VAC Owners:Outboard Phono Stage?

Alón, congratulations! That is exciting indeed.

A note of caution, though. Although the chances of a problem occurring would seem to be very remote, I personally would never connect the output of a component capable of supplying upwards of 2 volts or so into the input of a component that is designed to receive and process millivolts or less. Especially one as special and as expensive as this.

Yes, the CD may be designed to cause the player to output a suitable level, but things can go wrong. The player can fail abruptly in unpredictable ways, or go berserk. AC power can drop out, or flicker off and on, causing the player to briefly do who knows what.

As I say, chances of a problem occurring are very small. But I would take NO chances with a component as special as this one.

Best regards,
-- Al

KAB makes an inexpensive RIAA adapter that enables you to plug a CD player's output into the phono stage input to burn in the latter. I don't think it presents the same safety risk that Almarg described by using a 'burn-in' CD alone. I used the KAB device recently to burn in my new phono stage and had no issues. Almarg- think that's safer?

Bill, that looks to me like an excellent suggestion. You appear to be referring to the "KAB PreconLP™ Inverse RIAA Level Converter." It appears to be a purely passive device, using resistors and capacitors to divide down the signal level and also provide inverse RIAA equalization.

The only slight caveat I see is that when inputting to the preamp's LOMC inputs I would make sure that loading is set to 100 ohms, as opposed to a value that is much higher (e.g., thousands of ohms). Apparently the device relies on that loading, in conjunction with its own output impedance, to divide down what would otherwise be MM levels to LOMC levels.

In this case, though, even that concern is pretty much eliminated by the fact that the highest value load setting that is provided on the preamp for the LOMC inputs appears to be 470 ohms. That value would still reduce what would otherwise be MM levels by a substantial amount, probably something like 10 db (about a factor of 3 in voltage) according to my calculations.

Best regards,
-- Al

Thanks you guys! I wasn't planning to try anything without asking Kevin, but your advice has helped me be more prepared for the conversation.

I found this CD from Granite Audio and here's what they say:

Using this CD to burn-in your phono section will save needless wear on your record stylus and turntable.  Standard music CD's cannot be used for this purpose because their signal level at 240mv to as much as 4 volts would overload your phono inputs, which are designed to handle only about 4mv of input signal.  Also, conventional CD's would have their low frequencies boosted by 20dB more than a phonograph record that was encoded with the RIAA bass rolloff.  So, playing a standard music CD through your phono input could also damage your speakers with excessive bass tones.  DO NOT attempt to play any standard music CD's through your phono inputs.  You can only do this with the Granite Audio Model #CD-101 Phono Burn-In CD.  Our CD is the only one that has been engineered for this purpose.

Alón, yes, that is exactly what I am recommending that you do NOT use. Everything they say in the paragraph you quoted is essentially correct, but no matter how well the CD may be engineered for the particular purpose it cannot control what the PLAYER may do in the event of malfunction, momentary AC power dropouts, etc.

I believe that the moving coil section of the preamp employs a transformer at its input, which would be designed to handle signal levels measured in microvolts (millionths of a volt), and miniscule amounts of current. Misbehavior of the player, caused by the kinds of (admittedly unlikely) events I mentioned could easily put voltages across that transformer that are a couple of thousand times or more greater than those amounts. As well as overloading and stressing circuitry in the preamp that is downstream of the transformer.

Using the KAB device Bill suggested, you would use a conventional CD of your choice, and those risks would be eliminated.

Best regards,
-- Al