12AB5 pentodes?

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rfgordon
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12AB5 pentodes?

Post by rfgordon »

The efforts at building the amps with the tiny tubes got me thinking about doing something similar. However, I wanted to see if there were tubes that could be used with regular sockets, as opposed to having to be soldered in place.

So I came across the 12AB5 pentode. It's roughly the size of a 12AX7, and a pair in push-pull would make about 8 watts. Their plate voltages and cathode resistors are similar, also.

They were designed for use in car radios, and the filaments can take a fair range of voltages, as you would need to in the days of the mechanical voltage regulators.

I don't know if anyone here has any experience with these little guys. A forum search turned up nothing. They are dirt cheap from NOS dealers, too-about $4 each.

I have a basic Hammond PT and an OT from an amp that ran 50L6 power tubes, so I might give it a try and see what happens.

Any ideas on these tubes?
Rich Gordon
www.myspace.com/bigboyamplifiers

"The takers get the honey, the givers get the blues." --Robin Trower
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Structo
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Re: 12AB5 pentodes?

Post by Structo »

200 Mu

Looks like 250 Vamax

10 watt push/pull

http://www.nj7p.org/Tube4.php?tube=12AB5
Tom

Don't let that smoke out!
rfgordon
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Re: 12AB5 pentodes?

Post by rfgordon »

Tom,
Thanks for that link. I had looked up some of the data sheets. I reckon it's worth a try to see how these things sound.
Rich Gordon
www.myspace.com/bigboyamplifiers

"The takers get the honey, the givers get the blues." --Robin Trower
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Phil_S
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Re: 12AB5 pentodes?

Post by Phil_S »

I've got no experience with this tube, but my gut tells me not to push the B+. I'll bet this gives you a decent tone at around 200-225V.
tonewood
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12ab5 voltage

Post by tonewood »

I picked up a Webcor 12ab5 pp amp at the flea mkt. The schematic pasted inside claims 285 volts on the plates and screens. I'll test it today for actual voltage and sound (if i get it going).
scott
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Kagliostro
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Re: 12AB5 pentodes?

Post by Kagliostro »

Hi Tonewood

can you post the schematic ?

THANKS

Kagliostro
tonewood
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12ab5 schematic

Post by tonewood »

Hey Kagliostro

When trying to post the schematic I keep getting "No post mode specified" from the site. Anyone know what's up? I'll keep trying.

Not exactly a high gain guitar amp. Just one half 12ax7 for preamp and half for cathodyne splitter. The splitter uses almost the same numbers as the example in Merlin's book. The preamp is a bit cool biased & i will heat it up a bit.

scott
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Kagliostro
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Re: 12AB5 pentodes?

Post by Kagliostro »

Did you controlled the permitted extensions for the file to be posted ?

Kagliostro
Herec
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Re: 12AB5 pentodes?

Post by Herec »

Any progress on this? I've got an OT from a reel-to-reel tape recorder that used two 12AB5 in push-pull for its loudspeaker output section. Also got a PT that has both 6.3 V and 12.6 V taps for the filaments.
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