New triode strapped 6AV5 and 6B4G Curves (PDFs and XLS)

[Shannon Parks]

As far as tubes that have been implemented in audio that weren't originally designed for audio, certainly the 6AV5 tubes have received a huge following over the last few years. Ed Brown has definitely promoted them on these forums, and George has a nice write up at Tubelab. I tested some T-12 bulb 6AV5GT Tungsol that Ed sent me a few years ago. At the time, I tested them in my get*set*go, and while they biased up nicely and performed well, my 6B4s had less distortion. I've been doing small signal tube curve sweeping with my new Parks Audio tracer, and yesterday I did my first power tube tests.

Here's a typical old stock used 6B4G versus a NOS 6AV5GT (print PDFs to scale for proper aspect - suitable for plotting loadlines):
http://www.diytube.com/forumpix/6AV5.pdf
http://www.diytube.com/forumpix/6B4G.pdf
http://www.diytube.com/forumpix/6AV5.xls
http://www.diytube.com/forumpix/6B4G.xls

Nutshell: Both are 845 ohms Rp. 6AV5 has slightly higher Gm and Mu, with a little less linearity. While I like the 6B4G with a 2.5K to 3.5K loadline, I think the 6AV5 - at least this sample - would be best with a 5K load. Otherwise, it's pretty darn close to a 6B4, and definitely fit for audio use as many DIYers have already discovered.

I did a few 6L6s and KT90s, too. But everything needs formatting. I'm looking at trying to make my templates simpler (i.e. less post-processing). I intend to upload everything into an archive eventually. FWIW, I'm actually making good progress with the data collection.

Shannon

[EWBrown]

Great data, thanks!

I found, from my numerous measurements, that the 6AV5GAs behave more like "down-scaled" 300Bs, than 6B4Gs, when comparing my voltage & curent plots to those generated by SE-CAD.

My latest foray into "plinkerdom" was to run similar voltage vs current tests on RCA 6GE5s, these compare very closely (within 2%) of 6B4G using SE CAD. The 6GE5s have higher PD ratings (PD = 17.5W, G2D = 3.5W) and higher plate voltage tolerance.

The proof will be in the pudding, as they say, and once I build and evaluate a 6GE5 based SE amp (with my standard 12AT7 SRPP driver stage).

The best SE-CAD simulation results for 6GE5s, were with a B+ of 360-380VDC, and a cathode resistor of 820 ohms. I also tried it with 750 ohms and 620 ohms, with suitably lower B+ voltages. 820 Ohms was best, overall, and higher RK (1K ohms) was not quite as good for 2HD and 3HD figures. I tried both 3K and 5K OPTs in the simulations, either value is good, 3K offers more output power, but with a slightly higher 2HD and 3HD, than did 5K.

Both the 6AV5GA (and 12AV5GA) and the 6GE5 seem to be "happier" with higher B+ and plate currents then with "standard" 6B4G / 2A3 operating values. They're cheap tubes, so I don't have to worry about "trashing" those valuable NOS 6B4Gs and 2A3s, with over-spec voltage and current operation.

Another work in progress....

/ed B

[battradio]

Hi Shannon ,

When you say NOS 6B4G's , do you mean US made or Russian made .
Also have you ever tested the double boxed plate style verse the more common 2A3 style for linearity .

Mark

[Shannon Parks]

Mark, I'm not sure of your terminology. I just refer to twin plates and monoplates. The four old US 6B4Gs I tested were all twin plates and looked almost exactly the same. I plan to test my Sovtek monoplates next. I'll also test my EH 300Bs and a couple singles: a 45 and a 6A3.

Shannon

[EWBrown]

There are also 1950's vintage Russian made 6C4C / 6B4Gs, with the classic "twin plate" construction, as well as the newer and somewhat more rugged monoplates.

The older Russian twin plates which I have are marked as being Svetlana 6C4Cs, and test out as the same as vintage US made 6B4Gs.

/ed B

[battradio]

Raytheon Made a twin box structure 6B4G that looke like two 45's in one package

[Ty_Bower]

Mark, I'm not sure of your terminology. I just refer to twin plates and monoplates.

Some have plates with rounded edges, and some are the flat ladder/box style of construction. Lots of pics here:

http://emissionlab.net/2A3.html

[battradio]

http://emissionlab.net/2A3/TS6B4G.jpg
http://emissionlab.net/2A3/SYL6B4G.jpg

These type

[Geek]

Whatta great tube I.D. site. Thanks guys!

[Shannon Parks]

Thanks for the info guys. Out of my 14 US 6B4Gs (used mismatches I purchased years ago for less than $10 each), all but one is the double 45 plate style. I'll post the results of all of them this weekend if I can. But, to answer the original question, no - there is no difference that I see. Actually all but one of the tubes tests real nice, and it's just a worn out tube.

Shannon