A real Vendetta?

[john curl]

Interesting Groove T. Guess who bought the remaining 2SK146-73 combinations? Me, of course. Reza also tried to 'sell' me his remaining stock of components, but I politely declined. Did you buy any?

[Groove-T]

No, i did not, since im no DIY guy, im a hifidealer since 20 years now .

And his pricepolicy for old products is a little bit special.

Personally i spend a lot of money for audiogear at home, so this is not the point.

[john curl]

Reza is a pretty good 'rug' merchant, too! ;-)

[aszoke]

Originally Posted by EDDELARUE

Hi Raymond,

The Vendetta´s pre-preamp ( front-end stage ) uses passive network for 2120Hz correction. The others networks it uses active equalization ( feedback loop ) on the second stage.

For more details about these topologies please read this http://www.national.com/an/AN/AN-1651.pdf

regards
eD

Hi EDDELAURE

If you see figure 3 in your link, there is an equalization, where the 75 us roll off is obtained passively. The two parts (750 ohm, and 100 nF) are just the same as in Vendetta, but in Figure 3 those are in line, instead of parallel. Just as I supposed. I do not really understand, why does it work in that design.

[EDDELARUE]

Originally Posted by aszoke

Hi EDDELAURE

If you see figure 3 in your link, there is an equalization, where the 75 us roll off is obtained passively. The two parts (750 ohm, and 100 nF) are just the same as in Vendetta, but in Figure 3 those are in line, instead of parallel. Just as I supposed. I do not really understand, why does it work in that design.

Hi aszoke,

in the figure 3, the opamp U1 is a VOLTAGE AMPLIFIER and it has low output impedance. It works like a voltage source for that low pass network. See "Thevenin´s theorem ".
On the Vendetta, the first stage is a TRASNCONDUCTANCE AMPLIFIER and it has high output impedance without load. So, it works like a current source for that load ( 750R // 100nF ).
See "Norton´s theorem ".

regards
eD

[aszoke]

Originally Posted by EDDELARUE

Hi aszoke,

in the figure 3, the opamp U1 is a VOLTAGE AMPLIFIER and it has low output impedance. It works like a voltage source for that low pass network. See "Thevenin´s theorem ".
On the Vendetta, the first stage is a TRASNCONDUCTANCE AMPLIFIER and it has high output impedance without load. So, it works like a current source for that load ( 750R // 100nF ).
See "Norton´s theorem ".

regards
eD

Thanks eD. It's clear now.
I'm not professional, and I've no any experience in such designs, but it seems to me, that it is not a simple put it together, and works amplifier, since if we want correct RIAA equalization, then the output impedance should be set up correctly. It can take some time to set it up in within 1%. Or many parts are needed to select the correct one. Or am I wrong again?

[john curl]

This is a slightly different approach. The output of the amplifier is CURRENT and by definition, a high impedance. It works with just 2 parts, i.e. .1uf and 750 ohms.

[EDDELARUE]

Originally Posted by aszoke

Thanks eD. It's clear now.
I'm not professional, and I've no any experience in such designs, but it seems to me, that it is not a simple put it together, and works amplifier, since if we want correct RIAA equalization, then the output impedance should be set up correctly. It can take some time to set it up in within 1%. Or many parts are needed to select the correct one. Or am I wrong again?

Hi aszoke,

we can get the same result with various combinations of R//C at output, since the corner frequency be equal 2120Hz. But don´t forget the output resistor R sets the gain of the stage before the capacitor reactance does some effect . This is the flat frequency region.

regards
eD

[aszoke]

Originally Posted by EDDELARUE

Hi aszoke,

we can get the same result with various combinations of R//C at output, since the corner frequency be equal 2120Hz. But don´t forget the output resistor R sets the gain of the stage before the capacitor reactance does some effect . This is the flat frequency region.

regards
eD

Hi eD,

I'm not totally sure in myself, but as I calculated, the output impedance must be rather high, to get correct Riaa equalization. For example, if it is 75k, the error about 0.07 dB in the high frequencies, and as the output impedace decreases, the error increases. Maybe some adjustment can be made changing the R and C values, but the 750 ohm and 100 nF seem to me the ideal values. And in this case you will loose 99% of the amplification. Maybe I did some error in calculation?

It is also interesting, that the 100 nF capacitor seems to me rather demanding load. At least as I have read previously. It is really interesting for me, that it does not cause any problems in sound quality.

Thanks,

Attila

[john curl]

Think it through Attila, we have successfully used it for decades. There is more to it than you see.