6GE5 Triode

[famousmockingbird]

I was ordering some parts and was pretty close to getting free shipping so I started going through the NOS valves sections to see what they got. I feel like experimenting with some unfamiliar tubes and came across the 6GE5: http://frank.pocnet.net/sheets/123/6/6GE5.pdf


I found this looking through interwebs: VinylSavor: Tube of the Month : The 6GE5


I see in the data sheet where triode mode the tube has a mu=4.4. The website then shows some triode curves and I agree they look pretty good. He continues to calculate gm=5300 and Rp=820 which is similar to the 2A3.

I like Klipsch speakers and noticed a while ago that PK recommended in the Klipschorn brochure to pair the speaker with the Brook 12A amplifier, which is a push pull 2A3 amp. So I got my wheels turning and though it would be cool to try and make a poor mans version of the 12A seeing how 2A3's a super expensive.

SO before I check out I would like to buy a handful of these tubes but figured I would ask and see if anyone has tried them for audio. I don't want to waste money on a bb gun target. I remember a thread with someone comparing some TV tubes wired as triode vs. Schade and posting the curve tracer results. I will try and find that too, maybe the 6GE5 was one of the tubes tested.

Thanks,


-bird

 

[Vinylsavor]

Hi!

I built two different amps with this tube and it works nicely. See my other posts about the 6GE5:

VinylSavor: 6GE5

Thomas

 

[radiotron]

The 6GE5 has same innards as many that have been tested in various threads, 6AV5GA, 6FW5, 6DQ6B, 6JM6, 6JN6 and some others. PD 17.5 watts, Gm ~7300 uMhos. Nominal 220V screen rating, but they seem to take 300V as triodes 🙂 Take a look at any of the mid/late 60s RCA tube manuals, and you'll see the same specs turning up in a variety of packages, octal, novar, compactron, with or without plate cap, all the same electrically. [edit, more tube types added]

 

[JonSnell Electronic]

VinylSavor: Tube of the Month : The 6GE5
Beam Plate? What Beam Plate! It is a pentode not a Beam Tetrode!

 

[Vinylsavor]

Hi!

See attached photo, looks like a beam plate to me (second from the right)

Thomas

 

[TonyTecson]

i have never seen a tv hor. scanning tube that is a true pentode.....have you?

 

[Tubelab_com]

i have never seen a tv hor. scanning tube that is a true pentode.....have you?

I have not either.

The 6GE5 has same innards as many that have been tested in various threads, 6AV5GA, 6FW5, 6DQ6B, 6JM6, 6JN6

I have not specifically tested the 6GE5 in triode mode, but I have wound pair of them up to 100 watts in push pull pentode. Indeed they behave like most of the GE designed 18 watt sweep tubes like the 6AV5. All of these are best kept below 70 watts per pair in pentode use. 100 is a bit too much, but they will go there on music peaks.

Is it like the 2A3, or close enough for a simple triode SET? Many will agree that the 6A3 was made from the 2A3 by installing a 6.3 volt filament. The 6B4 was made by putting an octal base on the 6A3, so a 6B4 is electrically similar to the twin plate 2A3.

When vacuum tube production was winding down many manufacturers were holding supply contracts extending for years requiring production of outdated designs. In several cases the manufacturers found unique ways to fulfill those contracts. Sylvania / Phillips ECG in particular began stuffing the glass with some rather odd and interesting insides to fulfil these contracts.

We know that the 807 was designed in the late 1930's from the 6L6GA. I have seen "807's" with every newer generation of 6L6 type guts inside them including the 30 watt dissipation 7027A. These are valid general purpose substitutions for the original intended use of the 807, an RF amplifier for frequencies below 30 MHz. I have however seen "807's" without the RF shielding around the bottom of the guts. Will these work in ALL RF amps????

