[gibosi]

...the Osram looks to be a fake...

"Fake" implies the intention to deceive. A B36 simply isn't worth enough money to be worth the time and energy to make a fake. Rather, obtaining comparable products from competitors and relabeling was standard operating procedure back in the day. If a company didn't have enough stock to satisfy a customer's order, they would simply get on the phone and purchase comparable products from a competitor. Keeping customers happy was of utmost importance.

And so we commonly see rebranded and relabeled tubes from all the manufacturers. I routinely see product from Mullard and Fivre relabeled as GEC / Osram / Marconi. So no, it is not a fake. Even though it was not manufactured by Osram, the tube is legitimate. A customer needed a 12SN7GT and got one.

 

[rnros]

So the day has come - my new GOTL arrived a few days ago, but first now I have been able to spend time with it.

This amp is totally different to what I am used to (Little Dot MKIII, Feliks Audio Elise and Euforia). It likes different tubes and tube combinations and headphones compared to the other amps, and it is so much more sensitive, like a tube magnifying glass.
If a tube isn't just perfect it will let you know. Loudly.
Started out with 6 x 6BX7. How do you figure out a bad tube among 7? In addition, when turning on the amp, there was a whole plethora of sounds that I did not hear before: pops, ticks, tinkling, howling and something that sounded like crumpling cellophane paper. And microphonics - just touching the volume knob sent the speakers into a tizzy....( Used a Tung Sol 6F8G as driver)
Oh my gosh, what did I get myself into? How can I find the offending tubes?
At first I just shook my head, then shut the thing off and went to sleep for the night. Yeah - that's the punishment for buying bargain lots of mixed tubes 6BX7 - GE, Philco (Sylvania) and RCA.
OK - next day: Time to try again. Looked over the tubes, checked for corrosion on the pins. And discovered that all of the 6BX7 tubes, no matter what brand, were made by GE. The sandblasted dots are the telltale signs.
Turned on the amp, and based on JV's advice, I just let it sit 20 minutes to warm up without headphones or speakers plugged in - the amp has to keep the pops and ticks to itself....
Turned it on with my $12 headphones plugged in. Just in case. Much more quiet, but not good. Used the balance control to confirm that the noise was in one channel. At least I just need to check out three instead of six tubes.
Tried tapping on the tubes and found one offender. Luckily, I have eight 6BX7, and put in a different one. Finally quiet. Until I touched the volume knob. Microphonics galore - must be the driver tube. Tapped on the driver tube - ouch! Tapped on the chassis, tapped on the volume knob - NYET. How can such a gorgeous looking tube misbehave?

Luckily I have another rebranded one (both are ladder plate, not RP). It did rattle, but I put it in, and no microphonics.
Finally, the GOTL showed what it can do - the best sound I have heard to date. Full bodied, great bass slam and very natural sounding - it just sounds right.
I am just getting used to the amp now. Decided on a very simple set up - a Sylvania 6SN7WGT and a pair of Cetron 6336B. Them big tubes get superhot - measured over 350F! Amazing that the chassis does not have any ventilation holes and only gets fairly warm but not hot with these tubes. As ugly as they are, I am using the socket savers to cool down the chassis (and I turned on my fan for the 6336s - the chassis is barely warm with the fan pulling away hot air).
This combination is totally silent at even loud normal listening levels and very little hum even at full tilt.
And here is today's question: How can I save the TS microphonic tube from the garbage heap? Any tricks to get rid of the microphonics? (The less expensive the better.) I read about high temperature silicon tube rings, but I'll rather buy them from a car parts shop than a Hi Fi web site - any suggestions? Or something else - heard about heat resistant silicone tape as well.
Have fun!

Congrats, mordy! Glad to hear that it was worth the wait for you. And it's a beauty.
As you know, it will only get better as all the components run and settle in the coming months.

Yep, had the same problem with noisy GE 6BX7s, don't bother with them any more.
Also, the batch I have, IMO, don't sound as good as the other brands, TS, RCA, SYL, which sound really good.

Last couple of weeks have gone back to 596/C3g/CTN6336B, still one of the best trios for me. And Dead Quiet.
But so many great possibilities with GOTL.
I don't worry about the heat on any of the tubes, the heat we're discussing is all above deck.
As I sit, the 6336Bs are about 325F top of glass but only about 135F at the metal base. Deck surface is not even warm.
Even the 596 can go to 260F @ top of bulb.

Also excited that Glenn is one amp closer to my GEL3N.

 

[Phantaminum]

"Fake" implies the intention to deceive. A B36 simply isn't worth enough money to be worth the time and energy to make a fake. Rather, obtaining comparable products from competitors and relabeling was standard operating procedure back in the day. If a company didn't have enough stock to satisfy a customer's order, they would simply get on the phone and purchase comparable products from a competitor. Keeping customers happy was of utmost importance.

