[JazzVinyl]

.. I think I have just tube binge-bought. Is this hoarding?
I mean, I am just sat here and they are so cheap!

2x 6J7MG Visseaux (ping'd around here already I think)
2x KenRad VT-94 (6J5)
2x RCA 6C5 (beachball logo)
2x RCA VT-65 (6C5) (beachball logo)
... and 2x Phillips EL3N

They have not arrived, but here are the pix...

Looks great!!! Love RCA's and can't wait to get the sonic report on the Visseaux 6J7MG's!!

.

 

[chrisdrop]

This looks like a steal. Tempting, but maybe one of you would like more than I?

EDIT: not 'buy it now' but auction. Still perhaps interesting.

Also for winning auctions, I hope you all use Gixen.

 

[L0rdGwyn]

I have owned the Visseaux 6J5MG (metal can version of the 6J5G), they are very nice tubes, internals are identical to the more rare and expensive Visseaux 6J5G (shouldered). I haven't experimented with triode-strapped 6J7s, but if they are comparable in sound to their 6J5 brethren, those Visseaux 6J7s should be very nice sounding tubes.

 

[SilverEars]

Just a question guys. What does the value on the left and right of / mean?

Sometimes the listing would say 1200/1400 or 1250/1250

Is this the left and right channel strength values? What do they mean?

There is no standard value for NOS right? It's all relative to the test kit's relative good value score and varies testkit to testkit?

 

[L0rdGwyn]

Just a question guys. What does the value on the left and right of / mean?

Sometimes the listing would say 1200/1400 or 1250/1250

Is this the left and right channel strength values? What do they mean?

There is no standard value for NOS right? It's all relative to the test kit's relative good value score and varies testkit to testkit?

The values on the left and right can be two different things. Either the measured value for each half of a dual-triode tube, or sometimes it is the measured value in the numerator over the expected NOS value in the denominator. For example, a tube that tests 1500/2000 will be 75% of nominal value, if the seller is listing it as a fraction. You can always ask the seller.

Correct, you are most commonly going to find three different value ranges, although there can be more.

Numbers like you listed above are likely a measurement of a tubes transconductance. Tube testers that test transconductance are the most advanced and test the tube most similarly to how it would be used in a circuit. The nominal value will be specific to the tube under test, check the tester's manual for minimum expected value or the tube datasheet (manual is better since transconductance is not truly constant and the tester will use specific test parameters). The Amplitrex AT1000 electronic tester is the Rolls Royce of testers, it will give mutual conductance and plate current values.

Another type of value you will see might be in the 40-80 range. These are the TV7 type Hickok transconductance testers. They test a tube like above, but use their own normalized range of "good" values. NOS tubes tested by a TV7 will have a value around 70, you can check the TV7 manual for tube specifics.

Lastly, you will often see percentages listed, "95%" or "110%". These are emission testers, they test a tube's cathode emission by basically operating the tube as a diode with a specific plate voltage. Not as telling as a transconductance tester, but will give you an idea of the tube's usability and remaining lifespan.

There are other oddball testers used out there, but these are the most common values you will see on eBay. None of it is standardized.

 

[chrisdrop]

Will 12J7GTs work via the EL32 adapters in the C3G slots? I think the C3G slots only ever get 6v, regardless of 6/12/25v switch settings, so assuming not.

Also, I am tempted by these RCA 6AS7Gs. 2 sets of 2 are doable presently and I have no 6AS7Gs, and I won't buy the Ferrari ones discussed early. Any opinions on these?

EDIT: The RCA 6AS7Gs are used, so that is probably a no.

 

[SilverEars]

The values on the left and right can be two different things. Either the measured value for each half of a dual-triode tube, or sometimes it is the measured value in the numerator over the expected NOS value in the denominator. For example, a tube that tests 1500/2000 will be 75% of nominal value, if the seller is listing it as a fraction. You can always ask the seller.

Correct, you are most commonly going to find three different value ranges, although there can be more.

