[bcowen]

Yup, all very helpful thank you!, and I also think it will take more than a few back and forth posts over time to get *me* aligned/calibrated.

I think he's being honest, at least that's what most of his customers give as feedback. And, after all those years on the job, he probably feels he understands what he is doing as well. The Amplitrex is the same as used by other "big" tube suppliers as well, so I'm hoping his is calibrated and operating correctly.

"Your one-stop source for rare high quality new old stock vacuum tubes and valves. We have been in the vacuum tubes and valves Business Since 1970’s, and have approximately 3,00,000 Tubes in Stock."

I'll keep searching for NIB 6AS7G's, hopefully I can keep the cost down too. And, I'd still like to know if that 6AS7G measurements are "good". I'd like to test it myself, but I don't have a tester, and the testers I had access to are now gone, so I'll work to find another tester. The only way I'll know for sure is to test it myself...and know the setup parameters and tube data.

I'll read up and come back with more questions, and maybe some answers to my own questions...Thanks again.

The Amplitrex is an extremely nice tester...I'd love to have one myself. I see he also has my favorite Hickok (752A) and an AVO...both very nice for vintage testers. The Amplitrex will be more accurate and repeatable than either of those, and being a modern machine is probably easy to calibrate and will stay in calibration for a good period of time.

While I'm not familiar with the Amplitrex operation or data, I know the 752A like the back of my hand. If he hasn't already shipped the tube, ask him to plug it into the 752A and see what readings he gets. I can tell you quickly how it stacks up. One thing I've found with the 6AS7G / 6080 / 7236 / 5998 family of tubes is that it is not unusual for them to test well above bogey NOS values. This doesn't happen with other tubes, and I have no idea why this particular tube type does that, but I have several that test at 150% of bogey. They sound great and operate just fine so I haven't really put much effort into finding the 'why,' just kind of accept it as 'is.'

 

[hmscott]

The Amplitrex is an extremely nice tester...I'd love to have one myself. I see he also has my favorite Hickok (752A) and an AVO...both very nice for vintage testers. The Amplitrex will be more accurate and repeatable than either of those, and being a modern machine is probably easy to calibrate and will stay in calibration for a good period of time.

While I'm not familiar with the Amplitrex operation or data, I know the 752A like the back of my hand. If he hasn't already shipped the tube, ask him to plug it into the 752A and see what readings he gets. I can tell you quickly how it stacks up. One thing I've found with the 6AS7G / 6080 / 7236 / 5998 family of tubes is that it is not unusual for them to test well above bogey NOS values. This doesn't happen with other tubes, and I have no idea why this particular tube type does that, but I have several that test at 150% of bogey. They sound great and operate just fine so I haven't really put much effort into finding the 'why,' just kind of accept it as 'is.'

That is an interesting characteristic of the 6AS7G series, thanks for the insight

I'll ask him to test, but while we've slept they've had their "daytime" in Mumbai, it is now 5:09pm their time, it might have already been shipped...yup:

Tracking details DHL tracking #XXXXXX Feb 5, 2022 4:18pm Shipment picked up MUMBAI (BOMBAY)

What 752A test results do you want in particular? Please let me know exactly what to ask of him to test and I'll ask him for those 752A results on the #309005 6AS7G for comparison, and then we can compare using that tubes characteristics on both testers.

Update: I've asked for the 752A's "usual test results of interest" for that #309005 for comparison, if it isn't too much bother for him.

 

[hmscott]

@bcowen - I also picked up this 6AS7G variant tube for my TA-26:

NOS VINTAGE TUNG SOL CETRON 7236 5998 TUBE
https://www.ebay.com/itm/185266501341

From OP#1 post in this thread: 7236 - medium gain - great bass, fast and dynamic. Almost SS sounding
Some interesting comments about the 7236 characteristics: Tung-Sol 7236. UP FOR GRABS? Worth the BUY? WA3+ Owner.

