Change EL84 from Triode to Ultra linear

[mcgaag]

I recently built this amp. Great sound but it's a little low on output power.

The opt's i use have primary windings of 2.5, 3.5 and 4.5 Kohm. Now i only use the 4.5 K one. Would it be possible to use one of these windings for the ultra linear tab? If so, I suppose the 2.5K would be the best option? And do i need to make changes to the design or is removing the 100K resistor and connecting the ul tab instead?

Thanks,
Rob

 

[Allen Wright]

Yes you could use these taps for U/L, but the sound quality will vanish!

I dislike U/L intensly. Stay with triode, and build a bigger triode amp for mre power.

Regards, Allen

 

[mcgaag]

Thanks Allen.

I am going to use a switch so i can select the mode i want to use. This is a learning project for me and this way i can hear what is does to the sound.

I am planning on building a nice KT88 se amp. But i haven't decided witch one jet.

 

[Kashmire]

the sound quality will vanish! ... I dislike U/L intensely

I thought so, too. Until I attached my EL84 amplifier to my Triangle Acoustics loudspeakers. These speakers much prefer Pentode connection. Even UL sounds much better than Triode mode. I originally built the amplifier to operate in Triode mode. I thought it sounded good. When I experimented and moved the connection to UL or Pentode mode, the sound greatly improved.

I learned some lessons:

1. I believed the common wisdom that Triode mode was always better. I'm glad I experimented with UL and Pentode modes, because it proved the hypothesis was wrong.
2. I'm glad I experimented with the other modes, because it greatly improved both the amplifier's sound and my knowledge.
3. Common wisdom philosophies are commonly wrong ... "only such-and-such configuration is best" ... or "single-ended amplifiers always are superior to push-pull amplifiers".
4. Experience teaches us to disregard these types of common wisdom, and experiment with configurations that mainstream audiophiles reject.

 

[bigwill]

How about running pure pentode mode and Schading things up for better than triode linearity

 

[Eli Duttman]

I thought so, too. Until I attached my EL84 amplifier to my Triangle Acoustics loudspeakers. These speakers much prefer Pentode connection. Even UL sounds much better than Triode mode. I originally built the amplifier to operate in Triode mode. I thought it sounded good. When I experimented and moved the connection to UL or Pentode mode, the sound greatly improved.

I learned some lessons:

1. I believed the common wisdom that Triode mode was always better. I'm glad I experimented with UL and Pentode modes, because it proved the hypothesis was wrong.
2. I'm glad I experimented with the other modes, because it greatly improved both the amplifier's sound and my knowledge.
3. Common wisdom philosophies are commonly wrong ... "only such-and-such configuration is best" ... or "single-ended amplifiers always are superior to push-pull amplifiers".
4. Experience teaches us to disregard these types of common wisdom, and experiment with configurations that mainstream audiophiles reject.

This post is right on target. One size DOES NOT fit all. Synergy between various elements in the playback chain is what we are searching for.

 

[kevinkr]

I'd use the 3.5K tap instead of the 2.5K tap, otherwise it seems worth a shot.
Switch is a good idea, observe switch voltage ratings though..

 

[platplaas]

I am using a 6a 125v switch for selecting between pentode and ultralinear. Is this an issue?

 

[artosalo]

I learned some lessons:

1. I believed the common wisdom that Triode mode was always better. I'm glad I experimented with UL and Pentode modes, because it proved the hypothesis was wrong.
2. I'm glad I experimented with the other modes, because it greatly improved both the amplifier's sound and my knowledge.
3. Common wisdom philosophies are commonly wrong ... "only such-and-such configuration is best" ... or "single-ended amplifiers always are superior to push-pull amplifiers".
4. Experience teaches us to disregard these types of common wisdom, and experiment with configurations that mainstream audiophiles reject.

To read this is like good music to my ears.

 

[Miniwatt]

I recently built this amp. Great sound but it's a little low on output power.

I'm curious if you will be able to notice the increase in power..

 

[rvrazvan]

i have a triode/pentode SE with el84. I have no experience with UL. but from what i heard...it's dull. Take into acount also the change in sound not only the increase in power.

 

[chrish]

I built a similar design a few years ago. I ended up bypassing the cathode resistor in the 6N2P with a capacitor to increase its gain.