2E26 rather than EL84 tubes in the SIII build?

[offpeak]

Guys, my local tube tech guru is very fond of the 1965 military issue RCA 2E26 beam power pentode tubes he has on hand, and very strongly suggests I try building the power section with these instead of the EL84s, and adjusting the plate voltage and circuits as needed to accomodate.

I've used these as a substitute for an Ampeg V4 I just finished (with a B25 preamp). The Ampeg requires 7027s or 6550s, but 4 of these 2E2As sound fantastic and gives a sh%t load of power.

I want to do justice to the EL84 and the original TMB schematic, but the DIYer in me wants to try the 2E26 in the 18W.

Any reason NOT to try building the SIII preamp stage with the 2E26s driving the power stage? (Apart from that they require a "hat", which is easily workable)

[zaphod_phil]

If this is your first 18W amp then I recommend you use EL84s, or you'll never know what you missed. The whole 18W vibe is about the wonderful sound of overdriven EL84s. If it's not your first 18W amp, then you really should try those 2E26s.

[jockman]

2E26????????? is this a direct replacement for the EL84? How does it compare sound/tone wise.

Jon

[rjgtr]

I think you should build an EL84 based amp. If you need more power than 2 EL84s build a 36watt. Unlike some other amps, most of the Tone in the 18 watt is from the power stage and that requires EL84s.

I'm sort of sceptical about building an amp based around tubes that aren't very common. Even if your tech has some stashed away, what happens when those run out or can't be matched?

[zaphod_phil]

Looking at the specs those 2E26s appear to be about the same power range as EL84s, so it's not a matter of output power.

[rjgtr]

But given that EL84s and 6V6s are around the same power, they still sound really different. Since the 18 watt tone is in the power amp wouldn't that change the tone of the amp?

[offpeak]

This brings up the root of my question (I guess) which is how much the power circuit flavors the sound as compared to the preamp circuit.

Also, with new modern rectifiers/diodes out there, is it better to send "cleaner" power to the heaters, or stick with the straight-out-the-transformer electricity?

I guess I'm just pondering the effect of all this on the tone.

[chainsawmillerman]

DC heater supply has no benifit in the power section to speak of.

[zaphod_phil]

But given that EL84s and 6V6s are around the same power, they still sound really different. Since the 18 watt tone is in the power amp wouldn't that change the tone of the amp?

Absolutely.

...how much the power circuit flavors the sound as compared to the preamp circuit.

It depends on the amp. In an 18W a lot of the distortion comes from the power stage.

... is it better to send "cleaner" power to the heaters, or stick with the straight-out-the-transformer electricity?

This question comes up 100s of times. The answer is that the rectification normally introduces more noise into the heaters, and most people who've tried it have ended up removing the rectification and filtering circuitry. If you want to slightly improve heater noise, just elevate the heaters by connecting the center tap of the main 6.3V heater winding to the cathodes of your EL84s. I do this with all my cathode-biased amps.

[offpeak]

All this tube talk is getting to be almost like talking jazz substitution chords... There's a substitution of a substitution for everything!

If where I am, EL84s cost $30/ea, but I can get 6AQ5s for $2/each, should I just go the 6V6 (aka 6AQ5) route, and be happy I saved the $60, or is the EL84 really the heart/soul of this amp, and I must do the EL84s to really get the tone?

BTW, my other amp is a 5E3, and this 18W is for bands with 2 guitarists.

[zaphod_phil]

... or is the EL84 really the heart/soul of this amp, and I must do the EL84s to really get the tone?

It absolutely is! No question at all. Not even a tiny little bit of a question.

PS: Jazz sucks!

[cloudhopper]

SAFETY CONCERN!!!
The "hat" you speak of is the top cap connection to the plate of the tube. This means that there will be full B+ of probably over 300V on a wire above your main chassis. PLEASE! only do this if you have a fully enclosed cabinet that has no possibility for being run without the cover in place. If it is merely a screen over the back, some guitar player will remove it so he can see the "pretty glow" better. 300V can do some serious hurt if fingers get in the wrong place. Top cap sweep tubes can and have been utilized in audio amps successfully and can have some awesome tone but please beware of the dangers. As far as the 18W is concerned, I haven't found any tube that really matches the tone of the EL84's, they are really magic. Other tubes have magic of their own, but just not the same.

[AC-128]

I'll second cloudhopper's warning about B+ above the chassis. You will be putting a live wire with dangerous voltage 'outside of the box' so to speak. Be very careful.
On the personal note, care to share where 6AQ5's are $2 a piece?
Thank you!

[Ampdogg]

"If where I am, EL84s cost $30/ea, but I can get 6AQ5s for $2/each, should I just go the 6V6 (aka 6AQ5) route, and be happy I saved the $60, or is the EL84 really the heart/soul of this amp, and I must do the EL84s to really get the tone?"

you'd have to use one or the other(6V6 or 6AQ5).They may have similar specs,but the 6AQ5 is a seven pin socket and the 6V6 is octal.

$2 each is a great price I get mine for $4.