12BZ7 ///12AX7

Wow what a roller coaster. Fun to look at, but sure a lot of it..

Your on quit a journey indeed. "Burn in Theory" Take a little more time and let the things break in a bit, settle down. 

I'm reading some pretty crazy stuff here. Cables were swapped?

How may valves sounded bad during that time? How long were they that way?

I have quite a few different "TANKS" as you call them here..
Be careful. A valve can really cause problems.  You have a way to check your valves and make sure they are balanced? No issues to begin with. That's probably most of the issues with "sound bad" valves.  Like I said, a lot of words, but difficult to weed through it..

No lack of enthusiasm though..

Regards

@chinacat
The 5751 silver plates, as you mentioned, are very revealing. However in my system it was revealing to the point of being BRUTAL. Including an excess of high frequency energy. I liked the effect for up to 30 minutes at a time, but then it became too fatiguing to continue. The 12ax7 had the better, more natural balance. However the 5751 was very exciting at first, especially with certain recordings.

Then, of course every system and set of ears is different! To add some context, my Tannoy Canterbury GR speakers often don’t do well with upstream gear having any excess treble energy. I am glad you enjoy the tubes, regardless!

I have tried Mazda 12AX7( S) silver plate with Sylvania 12BH7(A) in my Rogue Apollo’s upgraded to Darks at factory, actually on Mulveling’s recommendation. I am very pleased with the results. Currently, I am using  Mazda 5751 silver plate 3mica and like them. They sound more revealing, albeit not as quiet as the silver plate 12AX7S. I understand it’s a matter of personal taste, but am I missing something here?

Yes 5751, horrible, 
I am bidding on  a pair of Tele, 16 hrs left,,I am winning at $81,,,tubes pulled from a  estate sale, working ociliscope, look NOS 100%, I am at top $, doubt i win. 
Might try in 2 yrs to pick upa  pair.

The Tele ribbed plates aren't as warm as the smooth plates - you may like those better. Surprised you didn't like the Mazdas, but systems change and optimal tube selections can change over time - are you sure they weren't the 5751 silver plates? Those were awful lol. 

@lowrider57 I responded to the Q concering so called ~~Burn In Theory~~ over at my New Kids topic.
There i completely expose that scam and believe my comment is 
verifible , believebale, honest, fair, unbiased.
I put the final, last nail in 
~~The  Snakeoil Coffin* once and for all.
 @ Mulveling
Someone here on audiogon mentioned in a  post, he has tried Teles and Siemens , the Teles he found more on the ~~warm~~~ side, vs the highly detailed Siemens. 
I always go for clean/clean/details. 
I have Siemens AX's / RCA AX's /tall blacks, arriving this week. 
Look or a YT vid upload , late sunday night. 
The Mazada's , chome plates, , I recall havinga  pair, i did not like them at all.

My system now with new added silver sterling to speakerwires (16 individual wires total, = biwire 1 copper + 1 sterling 14 ga silver  = 2 X 8 = 16 insul wires,,,
and the wires are correctly employed = no criss crossing .
+ took out the E188's in the Lite LS9 Jadis clone pre and installed tyhe stock EH 12AT7's and that as well made a futher gain in details, but is more *beefier* sound, not as laid back/quiet,  as the E188's. Prefer the AT's overall. and so the AT's will remain.
My system has made some progess, and will report back on futher mods/critque.
Our goal here is to finda  path to Pure Class A resolution/highest fidelity. 
3 things , no 4 things are required
1) Patience
2) reserachreserachresearch
3) trial and error
4) $$$$$$$$

Try some "used test strong" Telefunken 12ax7 when you get a chance. They’re solid all-rounders, and relatively common on the 2nd hand markets. But favorite 12ax7, by a good margin, has been the Mazda silver/chrome plate. Unfortunately they’re rare and expensive ($350+ a pair), and they have a bit of extra energy up top - so won’t be ideal for systems that need a push towards a relaxed top end.

Also I like those RCA tall black plates pretty well, but think the Mazdas are much better.

Mahlerfan, do you give your tubes time to break in??
It seems like they go in and out of your amp pretty fast.

