[reimar]

Hello, first sorry for my bad English but i hope you can understand everything.

I've played today a little with a Spectral Analysis Program and made following measurements :



The blue curve is a simple "Elektor" Pre I've bought him ready build.
The purple curve is the Hagtech Bugle, build by myself with selected components.  
The red curve is the Cornet Tube, build too by myself with selected components.

Left and right channel had the same curves so i only display the left channel.

The yellow spike is the 1kHz reference Signal.

The curves are very different i think, it looks like the Elektor have some wrong components at the lower frequency equalization.

I've compared the curves with the correct RIAA curve - the Bugle (purple) curve is almost perfectly the RIAA curve.

Some Questions : Is there a reason why the Cornet (and the Elektor in some kind) go down so much before 60 Hz? Is it maybe against rumble? What could be the reason for the Cornet "midrange boost"?

Something abut the measurement : Everything was made very simple that's for sure the reason for the big lost at around 20kHz. Frequency generator was a CD-Player with Denon-TestCD, Spectral Analysis Program Spectra Pro that was running on a Laptop.

Regards Reimar

[hagtech]

Reimar,

Interesting analysis.  My guess is that there is some significant resistive loading by the test equipment that shifts the low frequency rolloff way too high.  If you buffer the output, I'd bet the Bugle and Cornet are virtually identical.

Looks like about 50Hz at -3dB, which if you used the 0.47uF coupling cap would indicate about 6.8k load.  The Bugle doesn't have the coupling cap.

Not sure about the Elektor or why it is off so much.  

jh

[reimar]

Reimar,
Interesting analysis.  My guess is that there is some significant resistive loading by the test equipment that shifts the low frequency rolloff way too high.  If you buffer the output, I'd bet the Bugle and Cornet are virtually identical.

Looks like about 50Hz at -3dB, which if you used the 0.47uF coupling cap would indicate about 6.8k load.  The Bugle doesn't have the coupling cap.

This could be the reason for the difference, as I dont really hear the middle frequency difference between the Bugle and Cornet.

I've upgraded the coupling to 1uF  Mundorf Cap Could it be that my Amplifier has such a wrong input impendance?
To remove the coupling completly can I simply remove C6 and R19 (i have the "old" Cornet) ?

Thanks a lot
Reimar

[hagtech]

You cannot remove the caps, they are needed to block dc.  Did you run the test through an additional amplifier?  Find out the input loading impedance.  This is WAY too much loss of bass.

jh