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Robin H
Reply with quote  #16 

Yes. I will.
I'm traveling and it will take a while to get the JJ tubes.

If you can't wait, I would suggest you just go with JJ.
Definitely no GL PX300b on Pinnacle- we learned it in a hard way...

Robin H
Reply with quote  #17 

A quick up date:

Got my JJ 300B installed last night.
4 tubes are all factory tested with the same value.
However, at first installation. Bias can't be zeroed. Output is -0.1V even when the pod is turned all the way clockwise and the amp blow fuses when driving hard.
After I swapped V4 and V6, bias can be set to around 0.03V and then it worked fine.

I had only 3 hours on it.
They sound very good right out of the box.
Did not do serious AB comparison as it might get better after broken in.
Basically, I'm pretty happy with it.
First impression: It is pretty balance from low to high. Very good detail.
GL PX300B (similar price) has a little more body in the mid range and less high extension.
PSVan (half the price) is brighter, less body in the mid.

I found the big transformer is significantly hotter than running with PSVan or PX300B tubes.
It is too hot to put my fingers on it for more than a second.
I have not yet measure the temperature or the current through the plate resisters.
I'm wondering if the JJ is running drawing more current at the same bias.

It would be greatly helpful for users, if someone can provide a procedure or instruction on
- How um-matched tubes affect the amp. How far we can go if not matched?
- How to swap tubes to balance out the un-matching.
- I guess V4, V5 shall be matched and V6, V7 shall be matched. Is it less problem if V4/V5 don't match with V6/V7?
- Swapping V4/V5 or swapping V6/V7 doesn't make a difference, correct?


Reply with quote  #18 

You should always buy tubes matched for current. But normally they are matched at a different voltage/bias than in  your actual amps and they will not 100% match in your amps. In most cases this shouldn’t become a problem as little fluctuations can be handled and are normal.

As I have already mentioned in an earlier email you need to swap tubes –one at a time - and adjust the DC offset every time and find out whether it gets lower and more stable. That's the only way to make them "share" current in between more equally if one or more tubes are stronger than others and simply conduct more than the rest. As you can only adjust bias for one power rail with the DC offset pot (the other bias is set) you need to swap tubes if adjusting offset doesn't give you good results. Some PP amps have pots for both power rails but even then it’s impossible to match the tubes 100%. You would need one bias pot for each tube which can be adjusted separately from the rest or autobias where some electronics do this job continuously.  The Tentlab autobias doesn’t work with TS products, just FYI, as it needs ground as reference and the TS output is floating. Tentlab is working on a new autobias but it will take them a while.

I would also measure if the bias voltages are ok. If your transformers for B+ are running too hot it means that there is too much current through one or more tubes (idle current too high, one stronger tube hogging too much current). In an extreme case one tube could be red plating (anode too hot) and fuse would blow.

Tubes of the pos  need to be matched as close as possible to neg side in a PP amp. But also the position of the tubes on one side can matter (between 4 and 5/6 and 7 in your example) in order to achieve this. The rest you can adjust with the DC offset pot. So simply start with 7 in position 5/5 in position 7. Then swap 5 with 4 and adjust offset again. If not good enough swap 6 with 7 (former 5) etc. Without tube tester this is the only way to solve this problem. If all this doesn’t help, the tubes are current matched,  and your bias voltage is ok there must be a different problem causing the overheating of the transformers.

Reply with quote  #19 
With the Pinnacle on my wish list this is what I found ... 500US$ approx

Part of the hold up on this entire review has been, well, just as i found a killer tube like the Valve Art, another tube would come along and blow all others away when used as a direct normally electrically run 300B. These new JJ Electronic 300B tubes made in the Slovak Republic have won my heart as the all out winner of this grouping in my systems to my ears.

Although a bit microphonic, it seems to have the best balance of smooth mids with upper and lower frequency extension in my beloved Wavelength Audio Cardinal amplifier.  If fact i love it so much it now pretty much permanently resides on it as part of my main reference system, only giving way to the WE300B when i desire a more, um, seductive sound.  Ambience and imaging are excellent as it inner resolution too!  This is the latest 300B to arrive here in my humble abode and also the best so far for direct replacement on a normally run 300B amplifier.   Some of you might worry about a bit of that blue glow on the top, but then again so did the WE300B have that at the beginning too.  i feel there is just too much emphasis on that top blue glow.  Yes, it does mean a few things, yet it's not necessarily gonna make your system sound like junk, burn down a small village, and release a nuclear warhead on your government.  Sheeesh, relax and enjoy the music!

The JJ Electronic 300B seems to have all the things i love about 300B tubes!  What more can i say then that?  May i humbly suggest you try the JJ Electronic 300B?   You too might find yourself in love while enjoying the music.

Reply with quote  #20 

Hi (Robin),

I did measurements for you with combinations of three companies:

300B KR
300B JJ

JJ's measurements with the speakers show the same thing.

Only two additions / questions:

1. Who built the amplifiers for you?

2. Recommend you, because you make frequent breaks between the uses of amplifiers:

Turn on:

Source, pre-amplifier, after 2 minutes the amplifiers.

Turn off:

Amplifiers, after 30 seconds Pre-amplifier, Source.


Good luck to everyone,



Attached Images
Click image for larger version - Name: 300B JJ.jpg, Views: 24, Size: 308.45 KB  Click image for larger version - Name: kr 300b + 300B JJ.jpg, Views: 23, Size: 170.81 KB  Click image for larger version - Name: PX300B + 300B JJ (2).jpg, Views: 23, Size: 173.84 KB  Click image for larger version - Name: PX300B + 300B JJ.jpg, Views: 21, Size: 260.63 KB  Click image for larger version - Name: PX300B + KR300B (2).jpg, Views: 21, Size: 185.13 KB  Click image for larger version - Name: PX300B + KR300B.jpg, Views: 20, Size: 147.74 KB 

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