Audible Illusions Dual Mono Preamplifier - diyAudio
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Old 17th August 2006, 03:35 AM   #1
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Default Audible Illusions Dual Mono Preamplifier

I have gotten an old AI dual mono preamplifier which was i think the very first preamp from AI designed by Mr. Bruce Moore. My problem is that in the absence of manuals, I cannot distinguish as to which tubes are to be installed where. Checking the AI site made me more confused as the history says the AI dual mono has only 3 tubes per channel (1-12AX7 and 2-6DJ8). Mine has 4 tubes per channel. AI technical page right here:

http://www.audibleillusions.com/tech...PREAMP_HISTORY

I have already contacted AI but I do not have answers from them yet. Ill appreciate kind folks out here who can direct me to where I can purchase a copy of the manual or a tube placement diagram. I hope there are other AI dual mono owners here too. Thanks.
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Old 17th August 2006, 04:09 AM   #2
KBK is offline KBK  Canada
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12ax7 TEND to be phono pre, as a pair, in Mr. Moore's designs, and the 6DJ8's TEND to be the 'drive' or output section. So the ones near the phono inputs are likely the12ax7 pair and the the others, well, the others. the 6DJ8 positions. These are the overall, standard application for these tube types.

Can you follow the wiring at all?

If I had to guess, and being wrong would be death (as in a gun to my head) I would unhesitatingly go for the above mentioned scenario.

If the above AA unit came with tubes in it, and is functioning, then the look of the innards of the tubes will make it excruciatingly simple! Simply compare..or...

Go to 'the tube store' and select 12ax7, and then 6dj8 tubes, and you will note that in the pictures of the innards, they are strikingly different. This is generic to the tube type, not the brand. A 12ax7 will always look like the ones in the photos, and the 6dj8, will always look like the ones in the photos.
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Old 17th August 2006, 06:34 AM   #3
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the pre is functioning alright. the tubes installed is 1-12AX7 and 1 unidentified tube not similar to a 12AX7. These 2 I am sure are for the phonostage. The linestage tubes was 1-7308 (which looks like a 7199) and another 7199. This brings the total number of tubes of my AI pre to 4 per channel. Whilst Im sure the arrangement is similar to what you have outlined, I still want to have a copy of the manual and verify. Thanks KBK for that input of yours. appreciate it.
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Old 17th August 2006, 02:57 PM   #4
KBK is offline KBK  Canada
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Moore has some designs using a 12AT7 as a buffer on the output of the phono section, which is usually 12AX7 type tubes. This is similar to the Magus series of MFA preamps.
The 12AT7 has innards similar to the 12ax7, but are smaller.

It could also be 6An8 tubes in use, which look similar to the 7199. also, it could be ..I'm trying to remember 6EU7, I think, which was in the old heathkit preamps. Little triode-pentode tubes. Pin arrangement can be assayed, compared to the spec for these three different tubes, and then it can be figured out what tube is what.
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Old 18th August 2006, 02:40 AM   #5
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thanks KBK. will certainly evaluate those tubes
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Old 22nd October 2009, 05:59 AM   #6
daemise is offline daemise  Argentina
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Hello.I´bought one AI m3(is not new).It´s broken.It´not original.sam compoment is changet.I need the electrical circuit to repair.Sorry my inglish is bad.thanks
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Old 7th September 2011, 11:57 PM   #7
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You can fix the amp first then fix the english later when able. lol. I'm just kidding. Hope its fixed now hence you've posted 2 yrs ago.. cheers
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