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Old 4th November 2018, 02:31 PM   #121
Big Guy is offline Big Guy  United States
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Quote:
Originally Posted by Vix View Post
I was also thinking about this. "The normal mode of operation" as I would call this H2 generator, is the assumption that you have an "ordinary" amplifier, ie not SE, an amp that does not enhance second harmonic and that does not invert phase (most commercial amps). In that case, by adding H2 circuit, you would introduce a small amount of positively-phased second harmonic, but since it is inverting, you would have to invert speaker connections at the output of am amp, in order to "bring back the overall phase". But, by doing this, you would invert the phase of the second harmonic, which would now become nagative, as is the intention of the circuit.
The problem arises if your amplifier already inverts the phase (Zen amp for example). By adding H2 circuit, you make one more inversion at the input, so now you have to reverse your speaker connection, in order to get "the right phase". But, in this case, you will get positive second harmonic, both from H2 and the Zen amp, and your result may not be as expected.
Hence, for such cases, it is necessary to "invert the phase once again". That also applies if you don't want to invert speaker connections in case of an "ordinary amp".
So, the simplest thingvwould be to build an opamp based phase reverser, which is basically an opamp which input goes to - input, with 100% feedback. It't easy to do, I've seen such circuit on some "subwoofer phase switches". On the other side, I don't know what (negative) efect can an additional opamp with 100% feedback have on the sound, so maybe we want a different solution.
Sorry if all of this sounds confusing, but it is actually very simple. Remember, the aim is to get the right overall phase at the speaker, while adding a small amount of negatively-phased second harmonic.
I am saying this because I have seen the tube buffers added on front of amps that do not invert phase. The result of this is the addition of positively-phased second order harmonic, but we want it negative.
Now if what I said is confusing enough, maybe Nelson can draw a simple schematic
P.s. Just had an idea :lightbulb: What about using a 1:1 transformer at the input as phase reverser?

Yes, way out of my depth.
I will just wait for the DIYAudio version which hopefully has the switching option.
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Old 4th November 2018, 03:15 PM   #122
Baldin is offline Baldin  Denmark
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The idea is to avoid a lot of relays etc.
This sims ok.
You can leave out the buffer, if you are ok with the volume being lower in the mid position and in either end position. The following inverting amp can also be omitted if you just vant the unity gain

R10 and R11 is the potentiometer here set in mid position (22k lin pot)
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Old 4th November 2018, 03:20 PM   #123
Baldin is offline Baldin  Denmark
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Not to confuse with the following amp, here is the circuit proposed
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Old 5th November 2018, 10:46 AM   #124
marconi118 is offline marconi118  Germany
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is there a combination of jfet type (j111, j310 etc), bias and supply voltage that could give the same harmonic signature but with more output level? 4V instead if 1.5V

this would avoid me to put an extra preamp stage to drive a low gain amplifier
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Old 5th November 2018, 01:56 PM   #125
Mark Johnson is offline Mark Johnson  United States
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H2
Quote:
Originally Posted by marconi118 View Post
is there a combination of jfet type (j111, j310 etc), bias and supply voltage that could give the same harmonic signature but with more output level? 4V instead if 1.5V
Finding out the answer will require a LOT of lab experiments using a distortion tester and a bunch of other equipment. However I think that if you decide to try it, you will have a lot of fun and expand your knowledge considerably.

I have a feeling, an opinion (but no hard data!), that to make a large amplitude H2-enhancer you might get better results from a MOS field effect transistor than from a junction field effect transistor. Looking through a pile of datasheets, I found the very lovely curve attached below. It's a MOS field effect transistor. The output versus input appears to be quite a nice square-law characteristic, which in the realm of opinions instead of data, ought to give quite a nice amount of 2nd harmonic distortion. I've attached the manufacturer's datasheet.

Give it a try, see what you think. Replicate Nelson Pass's H2 experiments but this time using a PMOSFET instead of an NJFET. Fame, glory, and tremendous fun awaits you.

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File Type: pdf SSM3J15FV_datasheet_en_20171011.pdf (214.8 KB, 10 views)
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Old 5th November 2018, 02:39 PM   #126
Big Guy is offline Big Guy  United States
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Have several questions re the "original" H2 Generator board...


I understand that each board was calibrated to produce "optimum" level of H2s and the relevant volts was noted on each. I have marked the pot to allow resetting if it inadvertently moved or moved for experimentation.
Across what points on the board would a measurment be made to assure resetting to the original condition?


Other than music coming from the speakers with the H2 inserted between preamp and amp, is there a simple way to know that it is working?
Is there somewhere for an LED to be added which verify circuit operation?
I am aware that a bulb could be added across the DC input points but that only assures that SMPS is supplying power.


Would it be possible to add a mini-led voltage display across the points where the calibration voltage is determined to indicate both operation and verify oltage setting?
IF so, what display specs would be required?
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Old 5th November 2018, 03:44 PM   #127
Mark Johnson is offline Mark Johnson  United States
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H2
Maybe the pronoun "it" might be the source of your confusion (2nd red box in attached H2 manual below)? To what does "it" refer?