BZ7’s arrived, = No go, 12AX7’s out shot the BZ’s in every area.
Now i am on witness a shoot out twix several AX’s
RCA Tall Black Plates vs
 Philips Miniwatt vs
Shugaung T series vs
Siemens  ,
~~~USA vs
Gerjmany vs
Holland vs
China~~~~~
One of these 4 finalists will be given a ~~~Gold Medal~~Silver Medal~~Bronze Medal~~Copper Medal.
,i have no idea howm this Olympic battle will go down.
All 4 are Legenday and may result in all receiving Gold = Miniscule dif.
also want to try Baldwin Organ AX’s. which i am guessing is a RCA.
IMHO Philips is Amperex SQ , made in the legendary Herleen plant,
Phlips Mini watts = Amperex Bugle Boys.
what it comes down to is this
All NOS (rated at least strong) are near equalin voicing. The more important concern are what caps are employed in the amps design.
Tech guys with testing equipment lay claim that if low price cap A tests near equal to high price cap B, then sonaiclly both with sound very sililiar ina amp.
Yet my concern is the limitations imposed by measurable equipment.
IOW I believe there may be more to a cap’s voicing of music, that can not be meausredn ~~~~completely with NUANCES~~~ by a test screen.
Its kinda of likea botanist studing flowers. A text book along with disections/images, still misses the flower in its own enviornment in full bloom.
someone over at DIY mentioned it is near impossible to determine the sound quality of a unit, based ona compressed YT vid witha low level mic/camcorder.
True and yet not so true.
I have skill at listening to what a unit sunds like in real time. If you can not hear the high fidelity of these M caps, you need a hearing aid.
The M caps glorious sing the muisc.

https://www.youtube.com/watch?v=XfqWgHqiPwQ

The BH/BZ/AX data sheets all look similar in the same way that a bicycle is similar to a motorbike. They have the same number of wheels and you need to balance to ride them.
Well if nothing else you’re enthusiastic about it all! But don’t be disappointed if it doesn’t work out. Do yourself a favour and have a tech check the operation.
Gain in the tube also sets the circuit dc voltages, not just the volume control position. If you look at the data sheets you’ll notice the amplification factor and current ratings are totally different for each tube, reflecting the different control grid construction and size of each.

Those spec sheets on the 
BH/BZ/AX, all look similiar.
But note:
I am never using the vol on the preamp with much gain, My room is 10X12/8 ft ceiling, why crank it up??
= No reason at all.
The Jadis's trans , inspite of RUMORS of a  *previous model* (a  rumor I ain;'t buying). , the Jadis builds like tanks, indestructible. 
If the BZ, BZ has over heating issues, the tube will blow before anything inisde the Jadis./

Besides there are resistors inside the Jadis, either the  resist or tube will blow,,,
I will carefully note the BZ/BH's temp, while employed.

Also I made some changes in my speaker wiring, Added silver to the copper.
Thing is, as i was making that mod,,i noted one biwire was crossed wrong. I had one neg going to the opposite post, That is the left channel had 
the black lines crisscrossed, and THIS was no doubt causing HAVOC/HIGH DISTORTION in that cahnnel and completely annihiliating /destroying, mulitiating the fq resolution. 
.
So correcting that ~~unforgivable~~ error  
OKUS adding the silver sterling 92% silver line with fat copper strand.
= the resolution of fq's in super.
This Jadis sings now.
When I put more vol on the Lite LS9  Jadis clone, there is no ~~complete breakdown~~~ of fq's = the high level of distortion (which i attributed to the pre's low level of build quality) has all disappeared.
Perhaps the added silver did nothing at all to gain high fq resolution..= IOW was the whole issue the crisscrossed speaker wires??
Or did thev added silver add a  clean, clear, nice gain in resolution???
I have no idea and will not make any experiements with 
all copper vs 
silver/copper.
Time constraints.
The Bz/s'Bh's , will arrive late this week, will report back on how that tube roll went off. 
Let me finsih by saying the sound is completely 
~Non Fatiguing~ = Zero fatigue Factor~~ (aka ZFF)
I loistened to Mahavishnu Orchestra, Live Central park, and wasblown away at what serenity overcame me , which never on previous systems experienced.
That record is not high fidelity studio, Diana Krall was mesmerizing. 
I could retire from this mod adventure with what i am getting from the system. 
But as a  seeker of high fidelity, this desire to make futher discoveries is calling me onwards.
I have 20 M SGO caps to be employed in my cayin cd 17 Mark1.
later this year will rebuild the Thors xovers with M high level caps. 
Along with the cayin SC6.
The SC6 employs 4 AU's,,well you already know what i plan to do, and will ck the E80CC's tempt while in play, and also the heat level on tops of trans. 
Cayin is like Jdais, build quality impeccable, ~~build like tanks~
YT vid update comming  Sunday. will post a  link.
But as a  DIY member noted, a  YT vid offers little in forminga  opinion on a stereo sound.
I agree in part only.
