Tube Rolling w/Crack

[Tom-s]

How could i rebuild my Crack to work with this tube? http://tdsl.duncanamps.com/pdf/a2900.pdf
Or could it be done by just raising the R1 resistor to 1k ohm?
Or should i use another LED color for correct bias?

As a don't have a volume control in my Crack, i'm ok with the higher gain.

Edit: I can imagine it being a no-go as the current would be to low for the LED to light up/function for getting it within save function. And lower bias would trow off the 6080 function.

[Paul Birkeland]

That tube has way, way too much amplification factor.  The extra 15dB of gain that you will get from using that tube will be very unwelcome.

[Tom-s]

Aside from the fact that it would be a problem in a Crack with volume control.
I'm ok with the extra gain. I just want to try this tube, and run it in optimal conditions for Crack (if possible).
Could i just make the R1 resistor in speedball a bit higher to get it to work?

[Paul Birkeland]

No, I mean when you move the volume control 5 degrees or so, you'll likely be near full output on the Crack.  In order to run that particular tube with the red LEDs on the socket providing bias, you'll run so little current that you'll be off in the weeds in terms of where the linear operating areas are. 

[attmci]

Gracious, when did the 6F8G get so expensive?

Because they are cheap comparing to these:

https://www.ebay.com/itm/173774749419?ul_noapp=true

Happy Easter!

And much cheaper than these rebranded Mullard. (Mullard had never made 6SN7GT tubes).

https://www.ebay.com/itm/2-pcs-new-NOS-NIB-6SN7GT-ECC33-CV2821-Mullard-matched-pair-/254196502387?nma=true&si=UDPVVJzJhpzUeUHL000cyhiFdV0%253D&orig_cvip=true&nordt=true&rt=nc&_trksid=p2047675.l2557

[Tom-s]

Philips factories did make 6SN7's.
The Philips designation for the 6SN7 is r9x.
In my collection there's a few RCA licensed 6SN7's with Philips / Adzam logo's.
The only EU factory i've found in my Philips 6SN7 collection is Bruxelles r93 Lxx.

So a Mullard labeled 6SN7 can exist.
https://tubedatabase.co/tubes/mullard-6sn7gt-r92

[attmci]

Philips factories did make 6SN7's.
The Philips designation for the 6SN7 is r9x.
In my collection there's a few RCA licensed 6SN7's with Philips / Adzam logo's.
The only EU factory i've found in my Philips 6SN7 collection is Bruxelles r93 Lxx.

So a Mullard labeled 6SN7 can exist.
https://tubedatabase.co/tubes/mullard-6sn7gt-r92

Very true.  Philips/Brimar did make 6SN7/CV1988.

But not Mullard.

All those Mullard 6SN7 are rebranded ones (most of those are Brimar).

The pair sold in the previous link(2 pcs new, NOS NIB 6SN7GT ECC33 CV2821 Mullard matched pair) for $565 are identified as British Tungsram 6SN7GT.

Unfortunately, the bidders might not aware of the origin of those tubes.

[Tom-s]

I thought Brimar was a different company (STC->ITT), and not a Philips company.
And that Mullard was a Philips subsidiary?
https://en.wikipedia.org/wiki/Mullard%E2%80%93Philips_tube_designation

And the ones sold hold a J factory code (Totterham), which was a Mullard site (formerly Tungsram).
https://frank.pocnet.net/other/Philips/PhilipsCodeListAB.pdf

So these are Mullard 6SN7's, i think the seller is correct with this information.

Edit: https://mullard.org/blogs/our-product-manufacturers/tungsram

[attmci]

I thought Brimar was a different company (STC->ITT), and not a Philips company.
And that Mullard was a Philips subsidiary?
https://en.wikipedia.org/wiki/Mullard%E2%80%93Philips_tube_designation

And the ones sold hold a J factory code (Totterham), which was a Mullard site (formerly Tungsram).
https://frank.pocnet.net/other/Philips/PhilipsCodeListAB.pdf

So these are Mullard 6SN7's, i think the seller is correct with this information.

Tom, I don't want to argue with you here.

Again, Mullard had never made their own 6SN7GT tubes. Those "Mullard 6SN7GTs" are rebranded ones. If you like Mullards, you should try those GREAT ECCXX tubes.

If you like these British made Tungsram 6SN7GT, you can get these for about $50 (not from me).
Picture here:

https://www.head-fi.org/threads/sold-matched-pair-of-nos-mullard-6sn7gt-ecc33-brown-base-black-glass-black-plates.513347/

Statement here:
https://www.head-fi.org/threads/6sn7-tube-addicts.479031/page-32#post-7020122


markmaxx said: ↑

    I had no Idea there were so many different Brimar 6SN7GT..The 6SN7GTY hardly ever come up.
    http://cgi.ebay.com/6SN7GT-BRIMAR-BLACK-GLASS-NOS-/260646296312?pt=UK_Consumer_VintageAudio_RL&hash=item3cafbadaf8#ht_500wt_1156
    http://cgi.ebay.com/6SN7GT-CV1988-BRIMAR-NOS-/280538144036?pt=UK_Consumer_VintageAudio_RL&hash=item4151605d24#ht_500wt_1156
    http://cgi.ebay.com/6SN7GT-BRIMAR-NOS-/260639238170?pt=UK_Consumer_VintageAudio_RL&hash=item3caf4f281a#ht_500wt_1156

Be careful with this ebay seller. I bought a pair of Mullard 6SN7GT that originally he said that they were coded like that because they were made for the USA market. Blackmore identified them as not Mullard but Tungsram so after questioning him he admitted they were Tungsram made for Mullard. What I really believe they were actually Tungsram re-branded by himself as Mullard. I was able to return them and get a full refund. I would make a lot of specific questions before buying any of these Brimar. One thing strange is that the lettering looks very new just like those Mullard I bought.

