2. amps-preamps
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Use receiver for power output from integrated amp

For reasons I discussed on another thread I want to, at least temporarily, use the fixed pre out connections from my integrated amp to the CD input on my receiver. I did and it worked but, as much as I am able to discern, the sound is no different compared with using the signal directly from the CD player to the receiver CD input.

To see what might be the issue, I turned the stereo amp off and the signal was still reaching the receiver; unplugging the amp resulted in the same thing so the signal is obviously just passing through the tube section of the amplifier. I'm stumped.

The sound chain for this issue is: Shanling digital CD player, CAL Sigma 2 DAC, Rogue Audio integrated hybrid Stereo amp and B&K AVR3700 receiver.
128x128broadstone
tls49's avatar
tls49
1,351 posts
 
unplugging the amp resulted in the same thing so the signal is obviously just passing through the tube section of the amplifier
A signal will not pass through the tube section, unless power is applied to the tubes. The fixed pre out must be output prior to the tube section.
almarg's avatar
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almarg
9,670 posts
 
TLS49 is correct, of course. The fixed-level outputs of the integrated amp are most likely configured similarly to how the tape outputs on many older preamps were implemented. Namely, the input signals are routed to the source select switch, and the selected signal is then routed through a resistor to the fixed-level output jack, for each channel. So the tubes and transistors in the unit are not in the signal path between the input jacks and the fixed-level output jacks.

Regards,
-- Al
broadstone's avatar
broadstone OP
310 posts
 
Thank you for these comments. I spoke with the fine folks at Rogue Audio; they said to use the variable pre-out to the receiver from the Sphinx, find a level that is good on the Sphinx for CD and use the receiver for volume control. This setup is probably not as good as using the Sphinx by itself but I do gain output power and audio controls that are not available with the Sphinx.
I didn't ask but I wonder what, then, the purpose of the fixed pre-out connection might be.
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