7dj8 in ET5 not working

[jimbones]

Has anyone successfully used a 7dj8 in their ET5? I bought one and installed it and got a boatload of loud noise. I immediately shut down the unit no damage. I reinstalled my 6922 and it is fine. I spoke to Jeff and he said that it "may" work but advised against it. Just wanted to know your experience. Not sure if I got a bad tube or if it is not compatible.

[Big Dog RJ]

This very same topic has been discussed on WBF, where some claim to have tube rolled on their ART88... and found certain variants of 6922's/E88CC not compatible at all, whereas others and apparently the review on Hi-Fi+ seemed to have worked out ok.

First of all, why the heck would you want to change anything on an ART88...??? I really don't get it. Just enjoy it to the fullest! This is thing, someone gets a bright ass idea, changes tubes and claims the sound is out of this world! Whatever floats the boat I guess but if something goes quirky then blame either the cook or bottle washer (uh... both same person here I guess).

According to informed sources (with audio technical backgrounds) and mostly from trusted CJ techie, there are minor changes in their Voltages. Although these voltage differences may seem minor... the base circuit may not allow for higher tolerances. With certain tube gear, they used to allow 3-5% tolerances but now with CJ's latest gear, it may well be as low as 1% tolerance. So, certain tubes won't work. IF and only if you did try one of the 6922 variants and all is well... then perfect! Good for you, and just leave it in there! But, no... they don't leave it in there, rather they change again! and swap again... because they couldn't remember what that first tube sounded like... and then change again... and this utmost silly event of constant tube rolling cause shifts in voltages. This is not good for the preamp or any amp, simply because the tubes themselves take time to settle in... that amount of time could well be within a few 50 or even 100hrs but they're never given a chance. Call that bottle washer and tell him he's not washing the bottles properly! Oh, why bother.

Re: to your ET5, as far as I'm aware, I don't think the Phillips 7DJ8's would suit. These are more suitable towards the GAT series and ART line. Having said that, there well may be owners who've had successful results using this particular tube in their ET5's, as is the case with other types of 6922's. Maybe, they just got lucky or that star cook made an outstanding pasta dish!

As far as my experience goes with the ET5 (which is a mighty fine preamp!) the ones that were safely used with the best performance by far were either the EH6922 Gold pins or the GGL's E88CC. I know one chap who used the Siemens variety but then switched back to the EH gold pin version.
Cheers, RJ

[SolderSlinger]

I have used a NOS Philips 7dj8 without issue. I bought it from CJ maybe 4 years ago for around $100. I still have it along with other tubes that I've rolled in the ET5. Previously used about every new production 6922 brands and currently using a NOS Bugle Boy 6dj8.

My $0.02 is to try another 7dj8.

[jimbones]

Thanks. I ordered a NOS Siemens 6922. I also have read a lot about 7308 but they are mighty expensive

[Joe Appierto]

Should you decide to revisit 7DJ8 tubes, I found these to be quite good when I used them in a Premier 16LS2. It's been many years since I patronized the vendor but they never disappointed and especially given prices nowadays, worth it.

https://www.tubemonger.com/MP_MINT_NOS_ ... _p/756.htm

[microstrip]

The 7dj8 / PCC88 uses a 7v filament supply and the 6922/ECC88 uses 6.3V. Other than this aspect the specifications are similar. In my home made tester, that has exact 6.3V voltage I could operate and test Philips PCC88's with minimal differences in gain, noise and distortion compared to 6922. However as said by Big Dog RJ we are playing with luck and tolerances when using 7V filament tubes in equipment prepared for 6922's - in extreme cases the filament will not heat enough, resulting in increased noise. Remember that tolerance affects tube and equipment supply.

[Big Dog RJ]

110% correct!

That's what I was referring to, and most get carried away by tube rolling, not even knowing what exactly is going on in technical terms... and the tubes feel it! Not us.

We only feel/ hear it when those little buggers start yelping in terms of noise & distortions. IF and only if those variants tried out have worked (zero noise, zero distortion and no hiss...) then by all means use them! You've found a good match. The thing is, getting to that point... how much more are you wasting money on, trying to chase the ultimate. They're even chasing this ultimate in the ART88, which in my opinion is already an ultimate unit! Why even bother tube roll in an ART88? Doesn't make any sense to me, unless the owner isn't happy with the ART88 in the first instance. Of course different folks- different strokes I guess.

