Input & sensitivity

[V-bro]

You can do this, but it may pick up more noise....it's always best to keep traces and components small and short....

------X-max. can be several meters on any driver, too bad it can be done only once...------

[abelma]

After a few hundred hours of listening and test with differents size caps, i have two conclusions. The passive pre(10 KOhm Dact attenuator) do not work very well. No dynamics, not controlled bass, less details, etc. Without the passive pre it is fantastic !. I am wonder if the 10 Kohm resistance connected in parallel with the feedback resistance will do something. May be too much resistance load to my cd player (With variable volume)?. Also, having the 22 KOhm Rin and 22Kohm Rfdbk, i find the best sound the 1 uF caps, and the basses are excellent, they go very low in frequencies. Reading something on the net, i think, that the Rin with combination of the input cap is not a high pass filter. The resistance should be connected in parallel to the source to have a high pass filter architecture. So, the Rfdb should be the value for the frequency cut calculation formula?. May be the formula of Cin = 1 / ( 2 x Phi x R x Freq) is to have a impedance relationship idea of the capacitor with the Rin ?. I'll be glad to discuss this important factor.

Living in Belgium

[V-bro]

http://www.t-linespeakers.org/tech/f...ssiveHLxo.html

It's the C in series and R (or Z)in parallel that make a highpass filter...

------X-max. can be several meters on any driver, too bad it can be done only once...------

[abelma]

Ok. So, the idea that the formula Freq=1/(2xPhixRxC) , it is the formula for a high pass filter calculation, it is not a high pass filter model, because Ri and Ci are in series. I think it is more the idea of a impedance calculation or relationship between the capacitor impedance and the amplifier input impedance (?).

Living in Belgium

[V-bro]

The cap is in series, but the amp impedance is in parallel after. I thought that created the HP.

Strange thing is if I calculate this a 2.2uF cap should filter under 0hz with a 20K amp impedance...

I must be overlooking something, have seen people calculating this, will search that back and post it here later....

------X-max. can be several meters on any driver, too bad it can be done only once...------

[V-bro]

By the way Abelma, I made Dact-like attenuators in 50K and 100K on AMP32, AMP9, AMP4 and Truepath and it sounds great. I have Onkyo DX-7711 with variable output, it sounds much better with fixed output and attenuator than variable without....

------X-max. can be several meters on any driver, too bad it can be done only once...------

[abelma]

I find the use of the formula with Ci and Ri strange when is calculated for a high pass filter. It should be Rfdb instead.
I have some interesting links where people use "similar" formula with Ci and Ri, but, it's not for a high pass filter effect. It is for a relationship between the impedance of the input cap and the input impedance of the amplifier, so, Ri. About my bad experiences with the attenuator and this amplifier, i had a pair of flying mole dad m100pro monoblocks with 100 Kohm of input impedance. The attenuator connected to them was working excellent. That's why my surprise with the amp10 connected in the same way. I think that there is something with the impedance relationship between the amp, attenuator and also the source. Still investigating this, and when i'll be in my computer i'll send the links where they explain a little more about this issue.

Living in Belgium

[abelma]

HI Vbro...here at this link You can read another use or understanding of that formula..Please go to the last item "ALRIGHT, SO WHAT VALUE DO I USE? "
http://gabevee.tripod.com/capacitor.html

About the attenuator. The DACT's owner, told me that better with 10Kohm value to have better frequency bandwidth. I'll try to use 100 Kohm Ri, and to configure the gain for "passive pre" with a Rfdb choice of 200 Kohm (-2.1 Gain)...What Do You think?

Living in Belgium

[abelma]

I wish to add another question. Reading that the impedance between the source and the load should be at least 10 times more higher (Load), that's why I want to try a Ri=100 Kohm. But, what could happen if I do better, I say, Ri=220 Kohm (And Rfdb 400 Kohm). What could happen, any warning ?. The idea of all this is to build an integrated amplifier, without a preamplifier board.

Living in Belgium

[xenob]

The idea is not new.

Of course it is better to have an high input impedance, but you should also consider that resistors with higher value also have higher noise. So you have to find a balance between input resistance and resistor noise.