i placed an order at this site:
Electronic Parts Online Store - Tayda Electronics
i ordered a few trim pots to experiment with variable xo-frequencies.
with the pots a have, all got was reverberation.
Electronic Parts Online Store - Tayda Electronics
i ordered a few trim pots to experiment with variable xo-frequencies.
with the pots a have, all got was reverberation.
That's essentially correct. If you use the virtual ground arrangement then you must ensure that this point has a low impedance at AC, that is to say that it is immune to being modulated by the various AC currents that flow into and out of this point which includes the output current. The singe rail design doesn't have that limitation because battery negative is used as a ground.
wow, tayada-electronics is really fast.
it took only 6 days to ship from thailand.
could one of you more experienced guys please tell me, what the correct order of the components is, when i want to the following at the output of the preamp:
-inverting amplifier
-10uF capacitor (hp)
-100k reference to ground
-small series output resistor
-volume pot
?
it took only 6 days to ship from thailand.
could one of you more experienced guys please tell me, what the correct order of the components is, when i want to the following at the output of the preamp:
-inverting amplifier
-10uF capacitor (hp)
-100k reference to ground
-small series output resistor
-volume pot
?
Series output resistor comes first, then the series coupling cap. If you are adding a volume control after the cap, then the resistance of the control takes the place of the resistor to ground. You don't need both.
ok, but that would only be the case with volume at max.
wouldn´t an a10k-pot be a nice middle way?
wouldn´t an a10k-pot be a nice middle way?
10k is a more typical value, but you mentioned 5k (as if you might already have one) which is fine also 🙂
thanks mooly.
you are right.
i have the 5k pot.
but i'm gonna place another order.
the 10k costs $0,50.
you are right.
i have the 5k pot.
but i'm gonna place another order.
the 10k costs $0,50.
...again in the university full of silly ideas.
would this give me balanced outputs?
is there a need for output caps?
cap after the second hpf...
do i need that?
change into "nicer" 1u and 56k series resistor after the pot?
would this give me balanced outputs?
is there a need for output caps?
cap after the second hpf...
do i need that?
change into "nicer" 1u and 56k series resistor after the pot?
ahh!!!
maybe i should put another non-inverting unity-gain amp between the pot and the inverting opamp?
as drawn the pot is not only volume, but also gain-control, right?
maybe i should put another non-inverting unity-gain amp between the pot and the inverting opamp?
as drawn the pot is not only volume, but also gain-control, right?
You need caps if there is DC present on the outputs. The big question is as we covered before... are you running it as a DC coupled design with a virtual ground or is it true single where all the signal levels sit on Vcc/2 voltage.
The balanced thing is really only balanced if you run it as a split supply design where the signals swing equally above and below ground. On single rail they swing around a steady DC voltage.
As drawn you pot is correct, it controls the amplitude of the signal applied to the output opamp... the correct way of doing it because it reduces noise from the front end circuitry and provides a low output impedance because of the output buffers.
The balanced thing is really only balanced if you run it as a split supply design where the signals swing equally above and below ground. On single rail they swing around a steady DC voltage.
As drawn you pot is correct, it controls the amplitude of the signal applied to the output opamp... the correct way of doing it because it reduces noise from the front end circuitry and provides a low output impedance because of the output buffers.
If you use vm as "ground" and refer all inputs and outputs to vm then yes. That's how you seem to have it drawn, certainly at the inputs. The outputs are also taken between vm and the opamp output.
The 100k attached to R & L are not needed.
The 22k set the input impedance.
The two anti-phase outputs are "balanced" if and only if, the impedances are balanced.
The actual voltages on the outputs and whether they have a DC bias, or not, do not matter.
If the DC bias on BOTH outputs is ALWAYS IDENTICAL, then the next balanced impedance stage can ignore the DC bias, if it is designed to accept the DC bias.
The 22k set the input impedance.
The two anti-phase outputs are "balanced" if and only if, the impedances are balanced.
The actual voltages on the outputs and whether they have a DC bias, or not, do not matter.
If the DC bias on BOTH outputs is ALWAYS IDENTICAL, then the next balanced impedance stage can ignore the DC bias, if it is designed to accept the DC bias.
the latest edition of preamp i soldered to a pcb was a subsonic filter.
the hp filters have trimpots ( R8, R9, R25, R26) to have variable frequency.
i need that for outdoor use, where my fullrange speakers are easily driven with volumes, they don't like in the lower frequency area (please excuse my weird english).
the preamp works surprisingly good.
but just at home.
outside i want to drive it with the same sla-batteries as the power amp is driven.
but it doesn't work.
i guess the pcb of the amp has the dc-ground connected with signal-ground and that causes the problem.
is there a solution?
the hp filters have trimpots ( R8, R9, R25, R26) to have variable frequency.
i need that for outdoor use, where my fullrange speakers are easily driven with volumes, they don't like in the lower frequency area (please excuse my weird english).
the preamp works surprisingly good.
but just at home.
outside i want to drive it with the same sla-batteries as the power amp is driven.
but it doesn't work.
i guess the pcb of the amp has the dc-ground connected with signal-ground and that causes the problem.
is there a solution?
As drawn above, that should work on a battery OK. If V1 is connected across the total supply of the power amp then the above circuit is all AC coupled. I can't see any obvious problem tbh.
s**t!!!
i think i already had something like this working with the exact same amp.
maybe the splitter adapter causes the problem?
but i cannot see why it should....
i think i already had something like this working with the exact same amp.
maybe the splitter adapter causes the problem?
but i cannot see why it should....
Now that I don't know. I would need it all in front of me to answer that one.
Whatever is happening... basic fault finding rules apply. When powered by the battery amp, make sure that the opamp outputs are all biased to half supply. As drawn, your circuit shows you are measuring from the battery negative... that is your ground. If that's OK then the preamp should be functional. The inputs and outputs are AC coupled so no problem there.
mooly, please exlain it to me.
u3 is a tl071.
its negative input and the output are connected, that's where the rest of the circuit, including the output of the whole thing is getting its signal ground from.
when i connect an amp, that has signal and dc ground as the exact same plane, i have a connection between all the negative power pins of the opamps and virtual ground (via the amp-pcb).
how can that work?
u3 is a tl071.
its negative input and the output are connected, that's where the rest of the circuit, including the output of the whole thing is getting its signal ground from.
when i connect an amp, that has signal and dc ground as the exact same plane, i have a connection between all the negative power pins of the opamps and virtual ground (via the amp-pcb).
how can that work?
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