Maybe You Have A Juicy Question?

[Travis In Austin]

23 hours ago, RealMarkDeneen said:

Hi Dave,

The higher the load resistance, the more the external cable capacitance will interfere with HF response. I like the line out to pass very sharp 10k square waves. 

Cheers,

M

Wait. That’s engineering and technical language from someone knowledgeable.

 

Can I infer from that, that preamp design can in fact make interconnects have an impact on sound?

 

In other words, depending on the preamp, and the cable capacitance, there is a measurable difference on the high frequency response? 
 

Don’t care if it’s audible at this point, just that it can be measured. 

[RealMarkDeneen]

1 hour ago, Travis In Austin said:

Wait. That’s engineering and technical language from someone knowledgeable.

 

Can I infer from that, that preamp design can in fact make interconnects have an impact on sound?

 

In other words, depending on the preamp, and the cable capacitance, there is a measurable difference on the high frequency response? 
 

Don’t care if it’s audible at this point, just that it can be measured. 

 

The output tube of the preamp is working into a low pass filter where the total capacitance of the connecting cable is shunting the output of the tube. A typical rca cable might have 12pF/ft of capacitance between conductor and shield.

 

Example 1. 8-foot cable @ 12pF/ft.. is 96pF. A 12AX7 in the BBX with zero feedback has an output impedance of say 75k ohms. So using that 96pF cable gives an upper bandwidth of a mere 22kHz. That's not going to give you sharp square waves. If I cut the capacitance down to 40pF I get 53kHz which is better.

 

Example 2. Using a Peach in SuperLoZ mode, the output impedance is 600 ohms. So, I can connect 100 feet of cable @12pF/foot (total 1200pF), and I still get a whopping 220kHz bandwidth. THAT will have sharp square waves.

 

Now you understand the reason for the Peach!

 

Keep your cables short, and use low capacitance cable.

 

Now, whether any of this is audible is a complicated matter and depends on many other variables. So, I'm not making a big deal out of it for SQ. But by measurements it is easily measurable.

 

Cheers Travis,

M