They trumpet “low noise” for TL07x, but the the Vn spec for TL08x is exactly the same. (TL06x, not so much.)
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Yeah I just basically tried it by referencing where the inputs and outputs if the opamp pins and just used it as a guide, not a paint by numbers. Seeing the image like this just helps me with layout cause I stink at that.
I figured if it didn’t work I didn’t have much to lose.
I stumbled across that one too. Did you build it exactly like that (with red wire to pin 2) and does it work for splitting 1v/oct Signals?
And did someone find an envelope follower?
It’s four (*) DC-coupled TL07x voltage buffers, so they can typically handle voltages from −7.5 to +10 V, perhaps a bit more depending on load and your power supply.
*) Well, three if you leave the wire as is, the fourth doesn’t do much.
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maybe you should delete this diagram, since it is in the thread “Verified stripboard” to avoid that some one build it without reading the rest of the discussion ?
EDIT : I quickly made the correction
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No, not exactly like that. As @Dud pointed out a slight change is needed. I have updated my post in-line to use this layout to avoid confusion later.
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can confirm it works.
but another question: i have seen similar designs using a 1M resistor from the input to ground, what does that add to this circuit?
cheers
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It avoids a floating input, in case nothing’s plugged in. For AC-coupled inputs (which this isn’t), it also discharges the capacitor so the input doesn’t die after a while if there’s a non-trivial DC component in the signal.
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thanks! why would you want to avoid a floating input in this case?
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Floating input means that there’s no defined signal level, and the opamp input (in this case a JFET gate) is left to its own devices. In theory it may pick up random noise, but more common is that it’ll get stuck in some state, possibly causing extra power consumption and messing with the other opamps. Or maybe nothing happens, who knows. A resistor is a cheap way to make sure the circuit stays in a known state.
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Thanks a lot for explaining this!
2x3 Buffered Multiple
I extracted the buffered multiple part from https://noreurorack.wordpress.com/2015/03/13/4-channel-mixer-and-multiple/ and replaced the mixer part with a buffered input. The outcome is a TL074 based 2x3 buffered multiple.
I use input jacks with a switch, which turns it into 1x6 if there’s nothing plugged into the second input jack.
Stripboard layout:
All credits go to NOR EURORACK
Please bear in mind that this is the very first stripboard layout I made.
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2x3 Buffered Multiple Prototype:
Battered drilling holes do not matter. “if it sounds right - it is right”
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Cool. What’s the rationale for using inverting amplifiers instead of voltage followers, like e.g. this one? The Dave Jones / Horstronic multiple uses inverting amplifiers, but that’s to allow use of trimmers to get unity gain by calibration rather than by theory. I suppose @fredrik’s argument against non inverting amplifiers also applies at least in part to voltage followers, though.
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That mixer-multiple, incidentally, is my favorite multiple design. A shame to get rid of the mixer part, IMO.
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Historical reasons. I liked to mixer/multiple approach in the beginning and started to create a stripboard layout for it. Then I removed the mixer part because I was lazy and design became complicated and I ran out of potentiometers. Remeber this is my first stripboard layout ever.
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Ah, and I guess they needed an inverting amp to do the mixer summing…
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As can be seen from the “my ms-20 filter locked up” posts (it has two voltage followers in the filter chain).
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