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Old 8th December 2012, 02:16 PM   #1
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Default LM3875 Inverted Or Not?

Im thinking of building a valve buffered clone. Does it have to be an inverted setup? Am i over/under complicating things. Is non inverted possible?
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Old 8th December 2012, 02:25 PM   #2
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I get the impression you don't know what you are doing.

Post a schematic and hope that someone can guide you.
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Old 8th December 2012, 02:28 PM   #3
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You can take a peek at my project but the design isn't set yet and not explained. This will come later on. The schematics will also have variants.

My project is a single/dual E88CC tube buffer in cathode follower mode or "White Cathode Follower" mode + inverted/non-inverted gainclone (LM3886) + power supply.
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Old 8th December 2012, 02:33 PM   #4
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I understand the schematic in so far as ive built gainclones (non inverting kit) and wondered if i could builb a valve buffer for it. The schematics are all a variation on inverted designs. I dont fully understand the implications of using the valve with the chip
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Old 8th December 2012, 05:58 PM   #5
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You will get a rather low input impedance of the inverting amp so a buffer could be good to have and why not a tube buffer in order to get some tube flavored sound.
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Old 8th December 2012, 06:11 PM   #6
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But is it feasible to do with non inverting amp?
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Old 8th December 2012, 06:53 PM   #7
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Quote:
Originally Posted by tom wesley View Post
But is it feasible to do with non inverting amp?
yes, though no longer as necessary to have a buffer. you would just do it for colour.

perhaps people only use inverting to justify using a buffer to themselves, and hence valves.
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Old 8th December 2012, 07:06 PM   #8
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Unless you have whimp of a preamp, inverted config doesn't necessarily need a pre. You can get pretty high input impedance (like 10k) when using a T-network for the feeback path.
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Old 8th December 2012, 08:45 PM   #9
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Quote:
Originally Posted by tom wesley View Post
But is it feasible to do with non inverting amp?
Thorsten Loesch's design -- one of the originally published gainclones -- is inverted. The inverted version includes everything "before" it in the feedback loop so a buffer is really required. Buffered, inverted gainclones, in my experience, are best of breed. If using a cathode follwer, for best performance requires a CCS on the tail of the CF.

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Old 9th December 2012, 09:21 AM   #10
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Originally Posted by KSTR View Post
Unless you have whimp of a preamp, inverted config doesn't necessarily need a pre. You can get pretty high input impedance (like 10k) when using a T-network for the feeback path.
I have tried the t network on my inverting lm3886. The extra connection to ground seems to inject ground noise into the input... Any comments?

Ps can get 10k input impedance without t network in inverted mode
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