System needs more watts??

If I'm not mistaken, your preamp has only unbalanced inputs and outputs, which does not seem ideal for use in conjunction with your fully balanced amplifier. For that matter, what is the means by which you are connecting the two components, as I believe the VK75SE does not provide unbalanced inputs?

If you are doing it with a simple RCA-to-XLR adapter or adapter cable, that is absolutely not ideal. Depending on the design of the amplifier, it might even result in putting no signal through one of the two balanced signal paths through the entire amplifier, for each channel. In that situation the result would be (among other things) a reduction of the amp's power capability that approaches 75%, reducing the amp's capability from 75 watts to less than 20 watts.

Also, a point to be aware of is that the 89.5 db specified sensitivity of your speakers is with respect to 2.83 volts, not 1 watt. 2.83 volts corresponds to 1 watt into 8 ohms, but it corresponds to 2 watts into the 4 ohm nominal impedance of the speaker, which means that their sensitivity is only 86.5 db for a 1 watt input. And as a tube amplifier, the BAT is not able to deliver significantly more power into 4 ohms than it can deliver into 8 ohms, being rated at 75 watts into either impedance.

Regards,
-- Al

Following up on my previous post, based on the comments by Victor of BAT in this thread it appears that the concern I mentioned about possibly losing 75% of the amp's power capability when providing it with a single-ended input is not applicable to his designs, as they use differential stages, rather than independent paths for the two signal polarities.

However, if you are providing the amp with a single-ended input via an adapter or adapter cable, you are reducing gain by 6 db, and you are most likely compromising sonics to a perceptible degree in several ways. The best way of interfacing your preamp and amp would be with a Jensen transformer, such as their model PI-2RX (similar to the model PI-2XX shown near the bottom of this page, except with RCA input connectors). Here is the datasheet. That model would be located close to the amp, and connected to the amp via what must be a short XLR cable, and connected to the preamp with whatever length of RCA cable is required.

You should consult with Jensen by phone before finalizing selection of a particular model, though.

Regards,
-- Al

Al,

You wrote "That model would be located close to the amp, and connected to the amp via what must be a short XLR cable, and connected to the preamp with whatever length of RCA cable is required."

I have a pair of P1-XR ISOMAX units I've used to convert the XLR of an 18' cable from the processor to short RCA cable to a KEF KUBE near Proceed amps. My reasoning is to use XLR for the long cable run. Have I got that backward? The ISOMAXs removed an audible buzz encountered with a simple adapter. If I have it backward, then I'll just use RCA cables from processor to KUBE to amps.

db

Hi DB,

Your setup is fine. The PI models are what are known as input transformers, which have to be connected to the destination device (the device whose input they are connecting to) via a short length of cable, regardless of whether that cable is RCA or XLR. See the bold-faced statement near the bottom of page 1 of the manual, and the paragraph which follows it.

Best regards,
-- Al