Preamp concept

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#107
I wonder why have you put R42 and R38 together instead of one resistor?

I bet it's because U had such values in stock😀 .

Or is this value to be realy precise 1K97.

I thought about putting there 1K91 ( I can get this value) and it will be within 1% tolerance.


Am I clever :clown:
 
#109
Pavel

I have another question>

What if I changed in-capacitors and out-cap value.

e.g I would like to put there black gates N but there are no such values.


And does the in cap is not as important as out cap.
According to the picture you have put odinary mkp (wima?)cap at the input.

Wouldn't it be better to put pot instead of one of resistors for DC setting?
 
#114
marsel said:
Pavel.

I would like to know what is your idea for using ordiary cap at the input and a BIG one at the out put.

What may change in the sound if we would put a Big one at the input?

I am preparing PCB😀 😀
Click to expand...


marsel said:
How high can I go with the value of output caps as not to cut the low frequencies too much. 😕 :smash:
Click to expand...

I used the size of caps as I had them on stock. I am not about to discuss the "big" and the "small" ones.

Regarding low frequency corner, it can be calculated as:

F(low) = 1/(2 x 3.14159 x Rload x Cout)

I really do not have time enough to reply such questions.
 
#115
Nexus said:
Hello Pavel,

is there a pcb available for this preamp?

Best Regards:
Nexus.
🙂
Click to expand...

The PCB production data exist. About 30 pcs were produced, 15 sold as assembled boards and 15 as bare PCBs.

At the moment I have no PCB on stock and do not plan to start new production soon. The DIY support is very time consuming, and I cannot spend that much time doing that, I am quite busy in my professional projects.
 
#117
Hello!

Here is my version of dispre PCB😀 😀 😀

Any comments? Every suggestion will be welcomed!!!!
 

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#118
PMA said:
I am thinking about building a new preamp. The concept is shown in the attached image.
Click to expand...

It is of interest, perhaps, that, contrary to popular opinion, your preamplifier's second stage is a severely unbalanced differential amplifier and not the common-base element of a complementary cascode.

This imbalance is responsible for the relatively poor forward gain obtained with this arrangement.
 
#119
Re: Re: Preamp concept

mikeks said:


It is of interest, perhaps, that, contrary to popular opinion, your preamplifier's second stage is a severely unbalanced differential amplifier and not the common-base element of a complementary cascode.

This imbalance is responsible for the relatively poor forward gain obtained with this arrangement.
Click to expand...

Michael,

you are absolutely right. And you are also right that it is not much of interest for me, i.e. I am not going to modify it at all. This preamp had covered a kind of "social demand" 😉

Regards,
Pavel
 
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