Look for a beefy driver tube.

[Shoog]

I am currently running a ECL82 as a driver tube pushing an interstage transformer. I am not that happy with its sound so am looking for a substitute.

I need a driver which will work with the following criteria;

Va 100V
Ia 40mA
Gain of about 15.
Preferably 12.6V heater.
Preferably 9pin base.
Triode or pentode


I have spotted the 6H30 which looks just the job, but the heater is a problem. Also they seem outrageously expensive. Any good sources ?

I would appreciate any other ideas.

Shoog

 

[JoshK]

6n6p is similar to the 6n30p, but cheaper. Same problem with heater however. Unless you series connect the heaters.

 

[Wavebourn]

6n6p is similar to the 6n30p, but cheaper. Same problem with heater however. Unless you series connect the heaters.

6N6P is more linear than 6N30P, and in case of a stereo amp filaments may be connected in series.

 

[Shoog]

I was thinking of paralleling the sides of the 6H30 which would give me 20mA per side and a grid bias of about -5V - plenty of headroom. It would then let me series connect the heaters. At this operating point it should give a very long service life to.
The 6N6P looks a bit cramped at this sort of operating point.

Shoog

 

[Eli Duttman]

Shoog,

The 5687 is a possibility. You'll have to settle for I_B = 37 mA.

5687 data sheet here.

 

[Wavebourn]

EL84 triode strapped is another option.

 

[Shoog]

Running a single 5687 for both sides of a stereo pair is pushing it over it plate dissipation (just). Of course I could run the two triodes in parallel.
I have used the 5687 as a preamp tube and always had issues with hum, I really want to avoid the complexity of DC heaters.
A definite contender though and I even have some.

Shoog

 

[Shoog]

EL84 triode strapped is another option.

I thought of that already. works on most levels, but would it be happy at 100V.

Shoog

 

[Wavebourn]

An externally hosted image should be here but it was not working when we last tested it.

 

[Shoog]

Not really then.

Shoog

 

[Wavebourn]

12L6 would be an ideal, but it has octal base however...

 

[Brian Beck]

7119/E182CC? Superficially similar to a 5687 but has much larger plates, somewhat higher gm and mu. At 100 Vp and 40mA needs Vgk = -1V. Maybe run it at 30mA (Vgk = -1.5V)? Fairly high Cpg, so drive it with low rp stage.

EDIT: I don't know how much signal swing you need. This might run into a grid current problem. Why do you need 40mA? Are you driving the grids of the 6AS7s into the grid current region?

 

[gingertube]

Something for you to check - I haven't

Have a look at Electro-harmonix version of 6C45Pi.
I think it should go close - might need to parallel a pair.

Cheers,
Ian

 

[wrenchone]

You might want to look at a EL86/6CW5. These are supposed to be good down to fairly low voltage, though the triode-strapped gain may be a bit too low.

 

[jrdmedford]

What dont you like about the sound? I'm guessing that you
dont like the bass response. In such a case, you need a much
lower Rp.

The 7044 is nice too, Rp=1700 ohms Va=120 mu=21

Only thing that hasnt been mentioned.. This is a mighty
fine driver tube.

Can you suck it up and deal with more B+ ?? How about
the 12BH7 ? You need around 250V... mu=17, Rp=5500 ohms.
Then theres the 6V6/12V6/12AQ5 types with mu=9 but
Rp=1700... Going for a tube with Rp < 2000 ohms is a good
bet with the typical 5K:5K interstage trannies out there.

Crap... With the low B+ and moderate current, maybe you best
bet would be a MOSFET.

-- Jim

 

[Shoog]

I was thinking of the EL86 as I have a rake of the PL84, but the gm is to low at just 9.

EDIT: I don't know how much signal swing you need. This might run into a grid current problem. Why do you need 40mA? Are you driving the grids of the 6AS7s into the grid current region?

The problem is that the interstage is suboptimal, and capacitances become a real issue very quickly. 40mA seems to keep the top end sweet. I think if you scan the various interstage transformer based designs they like to push a lot of current to get over this particular issue.

I'am currently leaning towards trying the 5687 - its nearly perfect for the job.

I will keep an eye out for the mighty 6H30, as it really seems to be perfect for the job.

Shoog

 

[pedroskova]

12B4A ...make up the gain elsewhere (mu=8, IIRC).

 

[Eusebius]

The 6S4 is just about what you need - mu 16.5 and takes at least 24mA. sounds pretty nice.

Better sounding and you have 6AH4 - mu 8 and 30mA.

Better sounding again is the 1626 but that's down to mu of 5, but it is 12v filaments.

You have the 6BL7 which is exactly mu 15 and 40mA - don't know how it sounds. The 6BX7 sounds pretty good.

You might find a use for a dissimilar double triode like the 6DN7 - the beefy side of it is exactly what you want and you have another side as well. Sounds good too.

 

[dstockwell]

I have spotted the 6H30 which looks just the job, but the heater is a problem. Also they seem outrageously expensive. Any good sources ?

I would appreciate any other ideas.

Shoog [/B]

Maybe this is not the same, I don't know enough to say. But $20

http://store.tubedepot.com/so-6h30pi.html

 

[rcavictim]

I have yet to play with them but I have been looking at the 6CL6 as a candidate for a driver. That is a nice 9 pin miniature for you with 6.3 volt heater. The 6AG7 tall metal octal is it`s large equivalent predecessor.