After listening to countless YT uploads of stereo's in performance, I can now  hear through the compressed replay.

Here is a  example froma  YT vid with a  guy showing off the M high level caps mod in his amp. 
I can hear the M caps singing GORGEOUS.

Not the vid I was looking for , yet another testimony to M caps singing ~~Like Angels~~~

https://www.youtube.com/watch?v=3vLTeIDuWmM


Here is the reference vid i was looking for.
https://www.youtube.com/watch?v=XfqWgHqiPwQ

Now listen to this Class D/Class F sound with Jadis; audition room at a  stereo show

This is not the vid I was looking for, but it will work, showing how a  speaker can drag down a  complete $100K Jadis set up, to ~~Class F ~~ sound.

https://www.youtube.com/watch?v=CIut7iVo7DM&t=291s


and note carefully in this vid, where you can see one of the best mid/tweets ever made.
The Seas Millenium!!!, UNREAL, either the xover design/parts or that mid range is driving the entire Jadis + Millenium down to grade
Class F. 
No I can not grant a  ~~Grade D~~ to this horrific atrocious sound level. 
This is from a  Munich 2019 show

https://www.youtube.com/watch?v=Hzbz4b09bH8

So agisnt the opinion of the DIY member, a  stereo 's quality of resolution can be noted, at least on most vids. If you have a  
1) trained ear/sensibility 
2) practice makes perfect
3) listening attentively
4)  replay as often as needed to draw some conclusions.
Every Jadis showroom upload on YT, , has these horrific speaker set ups, dragging, what otherwise could be a  Pure Class A sound down to
~~Pure Class D~~ And in this Munich show, down to  pure class F Minus resolution of fq's. 

7308 is a 6dj8 equivalent, not 12au7.
The Defy 7 has the 12au7 as input tube, the 12ax7 is the driver tube. The extra current capability of a 12bh7 is unused in this circuit. Same for a 12bz7 in place of the 12ax7 at the same operating current. The miller capacitance is higher in the 12bz7 so the high frequency response will be more restricted. Without modifying the circuit, the performance overall should be worse.

@mozartfan,
I'm not understanding your opinion that the 12AU7/ECC82 sucks. In the Asylum shootout the clear winner was the Brimar Gold Aero Platinum grade 12AU7A.

There are superior drop in substitutes such as the 5814, 5814A, CV4003 Mullard & Brimar, 7316 & 7308 Amperex/Philips. All are in the AU7 family, all low-noise tubes. Many preamps and amps do not recommend using higher current tubes.

I'm not sure how the extra current capability of the 12bz7 over 12ax7 would be an advantage? Most designers place 12ax7 for their gain, not current. They're never reasonably going to be asked to drive a hard load, so you're perhaps not gaining anything meaningful. However the 12au7 is often used as a driver or follower, and I've always heard improvements by subbing in the much stouter 12bh7.

Yes, you have to be careful that you have enough overhead for the extra heater current draw. Always consider the component. For a preamp with 6x 12au7, yeah you're probably in trouble subbing 12bh7's and doubling the heater requirements. For my Rogue Apollos with 4x 12au7 and 12x KT120 - well more than 90% of the heater current is sucked down by the power tubes and an extra 0.3A per 12bh7 didn't pose a problem. And yes it sounded a lot better too!

I am willing to risk possible issues

OK, It’s your gear, but if your Defy 7 stops working don’t complain about Jadis if they won’t fix it.

Just looked at the Defy 7 schematic, audio section. It looks like the 12bz7 would work ok for the audio circuit voltage settings. BUT there is a danger it will draw too much heater current from the filament winding, along with the E80CC, which also draws double the heater current of the original 12au7. I don’t have the power supply section schematic here.
The gain of a 12bh7 is 16.5, the E80CC gain is 27, the ECC99 has a gain of 22. The 12au7 has a gain of 20. Since the 12au7 gain and transconductance sets the voltage for the rest of the input stage on the Defy 7 I’d have a tech familiar with tube circuits to check the voltages and currents over with these alternative tubes you’re trying. There might be a risk of frying the heater winding with too much heater current from these bigger tubes.

Jadis always *Please relate all concerns to our USA representative dealer*.
Bluebird, i believe, which is a dead end as for *~~cap I swap tubes,,,~~~
~~what we suggest,,,,,,~~ no doubt will be the answer..
As Blue and Jadis do not want to give the green light and if a curcuit blows, , can’t take the risk for blame..
Seems to me is the system is working with the E80’s, and no shorting/crackles, whistles, pops, then just let it play.
The Defy with AU’s does not offer the fq resolution, forward sound stage, that i require ina amp,.
= I am willing to risk possible issues.
EU E80CC = 12bh7, at least from looking at the 2 designs.
I just boughta bunch of bh’s along witha bunch of bz’s.
The bh’s i will try in the AU section and the bz’s in the Defy’s AX section, will post later this week how these 2 tube rolls went off.
maybe evena YT vid with the new bz’s and bh’s.

OK so the
12bh7 = EU E99CC.

