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Has anyone used an opamp to split phase for a tube amp?
Has anyone used an opamp to split phase for a tube amp?
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Old 5th April 2016, 04:34 AM   #11
Eli Duttman is offline Eli Duttman  United States
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repair guy,

You have shown why tubed paraphase splitters are out of favor. The current consensus is that split load, AKA "cathodyne", AKA "concertina", and differential (LTP) splitters are best.

I definitely want to see your schematic. FWIW, I'm thinking that it may be possible to drive the non-inverting opamp I/P with the signal from the 'X7 and apply the NFB to the chip's inverting I/P or vice versa.
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Old 5th April 2016, 04:35 AM   #12
repair guy is offline repair guy
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Here's the schematic so far. I didn't draw the opamp power supply, it's regulated +15, -15. I know it needs some optimizing, but it works really good. I might change out the 12AX7 for a 12AU7 for less gain. If anyone has any better design for the resistors, and how to add the global feedback I'd appreciate it.

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Old 5th April 2016, 07:02 AM   #13
ballpencil is offline ballpencil  Indonesia
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From here:
Tr-PS-2 & OpAmps and Tubes

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Old 5th April 2016, 07:39 AM   #14
theAnonymous1 is offline theAnonymous1  United States
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What about a fully differential op-amp like OPA1632/THS4131?
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Old 5th April 2016, 07:39 AM   #15
reenberg is offline reenberg  Denmark
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Most of today's hi-end dac have XLR output, should be possible to use that as well.

MC275 does it by the way
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Old 5th April 2016, 01:42 PM   #16
JPeitzman is offline JPeitzman  United States
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Has anyone tried using the DRV134/DRV135?
http://www.ti.com/lit/ds/sbos094b/sbos094b.pdf

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Old 5th April 2016, 02:31 PM   #17
Merlinb is offline Merlinb  United Kingdom
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Quote:
Originally Posted by JPeitzman View Post
Has anyone tried using the DRV134/DRV135?
http://www.ti.com/lit/ds/sbos094b/sbos094b.pdf
Unless you're driving long cables with unknown terminations, there is no point using DRV. Opamps will do.
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Old 5th April 2016, 06:36 PM   #18
JZatopa is offline JZatopa  United States
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Got any measurements you could post us of the amps performance? I'd be curious to see how this compares to other el84 amplifiers.
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Old 5th April 2016, 07:32 PM   #19
SpreadSpectrum is offline SpreadSpectrum  United States
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Quote:
Originally Posted by repair guy View Post
If anyone has any better design for the resistors, and how to add the global feedback I'd appreciate it.
The McIntosh MA2275 has an implementation of an opamp splitter with global feedback returned to the splitter. Here is a site with the schematic. The splitter is on page 16: here
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Old 5th April 2016, 08:56 PM   #20
BinaryMike is offline BinaryMike  United States
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Has anyone used an opamp to split phase for a tube amp?
My example linked in post #2 shows one way to add feedback.

Last edited by BinaryMike; 5th April 2016 at 09:03 PM.
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