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Old 19th September 2012, 11:09 AM   #1
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Default Tube ID help please.

Hi Guys, I recently went through my older tubes and found a couple I received in a mix box ages ago.

I didn't notice the Telefunken diamond on the base when I bought them.

Could I have a hand IDing them please?

Thanks!

Tube 1: (4 pics)

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Tube 2: (3 pics)

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Thanks again.
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Old 19th September 2012, 11:22 AM   #2
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Larger photos:
Tube 1:

Click the image to open in full size.



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The base is the same on both tubes:

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Last edited by tropicalmuz; 19th September 2012 at 11:30 AM. Reason: resolution
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Old 19th September 2012, 11:27 AM   #3
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And, better resolution for tube 2:
Click the image to open in full size.

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Old 19th September 2012, 11:51 AM   #4
DF96 is offline DF96  England
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They are both dual triodes, of conventional construction (so definitely not ECC88, for example). You probably already knew this, though.

You can work out the pinout by looking closely at the base connections. Then use a valve tester or lash-up circuit to see what they are.
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Old 19th September 2012, 12:16 PM   #5
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Thanks DF96, I have a vague recollection of them being somehow labelled 12au7.

I have no tube tester (I'd love to get in touch with someone who does here in Tasmania).... so I just tried them in the preamp socket of my amp (meant for a 12ax7) and tube 1 (red top) needs a volume boost to compare with the Raytheon blackplate I have in there but does sound pretty good. The other one (no red top) seems to have the same gain as a 12ax7 so maybe that's what it is?
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Old 19th September 2012, 01:50 PM   #6
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Location: Niederösterreich
Yup, look like telefunken 12AX7 or 12AU7, red usually means they were screened for microphonics or low-noise ect.
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Old 20th September 2012, 12:26 PM   #7
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Thanks guys.
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