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Originally 300bs were meant to run at 300volts but it seems that today everybody is running them at higher voltages. Is anyone running them at 300v. Do they sound better at this anode voltage with a bias of 60mA?
Comments Please
Regards Joćo
Follow Ups:
Hi Joao,
I have been using my Sun Audio SV300BE at Operation Point; 305V B+ (~256V anode), at 55ma. current, 3.5KOhm Output primary imp. for over 10 years.
And it seems that I will be using it for more time because I don't have any intention to replace it.
It gives ~5W and unbelievely (because of low dissipation)the original JJ300B tubes are still functioning not perfectly but satisfactorily.I know because I also have NOS Vaic 300B c37s to check them.
But as always YMMV, maybe this is because the synergy of my system built around this amp.
Regards,
Hakan
Hi Joao,
I can say that AVVT (Vaic) 300B C37 glass is the modern sounding 300B.It has more frequency extension and bandwidth, highly detailed, strong bass and very dynamic compared to standard ones.Original first generation JJ's are somewhere between classic sound and Vaic sound.Full music (TJ) mesh globe also has natural detail but in a relaxed way, softer bass and sweeter treble more like classic 300B sound.
These are the ones that I actually listened.
But as far as I know, if you want more modern 300B sound today, because AVVT-Vaic is out of production, the close choice is Emission Labs tubes.
If you already have a dynamic and analythic sounding system TJ 300B globes can be more appropriate.
Regards,
Hakan
Do you have an opinion on the c37s VAIC 300Bs. Compared with ElectroHarmonix Full Music and other regular 300b?
Regards Joćo
At 300v, you would want to use high current to get the dissipation up to 30 watts or so. At 18watts, you should use a 2A3, they sound sweeter.
It is only low relative to the higher dissipation points (yep, I just stated the obvious) and on a power per $$$ basis. It is not low in any important (for me) sense; for example, not so low it cannot operate effectively etc.Regarding sound quality, I think it depends on the 2A3 vs. 300B being used and the I/V ratios used. For ~ 4W output, I'd be inclined to think a 300B would be more appropriate. At 2W output, I'd likely opt for a 2A3 (at lower current and higher load than common). For 1W+ I'd likely opt for a 45 at the textbook 250V operating point.
I have read some claims of the 2A3 to be 'sweeter', especially in posts form back in day. I'd ask what 2A3 and what 300B, at what operating points and load, in what type of circuit? Others claim the 2A3 to be relatively tonally dry and mechanical yet airy. I'd ask the same questions...
If a NOS 2A3 and inexpensive modern 300B are compared, both using their more traditional operating points, then a 2A3 might likely sound sweeter. But...
Cheers.
Edits: 05/11/12
To quote Eric Barbour for the 300B, "thou shalt not exceed 60 ma and 450 volts"
I also agree with Barbour that an 811 properly implemented will slay any 300B design.
The Mind has No Firewall~ U.S. Army War College.
"Originally 300bs were meant to run at 300 volt"
I am not sure where you get that idea, but WE published a chart of recommended operating conditions that went from 200V to 450V. These specs. show lowest distortion at: 250V @ 60mA into 2.7k ohms; 300V @ 60mA into 3400 ohms; 350V @ 60mA into 4k ohms; 400V @ 60mA into 5k ohms; 450V @ 50mA into 6.5k ohms.
Personally the amp I am listening to now I built with 345V @ 62.5 mA into 3k.
IIRC the early sheets specified 300V at 57 / 60 mA? I think EML uses this spec for its current production 300B.
As always, I could be mistaken... I think Paul Joppa knows the history of this and might have something more (accurate) to say.
Cheers.
300volts(A to K) 60 mA bias.
one of my WE91 knockoffs runs 300b pretty easy, with a 5u4 rectifier, I am running 310 v A-K at 60ma (18.6w diss), it sounds very good, but then when I A-B it with another amp running up around 28w dissipation, I really cant hear any significant difference. What may occur, and I am guessing, is the amp running at the lower dissipation may sound the same for a longer period of time than the one running the tubes harder. Even the one running the 300b at 28 watts is still only running the tube at 75% of the original spec, and 70% of spec for later tubes.
I have had a few drinks, but the original WE datasheets show ~ max dissipation at ~ 28W, with recommended dissipation at ~ 18 W (or slightly less)
People's opinions on ideal operating points vary. and I/V ratio of 1ma:6 (or greater) volts with 5K load is often recommended for a more 45-type sound (especially if running at lower dissipation). Supposedly a 300B at a, say more 2A3 type operating point, at I/V of 1 mA:4 volts at 2k5 to 3k load lends itself to a more 'classic' 300B sound. That said, the latter could sound very nice in an appropriate circuit that runs the 300B below 18 W dissipation, especially if a slightly higher load is used....
I am building one of the latter at the moment and hope to compare it (roughly) to one of the former in the next couple of months...
Of course, the make of tube and circuit matter...
Cheers.
We data sheets show 40 watts for a 300A, 36 watts for a 300B. Many classic designs run them in the low 30's (JEL, Flesh and Blood). Must current production are rated for 40 watts, unless they are mesh plates.
"That is very low power output. At 300v, you would want to use high current to get the dissipation up to 30 watts or so."
This would be true if you were setting the tube up for maximum power. To set the tube up for minimum distortion you would use one of WE's recommended operating points:
250V @ 60mA into 2.7k ohms; 300V @ 60mA into 3400 ohms; 350V @ 60mA into 4k ohms; 400V @ 60mA into 5k ohms; 450V @ 50mA into 6.5k ohms.
300V @ 60mA into 3400 ohms yields 5.6W @ 18W plate dissipation.
450V @ 50mA into 6.5k ohms yields 9W @ 22.5W plate dissipation.
Using these minimum distortion operating points the tube will last for years.
WE gives 450V @ 80mA into 2k ohms as the highest power level yielding 17.8W at the highest distortion level of any operating point and a plate dissipation of 36W.
Clearly, the operating point is up to the circuit designer: low power and low distortion or high power and high distortion.
Lower dissipation supposedly results in a more relaxed/less stressed sound (and longer duration of use!), with I/V determining the general presentation.
This has been consistently reported by folks I tend to trust in these matters and it sounds plausible. I have not experience this personally (no 300B amp in the house) but should be able to by the end of the year.
Cheers.
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