Author Topic: Mars EL84PP  (Read 1690 times)

Offline Mars

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Mars EL84PP
« on: September 21, 2017, 12:29:03 PM »
Here I will post information regarding the Mars EL84PP kit and Stereo 20 amplifier.

IMG_1362 by Karel Mars, on Flickr

The EL84 tube is one of the stalwarts of the tube amplifier world, being used in famous amplifiers such as the VOX AC30 and LEAK Stereo 20.

If a pair of EL84's is configured as a push-pull amplifier, one can get up to 15watts of high quality sound. This kit is inspired by the Mullard 5-10 and Dynaco ST35 designs. Like the ST35, a dual pentode/triode (6U8) is used as a voltage amplifier and output tube driver. The EL84 pairs are cathode biased with individual, bypassed, cathode resistors for maximum reliability and increased DC current balance.

The transformers are tapped at 30% of the windings for ultra linear operation. This gives increased linearity, less distortion and more tolerance to loads that deviate from the standard loud speaker 4 and 8 ohm options.

IMG_5176 by Karel Mars, on Flickr

Solid state rectification is used and linearity is increased with global negative feedback.
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Offline Den123

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Re: Mars EL84PP
« Reply #1 on: September 21, 2017, 12:56:09 PM »
Very neat!

Offline El Sid

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Re: Mars EL84PP
« Reply #2 on: September 21, 2017, 04:19:49 PM »
My how I wish I had one of these!

Wait a minute.....   :Whoohoo: ;D

Offline Mars

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Re: Mars EL84PP
« Reply #3 on: November 01, 2017, 03:36:36 PM »
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Offline Mars

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Re: Mars EL84PP
« Reply #4 on: November 01, 2017, 05:07:04 PM »
Parts List

parts-list by Karel Mars, on Flickr
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Offline Mars

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Re: Mars EL84PP
« Reply #5 on: April 24, 2018, 04:39:13 PM »
Here is some photos of the EL84 push-pull wiring:

partial wiring around the EL84 tubes

IMG_20180412_120748 by Karel Mars, on Flickr

IMG_20180412_120810 by Karel Mars, on Flickr

completed wiring

IMG_20180419_163848 by Karel Mars, on Flickr
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Offline Mars

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Re: Mars EL84PP
« Reply #6 on: August 08, 2018, 04:28:15 PM »
Another EL84PP has been born. Same circuit, same layout. Here is the finished product:

Mars  EL84 by Karel Mars, on Flickr
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Offline Wietsche

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Re: Mars EL84PP
« Reply #7 on: August 08, 2018, 11:13:37 PM »
So nice! Love the looks, especially the plain black one at the top. One day..

Will there ever be a headphone tube amplifier version that will compete with the Bottlehead products (excluding import costs) that we can learn about and build locally?

Still, looking good and sure it sounds good as well!



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