Eliminating a preamplifier triode in radios made them cheaper. Please help improve this article by adding citations to reliable sources. I have seen SET amplifier schematics and they always use a semi-powerful tube in the “driver” stage to drive the output triode. Also plate impedance 38k ohms approx for the pentode mode 2k ohms in the triode mode the result the amplifier is more dampened in the triode mode closer to a solid state amplifier sound then in the pentode mode So triode mode not only drops power it reduce overshoot due to inductance, capactance and other effects relative to the speaker used over all it won’t sound as bright as the pentode mode. Triode mode also has better low frequency response Something I just started to look into is the effect of the transformer on frequency response.

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Bottom line the greater the primary inductance of the transformer the lower the frequency response so in simple terms a bigger output transformer will give you more bass response. The grid resistor of the power stage needs to be at least K to cope with this. The EL84 is a thermionic valve of the power pentode type. Developed by Philips in for use in the British Mullard amplifier, [ citation needed ] the EL84 came to prominence when used in Watkins and later the Vox amplifiers preferred by many British Invasion bands of the s.

Generally, I agree with most of the previous posts and the concepts. Vacuum tubes Guitar amplification tubes.

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DESIGNING EL84 PENTODE AMPLIFIER

We select R5 at 56KOhm. A lower-power triode such as a 12AU7 or 12AT7 might be better but I’d want something with a bit more juice.

A single EL84 was used in low-cost equipment, and a push—pull pair for lower distortion and higher power. From Wikipedia, the free encyclopedia. Triode mode also has better low frequency response Something I just started to look into is the effect of the transformer on frequency response. In the long run, I concluded that the SRPP with tubes like a 12AX7 was superior over the single ended versions for driving power tubes.

The tone is definitely not as brilliant as in pentode mode and does of course break up earlier.

By using this site, you agree to the Terms of Use and Privacy Policy. If you surf the web you will see tube HiFi folks like the triode mode with some amps that have volts on the plate and dollar tubes. I built a Spud amp that used the EL84 Pentode mode by itself to drive my speakers. And these cap’s will soak some current. The EL84 was developed to eliminate the need for a driver tube in radios, so it has rather more gain than is usual in a power pentode.

There are ways wl84 work around rl84 such as negative feedback, but good amp design is much better than such a band-aid.

Please help improve this article by adding citations to reliable sources. It can produce 17 W output in Class AB1 in push—pull configuration. But in A1 it works fine.

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In simpler term, triode is half of pentode. I’m not good at numbers so I don’t know how significant these capacitances are. The 6V6 ell84 very well behaved in class A2 and, with an appropriate driver, has a very unique sound when over driven.

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Results 1 to 10 of I got the idea from the Legacy amp of Thorsten as well as another project on the net that uses el84 triode strapped to drive a 2a3. For the EL84 this ratio is approximately 9: Mon Jan 30, 8: BTW for those curious Another way to increase bass response is adding feedback to the amplifier.

F in the formula below represents a cut-off frequency and is selected to be 1 Hz. The only reason to do this is to run the power stage in class A2. I will say this: The triode mode is self inflected feedback because the control grid is not isolated from seeing the output plate as it would be in the pentode mode.

What the triode mode does is change the plate impedance to 2k ohms from say 50k ohms so with 5k ohms reflected in the pentode mode you have 4.