There have been application specific substitutions also. The most absurd was the 6B4GA. The 6B4G is a DHT. The US military had an application for that tube that was still being used in the 1970's but Sylvania was killing off all DHT production. Sylvania engineers came up with a suitable replacement that worked in that application and the 6B4GA was made.

The 6B4GA is NOT a DHT, it is a triode wired sweep tube that looks a lot like the 6AV5GA. The existence of this "urban legend" had been rumored for a long time since a few had been found in military scrap. About 10 years ago I found one in my collection of military scrap tubes. It had a white getter, so it met the hammer. The guts indeed matched the guts of a Sylvania 6AV5 from the late 60's.

So at least for that specific application the 6AV5 can be triode wired and used as a 6B4. I then wired a 6AV5 and connected it into a Tubelab SE amplifier where a 2A3 could have gone. (the TSE can use a 45, 2A3 or 300B). The 6AV5 worked and sounded remarkably good.

So will a 6GE5 do as well? Probably, but observe the screen grid carefully for signs of redness, both at full power, and at idle (worst case on a class A amp). All 6GE5's that I have seen are made by GE. I have not tried them in triode or SE.

6AV5 Sweep Tube | Tubelab

 

[Vinylsavor]

Hi!

So will a 6GE5 do as well? Probably, but observe the screen grid carefully for signs of redness, both at full power, and at idle (worst case on a class A amp). All 6GE5's that I have seen are made by GE. I have not tried them in triode or SE.

It does. I have a SE 6GE5 amp in use since last November and it works fine.

Thomas

 

[smoking-amp]

Some curve tracer curves:
I think these (Triode cases) are all: 50 mA/div Vert., 50V/div Horiz., about 7 V grid steps. Pentode case would be smaller steps

12GE5 Triode

12GE5 Schade

12GE5 Pentode

21HB5 Triode

6HJ5 Triode

21LG6 Triode

35LR6 Triode

6LB6 Triode

24LQ6 Triode

26DQ6 Triode

 

[smoking-amp]

6CB5A Triode

12BQ6 Triode

6L6WXT Triode

26LX6 Triode ( may not like running in triode )

26HU5 Triode ( may not like running in triode )

36MC6 Triode ( may not like running in triode )

36LW6 Triode (I've heard these may not like running in triode )

miscellaneous of interest:

21HB5A grid2 drive

perfect (in) triode 1E7G (only 1.5 Watt)

The lowest g2 voltage spec tubes have g2 close spaced to g1, giving them excellent triode curves, but unfortunately less tolerant of high g2 voltage for triode use.

 

[smoking-amp]

g2 drive pics:

12GE5 grid2 drive 20 mA/div Vert., 50 V/div Horiz., 7 V g2 steps

6HJ5 grid2 drive

21HB5A grid2 drive

 

[smoking-amp]

Here is another of 12GE5 in grid2 drive.
+16V bias added to +7V steps on g2
20 mA/div Vert., 50V/div Horiz.

 

[famousmockingbird]

Hi!

I built two different amps with this tube and it works nicely. See my other posts about the 6GE5:

VinylSavor: 6GE5

Hello Thomas, Yes thank you for the great articles! Good to see you are on this forum. I bookmarked your website and plan to do more reading.

I have not specifically tested the 6GE5 in triode mode, but I have wound pair of them up to 100 watts in push pull pentode. Indeed they behave like most of the GE designed 18 watt sweep tubes like the 6AV5. All of these are best kept below 70 watts per pair in pentode use. 100 is a bit too much, but they will go there on music peaks.

Wow! 100 watts!!! I would be happy with 50 watts.

Is it like the 2A3, or close enough for a simple triode SET? Many will agree that the 6A3 was made from the 2A3 by installing a 6.3 volt filament. The 6B4 was made by putting an octal base on the 6A3, so a 6B4 is electrically similar to the twin plate 2A3.

When vacuum tube production was winding down many manufacturers were holding supply contracts extending for years requiring production of outdated designs. In several cases the manufacturers found unique ways to fulfill those contracts. Sylvania / Phillips ECG in particular began stuffing the glass with some rather odd and interesting insides to fulfil these contracts.

