2. amps-preamps
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Preamp output voltage...affect on volume???

I am in the middle of auditioning a new preamp which outputs 50 vrms max. My current preamp outputs 20vrms max. Assuming they are both pretty close in terms of gain and have the same number of volume steps (100 @ 0.5db each), does that mean the preamp with the 50vrms output will cause my sysem to sound louder than the 20vrms preamp (all else constant)? If so, how much louder?

thank you...
tboooe
tboooe's avatar
tboooe OP
1,009 posts
 
Ok, I switched to the single ended output on my Cary which is supposed to be at 3vrms. And even though the volume has decreased by a bit, it is still pretty loud even with the preamp at the lowest possible setting.

Also, the output impedance of the BAT CVK52se is listed as 200ohms and the Classe CP-700 is 100ohms.

Now I am really confused why their is such as big difference in volume between the BAT and Classe preamps.
herman
2,282 posts
 
That difference in output impedance isn't enough to make any difference. Until you find out what the gain of the Classe is we are wasting our time speculating about the difference.
shadorne's avatar
shadorne
7,491 posts
 
Quite simply a higher gain will result in a louder sound. The volume dial alows you to adjust the gain. A higher maximum ouput implies nothing unless you know the maximum input level.

Suppose that all signals are RCA line level and unbalanced; input is designed for a max of roughly 2 Vrms and therefore the gain at maximum output appears to be at least 25.

Suppose that all signals are line level and balanced; input is designed for a max of roughly 4 Vrms and therefore the gain at maximum output appears to be at least 12.

These high gains are unusual for a hi-fi pre-amp as most pre-amps are close to unity gain at maximum levels...the advantage will be better immunity to RF/EM noise (likely a lower noise floor downstage of the preamp).

To get back to normal volume levels you need to;

1) reduce the power amplifier gain stages to compensate for a large signal at the input of the power amplifier
2) attenuate the signal so that it matches the input capabilities of the power amplifier.
3) get a power amplifier that is specifically designed to accept this higher range of input signals

Good power amplifiers will often have potentiometers to provide flexibilty to handle various input level ranges.
tboooe's avatar
tboooe OP
1,009 posts
 
Ok, I found out the gain of the classe is 14db, the bat is 17db. any ideas?
tboooe's avatar
tboooe OP
1,009 posts
 
I got a response from BAT that explains the difference in volume control between my Classe preamp and the VK-52se even though they both have similar gain. I guess it comes down to digital volume control (Classe) vs discrete volume control (BAT). By the way, what is a "Discrete" volume control? Can someone explain why discrete volume control does not have as much attenuation as digital control?

Below is an exerpt from the email I got BAT sent me:

"...integrated digital volume controls give
you more room - they have 180 or more steps, allowing you to achieve greater
attenuation. I don't have solid information on Classe, but what you are
telling me is consistent with a use of such a volume control.

High quality discrete volume controls usually stop sooner. Reasons are
practical - cost and complexity...It is many times more expensive
than the integrated circuit attenuator. The reason we use that expensive
solution is the sound, of course.

Our volume attenuator has linear range of 70dB. We do not go further as
doing so would degrade the signal way too much. -60dB attenuation means you
are throwing away 99.9% of signal, letting just 1/1000 of it go through -
hardly good situation."
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