Elrog 300B vs Takatsuki 300B tubes

Hi,
May be, this reverse engineered circuit helps:

http://s89.photobucket.com/user/jeffreybehr/media/Coincident%20Frankenstein%20II%20monoamps/2014Mar20_Philsschematic2_1500w_zps98932676.jpg.html

I have simulated and measured with different tubes (WE, Psvane, Shughuang, Electro Harmonix...Elrog) The results are nearely the same...about 400V (405...420V) plate voltage (as Israel Blume responded) and the anode current was at about 80-90mA...a little bit more than 28W ;-).

Dissipation = anode current multiplied by anode voltage

If I take the 400 volts and 80mA (the lowest values) then it will result 32W. Using real measured values I get near 36W...not really cool running.

Gorge Lenz was talking about red glowing areas on the anode surface of the ER300B...We test and burn in the tubes at 400V/90mA (36W). If any tube is showing "red dots" on the anode surface while burn in or testing, we reject this tube immediately. So, if a tube has glowing anodes in a customer amp, there is a (massive) overload.

Btw, can anyone do some measurements on a real Frank?
I'm very intrested in the heater voltage using an EML XLS and an Elrog also.

Hi Matthias,
This been educational, all I want is the superb sound the Franks/Elrog provide.lsrael said the resistor change you recommend will definitely lower the plate voltage but also result in sonic degradation. Wish you two could somehow work together (fantasy I know).
Charles,

Matthias,
I do recognize that the Elrog is an excellent tube. The issue is the parameters/operating points of my particular amplifier. I'm very confident that I'll get a replacement pair that will work fine(now that the issue has been identified) and allow me to continue to enjoy their wonderful sound. Again I appreciate your expertise and input.
Charles,

06-19-15: Charles1dad
Al, I know your VAC REN 300b amplifier is considered a highly tuned design that's said to be tough on the 300b. Are certain tubes selected/screened by Kevin Hayes to match the amplifier's demands? The Pavane/Shuguang black glass that Israel uses very successfully is a good sounding tube but not in same tier as the Elrog.

Hi Charles,

Yes, the VAC Renaissance amps run the 300B's hard, but according to Kevin, and also A'gon member "Raquel" (Drake), who as you know is especially knowledgeable about those amps, as long as the tubes are truly WE spec compliant they will have no problems and last for many thousands of hours. As "Raquel" said in this thread:

I've owned VAC Renaissance amps for eight years. They require well vetted output tubes. In fact, Sophia used to market a special set of the Sophia tubes for VAC Renaissance amps, which were the basic Sophia tube, but particularly carefully tested at plate voltages that resemble the voltage that 300B's see in the Renaissance circuit. Generally, as for transconductance, output tubes for the Renaissance amps should test in the 3,000-5,000 range [edit by Al: I suspect he meant minimum, as the vintage WE's were rated a bit higher than that]. In addition, the plate-to-cathode voltage is approximately 430 volts dc, with idle current approximately 85 to 90 milliamperes in a self-bias (cathode bias) circuit. Again, this is approximately 5% below rating for the WeCo spec 300B. The milliamp and transconductance testing for purposes of matching must be done at those voltage levels.

I've always gotten 8,000-10,000 hours out of my output tubes, but tubes that are not good tubes will not hold up in the circuit.

The tubes in my amp, which are Chinese 300B-98's, I'm pretty certain were purchased from VAC by either the previous owner or by the dealer he sold it to, very shortly before I purchased the amp. Their bases are marked with measured data apparently taken by VAC during their screening process. I've had no problems with them after several years.

No doubt I could realize a substantial sonic upgrade by going to one of the upscale brands you've tried, IF I could be certain they could handle the operating conditions the amp would impose on them. But considering the cost of an octet of those tubes, or even a quartet if I were to run the amp in 30/30 configuration with four tubes removed, my recent investment in the DEQX HDP-5 you've probably seen me talking about with others in the current DEQX thread seemed to me to be a higher priority. As does a phono stage upgrade (probably to a Herron) at some point in the foreseeable future.

Matthias, thanks for your further inputs.

Best regards,
-- Al

Hi Al,
It's hard for me to response (quick), because my contributions must be verifyed by an admin ;-)

ok...try this link for the datasheet:
http://www.mif.pg.gda.pl/homepages/frank/sheets/084/3/300B.pdf

And yes, the ER300B can handle more than 800V of anode voltage (not specified, but tested yet ;-))
It can handle more than 200mA too, but not at the same time ;-)
Our datasheet specified the power dissipiaton at 40W.

I have build some reference designs for using the ER300B in a perfect environment. All they working with very high anode voltage but with lower anode current.

It is very important the anode dissipiaton is not higher than 40W in any case.
As I measured, the autobias will work well using a 1kOhm cathode resistor if the tubes are very close to the design center values and close to the plate curves in the datasheet.
But tubes have deviations any time. I own a lot of WE300B. And they have differences between 53mA and 82mA at the operating point 300V/-58V...where they should have an anode current of 60mA. This is absolutely normal...and all the tubes of all other manufacturers have deviations...

The problem is not the deviation itself, the problem is the handling by the amp. Autobiasing is a nice feature...but not at the top end of the operating conditions! If this should be done, a potentiometer (for changintg the resistance of the cathode resistor or for changing the fixed bias voltage) and a ampere meter should be the minimum equipment...

The next question is how the heater voltage looks like in this amp.
If an EML 300B XLS is the right choice we have 1.5A heater current at 5V. There is no voltage regulation. A transformer a rectifier bridge and a CLC only. May be the XLS is underheated (so I hope) ore all other (right) 300B are overheated, because they draw 1.2A (some russians and chinese 1.25A)only. This would result a heater voltage above 5V...not so good for any 300B and very bad for an Elrog 300B, because the use of thoriated tungsten for filaments. Higher heater voltage will result a (much) higher anode current and a much lower lifetime...

Regards, Matthias