[McPanse]

Trying to eliminate the speaker thump I get when I turn on my volume pot bypassed Trends TA-10.1 amp, I opened up the case, hooked up my multimeter leads to the speaker terminals and adjusted the DC bias offsets until I got a nice clean +/- 0 rating.

But here's the rub: my $20 multimeter can measure DC voltage from 500 volts down to 2 volts. The Trends manual makes reference to 200 mV. Am I correct that 200 mV = .02 volts (1 volt = 1000 mV)? And if that's so, is a multimeter that reads in the 2 volts range sensitive enough for what I'm trying to do here? (I get readings of .002 to .003 until I adjust the offsets to get it to read zero, so I think I'm doing the right thing here).

Rub #2: even with the bias zeroed out, I'm still getting speaker thump when I power on. I've notice I can avoid this by powering on my DAC first and feed it a signal from one of my sources. No signal -- thump at power on. Signal, even with volume at zero on the DAC, no or very minimal thump.

Can anyone explain why this happens, whether I should be concerned, and what to do about it?

[DaveC113]

200 mV = .2 V ... move the decimal pt. 3 places to the left. If your meter reads to the hundredth (X.XX Volts) it should be close enough.

If its a small thump, probably ok... I'm not sure why it does this, maybe someone else can explain...

[Steve]

Trying to eliminate the speaker thump I get when I turn on my volume pot bypassed Trends TA-10.1 amp, I opened up the case, hooked up my multimeter leads to the speaker terminals and adjusted the DC bias offsets until I got a nice clean +/- 0 rating.

But here's the rub: my $20 multimeter can measure DC voltage from 500 volts down to 2 volts. The Trends manual makes reference to 200 mV. Am I correct that 200 mV = .02 volts (1 volt = 1000 mV)? And if that's so, is a multimeter that reads in the 2 volts range sensitive enough for what I'm trying to do here? (I get readings of .002 to .003 until I adjust the offsets to get it to read zero, so I think I'm doing the right thing here).

Rub #2: even with the bias zeroed out, I'm still getting speaker thump when I power on. I've notice I can avoid this by powering on my DAC first and feed it a signal from one of my sources. No signal -- thump at power on. Signal, even with volume at zero on the DAC, no or very minimal thump.

Can anyone explain why this happens, whether I should be concerned, and what to do about it?

Hi McPanse,

Good question Mcpanse. Yes powering your dac on first, before the amp should eliminate the thump. The reason is that when the amp is on, any signal or pulse reaching the input will translate to output signal/pulse. In the case of  powering up the dac, dc voltages need to be established at the output of the last active device (SS or tube). I will assume the dac has a capacitive/transformer coupled output and no mute function. And even though the dac is capacitively coupled, a pulse (not being dc) will pass through the capacitor and reach the input of the next component.

Hope this helps Mcpanse.
Steve

[randytsuch]

When I power on my gear, I always start at the source, and work my way down to the amp, amp is the last think to turn on.

Power off in reverse order, amp first.

Randy