And so we commonly see rebranded and relabeled tubes from all the manufacturers. I routinely see product from Mullard and Fivre relabeled as GEC / Osram / Marconi. So no, it is not a fake. Even though it was not manufactured by Osram, the tube is legitimate. A customer needed a 12SN7GT and got one.

Gotcha. I’ll probably still return them to get a full on B36 or a few 13D1s. I would of kept these if I could readily identify the second tube.

 

[mordy]

Trudging along the tube rolling path with my new GOTL. ATM I am trying out different drivers that I haven't tried before and bought for the GOTL - power tubes are 10A of American Muscle (Cetron 6336B).
It would be easy to buy the expensive tubes with the best reputations, but that's not for me. You can buy a 40's Sylvania 6SN7W for $25 if you luck out, or for $350. Mind you, the same tube, so am I holding out for a lower price range, but it takes patience.
Meanwhile I got a Sylvania 6SN7WGT from June 1955 ($18). This is a very nice sounding tube with a somewhat bright, brassy presentation in my system with the Cetrons.
Jumped on the Tung Sol BGRP bandwagon. The 6F8G had problems with microphonics. My engineering staff is working overtime to find an antidote (not true). The TS 6SN7 BGRP is too expensive at the moment and I can't find the 12SN7 BGRP at the right price, so I got a TS 6SL7 BGRP relabeled Motorola for $29. Cannot find anything on the tube that says 6SL7 so I have to trust the seller. Sounds similar to the above Sylvania but not as bright.
A long time ago I read an article on the website of JACMusic about a very good sounding tube that isn't so well known - the 12SX7.
Thanks to myphone I am now able to listen to this 12V tube. The tubes I have are made by RCA, but there are a several manufacturers that made them (unless they all are rebranded).

Look at that - a 2018 tube! Well, January 1953 is more like it:

IMHO a great sounding tube and that can hold it's own and more to the Sylvania 6SN7WGT and the TS BGRP 6SL7.
There is a Taiwanese seller on eBay that has the RCAs for less $15 in the event that you think that you don't have enough tubes lol....
https://www.ebay.com/itm/1PCS-RCA-1...nkw=12SX7+tube&_from=R40&rt=nc&LH_TitleDesc=0

Again, YMMV, and so far I have not tried drivers with the six pack of 6BX7 tubes, but that's next on the list. But with this great sounding combination there is no rush......

 

[Xcalibur255]

Hi X255,
I find it interesting that the same tube that is quiet in a different amp becomes microphonic in the GOTL but I attribute it to the increased sensitivity and performance of the GOTL.
I don't have the 6520, but I have Chatham 6AS7G and TS 5998 in addition to a number of others (Svetlana, GEC, RCA etc). And the Brimar 13D1 is on my list. Funny, can't find much to choose from in 25V dual triodes.

One possible explanation for why noisy tubes are more of an issue for our amps is the operating points used. Glenn tends to push the tubes hard or run them at "full spec" to get the best sound out of them. A lot of commercial designs, on the other hand, actually operate the tubes very conservatively; often with some degree of sound quality penalty. I honestly don't blame them either. They are shooting for a quiet and reliable product that may be sold to somebody who knows nothing about tubes and won't be understanding of some of the quirks that can come along with this type of amp. This is one of the major areas of gain by having a custom or DIY amp, you can push the design for performance because you don't have to worry about your customer service department getting angry emails. Of course who knows maybe Glenn has gotten angry emails...... I certainly hope not! That's just my take on it anyway.

As for the 6520, I would not stress about it too much. It sounds very similar to the Chatham 6AS7. IMO the 6520 *is* better, but not so much so that you need to go on a whale hunt for a pair. I just find them a little more refined sounding with a slightly more pleasant upper range, otherwise they are largely similar to the Chatham/TungSol 6AS7.

Just a quick note about my last post: I'm not trying to be a downer for anybody here. Nobody is more proud or supportive of what Glenn accomplishes in these pages than I am. I just see some people really running away with the tube buying and I feel like it's healthy to offer some perspective sometimes that I don't really see anybody else offering, even if it means being the Gloomy Gus sometimes.

 

[mordy]

One possible explanation for why noisy tubes are more of an issue for our amps is the operating points used. Glenn tends to push the tubes hard or run them at "full spec" to get the best sound out of them. A lot of commercial designs, on the other hand, actually operate the tubes very conservatively; often with some degree of sound quality penalty. I honestly don't blame them either. They are shooting for a quiet and reliable product that may be sold to somebody who knows nothing about tubes and won't be understanding of some of the quirks that can come along with this type of amp. This is one of the major areas of gain by having a custom or DIY amp, you can push the design for performance because you don't have to worry about your customer service department getting angry emails. Of course who knows maybe Glenn has gotten angry emails...... I certainly hope not! That's just my take on it anyway.

