They are to the current return path, not necessarily "earth ground". We had a short discussion a few weeks back where we discussed how to join the chassis/return path to the AC/earth ground that you can find here:
https://www.diyaudio.com/forums/pas...-diy-headphone-amp-guide-271.html#post6284074
--Tom
https://www.diyaudio.com/forums/pas...-diy-headphone-amp-guide-271.html#post6284074
--Tom
The build guide says:
Also, while I can build these things, my understanding of the circuits is not great. Why is gain set by the ratio between these two values? Is this controlling the feedback that appears on the negative input of the op-amp? (Is even that right?)
Has anyone experimented with that? Any sense for how adjusting the gain affects the overall character of the circuit (if at all)?
Also, while I can build these things, my understanding of the circuits is not great. Why is gain set by the ratio between these two values? Is this controlling the feedback that appears on the negative input of the op-amp? (Is even that right?)
...my understanding of the circuits is not great. Why is gain set by the ratio between these two values?...
Have a look the link for basic non-inverting op-amp theory.
https://www.electronics-tutorials.ws/opamp/opamp_3.html
Have a look the link for basic non-inverting op-amp theory.
https://www.electronics-tutorials.ws/opamp/opamp_3.html
Why are you interested in increasing the gain?
From my end, I've not needed more gain from this circuit. I've driven a bunch of amplifiers and headphones with the stock build settings for gain/volume pot and have never had to go beyond 12 o'clock. Sound is spectacular anywhere from 6-12 o'clock for me and I've done a lot of critical listening both with headphones and various setups now. In fact, I started my second build with a different pot that resulted in more gain and I had to swap it out because I couldn't get past 9 o'clock without my ears bleeding.
Hi, thomasnadeau. For something like the reasons you explain, I'm thinking about decreasing the gain. I use the Whammy as a headphone amp exclusively and have to keep the volume control way down (not past 9 o'clock, with zero being at 6). Which makes the volume control overly sensitive.
Thanks very much for that link.
The formula given there says that voltage gain is (in this case) 1 + R8/R12 = 1 + 4.75k/1k = 5.75. The build guide says that unity gain is achieved at R12 = 10K, which would be 1 + 4.75k/10k =~ 1.5. Are there aspects of the circuit that also affect this number? E.g., the input resistor R7?
Also, while we're at it, why is C26 there? Wayne probably discusses it in the video, but I've watched it once and can't imagine trying to find one such comment in the whole thing!
Ah I get you. Yes decreasing is more along the lines of what I've had to think about, as I mentioned. If you are driving an amp that already has decent voltage gain you might need to reduce it. The trick (and benefit) of building both is that you can perfectly match them.
Quoting myself from post #3007 'C26 & C27 reduce the DC gain to unity with the added benefit of minimising the output offset voltage.'
R8/R12. You can adjust that if you want more gain.
Stock is 1000ohm/4750ohm, which makes a gain of 4.75. (Actually just a little less as the output stage is slightly less than unity...)
LCD4 are 200ohm and 97db/mw, Whammy will be able to drive them easily and smoothly to hearing-damage levels.
Stock is 1000ohm/4750ohm, which makes a gain of 4.75. (Actually just a little less as the output stage is slightly less than unity...)
LCD4 are 200ohm and 97db/mw, Whammy will be able to drive them easily and smoothly to hearing-damage levels.
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How much power? you might be better off building the M2x, it's similar. The diyAudio First Watt M2x