JohnRoberts said:you need a dc path (resistor to ground) at + input of second op amp.
JR
+1squarewave said:Just skip the first op amp entirely. 10M input Z resistor is too high. Make it 1M or 2.7M max.
Seems correct to me.And your pot is backwards.
Indeed. I had my glasses on upside down.abbey road d enfer said:Seems correct to me.
squarewave said:Indeed. I had my glasses on upside down.
RSRecords said:Trying to add an instrument input to a line level device.
Whoops said:Seems a good idea for a project.
Which "Line Level" do you want at the output? Balanced +4 dBu or unbalanced −10 dBV?
I guess it would be a pretty useful box if the output is +4 dBu Balanced.
I would use a FET front end, before the opamp and would make the input impedance 10Mega, that makes it useful also for all kinds of piezo pickups (acoustic guitar, Doublebass, Cello, etc)
The idea is to interface with another mixer sort of unit I'm working out. Eventually the output will be +4 balanced.
I have always found that having that kind of input impedance resulted in too much boominess.Whoops said:Seems a good idea for a project.
Which "Line Level" do you want at the output? Balanced +4 dBu or unbalanced −10 dBV?
I guess it would be a pretty useful box if the output is +4 dBu Balanced.
I would use a FET front end, before the opamp and would make the input impedance 10Mega, that makes it useful also for all kinds of piezo pickups (acoustic guitar, Doublebass, Cello, etc)
abbey road d enfer said:Of course, I don't use them for recording, just for rehearsals.
This is not what I found, and K&K and Ovation seem to agree with me...Each one his own, I guess.Whoops said:I use piezo pickups on Doublebass, Cello, acoustic Guitar and Piano both for recording and Live sound.
Connecting the Piezo to a DI with 10 Mega input impedance sound much better than a typical 1 Mega input DI, that always sounded harsh and thin to me.
I found that 5M to 10M is my favourite load for Piezos, many people seem to have found the same also.
Like Radial says on their website "The ultra-high 10 meg-ohm impedance is used to compensate for the harsh, squawky tone that usually plagues piezo-equipped instruments.", I totally agree with their statement.
Whoops said:I use piezo pickups on Doublebass, Cello, acoustic Guitar and Piano both for recording and Live sound.
Connecting the Piezo to a DI with 10 Mega input impedance sound much better than a typical 1 Mega input DI, that always sounded harsh and thin to me.
I found that 5M to 10M is my favourite load for Piezos, many people seem to have found the same also.
Like Radial says on their website "The ultra-high 10 meg-ohm impedance is used to compensate for the harsh, squawky tone that usually plagues piezo-equipped instruments.", I totally agree with their statement.
abbey road d enfer said:This is not what I found, and K&K and Ovation seem to agree with me...Each one his own, I guess.
And there is actually such a variety of piezo pick-ups that what is right for one maybe marginal for another.
RSRecords said:Would be simple enough to have a dip switch or something to change the resistor value. This will be used as part of a tape delay so lack of low end isn't a problem. I think it would actually be a good thing to roll off some lows...Who puts delay on bass?!?
Whoops said:Well if you are using your circuit with a Tape Delay output then you don't need an instrument input (Hi-Z), the output of the Tape Delay is already Low-Z Line Level.
dbelousov said:An "instrument level" is a very vague term. I have a guitar with the Bare Knuckle Nailbombs (passive) and a bass with Bartolini guts, both of them easily overload professional ADCs with a rail-to-rail buffer, so they have to be attenuated, not boosted.
dbelousov said:An "instrument level" is a very vague term. I have a guitar with the Bare Knuckle Nailbombs (passive) and a bass with Bartolini guts, both of them easily overload professional ADCs with a rail-to-rail buffer, so they have to be attenuated, not boosted.
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