Help preamp problem: overload?
There are several possibilites. --You may be overdriving the preamp with your CD player. If you have a variable output try turning down the CD player output. --There could be a short in one of you output cable of the preamp. -- While calling bryston might help I would try to contact a Sonic Frontier expert to find out what causes the preamp to mute on its own. |
If that Sibelius CD is not overly compressed, and actually exhibiting the dynamic range that the medium is capable of: When your pre's volume knob is turned to the level you mentioned(to sound good at the lower end of the dynamic range)- at the orchestra's FFF or FFFF levels you're asking for more output from the pre than it can deliver, and it's "muting". Does the new amp have less sensitivity or lower power than your old one, or were you (perhaps) trying to listen at a louder level than normal? The fact that you're experiencing no problem with the gain reduced points to the pre protecting your downstream components. Instead of using(as most tube designers do) a capacitor to block DC at the output of the line stage, Sonic Frontiers uses a DC servo mechanism to minimize DC offset. |
I'm with the asking SF support waht's up? poster. I also am wondering about the tubes in the preamp... and if this event occurs with any other music, media, etc., given the same conditions. I'd try to recreate the same event using other music or media. I'd also recommend checking the connections yet a second time or more to ensure in the haste of anxious setting up, some loose fit along the way was not present, thereby causing a resistive connection and increasing the power draw inadvertently, further taxing the system. Brand spankity new amp or not, I'm still thinking the issue lays within the SF III line stages tube compliment, or it's output circuitry... provided all is connected well... ICs, PCs, etc. Sonic/Anthem support is very good indeedd and they respond quickly via email too... and Bryston is not far from them either... give 'em a shout ASAP. |
The max output levels of your BCD-1 are 2.3v(single-ended) and 4.6v(balanced), which are both quite high. Again- That the "relay clicking" and going into "standby" disappear at a lower gain setting indicates a muting circuit protecting everything from overload. BTW: The DC servo system should be un-noticeable in operation, but may cause a problem if mal-functioning. DC offset will rob a circuit of headroom/create an overload situation. It was late, and I didn't finish that thought in my previous post. By all means- Contact Anthem for support/info: ([email protected]) (905-362-0958) |
Twoleftears, put on the CD, set the preamp at the same volume, advance to the final bars where this problem occurs, but this time don't have the power amp connected. Does the display act the same way? If not, the power amp may have an input impedance that is too low for the preamp to drive easily. If yes, either you have weak tubes or you are simply overloading the preamp. To test the latter, running a sine wave into the preamp and measuring the output voltage should tell one a lot about what is happening, especially if the output is displayed on a scope. Good Luck! |
