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Old 20th May 2012, 05:43 PM   #1
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Default Use a Pioneer A400 as a Power Amplifier

I have an Audiolab 8000C preamplifier and a Pioneer A400 integrated amplifier as parts of my system.

I want to compare the Pioneer A400 on its own to the A400 power section with the Audiolab as the volume control, in other words, compare the pre-amp sections of the Audiolab 8000C and the Pioneer A400, when using CD as a source.

It has been suggested to me that the Pioneer Tape Outputs could be used as Line Inputs when selecting Source on the Rec Selecter.

This would work, I assume, when the pioneer pre-amp out is connected the the Tape Output in parallel with the pioneer power amp section. Then the Tape Output could be used in a Line In. I also assume this does work for some integrated amplifiers. However, the A400 has separate Input and Rec selecters such that, in principle, you can listen to one input source whilst recording from another input source. I have tried this method and could not get it to work.

What I am trying to do is avoid two volume controls, working on the principle "less is more". Any sugestions on how I could achieve my goal ?
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Old 20th May 2012, 06:13 PM   #2
AndrewT is offline AndrewT  Scotland
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a pic of the back of the Pioneer with legible labeling would help us to help you.
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Old 20th May 2012, 08:55 PM   #3
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here is the rear of an A400X. The A400 is identical other than captive mains lead and does not have bi-wiring.
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File Type: jpg A400X.jpg (151.3 KB, 135 views)
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Old 21st May 2012, 03:47 AM   #4
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For the requirement you have, where you want to retrieve signal after the controls, you need a pre-out/main-in group of 4 RCA sockets at the rear. In vintage Japanese amps.these are normally bridged with plated, heavy wire "U" links. Pre. and power amps are obviously divided when removed.

Being a budget amplifier, it seems you don't have this luxury so it means digging inside to wire and fit your own sockets at the rear possibly, or you couldsave yourself some effort and parts by "borrowing" one of the unused tape-in/out groups of sockets for the same purpose. The manual is available free on a couple of risky sites and Eservice's PDF is badly split- just where you need to find the connection points after the balance and volume controls!
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Last edited by Ian Finch; 21st May 2012 at 03:49 AM.
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Old 23rd May 2012, 08:29 PM   #5
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This amplifier belong to the group that does the entire voltage gain in one go in the power amp, i.e. the gain is not split between pre and power amp. These are not (particularly) suited for pre/main splitting.
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Old 24th May 2012, 02:03 AM   #6
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Yes, the A400 Service Manual splits the schematic right at the point where you should go in with an external preamp, which I think should be after C201 and C202, which you would have to lift and add a switch to connect to. Then the A400 volume pot would be disconnected.

Yes, it's a fact that the A400 uses a chip (M5220P) as the power amp's first stage. So you can't disconnect it.

But this is a DIY forum, so I would say use this chance to do some parts upgrade on the chip stage and add an external input connecting to it, switching after the caps.
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