I asked in the H2 V2 Thread but did not get very much of a response so I would lie to ask here:
Could an inverting op-amp stage be added to restore the signal to the correct phase?
Or could two H2 boards be put in series with the second one set up with no distortion?
I'd like to set this up for unity gain with the same phase in and out so I can easily switch it in and out.
Could an inverting op-amp stage be added to restore the signal to the correct phase?
Or could two H2 boards be put in series with the second one set up with no distortion?
I'd like to set this up for unity gain with the same phase in and out so I can easily switch it in and out.
Yes. Keep in mind that two similar stages with 2nd harmonic will see cancelation of the 2nd.
Assume the existence of perfect, distortion-free, sonically uncolored, buffer circuits**. They are available with gain -1.000 (perfect inverting) and also with gain +1.000 (perfect noninverting).
Now you can arrange a single H2 generator PCB, plus a swarm of inverting and noninverting buffers, plus a herd of gold contact signal relays. This lets you create whichever signal path you desire, merely by activating some relays and deactivating others. Some examples might include
and I'm sure you can think of many others. Perhaps after constructing your own list, you will conclude that although the swarm of buffers and the herd of relays offer a gigantic number of possibilities, you are most interested in these four
**search terms LME49720 and OPA1612
Now you can arrange a single H2 generator PCB, plus a swarm of inverting and noninverting buffers, plus a herd of gold contact signal relays. This lets you create whichever signal path you desire, merely by activating some relays and deactivating others. Some examples might include
- (input jack) --> (gain = +1) --> (H2 gen) --> output jack
- (input jack) --> (gain = -1) --> (H2 gen) --> output jack
- (input jack) --> (H2 gen) --> (gain = +1) --> output jack
- (input jack) --> (H2 gen) --> (gain = -1) --> output jack
- (input jack) --> (gain = +1) --> (H2 gen) --> (gain = +1) --> output jack
- (input jack) --> (gain = +1) --> (H2 gen) --> (gain = -1) --> output jack
- (input jack) --> (gain = -1) --> (H2 gen) --> (gain = +1) --> output jack
- (input jack) --> (gain = -1) --> (H2 gen) --> (gain = -1) --> output jack
and I'm sure you can think of many others. Perhaps after constructing your own list, you will conclude that although the swarm of buffers and the herd of relays offer a gigantic number of possibilities, you are most interested in these four
- Negative phase H2, end-to-end signal path is inverting
- Positive phase H2, end-to-end signal path is inverting
- Negative phase H2, end-to-end signal path is noninverting
- Positive phase H2, end-to-end signal path is noninverting
**search terms LME49720 and OPA1612
Hey Mark, this is really interesting. I can determine the ultimate path of inverting or non-inverting in your examples but can you help me understand the H2 phase result in those examples? I can't get my head around that yet.
This is my simple explanation. I posted this earlier in the ACA thread and nobody shot it down. When the H2 is adjusted to produce negative phase 2nd harmonic, it squishes the top of the waveform as seen on the output. You want your speaker cone moving away from you when the waveform is being squished. If you are sensitive to absolute phase as some have suggested above, phase reversal should probably be accomplished before the H2 in the signal chain.
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@YouAgain -
If you're asking "how" you manipulate to get positive or negative phase 2nd harmonic distortion, and "why" it results that way; perhaps no one explains it better than Nelson Pass.
https://firstwatt.com/pdf/art_h2.pdf
Key section starts on Page 3 - "The Importance of Phase". After reading that section, and flipping a few pages upside down, you can hopefully determine within your end-to-end chain how to achieve results 1 through 4 that Mark listed.
For me, the sentence starting with "I know this might be confusing"... was perfect.
If you're asking "how" you manipulate to get positive or negative phase 2nd harmonic distortion, and "why" it results that way; perhaps no one explains it better than Nelson Pass.
https://firstwatt.com/pdf/art_h2.pdf
Key section starts on Page 3 - "The Importance of Phase". After reading that section, and flipping a few pages upside down, you can hopefully determine within your end-to-end chain how to achieve results 1 through 4 that Mark listed.
For me, the sentence starting with "I know this might be confusing"... was perfect.
I should have been more clear. What I was referring to is these examples:
(input jack) --> (gain = +1) --> (H2 gen) --> output jack = Audio phase inversion
(input jack) --> (gain = -1) --> (H2 gen) --> output jack = Audio phase not inverted
(input jack) --> (H2 gen) --> (gain = +1) --> output jack = Audio phase inversion
(input jack) --> (H2 gen) --> (gain = -1) --> output jack = Audio phase not inverted
(input jack) --> (gain = +1) --> (H2 gen) --> (gain = +1) --> output jack = Audio phase invertsion
(input jack) --> (gain = +1) --> (H2 gen) --> (gain = -1) --> output jack = Audio phase not inverted
(input jack) --> (gain = -1) --> (H2 gen) --> (gain = +1) --> output jack = Audio phase not inverted
(input jack) --> (gain = -1) --> (H2 gen) --> (gain = -1) --> output jack = Audio phase inversion
As I see it the +1 stage doesn't change the phase of audio passing through it but the -1 stage and the H2 gen stages each invert the phase. Two phase inversions in series makes it positive again. So if I'm correct about that I'm trying to understand how these combinations result in one of the four possibilities that Mark listed. Maybe listing 1,2,3 or 4 to each of these would make it click for me.
(input jack) --> (gain = +1) --> (H2 gen) --> output jack = Audio phase inversion
(input jack) --> (gain = -1) --> (H2 gen) --> output jack = Audio phase not inverted
(input jack) --> (H2 gen) --> (gain = +1) --> output jack = Audio phase inversion
(input jack) --> (H2 gen) --> (gain = -1) --> output jack = Audio phase not inverted
(input jack) --> (gain = +1) --> (H2 gen) --> (gain = +1) --> output jack = Audio phase invertsion
(input jack) --> (gain = +1) --> (H2 gen) --> (gain = -1) --> output jack = Audio phase not inverted
(input jack) --> (gain = -1) --> (H2 gen) --> (gain = +1) --> output jack = Audio phase not inverted
(input jack) --> (gain = -1) --> (H2 gen) --> (gain = -1) --> output jack = Audio phase inversion
As I see it the +1 stage doesn't change the phase of audio passing through it but the -1 stage and the H2 gen stages each invert the phase. Two phase inversions in series makes it positive again. So if I'm correct about that I'm trying to understand how these combinations result in one of the four possibilities that Mark listed. Maybe listing 1,2,3 or 4 to each of these would make it click for me.