~~Ck with your amp manufacturer~~~
(a bit late for the roll to the E80CC)
https://www.tubesforamps.com/products/12bh7

+1 ndevamp.
Check with the manufacturer.

The 12bz7 is basically a double 12ax7, ie. Each 12bz7 triode is similar to two 12ax7 triodes in parallel. It draws double the heater current of a 12ax7 (600mA vs 300mA) and has twice the transconductance. It has a gain of 100, like the 12ax7. Not sure if your Defy 7 can take it, you might need to ask Jadis for help with that. If the circuit was designed for 12ax7s, dropping in a 12bz7 might cause the circuit not to work properly.
In the same way a 12bh7 is similar to a double 12au7 and also draws twice the heater current, and a gain of 20.
I used to use 12bz7s in my tube phono pre of the 90s.

mozartfan, The E80CC is a European designation for a tube. The European designation for the 12AU7 is E82CC and for the 12AT7 it’s E81CC, for example. I don’t know if there is an American designation for the E80CC.

Different tubes have different electrical characteristics. You need to check with the maker of your Defy 7 to make sure that the E80CC’s electrical characteristics won’t damage it over time. It’s really not a good idea to substitute different tube types without finding out if they’re compatible with the equipment.

I checked at Brent Jessee Tubes and it appears that the E80CC is considered a substitute for the E82CC with the caveat that you check with the manufacturer about suitability:

E80CC / 6085:This unusual European tube is basically an industrial type 6085. However, it’s specs are similar enough to a 12AU7 that audiophiles are grabbing them up while the prices are still reasonable. The heater life is rated at 10,000 hours, and some have gold pins. The larger box plate structure gives this tube low microphonics and silky smooth sonics. Since this tube has a much higher Gm and Mu factor than a 12AU7, the gain is going to be greater and this tube will give a more forward presentation. Awesome in phase splitter applications. If in doubt, check with your amp or preamp manufacturer to see if this tube will work OK in your application.

@ Mulveling, Its about time someone tells 
It eaxtaly as needs be siad
*basic AU suck* including the Holy graisl,,,note even Siemens/Teles AU's can be had pretty cheap.
Its the AX's which go for GOLD.
Yes there are at least 2 or 3 other tubes can be ub for the AU;'s.


@ 
noromance
Great find, well done my friend, backs up some of my findings on the E80CC.
I have to disagree in part,, yet agree in other ideas made from this 2000 post on Audioasylum

*The E80CC projects a  very odd sound stage,,,~~~indeed it does~~~which gives a  MUCH LARGER THAN LIFE SOUNDSTAGE~~~ Indeed. 
My defy was dead, and could not sing due to the Class D chinese clone jadis  preamp,,,with the employment of the E80CC, the jadis came to life, though still at Class B/C fq resolution..Still, thats better than the Class C/D fq resolution with the AU's employed.
~~~~VERY VERY HIFI SOUNDING~~~ The E80CC is High Fidelighy. 
The AU is Low Fidelity = Class C tube. The E80CC is a a Class A design. 
The author goes on to say
~~~ we need futher testing to make a  complete testing vs the AU..~~~
lastly he suggests that his questioner, just avoid the E80CC and stick with 
~~The old tried and true~~
AU.
Based on my testing, the E80CC is The King of all AU's, while all others/Siemens/Teles are mere rogues in comparison.
Now i am on to  discovering the 
~~King of all AX's~~~
which i do believe have found in the 
,,well the Valve Museum does not list a  
12bz7
does list its cousin
The 12BH7A
The build of this 12BZ7 looks identical to the AX design, except a  taller version...

http://www.r-type.org/exhib/aaa1764.htm

The 12bz7's go cheap on ebay,,now after my testing and following up witha  YT vid, that market price might jump.

Note how mucha  single Philips mini watt E80 got today on ebay,,~~$150~~!!!
lsiting says, pinch waist/D ring,,= pure snakeoil.

A E80CC is a  E80CC is a E80CC. The Siemens did, if memory serves me, makea  miniscule pop in fq resolution,,,yet i need to  makea  further testing vs the Philips E80, maybe tomorrow. 
The author in the above Audioasylum mentioned the Philips was superior to Tungstrum,,,which i might also believe is true. But as i say, the pop is so miniscule, its reallya  matter of what you are willing to pay.
A system which lacks the sensitivity to pick up the added fq resolution  of the Siemens, may do equally as well just to grab any E80CC.
As I say, in order fora  Class A tube to operate in 
~~~pure class A~~~ resolution,  the system has to possess ~~Class A sensitivity~~.
My preamp is Class D, The Cayin Class A/B The Thors Class A/B , thus the Lite LS9 pre(Class D) drags the entire Class A/B system down to class B/C. 
Yet in spite of this drag on the resolution, the Defy with its Class A build, does quite well at registering the incredible life offered by the sublime E80CC. 
I've got my work cut out over the next 6 months, and slowly but surely hope to acheieve Class A/B resolution by mid summer. 
In 2021 I hope to achieve 
Pure Class A Resolution of fq's. 