I spotted the Cetron 7236 in pauls994 ebay inventory while picking up this pair for my TA-20:
NOS NIB PHILIPS HOLLAND PINCHED WAIST D FOIL GETTER E180CC 7062 12AT7 E81CC

Having "2 mouths" to feed really is a tough job

 

[bcowen]

That is an interesting characteristic of the 6AS7G series, thanks for the insight

I'll ask him to test, but while we've slept they've had their "daytime" in Mumbai, it is now 5:09pm their time, it might have already been shipped...yup:

Tracking details DHL tracking #XXXXXX Feb 5, 2022 4:18pm Shipment picked up MUMBAI (BOMBAY)

What 752A test results do you want in particular? Please let me know exactly what to ask of him to test and I'll ask him for those 752A results on the #309005 6AS7G for comparison, and then we can compare using that tubes characteristics on both testers.

Update: I've asked for the 752A's "usual test results of interest" for that #309005 for comparison, if it isn't too much bother for him.

See if you can get the GM readings, either raw or multiplied. All I need really to compare. The 752A uses a rotary multiplier switch to keep the meter needle in an appropriate range, and for the 6AS7G, it uses a 4x multiplier. So whatever the raw reading is on the meter you multiply by 4 to get the (supposed) actual GM number. The minimum good number is 625 (raw). Most of the NOS ones I have nearly peg the meter at 1500 (raw). Now hold on just a minute I think I hear you saying. 625 x 4 = 2500 for minimum, and if that's 60% of NOS, then NOS should be ~1040 x 4 = 4160. The data sheets show 7,000 as the average NOS value?!? All true, but this is just one of the cases where the numbers (and settings) specified by Hickok don't line up with a tube data sheet. The 6AS7 is tested at 7.5v on the heaters (versus their normal spec of 6.3v), and you push a "low plate" button to get the GM measurement. The regular GM button shoots 150v to the tube's plates, but the low plate button shoots only 68v. If I hit the regular GM button on a 6AS7 (which I've done by mistake a time or two) it pegs and bounces the meter needle past max. So higher heater voltage, less than half of the plate voltage, and this is why the numbers Hickok provides don't line up with a data sheet. I have no idea exactly what's happening electrically here, and just trust that Hickok's engineers knew what they were doing.

Anyway, if he has a 6AS7G that measures about the same on his Amplitrex as the one he just sent you, and we can get the Hickok readings for that tube it'll be a good indicator of how it stacks up overall.

 

[bcowen]

@bcowen - I also picked up this 6AS7G variant tube for my TA-26:

NOS VINTAGE TUNG SOL CETRON 7236 5998 TUBE
https://www.ebay.com/itm/185266501341

From OP#1 post in this thread: 7236 - medium gain - great bass, fast and dynamic. Almost SS sounding
Some interesting comments about the 7236 characteristics: Tung-Sol 7236. UP FOR GRABS? Worth the BUY? WA3+ Owner.

I spotted the Cetron 7236 in pauls994 ebay inventory while picking up this pair for my TA-20:
NOS NIB PHILIPS HOLLAND PINCHED WAIST D FOIL GETTER E180CC 7062 12AT7 E81CC

Having "2 mouths" to feed really is a tough job

Funny, that tube was just being mentioned in anther thread:

https://www.head-fi.org/threads/the-reference-6sn7-thread.117677/page-384#post-16800480

I have a few of those. Very fast, dynamic, and clean, but also somewhat lean sounding and lacking warmth and bloom in the mids (in my amp). I think it needs a warmer-balanced driver tube than what I've paired it with before, so I'll try a '40's gray glass RCA 6SN7 with it the next chance I get and see what happens. The RCA is almost too warm and bloomy in the midrange in and of itself, but it may be a very synergistic partner for the Cetron. I'd also love to hear the actual TungSol version of this which I don't have. Cetron (Richardson Electronics) took over production of this tube when Tung Sol stopped, and to my knowledge used their equipment (and certainly their design) to make them. Just always wondering if anything got lost in the transition....

 

[hmscott]

Funny, that tube was just being mentioned in anther thread:

https://www.head-fi.org/threads/the-reference-6sn7-thread.117677/page-384#post-16800480

I have a few of those. Very fast, dynamic, and clean, but also somewhat lean sounding and lacking warmth and bloom in the mids (in my amp). I think it needs a warmer-balanced driver tube than what I've paired it with before, so I'll try a '40's gray glass RCA 6SN7 with it the next chance I get and see what happens. The RCA is almost too warm and bloomy in the midrange in and of itself, but it may be a very synergistic partner for the Cetron. I'd also love to hear the actual TungSol version of this which I don't have. Cetron (Richardson Electronics) took over production of this tube when Tung Sol stopped, and to my knowledge used their equipment (and certainly their design) to make them. Just always wondering if anything got lost in the transition....