I just prefer to sit back and enjoy those finest tunes. Life's too short to be tube rolling, chasing the ultimate... and casting negative effects on gear... just enjoy the music and what you've got, after all it's what you've earned.

Cheers, RJ

[microstrip]

Although I share the feelings of the previous post concerning tube rolling I see that it can be a nice and interesting way of living the hobby - each of us chooses his way to carry it.

However IMHO people entering it should accept the risks. In my opinion if we enter this activity we should have a way of testing and measuring the tubes before putting them in expensive equipment - a faulty tube can easily damage the solid state regulators of cj equipment. Unfortunately very few testers test double triodes for balance and in some circuits an unbalanced tube can do real damage. Forums are filled with guesses and misleading opinion about possibilities - in my opinion tube rolling should be backed by factual technical data and measurements, not just by probability and guess. Ask the manufacturer if you can't measure it. The notion of "equivalent" can be very ambiguous in the high-end.

Although I have reduced experience with the pleasures of tube rolling I have sometimes carried measurements of tube for good fiends who love it. I am always happy to help them, but since long I learned not to lend them my ears for their non methodical, almost anarchical listening sessions ...

BTW, buy expensive tubes from people you know well and can trust - a few days ago I was asked to test a fake Telefunken PCC88 with a perfect diamond bottom. Counterfeiters are perfecting their products. Comparison of measurements of real vintage tubes have shown the tubes did not have the expected curve.

[jimbones]

yea I usually test tube pulls from suppliers, but for new tubes from reputable sources I dont test. I will from now on. In a previous post I said I purchased a Siemens 6922, that is wrong I purchased a new Mullard 6922.

[microstrip]

The ET5 uses a single triode - this means that it shares the triodes of the tube between channels. DC balancing of the triodes is not critical but matched transconductance is a must. I have a few Mullard double triode tubes and they are all high quality with low noise.

[jimbones]

WHEW! But do they sound good lol

[jimbones]

OK so the retailer got the tube back and confirmed it WAS BAD. In the meantime UPS of course lost the replacement tube in shipping, ffffffaaaaaacccckkkk

[admin]

Ahhh, frustrating. I think this time of year all the shippers are so crazy busy I'm not surprised things may get lost at a higher rate. I hope it turns up.

[Big Dog RJ]

Hey JB mate, just checking in... did you manage to locate what happened to that Mullard 6922?
Hopefully you'll find another one to replace the one that went missing.

BTW, also a big fan of those Mullards, exceptional quality!
Cheers, fine tunes are around the corner.
Woof! RJ

[jimbones]

Nope it fell into the UPS black hole. Never to be seen from again.

[admin]

If it's any consolation, I've had packages "disappear" for even a couple of weeks and then finally turn up. I think my example was with USPS but there may be some glimmer of hope that it turns up after the holidays. But I wouldn't hold my breath.

[jimbones]

So the Mullard 6922 (finally) arrived. Compared to the Tesla, it is not as lively. The bass is better on the Mullard and the Mullard is also quieter. The Mullard however almost seems muted compared to the Tesla (as I mentioned it was lively) The thing I have to listen for is does the Mullard sound realistic? or is it too dead? Or maybe the Tesla is too lively....To be continued

[admin]

Was this the "lost package" or they sent replacements?

I would give it some time before making a firm conclusion. I've found that often with extended listening my opinion changes. It may also take some time for the tubes to burn in and you may like the sound better once they do.

[jimbones]

Yes more time is needed. Ive read that tubes need 20-40 hrs as well as my ears.

[Joe Appierto]

Just out of curiosity is the Mullard 6922 that you're using from original production or the New Sensor reissue?

I never did get around to trying the New Sensor reissue but did try the Mullard CV2493 which I used as the input tube on a Premier 140 and the Mullard PCC88/7DJ8 in a Premier 16LS2. I liked those particular tubes very much in those applications.