Near field use on 87db speakers in a masive room.

[currly30]

<<If I get the BeePre2 and the Kaiju would the 300Bs in both need to be matched?  Would upgrading the tube on only 1 be waste?>>
I have the beepre and a 300b BH amp. I think one pair of upgraded tubes is worth it. The nice thing is you can try them in both the amp and pre and see where you like them better.

Thanks for the information.

[Paul Birkeland]

A normal 300B can be made to give about 18W if desired.  The plate structure looks like it could be larger, which might mean longer filament wires, and this leads to questions about how much current the filament draws. 

If someone wants to take one for the team, a basic DC bench supply can be set to 5V and the alligator clip leads can be placed across the filament pins to see how much current it draws for heating.  If the filament current is the same as a 300B, then you're likely good to go!

[currly30]

Do 6300B style tubes work? https://www.hifi-amplifiers.com/en/shuguang-electronic-tube-valve-c-68/shuguang-6300bta-vacuum-tubes-matched-pair-replace-300b98-2018-new-p-5252.html

[currly30]

I did get a sorta answer about the 52B.
"The technician from our manufacturer told us that 52B-TA can fully replace 300B Series Electron Tube.
Please don't worry.
The data sheet of 52B-TA also not available due to the relocation of the factory, it may need 6 more months to reopen the database."

[Paul Birkeland]

The 6300 at least lists that the filament specifications are compatible with a normal 300B.  This tube is likely to work fine in a BeePre or Kaiju, but it sure would be nice to get a set of plate curves out of them.

Do keep in mind that a tube like the 6300 won't make any extra power over a normal 300B without a different circuit, much like the JJ 2A3-40 in the Stereomour.

[currly30]

What is the normal range for filament current for a 300B? I see 300Bs with longer plates, like the TJ music 300B/C/+ is 2.4A. Is that drawing to much to work in the Kaiju?

https://www.eectech.store/fullmusic-300b-cne-innovative-version-of-the-tube-gold-feet-advanced-graphite-screen-p1003.html

Link with graphs.

http://www.mableaudio.com/en/productview.asp?sid=4045

[Paul Birkeland]

Yes, 2.4A is about twice what a normal 300B requires, so that tube is very likely to cause major issues in most DC heated 300B amps. You also get no additional power out of a tube like that in a Kaiju.

[Doc B.]

This has been a problem since the early oughts when a certain European manufacturer created a hierarchy of tubes that didn't really plug into a 300B amp because of the filament current requirement or at least would not perform at their advertised maximum output in a 300B amp because of the amp circuit's designated operating point. They used a naming convention that implied they were an uprated 300B. A Chinese manufacturer started to emulate the tubes and used similar confusing names that had a "300" in them. The most extreme of these tubes can be good sounding and produce a fair amount more power, but need a whole 'nother amp to perform to their optimum.

[currly30]

Okay, so any 300B that is 2.4A is not actually a 300B. So, it seems like I need to double check any Chinese 300B to make sure it is actually 1.2A instead of 2.4A. I do see that there are a lot chinese tubes that say they replace 300B but are called 7300/6300/52/4300/30098 etc.

Or would the 2.4A work in the non-DC filament upgraded Kaiju?

[Paul Birkeland]

Nope, the Kaiju has a small amount of series resistance between each heater winding on the power transformer and the 300B.  If you double the voltage drop across these resistors, you'll be out of tolerance for the 300B filament.  Even for 300B amps with the filaments connected directly to the power transformer secondary winding, you would need a 3A rated winding to properly heat that tube, and that's not always what's available! 

You could modify a Kaiju to properly AC heat this tube, but then it will eat up normal 300Bs if you forget and plug them in.  Again though, these tubes make no additional power in the Kaiju and are likely to have higher Miller capacitance, so I would not suggest using them.

[currly30]

well, I glad I asked before buying any Chinese tubes.

[Paul Birkeland]

You can buy Chinese 300Bs.  There are oodles of them that work just fine. 

[currly30]

I'm going to buy some. Just didn't realize that there are ones labeled as 300B that wouldn't work in the Kaiju since they are 2.4A.

[currly30]

I finished the Kaiju and it works super well on my 87db speakers. I have the Kaiju hooked up to my Audio-GD Master-9 outs which uses a logarithmic volume control. I typically run the Master-9 at 28-33 out of 100 on the volume setting. So The Kaiju has plenty of power to work for low sensitivity near field speakers.

I can run the speakers to uncomfortably loud levels.

Though to get to a loud enough level to fill a large room the noise floor is to great for the speakers. So you end up with quite a bit of distortion.

Overall I'm very happy with the amp it sounds great and has lots of upgrade potential.

[Paul Birkeland]

I typically run the Master-9 at 28-33 out of 100 on the volume setting. So The Kaiju has plenty of power to work for low sensitivity near field speakers.

The position of a volume control doesn't tell you much about what the amp is doing.  You could put a Pass F4 in place of the Kaiju and you'd have to crank that volume control way up, but the F4 has 4x the power of the Kaiju.

I can run the speakers to uncomfortably loud levels.

Though to get to a loud enough level to fill a large room the noise floor is to great for the speakers. So you end up with quite a bit of distortion.

Noise that varies with the output level of your source is likely an issue that could be addressed on its own. If you have audible 60Hz hum from the Kaiju, the DC filament upgrade will address that.