Interesting...
https://www.audioasylum.com/messages/tubes/25401/12au7-vs-e80cc

Well 12au7 suck, so it’s not uncommon for folks to find a different sub type that blows all the best 12au7 away. Many tubes operate similarly to a 12au7 and do it better. 12ax7 is a better sounding tube albeit with a very different use/purpose, and you may have a much harder time finding a sub to beat the greats.

The Philips E80CC sold for
~~~~~~ONE HUNDRED AND FIFTYYYYYYYY <<<WORTHLESS>>> USA DOLLARS~~~~~~
UNREAL.
WOW,,I am stocking up,
when i pay off my $5K paypal I will load up 100+ E80CC’s, if you want a E80CC, you will have to go THROUGH ME.
lol

,,,wait a  minute,,Not $50 each, I am bidding ona  Philips Miniwatt E80,,,ends in 4 hours Current bid
~~$114/10ship~~~
UNREAL.
Thats crazy,,, as i say,,
IMHO
all E80's , are near equal, the sonics are so ~~Miniscule~~ (as my tech guy in  Bato Rouge would say) , its not worthm paying more than $50 each. 
at least in today's, jan 2020 selling price.
Just think if word gets out about this tube as a  ~~Super Tube~~ swap for the AU.
Prices could double over night.
Once I see prices jumping, I am going to load up and scalp later.
I've lost so much money on buying and selling tubes past 2 years, time for me to make it back/ anyway, back to 
12BZ7.
If that tube pops the AX section in my Defy,,thats another tube that could jump in prices.
They go cheap now.