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 Post subject: Pentode versus triode
PostPosted: 11 Jul 2015, 08:51 
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Joined: 04 Feb 2013, 06:52
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Location: North Wales
I'm making a simple single ended amp using EL34 output valves. Instead of a triode front end I'm considering using an EF86 pentode, though it will be wired as a triode. The circuit is simple, requires no elevated heater voltage and the EF86 is readily available here in the UK.
The question then is; will it sound as good as a triode?


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PostPosted: 11 Jul 2015, 11:48 
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Joined: 08 Aug 2009, 03:11
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Location: Chilliwack, BC
Maybe. The only one that can answer that is you. It's your ears.

Try an EF184 trioded, as well. better transconductance and for my personal tastes, blows an EF86 out of the water.

Cheers!

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PostPosted: 11 Jul 2015, 13:47 
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Yes, I realise it's subjective. Just thought there may be logical reason to prefer one or the other as I have read that pentodes are more microphonic than triodes.


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PostPosted: 11 Jul 2015, 17:54 
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Joined: 04 Jun 2008, 20:59
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Hi, I suppose the question is why not use a triode? I don't want to start a commotion, but IMO most triodes work and sound better than pentodes used as triode.

Good listening
Bruce

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PostPosted: 12 Jul 2015, 00:07 
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Joined: 24 Feb 2009, 03:24
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Gain of triodes is between 20 - 100 with different sounding. Gain of penthodes in triode mode is about 40-50...../Very good penthode IMO is E180F-Phillips in my SE 2A3 RCA/.

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PostPosted: 12 Jul 2015, 00:47 
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You can actively load a trioded pentode (CCS with a valve or sand or mu-stage) to get the max gain practical. For a trioded E180F or as I mentioned, EF184/E184F/6EJ7, you can get about 60.

Rolling triodes will have a big impact too, if that's what you want. Rolling trioded pentodes, not so much... they're fairly consistent sonically.

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* Ratings are for transistors - tubes have guidelines*
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PostPosted: 14 Jul 2015, 20:27 
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Joined: 20 Mar 2014, 20:36
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dudleyperkins wrote:
The circuit is simple, requires no elevated heater voltage


As opposed to triode? I don't see any need to elevate the heater voltage in both case, depending on the design of course.


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