Numbers like you listed above are likely a measurement of a tubes transconductance. Tube testers that test transconductance are the most advanced and test the tube most similarly to how it would be used in a circuit. The nominal value will be specific to the tube under test, check the tester's manual for minimum expected value or the tube datasheet (manual is better since transconductance is not truly constant and the tester will use specific test parameters). The Amplitrex AT1000 electronic tester is the Rolls Royce of testers, it will give mutual conductance and plate current values.

Another type of value you will see might be in the 40-80 range. These are the TV7 type Hickok transconductance testers. They test a tube like above, but use their own normalized range of "good" values. NOS tubes tested by a TV7 will have a value around 70, you can check the TV7 manual for tube specifics.

Lastly, you will often see percentages listed, "95%" or "110%". These are emission testers, they test a tube's cathode emission by basically operating the tube as a diode with a specific plate voltage. Not as telling as a transconductance tester, but will give you an idea of the tube's usability and remaining lifespan.

There are other oddball testers used out there, but these are the most common values you will see on eBay. None of it is standardized.

Thank you for the response. I search Google, but there were no uniform answer to this question. I was wondering if there are any webpages that details what you have stated in regards to left and right values of '/' because I fail to find any besides people asking in forums. And that didn't put out anything definitive. I take it that there is no tube testing standard is why it is the way it is.

Usually the tube listing will state what '/' value is minium good. In this case, what is the value on the left and right of '/' mean? I have usually seen Hickok tests that put out values around the 1000s, but other type of test putting out values in the 40-80 range.

From what I understand Hickok tests are the ones usually recommend for better accuracy.

 

[L0rdGwyn]

Thank you for the response. I search Google, but there were no uniform answer to this question. I was wondering if there are any webpages that details what you have stated in regards to left and right values of '/' because I fail to find any besides people asking in forums. And that didn't put out anything definitive. I take it that there is no tube testing standard is why it is the way it is.

Usually the tube listing will state what '/' value is minium good. I have usually seen Hickok tests that put out values around the 1000s, but other type of test putting out values in the 40-80 range.

Yes, I explained that in my post. It's unlikely you are going to find webpages devoted to how eBay sellers are listing the parameters. To understand, you have to learn a little bit about how these tubes are being tested, what is being measured.

http://tone-lizard.com/tube-testers/
http://www.tungsol.com/html/faqs7.html

The "minimum good" values are from the tube tester manuals. If the seller states the type of tester used, you can Google "X tester tube data" or "X tester manual" and try to find a scanned copy of the tube test parameters, they are quite common online. Then find the tube that is being sold in the listing and find its "minimum good" value in the document. But note, the minimum good is the minimum value where the tube is functional, really you should be looking for tubes that test NOS for longevity. Minimum good values are typically 65% of the nominal value. So if the minimum good value in the manual of a tube is 4000umhos, the NOS spec would be 4000/0.65 = 6150. As I said, for a TV7 series tester, that will be typically around 60-70. Minimum value for most tubes on a TV-7 is 40, but consult the tube data for the tester.

TV-7 series tube data: https://frank.pocnet.net/instruments/Military_us/TV7/TB-11-6625-274-12.1.pdf

For values in the 1000s, search for the manual of the tester to find minimum values or average values, how they list them is dependent on the tester type. Again, it is not standardized so you have to do your homework for the tester being used, unless it is an emission tester, which will list the values as a percentage across the board.

 

[jmac1516]

I have owned the Visseaux 6J5MG (metal can version of the 6J5G), they are very nice tubes, internals are identical to the more rare and expensive Visseaux 6J5G (shouldered). I haven't experimented with triode-strapped 6J7s, but if they are comparable in sound to their 6J5 brethren, those Visseaux 6J7s should be very nice sounding tubes.

Can the 6J7 tubes be used in the 6SN7 socket with an adapter (i.e. with dual CJ5 to 6SN7 adapter)? On the GOTL Tube Compatibility Table it shows in the C3g driver section.

 

[Xcalibur255]

To add to this a bit, one of the reasons different sellers report readings in different formats is going to be due to the type of tube tester they are using. Some report tube life in a percentage, some report a transconductance value (not all tube testers are transconductance testers), some an emission value. An AT1000 will even give you the plate current values. There was no one standard or method. So a seller will usually be working in whatever format that matches the function of their tester.

