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Topic: Do preamps need to be level-matched (Read 9998 times) previous topic - next topic
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Do preamps need to be level-matched

Reply #25 –
What is the easiest method of A/Bing two pre-amps using tools that are commonly available to the consumer?

Do preamps need to be level-matched

Reply #26 –
You don't even need to go that far. The mere fact that different SPL allows the devices to be distinguished screams for bias (consciously and subconsciously).
"I hear it when I see it."

Do preamps need to be level-matched

Reply #27 –
Quote from: xnor on
You don't even need to go that far. The mere fact that different SPL allows the devices to be distinguished screams for bias (consciously and subconsciously).



Agreed. At the very least any relevant difference in SPL  is a spurious cue that can act as an anchor for the laundry list of human biases.  0.1 dB is usually an overkill number, but it is easy enough to achieve reliably.  It corresponds to a 1% change in voltage, which is easy enough to detect reliably with even the cheapest modern DVM. Back in the days of analog 1% was small enough to get lost in pivot friction so the Taut Band meter technology showed up for us just in time.

Do preamps need to be level-matched

Reply #28 –
Quote from: Rich B on
What is the easiest method of A/Bing two pre-amps using tools that are commonly available to the consumer?


If you go for Arny's Method of measuring levels on the speaker terminals, you need a conventional multimeter with an AC voltage measurement range in the single figure volts. Even rather basic multimeters can do that. Having one around at home is a good idea anyhow.

You use a sine wave for the level matching, which you can generate any way you like - there are numerous options, for example create them on the computer.

For doing the test, it helps greatly to have a means of switching the units under test quickly and without leaving the listening position. You will need to trust the switch - if you are one of the people who dismiss switching gear for fear of their having an audible effect on the signal, you have a problem. However, even in that case, you might test that hypothesis first, i.e. test the switcher before you test the preamps.

Even when you accept the switcher, you may run into problems. Some preamps have volume adjustments that go in steps rather than being continuous. That may prevent you from getting an accurate level match. That means you have to find another way to trim out the difference, at which point it ceases to be simple enough for the average consumer.

Do preamps need to be level-matched

Reply #29 –
Quote from: pelmazo on
Quote from: Rich B on
What is the easiest method of A/Bing two pre-amps using tools that are commonly available to the consumer?


If you go for Arny's Method of measuring levels on the speaker terminals, you need a conventional multimeter with an AC voltage measurement range in the single figure volts. Even rather basic multimeters can do that. Having one around at home is a good idea anyhow.

You use a sine wave for the level matching, which you can generate any way you like - there are numerous options, for example create them on the computer.

For doing the test, it helps greatly to have a means of switching the units under test quickly and without leaving the listening position. You will need to trust the switch - if you are one of the people who dismiss switching gear for fear of their having an audible effect on the signal, you have a problem. However, even in that case, you might test that hypothesis first, i.e. test the switcher before you test the preamps.

Even when you accept the switcher, you may run into problems. Some preamps have volume adjustments that go in steps rather than being continuous. That may prevent you from getting an accurate level match. That means you have to find another way to trim out the difference, at which point it ceases to be simple enough for the average consumer.


Could you recommend a switcher that would allow me to switch between two preamps quickly?

Do preamps need to be level-matched

Reply #31 –
http://www.ebay.com/itm/RCA-2X1-2-In-1-Out...=item3cf14acf53

Much like AVRs are the thing to buy, even if you don't care about half of the features on them that you'll be ignoring, when it comes to switch boxes you should consider ones with more ports than you actually need, including video, just because the fancier ones often cost less, oddly.

Also, do you even need to buy a switch? Maybe try using different inputs on your existing audio system, you know, like "CD" vs "Aux", and then either listening that way between sources or feeding the selected device out the tape record out port (fixed level, but then again so are these switches) to your other setup [which is not clear to me].
 

Do preamps need to be level-matched

Reply #32 –
So I emailed Bob Cordell asking for his advice on amplifier switch boxes, and he said it would be too time consuming to build a speaker/ABX style box that allows for level matching. He said it would be very expensive and that he wouldn't want to go through the effort of building another one. Apparently he did a bunch of tests a while back with custom designed switch boxes, but when asked, he didn't budge.