LSK pre - BAF 2013

[potstip]

Lsk pre has a 100k input impedance. You need greater than that? I don’t think so. You could use a source with a 25k output impedance with no problems. And you are worried about a few couple hundred ohms?

But

R18

R18 is 15ohm

 

[Zen Mod]

sorry, I was referring to schm in post #1

if you look at schm in post #66 , that would be R1

schm from #66:

 

[propitious]

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.

 

[potstip]

I will use volume Attenuator in front of preamp so which is better 27Kohm or 10Kohm Attenuator?

 

[Zen Mod]

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

 

[potstip]

I dont like lights in my amplifier
In 12v psu version am i have to use them. If yes can i replace LED witn 1N4007 diodes or any suggestions?

 

[Zen Mod]

funny guy .......

something else to complain about ?



use 2V5 ref. zeners

 

[rookakoma]

Put a piece of heatshrink on the LED..

 

[Zen Mod]

 

[potstip]

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?

 

[Zen Mod]

Zatt at least 25K , better 50K

Zload is 100K

 

[potstip]

Great as always thank you Zen

Zatt at least 25K , better 50K

Zload is 100K

 

[brianco]

Zatt at least 25K , better 50K

Zload is 100K

US/CAN $s?

 

[potstip]

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?

 

[Hikari1]

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.

 

[prasi]

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

 

[rookakoma]

Very nice and compact. I like it!

 

[Hikari1]

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

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.

 

[prasi]

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

 

[prasi]

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

version with 10 ohm rail resistors, decoupling caps ,and also output caps and resistors.