sorry, I was referring to schm in post #1
if you look at schm in post #66 , that would be R1
schm from #66:
if you look at schm in post #66 , that would be R1
schm from #66:
The first load your sources will see will be the volume control, not this preamp. Choosing a 10k pot will probably give you the most high frequency detail, even with a few hundred ohms output impedance. This preamp will work beautifully for you.
I will use volume Attenuator in front of preamp so which is better 27Kohm or 10Kohm Attenuator?
ask your sources .....
if more potent ( lesser Rout) , you can use lower value for attenuator
preamp doesn't care what value of pot is in front of it
if more potent ( lesser Rout) , you can use lower value for attenuator
preamp doesn't care what value of pot is in front of it
Hello,
I will use r2r volume atteunator between my dac and lks pre (12v)
As far as as i know low value pot is better if source is suitable with it.
My dac zout is 1.6v 700ohm
The imput impwdance 12v lsk pre is 100k
I make r2r attenuator resistor configration (in the attachments) according to configrator here below;
Do you thing this configration is correct?
I will use r2r volume atteunator between my dac and lks pre (12v)
As far as as i know low value pot is better if source is suitable with it.
My dac zout is 1.6v 700ohm
The imput impwdance 12v lsk pre is 100k
I make r2r attenuator resistor configration (in the attachments) according to configrator here below;
Do you thing this configration is correct?
Attachments
Hello;
1. My power supply is very stable and close to preamp pcb also i have caps right after power supply. Do i still need 10R resister and 47uF capasitor at 12v inputs?
2. Min 5uF output capacitor suggested for 22K ohms input impedance power amplifier. Is there any way to not use it?
3. my dac output 600 ohm and 12v version is 101k ohm (1K+100K) input impedance.
can i lower it to any value i want lets say 5k ohm?
Is it effect other components or only replace 100k with 4k is enough?
If i lower input impedance is it also have any positive effect for not using output capacitor?
1. My power supply is very stable and close to preamp pcb also i have caps right after power supply. Do i still need 10R resister and 47uF capasitor at 12v inputs?
2. Min 5uF output capacitor suggested for 22K ohms input impedance power amplifier. Is there any way to not use it?
3. my dac output 600 ohm and 12v version is 101k ohm (1K+100K) input impedance.
can i lower it to any value i want lets say 5k ohm?
Is it effect other components or only replace 100k with 4k is enough?
If i lower input impedance is it also have any positive effect for not using output capacitor?
Attachments
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1. You do not NEED these. Although they help prevent harmful interaction between the preamp and power supply. They are optional.
2. You need the caps to prevent dc on output unless you can find a way to prevent thermal drift in the bjt transistors. That means heat sink or thermal coupling. Or you can design a dc servo. I would use the caps. Not a big deal.
3. Why would you want to lower the input impedance? Higher is better no matter what you dac’s output impedance is. It will have no effect on dc stability and the need for caps on output.
2. You need the caps to prevent dc on output unless you can find a way to prevent thermal drift in the bjt transistors. That means heat sink or thermal coupling. Or you can design a dc servo. I would use the caps. Not a big deal.
3. Why would you want to lower the input impedance? Higher is better no matter what you dac’s output impedance is. It will have no effect on dc stability and the need for caps on output.
Hello Juma,
Here is a layout for preamp as per post nr. 485.
I have retained the same LM7812/7912 supply as per below preamp. is it ok?
Preamp ideas for F5
regards
prasi
Here is a layout for preamp as per post nr. 485.
I have retained the same LM7812/7912 supply as per below preamp. is it ok?
Preamp ideas for F5
regards
prasi
Attachments
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That circuit will need an output cap. Especially if the transistors are not thermally connected. I’ve built it. It’s one of my favorites.
Hello Hikari1,
As you can see , the transistors are adjacent and can be thermally coupled. and also pot P1 is there.
If still there is a need, then cap can be used off-board. Thanks for sharing your impression.
regards
prasi
As you can see , the transistors are adjacent and can be thermally coupled. and also pot P1 is there.
If still there is a need, then cap can be used off-board. Thanks for sharing your impression.
regards
prasi
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version with 10 ohm rail resistors, decoupling caps ,and also output caps and resistors.
Attachments
Last edited: