QuestionQUESTION: i have an adcom 710 preamp and a m504 onkyo power amp. the problem is whenever i turn my power amp on first and then the preamp, i get a pop sound through my speakers.i also used to use a sansui au-d9 integrated amp for my pre which made the same sound but not quite as pronounced. cables, connections, and power cords seem to be in order. any advice?
ANSWER: Question: Does the speaker pop when you turn the preamp on first?
There are two cases that will cause the startup pop: 1. in the power amp and the voltages are applied to the output stage at the same time as the front end. Most amplifiers are design to bring up the output voltage after the power to the front end amplifier stages have settled in. 2. If the preamp connected to the inputs of the amp are direct coupled they may have residual dc on the output which causes the power amp to do a dc discharge pop sound.
I pulled the owners manual on the amp and it does not state whether or not is has the turn-on pop reducer. If it does not and if you find the pop is always there regardless of the turn-on cycle then you may not be able to get rid of this startup condition.
ONE: Try the turning ON cycle with the preamp disconnected from the amp. Do you get the pop?
TWO: Try the other set (main or bypass) outputs to see if that makes a difference.
If nothing seems to be making any differences AND you find no pop when there is no connection to the power amp input you may need to put in a bleeding resistor at the input of the power amp (or the output of the preamp) to keep the capacitance discharge from taking place at turnon.
Let me know the output of the above suggestion/trials and I will tell you more.
Meantime, this is a fine, outstanding amplifier and the pop is doing no harm to your amplifier. If it is really loud it could be doing harm to the speakers, however.
Hope this first session helps.
C
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QUESTION: no, the speaker does not pop when i turn the preamp on first. i do not get the pop when preamp is disconnected from amp. main or bypass does not make a difference (pop is active either way). anything more you could help me with?
ANSWER: Based on your last reply, the amp is acting properly.
The preamp is likely dc coupled and is the case of the pop by putting an unbalanced load on the input of the amp.
It is doing no harm. So, why don't you turn on the preamp first?
If you want to correct this, for some reason, you must apply a bleeding resistor to the I/O between the preamp out and the amp in.
C
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QUESTION: what sort of bleeding resistor should i look for. im not really familiar with it. is it something i should look for with rca connectors and is it placed between my rca connectors from pre out to amp in?
AnswerThis is not a home remedy situation. It requires one with audio circuit know how. One must determine the input characteristic impedance and calculate the best value based on the design of the power amp.
I am concerned why this is so important to you. As indicated to you, it is causing no harm. And you know how to power the system up to avoid the pop if it is embarassing to you. Let me know why you are insisting on this so strongly.
To install the bleeding resistor (or capacitor if the input circuit requires it instead) requires special soldering skills and creation of the proper place to install the de-popper. You should call upon an audio engineer or qualified technician to do this.
C