Yup, the 7236 is an interesting tube variant for the 6AS7G - I'd also like to find a 5998 and WE421A, I've also added a few more 6SN7 type tubes to pair with the new 6AS7G's, more on those later in another thread.

pauls944 listing for the Cetron 7236 says "Last One", IDK if he has more in the "back storage" or not... also if you work with him, you might get a better price on a few tubes together in one order...

 

[hmscott]

See if you can get the GM readings, either raw or multiplied. All I need really to compare. The 752A uses a rotary multiplier switch to keep the meter needle in an appropriate range, and for the 6AS7G, it uses a 4x multiplier. So whatever the raw reading is on the meter you multiply by 4 to get the (supposed) actual GM number. The minimum good number is 625 (raw). Most of the NOS ones I have nearly peg the meter at 1500 (raw). Now hold on just a minute I think I hear you saying. 625 x 4 = 2500 for minimum, and if that's 60% of NOS, then NOS should be ~1040 x 4 = 4160. The data sheets show 7,000 as the average NOS value?!? All true, but this is just one of the cases where the numbers (and settings) specified by Hickok don't line up with a tube data sheet. The 6AS7 is tested at 7.5v on the heaters (versus their normal spec of 6.3v), and you push a "low plate" button to get the GM measurement. The regular GM button shoots 150v to the tube's plates, but the low plate button shoots only 68v. If I hit the regular GM button on a 6AS7 (which I've done by mistake a time or two) it pegs and bounces the meter needle past max. So higher heater voltage, less than half of the plate voltage, and this is why the numbers Hickok provides don't line up with a data sheet. I have no idea exactly what's happening electrically here, and just trust that Hickok's engineers knew what they were doing.

Anyway, if he has a 6AS7G that measures about the same on his Amplitrex as the one he just sent you, and we can get the Hickok readings for that tube it'll be a good indicator of how it stacks up overall.

I sent him your specific requests, and low and behold, totempole_999 posted the Amplitrex test run of the current #309005 tube eBay listing, and it shows expected "Spec" values of the Amplitrex for the 6AS7!!:

I've noticed the "Plate Resistance RP Ohms" and "Tube Gain Mu" have no Spec reference value listed for those parameters...so IDK if RP Ohms of 0.3K being lower is better, and the same goes for the Mu of 1.5. But, the "DC Plate Current ip mAdc" Spec of 100 vs 105.6/89.6 and "Mutual Conductance" of 5040/5020 suggests my tube is "New-ish".

I also noticed that "Right" channel (column of his Amplitrex seems to consistently indicates "Lower" as compared to the "Left" channel (column), I may ask him about that...at least for the results of interest to me. Same on both tubes results.

And, I've asked totempole_999 for the Amplitrex run for my 6AS7G, #309008

 

[Velozity]

@hmscott , I told you to pm me, lol. I could've sold you one, that reads above 100% on both triodes on my Jackson tester and for a lot less than $110.

 

[hmscott]

As @gibosi said, these are not made in England. I posted that as joke for the veterans and a warning to unsuspecting buyers such as yourself, so mission accomplished . If you are looking for authentic tubes it's best to check here first (as you have) because this thread has a brain-trust of tubephiles (new word) who can steer you in the right direction. That said if you want RCA tubes specifically I have several matched pairs in various styles that are NOS, tested, and authentic. I think I have some singles too. Shoot me a pm if interested.

Well, look at this, I totally missed your offer, sigh, so close and yet so far

I would have still purchased the RCA 6AS7G from totempole_999 as I asked him to find one for me that measured better than he had already listed last month, he said he would, and when he got back to me it looked much better, so here I am.

@hmscott , I told you to pm me, lol. I could've sold you one, that reads above 100% on both triodes on my Jackson tester and for a lot less than $110.

Thank you!, I'll need to wait till March now, but that will give me some time to get used to the "not 100%" tube, and then I can hear the stiff new 100%+/100+ tube stand out.