As for the 6520, I would not stress about it too much. It sounds very similar to the Chatham 6AS7. IMO the 6520 *is* better, but not so much so that you need to go on a whale hunt for a pair. I just find them a little more refined sounding with a slightly more pleasant upper range, otherwise they are largely similar to the Chatham/TungSol 6AS7.

Just a quick note about my last post: I'm not trying to be a downer for anybody here. Nobody is more proud or supportive of what Glenn accomplishes in these pages than I am. I just see some people really running away with the tube buying and I feel like it's healthy to offer some perspective sometimes that I don't really see anybody else offering, even if it means being the Gloomy Gus sometimes.

Hi X255,
When you speak of the TS 6520, do you mean dimpled plates or regular plates? I think I read that there are two variants. How close are the 6520s to the 5998s?
Re the Chathams I never really liked them, but that was in different amps. Got to try them again in the GOTL.

Hi rnros,
Also have to try the C3g tubes. Do I have to be extra careful when pulling them out not to break the glass inside the cover, or are the GOTL sockets easy to use?

Hi 2359glenn,
Since the amp did not come with a manual, could you please tell us which tubes NOT to use in the GOTL? So far I only know about the 12AX7. I also seem to remember that you said that the safety feature for using the wrong voltage tubes does not work for certain tubes.
Thanks,

 

[rnros]

Hi X255,
Hi rnros,
Also have to try the C3g tubes. Do I have to be extra careful when pulling them out not to break the glass inside the cover, or are the GOTL sockets easy to use?

The C3g sockets are very easy to use, no difficulty or danger to tube.

 

[Xcalibur255]

Hi X255,
When you speak of the TS 6520, do you mean dimpled plates or regular plates? I think I read that there are two variants. How close are the 6520s to the 5998s?
Re the Chathams I never really liked them, but that was in different amps. Got to try them again in the GOTL.

Mine do not have dimple plates, they look the same as the plates you would see on a Tung Sol 6AS7G. I can't speak to the dimple plate version because I only own the one pair. IMO these tubes sound very different from a 5998 both tonally and in presentation. They are a smoother and less aggressive sound with more presence in the midrange and a warm glow to the upper range that's sweet and detailed but not bright at all. If you have ever compared a good RCA 6SN7 tube to a good Tungsol 6SN7 the difference in tonality you would hear in that comparison is fairly similar to the 6520 - 5998 comparison I'm trying to make here.

FWIW over the years I have gravitated away from liking the 5998 sound and have begun to prefer the sound of the 6520 more and more. They're the only output tubes I own that actually make me like the sound of my Beyer DT880s too. The only reason the 5998s are in my OTL right now is due to heat. The chassis is getting alarmingly hot at work and the 5998 helps a bit with that.

 

[Xcalibur255]

@mordy
The only handling concern you have with the C3g is when they are warm. The filaments break easily when exposed to shock in this state. It's best to wait until they cool down before inserting/removing. Otherwise they are no more fragile than any other tube and you don't have to tip-toe around them. If you have the Yamamoto sockets the insertion feels like a mechanical "click" when the center pin locks. It doesn't take all that much force to get them in, and when they are in you will know it. They're good sockets.

 

[rnros]

Hi X255,
When you speak of the TS 6520, do you mean dimpled plates or regular plates? I think I read that there are two variants. How close are the 6520s to the 5998s?
Re the Chathams I never really liked them, but that was in different amps. Got to try them again in the GOTL.

I do have the dimple plate 6520 that resembles the 5998, and those do have a similar sound to 5998.
IMO, if you have the 5998 you don't really need the dimple plate 6520.
But the 6520 does have a different amplification factor and transconductance than 5998. (6520 AF is 2, same as 6AS7, 5998 AF is 5.5.)
Not familiar with the TS 6520 that Xcal is describing.

 

[Xcalibur255]

A really easy way to put it would be that the TS 6520 is a more refined sounding TS/Chatham 6AS7G. The tone is a bit sweeter, in a good way, but you can clearly tell the tubes are related.

IMO the worst thing about the 5998 was always the higher amplification factor, which the amp didn't need. All it does is draw out any noise issues. The only time I can hear hum on my OTL is when the 5998 are in, it has always been silent using 6080/6AS7 tubes unless the tubes themselves have something weird going on.

 

[whirlwind]

I am building another 300B amp yours was the last one I built. This one will use HEXFRED rectifiers and a timer for soft start of B+. I would prefer to use the 42EC4 Damper diodes
but Tony had one fail and the circuit breaker in his house blew before the 2 amp fuse in the amp did. I never had a problem with these tubes before just a bad tube and maybe
a weak breaker. Now this tube has a bad rep. I did have a 6EC4 fail really the same tube but it was in a SV572-3 amp running at 1200 volts that would be 2400 or more PIV
across the tube. Only the fuse in the amp blew.
Will see how this one sounds all else will be the same with C3g drivers. Making the most neutral sounding amp. Maybe better sounding who knows.

