not overpowering and vocals sound gorgeous.

i have almost the same config on the mk2. in place of the sylvies are a pair of cbs 5962 triple mica brown base.

i swapped out the siemens c3s for the cv4014 and they sound way better. as u described it the vox rocks.

running the 600ohms beyer 880 effortlessly

 

[Onik]

i have almost the same config on the mk2. in place of the sylvies are a pair of cbs 5962 triple mica brown base.

i swapped out the siemens c3s for the cv4014 and they sound way better. as u described it the vox rocks.

running the 600ohms beyer 880 effortlessly

Which Adapter did you buy for the power tubes? Is it just plug and play with the adapter or you have to swap the pins inside mkii?

 

[marcomalaca]

Today I received the matched pair of Mullard CV8100 I ordered a couple of weeks back. I totally fell in love with the Mullard house sound within the first few minutes of listening. Probably the best sound I ever heard in my life. Laid back, warm, so smooth I haven't got the right words to describe it. Like many audiophiles and experts say the sound is something personal, it is different from person to person and I guess I just found the sound I am looking for.

Right now I am listening to "Gerry Mulligan - The Art of Gerry Mulligan (Final recordings)",

I think my journey to find the perfect sound that could please me 100% has come to an end with Mullards on the MKII.

can you share the link where you got the tubes. thanks

 

[nofacemonster]

Got it off the ebay. Just search mullard cv8100

 

[nofacemonster]

can you share the link where you got the tubes. thanks

Got it off the ebay. Just search mullard cv8100. You will get plenty.

 

[mordy]

can you share the link where you got the tubes. thanks

Hi marcomalaca,
CV means Common Valve (civilian use) as opposed to the M designation which means Military.
Searching for CV8100 on eBay I did not get any hits, but many for M8100. You can also look for Mullard E95 which is another designation for the same tube.
Other Mullard designation for the M8100 is CV 4010 and also CV850, but the last tube is harder to find.
I admit that it is confusing with all these designations for the same tube. Think of synonyms or the same word in different languages. US made tubes of this type could be called 6AK5, 5654, not to mention Czechoslovakian 6F32 and various Russian designations such as 6Ж1П and 61JP etc. And there are more....
One seller called this small tubes "peanut tubes"!

 

[marcomalaca]

Hi marcomalaca,
CV means Common Valve (civilian use) as opposed to the M designation which means Military.
Searching for CV8100 on eBay I did not get any hits, but many for M8100. You can also look for Mullard E95 which is another designation for the same tube.
Other Mullard designation for the M8100 is CV 4010 and also CV850, but the last tube is harder to find.
I admit that it is confusing with all these designations for the same tube. Think of synonyms or the same word in different languages. US made tubes of this type could be called 6AK5, 5654, not to mention Czechoslovakian 6F32 and various Russian designations such as 6Ж1П and 61JP etc. And there are more....
One seller called this small tubes "peanut tubes"!

thanks!

 

[westsounds]

Hi I have a little dot tube amp already and really enjoy using it. I am thinking of getting another valve pre amp though and I see there are ones which use 6J2 tubes as well. Can anyone tell me please if 6J1 and 6J2 tubes are compatible?

 

[Datun Walnut]

Which Adapter did you buy for the power tubes? Is it just plug and play with the adapter or you have to swap the pins inside mkii?

On ebay I searched for: 6SN7 TO 6CG7 6FQ7