We know that the 807 was designed in the late 1930's from the 6L6GA. I have seen "807's" with every newer generation of 6L6 type guts inside them including the 30 watt dissipation 7027A. These are valid general purpose substitutions for the original intended use of the 807, an RF amplifier for frequencies below 30 MHz. I have however seen "807's" without the RF shielding around the bottom of the guts. Will these work in ALL RF amps????

There have been application specific substitutions also. The most absurd was the 6B4GA. The 6B4G is a DHT. The US military had an application for that tube that was still being used in the 1970's but Sylvania was killing off all DHT production. Sylvania engineers came up with a suitable replacement that worked in that application and the 6B4GA was made.

The 6B4GA is NOT a DHT, it is a triode wired sweep tube that looks a lot like the 6AV5GA. The existence of this "urban legend" had been rumored for a long time since a few had been found in military scrap. About 10 years ago I found one in my collection of military scrap tubes. It had a white getter, so it met the hammer. The guts indeed matched the guts of a Sylvania 6AV5 from the late 60's.

So at least for that specific application the 6AV5 can be triode wired and used as a 6B4. I then wired a 6AV5 and connected it into a Tubelab SE amplifier where a 2A3 could have gone. (the TSE can use a 45, 2A3 or 300B). The 6AV5 worked and sounded remarkably good.

So will a 6GE5 do as well? Probably, but observe the screen grid carefully for signs of redness, both at full power, and at idle (worst case on a class A amp). All 6GE5's that I have seen are made by GE. I have not tried them in triode or SE.

6AV5 Sweep Tube | Tubelab

Great information here. We are so lucky to have you and others around who do all these experiments and shares the results. It seems like triode and pentode will work fine. I took note that when you switched to the 6AV5 you got oscillation and the grid stoppers fixed that. Screen drive is also very interesting but I don't think I will be looking for high power.

I can get the 6AV5GA for $7 each. Not too sure what brand. I think I might pull the trigger and get some 🙂

Some curve tracer curves:

Hello smoking amp, thank you for reposting those curves!! I remembered someone had done a lot of work posting triode and Schade curves for sweep tubes but I couldn't find the thread. Great information.


Got to love them sweep tubes😀

 

[smoking-amp]

12GE5, and 21HB5A were on sale at $1 a few years ago, but more now unfortunately. Excellent tubes.

You really can't go wrong with most Sweep tubes. You will wonder why you ever bought "audio" tubes after using Sweeps. And cheap, so you can try all the configurations without worry. Burn a few up just for fun. (with a current limiting/fusing 1 to 10 Ohm resistor under the cathode to protect the OT)

You can get 26DQ5 for $3 (Octal)
12GE5 for $3
12GT5 for $3
21HB5 for $6
21GY5 for $3
21EX6 for $3
21JV6 for $3
21LG6 for $4 (similar to the 6HJ5 except with a top cap)
6HJ5 for $4 if you can find them anymore
6CB5A for $5 (Octal)

Get a 3.3K primary OT for the 24 Watt tubes, or a 4K to 5K primary OT for the 18 Watt tubes (nothing set in stone), and you are set for many adventures.

 

[famousmockingbird]

Get a 3.3K primary OT for the 24 Watt tubes, or a 4K to 5K primary OT for the 18 Watt tubes (nothing set in stone), and you are set for many adventures.

So for the 18 watt tubes 4k-5k primary is for SE? I just ask because I would have thought 2.5k if I wire em as triodes. Rp=900ish ?

Here is my dilemma. I like vintage made tubes better then current production. It seems that the vendors I find for these sweep tubes don't offer them as matched sets. I would only like to buy 4 to play with and don't want there to be a wide variance between them. I am still thinking that $7 for vintage power tubes is pretty good, I know it's not $1 but the 6AV5GA seems to be the best documented for experiments thanks to tubelab.

