Pentode sounds great

[Cassiel]

Hi, i have built a little amp with the ecl86.

My surprise is that it sounded better in pentode mode. Triode had a good tone (doesn't always) but the sound was a little opaque and too much laid off for my taste.
Try this with any pentode, el84 anyone?
Only requirement is no bypass caps,input and output stage, and a higher than normal primary impedance - 10.000 Ohms or maybe more if you can.

Lovely sound, clear and natural.

 

[Jeb-D.]

Try this with any pentode, el84 anyone?

George (tubelab) did. He seemed happy with the result.

I've had good luck with other Pentodes as well.

 

[Boris_The_Blade]

Sometimes those extra two connections scare people, but there's nothing wrong with pentodes!

 

[ray_moth]

Stalker, did you use negative feedback (other than unbypassed cathode resistors)? It's common to use it to improve pentode harmonics and damping factor.

 

[Cassiel]

No Ray, only current feedback...but when i get used to the sound i'll try
a voltage feedback loop too. Thought i suspect i'll get an even cleaner sound but with less air and openness.

 

[aletheian]

You are not alone, I tend to like the sound of pentodes too--more bite and a more aggressive response typically-- but since I listen to heavier music it makes sense for me. They just seem so unpopular that I have never bothered posting about it.

 

[ray_moth]

Well, aletheian, I'll join you as a pentode fan.

My attraction to pentodes started over 40 years ago and hasn't abated yet. Expressions like pentode authority and pentode slam get the old pulses racing. Of course, I know that triode sound is 'purer', but where's the fun in that?

 

[JandG]

I too am getting a high respect for Pentodes in SE as that is all the OT;s I have are SE, but in the last month or so I have ripped though many, many Pentodes & many sound excellent in the normal mode. Now I am off to learn NFB ways, I see there is many, many differnat ways to do it.I tried sceen dive this mourning on a 807 & couldn't get it to work, another day for that G2 drive thing. I like building sperate PS's & Pentodes in that mode give me a good reason to do g2 supplies & experiments. my top dog amp is a DIY PP 6l6 jobber from a very talented fella that used a Fisher 200 OT & adjustable NFB, it is a stunning sounding amp. Yep I like em..

 

[azazello]

Well, aletheian, I'll join you as a pentode fan.

My attraction to pentodes started over 40 years ago and hasn't abated yet. Expressions like pentode authority and pentode slam get the old pulses racing. Of course, I know that triode sound is 'purer', but where's the fun in that?

What is better ? Pure, real sound .....or fun ?
/6C41C - 1/2 of 6C33C -.... sounds like pentod...compromise?/.

 

[ray_moth]

What is better ? Pure, real sound .....or fun ?

I'm going to respond with the dreaded words "it depends", in this case on your reason for being in this hobby of ours. Good triode sound is well within reach for most people, whereas good pentode sound is more of a challenge (but also more rewarding when you get it right).

Maybe the best approach is to build a nice triode amp and keep it for listening, then build a pentode amp to use for experimenting.

 

[Geek]

Pentodes can sound spectacular, if you chose the right one and operating point/load

Cheers!
(loves 6V6 pentodes as much as true triode amps)

 

[Cassiel]

Yes Aletheian, i too like the adrenaline of pentodes,their speed and presence...not as deep as triodes thought.
I can't have it all so i have to choose.

 

[azazello]

Sory, for my bad english.....
Tne pentod has very hight Ri / 2 - and more kom/ and is dificult to make output transformer for real sound /I calculat my transfomers end
order them..../ There is a compromise - triod mode and sound is aprox.
between pentod and triod. / EL 34 - 2,5 kom in pentod mod and 1,2 kom in triod mode, Ra=3-5Ri...Ra=7-10kom for pentod or 4-5 kom for triod....this is easy to make out. trans /. Also...more coils - more caps
between coils, and no real sound !!! For my 6C41C Ra= 1 kom!! Trans-
former - 16 sq. cm, primary - 1500 co., Ia - 140 ma. And sound is very, very....with
8 watts per chanel !

 

[Miles Prower]

You are not alone, I tend to like the sound of pentodes too--more bite and a more aggressive response typically-- but since I listen to heavier music it makes sense for me. They just seem so unpopular that I have never bothered posting about it.

Me three. I did two projects, an 807 PP design and a 6BQ6GTB design, both running in pentode mode. I get great sound from both, though 807s require a bit of help from local NFB that the 6BQ6s don't need -- just a bit of gNFB to take the excessive edge off and to improve woofer damping. Part of the key to getting good pentode sound is active screen voltage regulation and fixed bias. Cathode follower grid drivers also help with overdrive behaviour. For both projects, I included a hollow state active voltage regulator.

 

[SY]

Part of the key to getting good pentode sound is active screen voltage regulation and fixed bias.

Couldn't agree more. It's far and away the most important thing.

 

[Bandersnatch]

I'm going to respond with the dreaded words "it depends", in this case on your reason for being in this hobby of ours. Good triode sound is well within reach for most people, whereas good pentode sound is more of a challenge (but also more rewarding when you get it right).

heh-heh-heh...pentodes are rather like like a high-Q circuit. Nothing much happening until you get on the pipe. Lower, but broader hump is available to the open-loop triode fans. Pay close attention and design carefully and the pentode *WILL* deliver...
cheers,
Douglas