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Passive Pre-Amp into Integrated Amp to Prevent Clipping?

On my previous system (DAC -> active speakers), I had some serious issue with clipping, even at low volume (volume was controlled by the active speakers). So I solved that by sticking a passive pre-amp (Schiit Sys which is a pot-based passive attenuator) in between the DAC and the active speakers. I used a 0 dbFS 60 Hz sine wave test tone (60 Hz because I would be sure my Fluke TrueRMS multimeter would measure it accurately since the Fluke is mainly used for home AC power applications) from my PC into the DAC-Preamp chain and measured the RCA output level with the multimeter at the SYS outputs. Then I turned the SYS volume down from 100% (measured 2 Vrms) until the multimeter measurement matched the active speakers’ input sensitivity (750 mVrms). Never touched the SYS volume knob again (I used the active speakers’ volume knob for adjusting listening level) and never had any clipping issues afterwards. And as they say, the rest is history. (Actually, if anybody has any feedback on my methodology, that’d be great).

Not quite. I finally decided to upgrade my system to one with passive speakers. The system I decided to go with is a Yamaha R-S202 stereo receiver with ELAC Debut 2.0 B6.2 speakers. The DAC hasn’t changed. (It’s an old DIY Ross Martin 24-bit DAC I was gifted from a friend. I don’t think Ross Martin is in business anymore because his website is down.)

The Yamaha receiver, being an integrated amp, already has a built-in pre-amp (I do not know if it has an active pre-amp stage or simply a passive volume control upstream of the power-amp section - does anybody know?). The spec’ed input sensitivity is 500 mVrms. Given that I had clipping issues with the old active speakers, which had a sensitivity of 750 mVrms, I assume that my clipping issues would get worse if I go DAC -> Yamaha?

Do I need to stick the SYS in between DAC and Yamaha (calibrate SYS volume to 500 mVrms output and do not change so I can use the full range of the Yamaha’s volume knob for adjusting listening level without ever clipping)? Would there be any disadvantages with respect to sound quality?

I did check the chain for proper impedance bridging. The minimum damping factors I calculated would be SYS/DAC = 13.74 and Yamaha/SYS = 17.74 so I wouldn’t be running into many issues with frequency roll-of. I’ve frequently come across the statement that damping factors > 10 is a minimum and >20 is best. Would there be any issues with respect to sound quality using damping factors between 10 and 20?

Thanks.
carlosaudio51

Showing 4 responses by atmasphere

atmasphere's avatar
atmasphere
11,574 posts
 
-Atmasphere said that the receiver likely has active circuitry (such as a DAC) built-on which can be overloaded.
I was not talking about a DAC- just that there is active circuitry prior to the volume control. If you were using the built-in DAC this wouldn't be happening.


Are there better designed receivers that have built-in DACs but do NOT suffer from overloading the input, if an external DAC is the source?
Of course! Price plays a role of course.
atmasphere's avatar
atmasphere
11,574 posts
 
OK. What do you think is happening on my system? If I go DAC -> receiver I have clipping even at low volumes (20/100). If I add the SYS before the receiver and reduce the volume to about 3 o'clock, the clipping is gone.
Its pretty obvious that the receiver has active circuitry which can be overloaded before the volume control. The only good reason I can think of for a design character like this is that the receiver also has a DAC built-in, to which you are supposed to connect your digital source using a TOSLINK or HDMI connection.
atmasphere's avatar
atmasphere
11,574 posts
 
That suggests that the Yamaha also has active circuitry prior to the signal reaching the volume control. IMO as a designer this is a bad move as this means the input circuitry can be overloaded as you've experienced. If the volume control was properly placed as the first thing the signal encounters overload would be impossible. Soit sounds like the SYS is still important to be that first volume control.


This has nothing to do with the age of your DAC.
atmasphere's avatar
atmasphere
11,574 posts
 
The spec’ed input sensitivity is 500 mVrms. Given that I had clipping issues with the old active speakers, which had a sensitivity of 750 mVrms, I assume that my clipping issues would get worse if I go DAC -> Yamaha?
I doubt it.
Apparently the volume control of the active speakers was downstream from the input (IMO a poor design choice), which meant the input could be overloaded.


If you are running into the line level input of your amp, the first thing the signal is likely to see is the volume control, so overloading the input will be impossible.
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