I was looking for a '50's RCA JAN tube, but more important is the 100%+/100+, If you want to get rid of a couple different types, I would consider that too, the 2nd one doesn't need to be RCA either. I don't need a pair, but single variations where I might hear a difference are welcome.
That's awfully nice to offer, I'll PM you for the rest

 

[hmscott]

Guys, I just received a message from the seller reminding about this item, so now I need to follow through as promised.

The good news is he has a "Make Offer" button on the listing, I don't think the price is too much, but what do you guys think?

How much should I offer him?

Jan RCA 6AS7G Military Audio Radio Vintage Tube NOS 1950s" Price: US $89.99
https://www.ebay.com/itm/275069376271

I am a bit concerned whether the tube is functional, and how good it is, since he doesn't have any measurements or tests done on it. I responded asking him to test the 2 tubes he has and let me know. It is supposed to be a NIB item, but I prefer buying a known quantity rather than plugging in an "unknown" into my only TA-26 Headphone Amplifier.

What do you all think I should offer?

Update: The interface said he would accept $67.49 (25% off), so that is what I offered.

Update: The seller responded to my request to test the tubes to make sure the one he send works and is the highest "Lifetime" / "Good" reading of the two he has, and here is his response:

"...All i have is a regular emissions type tester for these bigger tubes. It will only test good or bad on it.. I can test them to make sure everything is ok, and send you the higher testing one.. Also, I can change the return policy on the listing.. Just incase there's an issue..."

I replied that I accept those terms and conditions and appreciated his effort and help to make sure the tubes work. I wonder why he hadn't tested them before listing them? I also said that if he accepts my requests please accept my offer, and if both tubes don't pass the testing he can cancel the transaction from his end. That is so great, now I am that much closer to getting a tested 50's RCA JAN 6AS7G I've hoped to find.

Update: The seller accepted my offer of $67.49 and the total with shipping and taxes is: Total: $78.98

 

[hmscott]

I guess since I looked at the listing, I got an offer too. ROFL!!! I countered at $5 and noted that was a reasonable price for Svetlana 6N13S tubes currently.

Did you get an offer update too? He's dropped down to:

Tube Pair 6as7g NOS Made In England
Previous price was C $200.00
Seller's Offer C $120.00 (C $80.00 off) (Approx. $93.94)

Those are nice looking Boxes, maybe with a brief message to the seller someone else here can get them for close to "Svetlana" money?

 

[bcowen]

Did you get an offer update too? He's dropped down to:

Tube Pair 6as7g NOS Made In England
Previous price was C $200.00
Seller's Offer C $120.00 (C $80.00 off) (Approx. $93.94)

Those are nice looking Boxes, maybe with a brief message to the seller someone else here can get them for close to "Svetlana" money?

Yeah, for some reason he rejected my offer?!?!? Oh well. Since I already have a pair of "Made in England" Svetlana's with Amperex labeling, I'll probably survive.

 

[Velozity]

While looking through my stash to find the RCA tubes I found these that I forgot I had. Branded GE, likely made by RCA but have copper grid posts like a Chatham.

 

[bcowen]

While looking through my stash to find the RCA tubes I found these that I forgot I had. Branded GE, likely made by RCA but have copper grid posts like a Chatham.

None of the Chathams I've seen have the bottom shield pieces. But on the plus side, they *are* most probably RCA's and not GE's.

 

[bcowen]

These are extremely rare. I am not vouching for the seller OR the tube itself, just posting in case anyone is interested.

https://www.ebay.com/itm/203823301668?hash=item2f74d0c424:g:CwsAAOSwWyph~rbV

Since we've just been talking about tester readings and such, the seller states readings of 92/90 on a Hickok 539C but with no minimum or bogey value to compare to. Unfortunately, the 539C does not give a GM value for these tubes (or 6080's) as you can't do a mutual conductance test on them, only emission. The mark on the meter for diodes and rectifiers is at about 53 - below that would be "bad" and above that would be "good." So it appears this tube has good and strong emission. Some would argue that an emission test is actually a better measurement for power tubes, as most vintage testers don't apply a high enough plate voltage to them to make a transconductance measurement very meaningful. No desire to start a debate on that here, just that I won't argue an emission-only test on a power tube is a worthwhile measurement to use.