So What Is Closest to a 6AQ5, but Lower Power?

[s2]

I need to build a 3W SE amp. The OT I have will work for a 6V6/6AQ5 type tube (7.7K / 8 Ohms / 5W), but the PT only puts out 50mA current at 260VDC. Is there a slightly smaller beam power pentode similar in sound to a 6AQ5 that I'm not finding?

[UR12]

Yo Steve!


I was looking at something similar a few weeks ago to build for my grandaughter. I finally went with a firefly just because it was a easy build and I already had all the parts. I started out looking ate the 50c5 that was ues as an output tube for most of the old 5 tube super hetrodyne AM radios. They made a 12c5 but nothing in the 6 volt range I did find a cross for the 12c5 being the 12cu5, so I looked up a 6cu5 and lo and behold here we have a winner. It is a little off as far as the load (2500 instead of 7500 ) but might be usable.

[Andy Le Blanc]

you can broaden your search.....if your transformer gives you an effective impedance of 7700 ohms with an 8 ohm load this is a ratio of 962.5 to 1
this give you a few choices of effective impedance

15.4 K at 16 ohms
7.7 K at 8 ohms
3.85 K at 4 ohms

happy hunting

[Funkalicousgroove]

Howzabout a 6K6GT?? makes a cool 3 watts or so, and sounds like a little EL34.

[Andy Le Blanc]

The 6k6 at 250v with a 7.6k load can be biased to a 33ma. max dissipation makes around 3.4 W (ref. RCA RC-21) and is worth a try.....but is in no way like a little EL34....this is not to say it will sound badly for your application ....the 6BQ5 or EL84 which is sometimes called a miniature EL34..... will make almost 6 watts biased to a max dissipation of 50 ma. at 250v with a load of 4.5k..... this wouldn't leave you enough ma. to run a pre.... and wouldn't see an optimal effective load.... the 6k6 looks good.....but browse the tube manuals..... you might find that some of the larger power tubes run in triode fit the criteria stated....

[Phil_S]

You might look at the EL95 for a 3W tube. At that power level, I do not believe the zout difference is all that critical. This tube is spec'd Ia=24mA, so your PT should have plenty of headroom.

[Funkalicousgroove]

The 6k6 at 250v with a 7.6k load can be biased to a 33ma. max dissipation makes around 3.4 W (ref. RCA RC-21) and is worth a try.....but is in no way like a little EL34....this is not to say it will sound badly for your application ....the 6BQ5 or EL84 which is sometimes called a miniature EL34..... will make almost 6 watts biased to a max dissipation of 50 ma. at 250v with a load of 4.5k..... this wouldn't leave you enough ma. to run a pre.... and wouldn't see an optimal effective load.... the 6k6 looks good.....but browse the tube manuals..... you might find that some of the larger power tubes run in triode fit the criteria stated....

Andy, I think they sound very similar to a little EL34, and have used them for quite a few projects, Please enlighten us on your VAST experience with this little pentode that would cause you to say that it is "NOTHING" like a little EL34-

[cobalt]

Hey s2,

You might also look at the 6CL6/6197. The numbers look close to what you need, and they are CHEAP!


cobalt

[s2]

[double post]

[s2]

Yo Steve!


I was looking at something similar a few weeks ago to build for my grandaughter. I finally went with a firefly just because it was a easy build and I already had all the parts. I started out looking ate the 50c5 that was ues as an output tube for most of the old 5 tube super hetrodyne AM radios. They made a 12c5 but nothing in the 6 volt range I did find a cross for the 12c5 being the 12cu5, so I looked up a 6cu5 and lo and behold here we have a winner. It is a little off as far as the load (2500 instead of 7500 ) but might be usable.

Thanks ur12! I suppose if I go regulated DC for the heaters I can use a 5V tube. I think I even happen to have a couple of spare voltage regulators around here somewhere. I've give those a look!

[dartanion]

How about the following tubes

6G6GT / 6AK6
6BK5
12A6
5686

Wasn't sure if you had a target filament current, so check this list:

http://www.nj7p.org/Tube4.php?char=Beam ... %20Pentode

Not super current in terms of having all possible tubes, but you should be able to pick something out here. The are listed as the American "Beam Power Pentode" though

[skyboltone]

6F6 SE load impedence 7000
bias at -16 makes 3.2 with 250 on the plate at 34ma
bias at -20 makes 4.5 with 275 on the plate at 38ma
use a triode switch make .85 biased at -20 at 250 and 31ma load 4k

Use a 5E3 front end an you're there. Sounds exactly like a little 6F6

Nice tube cause they take so much input and do almost nothing with it.

Dan H

[UR12]

Thanks ur12! I suppose if I go regulated DC for the heaters I can use a 5V tube. I think I even happen to have a couple of spare voltage regulators around here somewhere. I've give those a look!

5 volt tube??

[s2]

5.6 Volt filament.

[skyboltone]

6F6 SE load impedence 7000
bias at -16 makes 3.2 with 250 on the plate at 34ma
bias at -20 makes 4.5 with 275 on the plate at 38ma
use a triode switch make .85 biased at -20 at 250 and 31ma load 4k

Use a 5E3 front end an you're there. Sounds exactly like a little 6F6

Nice tube cause they take so much input and do almost nothing with it.

Dan H

Hey Brandon, this would work with Class Act too right? You may need to loose some gain someplace though maybe?