 

[mordy]

Can the 6J7 tubes be used in the 6SN7 socket with an adapter (i.e. with dual CJ5 to 6SN7 adapter)? On the GOTL Tube Compatibility Table it shows in the C3g driver section.

It appears to me that you could use pair of 6J7 tubes in the 6SN7 socket but it requires a custom made adapter that is not available commercially. The 6C/J5 do not have the same pinout as the 6J7.
You could ask Deyan of the feasibility to make a dual 6J7 to 6SN7 adapter.
The C3g is a pentode and so is the 6J7 and this would make it preferable to use it in the C3g sockets (with the special adapter) according to Glenn.

 

[jmac1516]

It appears to me that you could use pair of 6J7 tubes in the 6SN7 socket but it requires a custom made adapter that is not available commercially. The 6C/J5 do not have the same pinout as the 6J7.
You could ask Deyan of the feasibility to make a dual 6J7 to 6SN7 adapter.
The C3g is a pentode and so is the 6J7 and this would make it preferable to use it in the C3g sockets (with the special adapter) according to Glenn.

Got it. Thanks.

 

[mordy]

Will 12J7GTs work via the EL32 adapters in the C3G slots? I think the C3G slots only ever get 6v, regardless of 6/12/25v switch settings, so assuming not.

Also, I am tempted by these RCA 6AS7Gs. 2 sets of 2 are doable presently and I have no 6AS7Gs, and I won't buy the Ferrari ones discussed early. Any opinions on these?

EDIT: The RCA 6AS7Gs are used, so that is probably a no.

Re the 12J7 tubes, they will not work in the C3g sockets since the voltage is set to 6.3V, just as you surmised.
The RCA 6AS7G tubes are warm sounding but they don't seem to get much love - if you want them you could get them for around half the price (in the US) of the offer you posted. I have maybe 5 of them but they don't get much use so far. It is interesting that almost any US brand of the ST type 6AS7 were made by RCA, but other brands sell for more usually. It also occurs to me that the Russian 6H13C with variants was modeled on this tube, especially since Svetlana bought RCA made factory equipment in the late 30's.

 

[mordy]

Looks great!!! Love RCA's and can't wait to get the sonic report on the Visseaux 6J7MG's!!

.

I assume the RCA 6080 rather than the 6AS7G?

 

[mordy]

Thank you for the response. I search Google, but there were no uniform answer to this question. I was wondering if there are any webpages that details what you have stated in regards to left and right values of '/' because I fail to find any besides people asking in forums. And that didn't put out anything definitive. I take it that there is no tube testing standard is why it is the way it is.

Usually the tube listing will state what '/' value is minium good. In this case, what is the value on the left and right of '/' mean? I have usually seen Hickok tests that put out values around the 1000s, but other type of test putting out values in the 40-80 range.

From what I understand Hickok tests are the ones usually recommend for better accuracy.

Hi SE,
What I am saying here is my personal opinion, and there is certainly room for other opinions:
Given the lack of standards in measuring vacuum tubes, and the possibility that a tube can measure good (by whatever tester it is being tested with) and still be a dud (noisy, emitting crackling or popping sounds, sometimes even causing damage ) I do not put too much significance to measurements.
The majority of tubes I have bought used have been good. It is rare for a tube to wear out from use - most tubes that give out seem to be from a malfunction or mishandling (sudden shorts, used the wrong way, or dropped on the floor). People have reported using tubes for 10 years and they still have some life left.
As far as I am concerned, I try to buy from reputable sources (if the price is right) and people with good feedback. In the rare cases when something went wrong I can always fall back on the eBay protection and also protection from PayPal (which can offer another layer of protection by using a credit card).
I'll rather buy from somebody selling off his grandfather's radio shop inventory than from a professional seller who many times is high priced. The tubes are the same, but there could be a very substantial price difference.
I figure like this - if somebody bothered to save the tubes for 50-70 years or more, they probably are good!