This seems as good a forum as any to post this question.
I like to build and put together pre/amps from many of the modules from various vendors including those in Asia. Since I'm not too knowledgeable in the theory, one of the questions I continue to ponder is; what is the best way to match the impedances between pre-amp, DAC, input switcher (which theoretically shouldn't introduce any matching issues), and amp modules if you don't know what it is, and have no means to measure it properly.
I recently put together an integrated amp using such modules and it didn't sound too good. My first inclination was that the impedances didn't match too well, but I had no way of conclusively knowing. I also won't discount the 'quality level' of the modules I used that may have played a part as well. But I would like to know if the impedance matching was the real issue or not.
Are there some simple steps, or measurements I can do to help determine if I have my modules matched as well as I can?
Rick
I like to build and put together pre/amps from many of the modules from various vendors including those in Asia. Since I'm not too knowledgeable in the theory, one of the questions I continue to ponder is; what is the best way to match the impedances between pre-amp, DAC, input switcher (which theoretically shouldn't introduce any matching issues), and amp modules if you don't know what it is, and have no means to measure it properly.
I recently put together an integrated amp using such modules and it didn't sound too good. My first inclination was that the impedances didn't match too well, but I had no way of conclusively knowing. I also won't discount the 'quality level' of the modules I used that may have played a part as well. But I would like to know if the impedance matching was the real issue or not.
Are there some simple steps, or measurements I can do to help determine if I have my modules matched as well as I can?
Rick
Generally speaking matching is not an issue, as long as the 'sending' module has sufficiently low output impedance, and the 'receiving' module has sufficiently high input impedance. That way, the signal from the 'sender' is not too much attenuated.
Output impedances are mostly a few 100 ohms, except tube 'senders' that can be 1k or more.
Most input Z's are several 10's of kohms.
So, bottom line: not an issue except in pathological cases.
So it is highly unlikely that your issues are caused by input-output Z issues.
Jan
Output impedances are mostly a few 100 ohms, except tube 'senders' that can be 1k or more.
Most input Z's are several 10's of kohms.
So, bottom line: not an issue except in pathological cases.
So it is highly unlikely that your issues are caused by input-output Z issues.
Jan
Thanks Jan. Well then could it be gain related? One overpower the other possibly, hence the need to reduce/attenuate something on either the sender or receiver device? If that's the case, do you just fall back to the old potentiometer solution, or stepped volume control - on either the pre-amp or amp? That brings up another question... Should power amps have a 'volume' control. Seen lots of them here on DIY that do - just not sure if that's the best solution.
Rick
Rick
Fair enough Jan. No offense taken. It's been well over a year since I turned on the particular amp in question. I'll go back, hook it up and do it bit more listening to observe just what it was I didn't like and reply back. Whatever it was I quickly put it on shelf. Maybe tomorrow when I have more time. Big east-coast snow storm expected tonight. - RickThere are three issues that could interfere with the quality of the In/Out of a connection.
a.) Balanced Impedance interconnections.
These are somewhat different from all the "unbalanced interconnections".
If your's are not balanced, then ignore this category.
b.) Impedance ratios.
Normally we expect the ratio of Receiver impedance to Source impedance to be more than 5:1 and preferably >10:1. 100:1 does no harm when the connection is made. This extremely high ratio does have a downside when the connection is not made.
c.) Current capability to drive parasitic capacitances.
All the preceding considered only resistance of inputs and outputs. Capacitance also draws current from the Source component. The current capability must satisfy the resistance load/s plus the current demanded in charging and discharging the parasitic capacitances of (especially) cables and the RF attenuator at the input of the Receiver components plus some other usually very small true parasitics.
Insufficient current capability usually results in reduced treble.
a.) Balanced Impedance interconnections.
These are somewhat different from all the "unbalanced interconnections".
If your's are not balanced, then ignore this category.
b.) Impedance ratios.
Normally we expect the ratio of Receiver impedance to Source impedance to be more than 5:1 and preferably >10:1. 100:1 does no harm when the connection is made. This extremely high ratio does have a downside when the connection is not made.
c.) Current capability to drive parasitic capacitances.
All the preceding considered only resistance of inputs and outputs. Capacitance also draws current from the Source component. The current capability must satisfy the resistance load/s plus the current demanded in charging and discharging the parasitic capacitances of (especially) cables and the RF attenuator at the input of the Receiver components plus some other usually very small true parasitics.
Insufficient current capability usually results in reduced treble.
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