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Which pentode for AC10 clone?

 
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Phil_S



Joined: 23 Oct 2007
Posts: 3564
Location: Baltimore, MD

PostPosted: Thu Dec 15, 2011 6:40 pm    Post subject: Which pentode for AC10 clone? Reply with quote

It's not easy trying to keep busy with this sort of thing and worse on account of the tubes Shocked

I'd like to build something from stuff I've got on-hand and am thinking about how nice it would be to have an AC10-like amp in a head. Besides, then that pair of Mullard EL84's I've got can find a home. I've heard that EF-86's tend to be microphonic. Since I don't already own some, I took a look at pentodes I already have. I have several to choose from: 6AU6, 6SJ7, and 6AC7 (no, not EL34, not a typo). Looking at the data sheets, these seem to hold out some promise as a decent input tube. I've used the 6SJ7 before in a Gibson GA20 "lite" circuit (one channel only) and liked the result.

It it a fools errand to use something besides the EF86? How essential is that particular tube to the tone? I'm not all that picky. If I can get close, I'll be very happy. When I build, I never expect the outcome to sound like a production amp because I monkey with lots of variables, including the iron. I"m looking at a used universal Merit OT for this. I just like it to sound good.

Opinions please? Thanks.

Phil
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Reeltarded



Joined: 14 Feb 2009
Posts: 6990
Location: GA USA

PostPosted: Thu Dec 15, 2011 7:00 pm    Post subject: Reply with quote

Just me talking from writ, but I read something a while back were a guy described a great outcome with the 6ac7. (notta typo)

I have some lil grey amps with Ef86s though. No problems with them, always the outputs.

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tubelectron



Joined: 04 Dec 2011
Posts: 66
Location: France

PostPosted: Thu Dec 15, 2011 8:52 pm    Post subject: Reply with quote

Hi,

EF86 were designed to be anti-microphonic and low-noise audio pentodes, but sometimes they didn't meet their requirements, often when it's rebranded items from the late 70's, where it can vary from one batch (or even sample) to another. Among the best were the Telefunken gold pins EF86, by experience.

Nonetheless, a excellent substitute to the EF86 is the 6AU6, which proved to be more consistent than the all-around EF86 in terms of noise and microphony, when I tested it.

I wouldn't use an octal pentode here, as I found them too vibration sensitive.

A+!

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10thTx



Joined: 30 Dec 2006
Posts: 1055

PostPosted: Thu Dec 15, 2011 10:57 pm    Post subject: Reply with quote

5879 pentode is a good tube but if you don't have it then I'd opt for the 6AU6. Also a 5654 and 6AU6 have similar pinouts.

With respect, 10thtx
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Phil_S



Joined: 23 Oct 2007
Posts: 3564
Location: Baltimore, MD

PostPosted: Thu Dec 15, 2011 11:31 pm    Post subject: Reply with quote

I think I have 6 or 8 6AU6's. I'll give them a try. Any reason to treat it differently from EF86? Or just build to the schematic and tweak after?

Thanks everyone for the input. Much appreciated.
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