"It" is the voltage regulator (1st red box in attached H2 manual).

The regulator has to be adjusted to a specific voltage, to get the target distortion curves. Nelson Pass measured the H2 distortion on your individual board, while he adjusted the regulator's output voltage. He wrote a voltage on your individual board, where he thinks the H2 distortion is Just Right. You are free to fiddle around with the potentiometer and to adjust the regulator's output voltage however you like. But if you ever want to set it back to NP's "Just Right" voltage, the number is written right there on the board.

Simply attach your digital voltmeter between node "V+" (the voltage regulator output) and "GND". Twirl the pot control until the DVM shows the same number as NP wrote on your board. Done.

If you want to build or buy a digital voltmeter display which is permanently connected between "V+" and "GND", and which is glued to the H2 PCB, that is your right. You own it, you can DIY it however you wish. Perhaps one of these cheap jobbies from eBay might do what you want? I haven't bought or used any of them myself so I can't promise they are easy to interface or they give accurate readings.

5PCS Mini Blue DC 0-30V LED Panel Voltmeter 3-Digital Display Voltage Meter 708624425963 | eBay

12V-60V Car Marine Motorcycle LED Digital Voltmeter Voltage Meter Battery Gauge | eBay

Waterproof Monitor 12V Battery Meter 2.5-30V DC Auto Gauge Digital Voltmeter LED | eBay

3pcs DC 0-30V Red LED 3-Digital Display Voltage Meter Voltmeter Panel Motorcycle 6971216072843 | eBay

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File Type: png part2.png (73.1 KB, 176 views)
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Old 5th November 2018, 04:25 PM   #128
Big Guy is offline Big Guy  United States
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Thanks, Mark. See my follow-up questions in maroon below...



Quote:
Originally Posted by Mark Johnson View Post
Maybe the pronoun "it" might be the source of your confusion (2nd red box in attached H2 manual below)? To what does "it" refer?

"It" is the voltage regulator (1st red box in attached H2 manual).


I see the "it" as well as the P1 adjustment pot on which I made hash marks to denote Nelson's setpoint.
However, I do not see the 317 regulator position marked either on the actual board or the Red/Green PC board rendering in the manual.
Which component on the board is the regulator? The tall black cylinder next to P1?


The regulator has to be adjusted to a specific voltage, to get the target distortion curves. Nelson Pass measured the H2 distortion on your individual board, while he adjusted the regulator's output voltage. He wrote a voltage on your individual board, where he thinks the H2 distortion is Just Right. You are free to fiddle around with the potentiometer and to adjust the regulator's output voltage however you like. But if you ever want to set it back to NP's "Just Right" voltage, the number is written right there on the board.

Simply attach your digital voltmeter between node "V+" (the voltage regulator output) and "GND". Twirl the pot control until the DVM shows the same number as NP wrote on your board. Done.


Will Nelson's adjustment voltage be measurable even without RCA inputs and outputs connected?


If you want to build or buy a digital voltmeter display which is permanently connected between "V+" and "GND", and which is glued to the H2 PCB, that is your right. You own it, you can DIY it however you wish. Perhaps one of these cheap jobbies from eBay might do what you want? I haven't bought or used any of them myself so I can't promise they are easy to interface or they give accurate readings.


Appreciate the recs!


5PCS Mini Blue DC 0-30V LED Panel Voltmeter 3-Digital Display Voltage Meter 708624425963 | eBay

12V-60V Car Marine Motorcycle LED Digital Voltmeter Voltage Meter Battery Gauge | eBay

Waterproof Monitor 12V Battery Meter 2.5-30V DC Auto Gauge Digital Voltmeter LED | eBay

3pcs DC 0-30V Red LED 3-Digital Display Voltage Meter Voltmeter Panel Motorcycle 6971216072843 | eBay

_
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Old 5th November 2018, 04:44 PM   #129
DougL is offline DougL  United States
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Here is a link to a data sheet.:
http://www.ti.com/lit/ds/symlink/lm317.pdf

If you fire up Google, the pictures are the 3 terminal IC with a metal heat spreader.
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Old 5th November 2018, 05:56 PM   #130
Big Guy is offline Big Guy  United States
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Quote:
Originally Posted by DougL View Post
Here is a link to a data sheet.:
http://www.ti.com/lit/ds/symlink/lm317.pdf

If you fire up Google, the pictures are the 3 terminal IC with a metal heat spreader.

Bear with me here...


When I google LM317, I get something like the figure below which shows the regulator as having 3 legs and a tab with hole at the top.


I DO not see any components like this on the H2 board. I DO see 3 half cylinders with 3 legs but NO tab at the top. The one closest to the P1 pot has its curved surface facing the pot. I am guessing the round vs flat surfaces determine the pin assignment?!


The tutoring is appreciated!

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