[Chazz5]

The Transcendence RB 10 has a white line on the volume control. Where is unity gain () dB)?

Thanks for a reply.

[danielgk]

I don't have an RB10 in front of me to measure, but typically unity gain is 12:00 straight up and down.

By the way, there is nothing wrong with moving the knob so unity gain is straight up and down, or anywhere else you want to put it (it is your preamp after all).


Dan

[Jeff_From_Michigan]

I don't have an RB10 in front of me to measure, but typically unity gain is 12:00 straight up and down.

By the way, there is nothing wrong with moving the knob so unity gain is straight up and down, or anywhere else you want to put it (it is your preamp after all).


Dan

If you did have one (or any other preamp) in front of you, how would you measure the unity gain?

[danielgk]

Jeff

That is the way I have observed most preamps to behave.  About x7-x10 gain at full, about x1 at mid point, fading down to no output at zero.

If the RB10 didn't behave that way, I think I would have noticed as I have worked on and listened to a number of RB10's.


Dan

[GeorgeAb]

If you did have one (or any other preamp) in front of you, how would you measure the unity gain?

Here are a couple of ways. Second method is easier.

Measure voltage at input to preamp with 1Khz (for example) test signal applied. Measure voltage at output to preamp and increase volume control until voltage is equal to what you previosuly measured. 

Take input and bypass preamp putting directly into amplifier. Play attenuated test signal and record sound pressure level (SPL) using phone application such as Decibal X. Put input back into preamp and increase volume until you get the same SPL as previously recorded.

[jedgar]

I wonder if there is a good summary of the unity gain concept you can recommend? 

On my Transcendence 10 SLR, I almost never have the volume past 9 o'clock with CDs, 10 with LPs.  Only on a bluetooth receiver does it get to 12.  And I do rock out often and listen to The Messiah yearly.

My Tannoy DC4000s are efficient (92 dB).  The amp is AVA Synergy 240 ss at 120 wpc.

Is this a reason to use the preamp's low gain button?

I am very happy with my music, but maybe I will experiment some.

[Chazz5]

... use the preamp's low gain button?

My surmise:

As GeorgeAB's suggestions imply, at unity gain the voltage out equals the voltage in. Your CD, phono source, and Bluetooth receiver supply different voltages in, so the preamp at unity gain will give the amplifier different voltages.

With the volume settings you report, there is no reason to use the low gain button.

[opnly bafld]

No harm in trying a low gain setting and seeing what you think.

[Jeff_From_Michigan]

Here are a couple of ways. Second method is easier.

Measure voltage at input to preamp with 1Khz (for example) test signal applied. Measure voltage at output to preamp and increase volume control until voltage is equal to what you previosuly measured. 

Take input and bypass preamp putting directly into amplifier. Play attenuated test signal and record sound pressure level (SPL) using phone application such as Decibal X. Put input back into preamp and increase volume until you get the same SPL as previously recorded.

Thank you, George.  That's the first time that I've seen anyone explain this and provide a procedure for testing.  With this information in hand, I am excited to see what the differences between my two preamps might be.

For the record, I have at any given time either a T10 RB or Odyssey Candela preamp feeding 200wpc amps (at 8 ohm, not sure about the 4 ohm rating but they have plenty of current and no issues driving the Maggies). Regular listening is done between 9:00-11:00 on the volume dial, and anything in the 1:00-2:00 range is only practical on weekdays while my neighbors are at work.

Again, much appreciated!