I am waiting for the new WE300Bs to be on sale I need a pair as the filament in one of my KR globe 300Bs burned out now have one KR and one Sovteck
TAKs are way to expensive.

I won't be getting a 300B amp, but in my upcoming OTL I will be using the 42EC4 damper diodes....love the soft start of these not to mention that they sound great and are dirt cheap.

 

[gibosi]

I do have the dimple plate 6520 that resembles the 5998, and those do have a similar sound to 5998.
IMO, if you have the 5998 you don't really need the dimple plate 6520.
But the 6520 does have a different amplification factor and transconductance than 5998. (6520 AF is 2, same as 6AS7, 5998 AF is 5.5.)
Not familiar with the TS 6520 that Xcal is describing.

I have seen 6520's that look identical to the TS-6AS7 and others that look identical to the TS-5998. Given that the spec sheet for the 6520 states that it has the same characteristics as the 6AS7, but with a few tweaks, I am inclined to believe that a real 6520 looks identical to the TS-6AS7. The version that looks like a TS-5998 is likely just a 5998 that was labeled as a 6520 at the factory. After all, the 5998 and 6520 are similar enough that in many situations one can be substituted for the other. And back in the day, this sort of deliberate mislabeling at the factory was not uncommon....

 

[2359glenn]

Trudging along the tube rolling path with my new GOTL. ATM I am trying out different drivers that I haven't tried before and bought for the GOTL - power tubes are 10A of American Muscle (Cetron 6336B).
It would be easy to buy the expensive tubes with the best reputations, but that's not for me. You can buy a 40's Sylvania 6SN7W for $25 if you luck out, or for $350. Mind you, the same tube, so am I holding out for a lower price range, but it takes patience.
Meanwhile I got a Sylvania 6SN7WGT from June 1955 ($18). This is a very nice sounding tube with a somewhat bright, brassy presentation in my system with the Cetrons.
Jumped on the Tung Sol BGRP bandwagon. The 6F8G had problems with microphonics. My engineering staff is working overtime to find an antidote (not true). The TS 6SN7 BGRP is too expensive at the moment and I can't find the 12SN7 BGRP at the right price, so I got a TS 6SL7 BGRP relabeled Motorola for $29. Cannot find anything on the tube that says 6SL7 so I have to trust the seller. Sounds similar to the above Sylvania but not as bright.
A long time ago I read an article on the website of JACMusic about a very good sounding tube that isn't so well known - the 12SX7.
Thanks to myphone I am now able to listen to this 12V tube. The tubes I have are made by RCA, but there are a several manufacturers that made them (unless they all are rebranded).

Look at that - a 2018 tube! Well, January 1953 is more like it:

IMHO a great sounding tube and that can hold it's own and more to the Sylvania 6SN7WGT and the TS BGRP 6SL7.
There is a Taiwanese seller on eBay that has the RCAs for less $15 in the event that you think that you don't have enough tubes lol....
https://www.ebay.com/itm/1PCS-RCA-12SX7-12SX7-GT-Vacuum-tube/152839422530?hash=item2395f08242:g:FTYAAOSwt6ZWVJkJ&_sacat=0&_nkw=12SX7+tube&_from=R40&rt=nc&LH_TitleDesc=0

Again, YMMV, and so far I have not tried drivers with the six pack of 6BX7 tubes, but that's next on the list. But with this great sounding combination there is no rush......

Mordy
Here are a pair of Tung-Sol round plate tubes not so bad if you sell one to someone that has a GOTL and wants one.
https://www.ebay.com/itm/Matched-Pa...&_sacat=0&_nkw=tung+sol+12SN7&_from=R40&rt=nc
Who knows maybe Santa will send you a 13D1/25SN7

 

[mordy]

Mordy
Here are a pair of Tung-Sol round plate tubes not so bad if you sell one to someone that has a GOTL and wants one.
https://www.ebay.com/itm/Matched-Pair-Tung-Sol-Fordom-MR-12SN7-GT-Black-Glass-Vacuum-Tubes-Very-Strong/183299486656?hash=item2aad8033c0:g:8~oAAOSwFtZamdRP&_pgn=1&_sacat=0&_nkw=tung+sol+12SN7&_from=R40&rt=nc
Who knows maybe Santa will send you a 13D1/25SN7

Hi 2359glenn,
Have been eyeing those for a while - looks like the seller greengirl likes green...
I'd rather look for a different rebranded TS 12SN7 BGRP that was bought for $13 shipped not long ago.
Did you say EF86 was a no-no?