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Hi, I own a 18 watt sIII head 2 years back works fine, now I plan to install it in a combo cab. I am concerned if there is any real issues like grid sag in 3 grid pentode EL84 tubes, by the horizontal mounting of the chassis and speaker, tubes proximity vibration. What are the correct pin orientation for horizontal mounting EL84 and EZ81 tubes to function safely.

Vertical would be ideal but i havent heard of any issues with horizontal mounting. the original bluesbreakers were done that way.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Thanks Coco. Is the EL84 and EZ81 tube pins 1 and 6 need to be in the vertical plane when mount in horizontally, or any other direction? Does it shorten tube life someway.

The factors to consider would be having adequate ventilation to avoid overheating, and vibration to cause microphony in the tubes. Combos are thought to be harder on tubes due to the speaker vibration... it's hard to predict, I wouldn't worry about it, just bear it in mind with your design.

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Corey

I dont really believe so.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Hello. Has anybody built a combo out of a 18watt head chassis here in this forum any opinion and issues about it. could you show some pics of it. Vinu

We have successfully done this and it works fine. It's just a little harder to change tubes. I dont think we have any pictures because its almost impossible to get a picture from inside the cabinet!

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Here is my 18 watt Plexi build in a Bluesbreaker style 2x12.

Its's been set up and played almost every day for the last 2 months with no issues. Several 2 hour jam sessions with drummer ( ie - amp cranked) with no issues, other than the shock over how awesome this amp sounds!

To echo Stephen, changing tubes is a pain. Using flashlight and small mirror makes it much easier.

My advice is if this is the config that works for you - go for it!