[Tom-s]

Also not here for the argument. With all information gathered. I think everyone could be correct. 

In my ECC collection i see the same happening over and over again. Blackburn made ECC82 tubes labeled Philips (or Adzam, Valvo) and Mullard labeled ECC82 made in Heerlen, Holland.

Labels of tubes don't tell the whole story. Always look at the tube code. Don't mind the label.

The Totterham problem is explained best in this blog: https://mullard.org/blogs/our-product-manufacturers/tungsram

They have codes J5B and J5D
J = Totterham
5 = July
B and D are 1953 change symbols.

Edit: So these are genuine "Mullard" and could be relabeled from Tungsram factories or foreign import from other factories.

Brimar 6SN7 tubes look distinctly different from Philips'. For this you can look at the way the support rods are fixed to the mica, the build of the mica (without "teeth") etc. I do like the Brimar 6SN7's a lot. Very nice tubes.

Other then Bruxelles, haven't heard other 6SN7's from Philips Europe.
On another note. For the German market and military, Valvo in Hamburg made the 12SX7 (special version 12SN7) but can't find proof of a 6SN7's.  From my experience with Valvo tubes, if they made a 6SN7 these could be very very very good performers. Possibly the best sounding SN7's you could buy.

[Tom-s]

Yes. Brimar 6SN7 tubes have the rivets like that.
Mine don't have the cooling "wings" and are normal versions.


Had a bit of a "facepalm" moment. As i was writing about the 12SX7 yesterday i remembered that i never actually opened a box of those. So went searching for them in my collection today. And based on the box you could figure it's Valvo made (BUT, it is a USA military box). ALWAYS look at the tube code. And it reads 274 (RCA)... ... .. 

Another "SN7" thats not EU made. I think these are imported and boxed in Hamburg for European military supply.

My sincere apologies for the misinformation. 

https://ep1.pinkbike.org/p5pb17144214/p5pb17144214.jpg
https://ep1.pinkbike.org/p5pb17144215/p5pb17144215.jpg

[m17xr2b]

Just one more tube to try and I've reached the peak tube rolling in the Crack. This was so much fun.
Currently running a ECC32 with 470ohm for R1 on speedball.
Can the crack take the BL63 at 1.2A of current? What's another 0.3A between friends?

[Tom-s]

The Crack's transformer is designed to provide a maximum of 3.5A from the heater winding.

So even with a 2.4 amp 5998 you'll be at 3.6A which can cause the transformer to overheat and burn out.

Maximum i've used is 3.45A from the heater(with the ECC32 and a 6AS7G).

If you find a 1.2-1.3A output tube that works, you could try the BL63.

Tell us about your experience with the ECC32's?

[m17xr2b]

The ECC32 is one of my all time favourite tubes in the Crack, Apex Teton and Peak, Woo WA5 and Cavalli liquid glass.
Highly musical, mid range could be perceived as coloured when compared to other tubes and is the highlight. Very smooth overall no grain to speak of, can create a very realistic soundstage with plenty of air.
I'd recommend it with a neutral tube that doesn't emphasise the mid range. GEC 6080 is too warm but GEC 6AS7G/Bendix/5998 are ideal matches.
Low end is not as tight as others say ECC40 and it strikes a good balance between relaxed and aggressive.
With the GEC 6AS7G on a very subjective rating would be ECC32/ECC40 > ECC33/TSRP/13D2 > E80CC/ECC31 > other 6SN7 and 12AU7.

My crack has speedball, film output and last cap in PSU, choke and cree diodes. I wouldn't recommend the ECC32 unless the crack is already maxed out and want a bit more. On just stock crack and speedball the differences between tubes are not as obvious.

Looks like with the BL63 I can only use it for a short session to get an idea of how it sounds. Otherwise I'll have to upgrade to Crackatwoa  but I really like the small form factor of the crack and would hesitate to replace it.

Silly question, could I use the Crackatwoa transformer in the crack?

[Tom-s]

The ECC32 is one of my all time favourite tubes in the Crack, Apex Teton and Peak, Woo WA5 and Cavalli liquid glass.
Highly musical, mid range could be perceived as coloured when compared to other tubes and is the highlight. Very smooth overall no grain to speak of, can create a very realistic soundstage with plenty of air.
I'd recommend it with a neutral tube that doesn't emphasise the mid range. GEC 6080 is too warm but GEC 6AS7G/Bendix/5998 are ideal matches.
Low end is not as tight as others say ECC40 and it strikes a good balance between relaxed and aggressive.
With the GEC 6AS7G on a very subjective rating would be ECC32/ECC40 > ECC33/TSRP/13D2 > E80CC/ECC31 > other 6SN7 and 12AU7.

My crack has speedball, film output and last cap in PSU, choke and cree diodes. I wouldn't recommend the ECC32 unless the crack is already maxed out and want a bit more. On just stock crack and speedball the differences between tubes are not as obvious.

Looks like with the BL63 I can only use it for a short session to get an idea of how it sounds. Otherwise I'll have to upgrade to Crackatwoa  but I really like the small form factor of the crack and would hesitate to replace it.

Silly question, could I use the Crackatwoa transformer in the crack?

Thanks for your review. Good to see another fan of ECC40's. They have a nice sound and i use them a lot.
Even acquired a few new ones last week!

Go for the Crackatwoa. I can see why a shunt regulated powersupply will be a very nice upgrade to the standard Crack. It's on my wishlist aswel.