 

[smoking-amp]

OH, I was talking for P-P.

For SE, as you said. Around 5x Rp usually for low distortion. Around 2x Rp for maximum power.

At $1 each, one can buy a box load and match them up with a simple test rig or in the amp itself. (or a curve tracer!)

You can get Rp for triode mode off most of the datasheets by dividing gm1 by Mu. Then invert for Rp.

gm1 varies roughly as the 0.6 power versus plate current, if you want it specified at some different current than the datasheet lists.

 

[famousmockingbird]

At $1 each, one can buy a box load and match them up with a simple test rig or in the amp itself. (or a curve tracer!)

I wish they were $1ea then I would have no problem buying a box. BUT they are $7ea. If you can find them for $1 please pm me a link🙂

You can get Rp for triode mode off most of the datasheets by dividing gm1 by Mu. Then invert for Rp.

So for the 6AV5GA:

.0055/4.3=.00127

1/.00127=781

I was just dividing the mu by gm1 which got me the same results

4.3/.0055=781

gm1 varies roughly as the 0.6 power versus plate current, if you want it specified at some different current than the datasheet lists.

Makes sense.


I remember some good reading here: http://www.diyaudio.com/forums/tube...ode-load-overcomes-3-2-law-non-linearity.html

 

[famousmockingbird]

I was reading through some old Klipsch brochures and saw that the Klipschorn was recommended to be used with a push pull 2A3 amp, the Brook 12A.

Maybe I will go push pull triode 6AV5GA.

Schematic attached.

 

[smoking-amp]

6AV5GA is $5 here:
4-65A to 6BZ8

Most of the $1 sale tubes are gone now. But 15HB6 is $1 and 12HE7/38HE7 are $1 here:
Summer Dollar Days - Vacuum Tube Sale - $1.00 Vacuum Tubes

The 38HE7 has a beam pentode and a damper diode in it. Many of the 38HE7 tubes have an "IC" pin (pin 10 to pin 12) on the base that allows you to run just the pentode at 21 VAC for the heater. That frees up some heat dissipation so the pentode can run around 15 Watts diss. (10 Watt diss. with the damper operating)

http://frank.pocnet.net/sheets/123/3/38HE7.pdf

12GE5 ($3) is just a bigger 6AV5GA (apparently some later 6AV5GA tubes just had 6GE5/6JN6 guts in them)
and 6HJ5 21LG6 are a bigger 12GE5 for $4

 

[Tubelab_com]

Get a 3.3K primary OT for the 24 Watt tubes, or a 4K to 5K primary OT for the 18 Watt tubes

I had a setup that made it easy to test P-P amps with 1250 ohms, 2500 ohms, 3300 ohms, 5000 ohms and 6600 ohms, with B+ voltages up to 650 volts and B+ current up to 1.7 amps, although operation at those levels would trip the bench breaker after a minute or so.

A 3300 ohm CT OPT works great for all of the 22 to 30 watt tubes at around 450 volts. 5000 ohms CT is good for the 17 to 20 watt tubes although 4000 would probably be good with B+ voltages in the 450 and down range. 6600 is good for the tiny tubes and big B+ voltages.....over 600 volts.

The 30 watt and up tubes can go to 2500 ohms, and 1250 ohms is reserved for multiple tubes. With 4 X 35LR6, 1250 ohms, 650 volts, and 1.2 AMPS of total B+ current, I saw 525 watts at clipping with a dull red glow in a dark room on the plates.

All testing was done in Pete Millett's Engineers Amp PC board.

Most of my SE testing was done with 5000 ohms since I had some Edcor OPT's to play with.

I did quite a bit of push pull triode mode testing with the typical audio tubes, some sweep tubes and a few others....even 300B's. The driver circuit I developed in this amp provided excellent results.

http://www.diyaudio.com/forums/tubes-valves/133034-6l6gc-ab2-amp.html?highlight=6L6GC+AB2