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Low gain amp system matching

Dear Audiogoner,

Need your advise regarding system matching with low gain amplifier.

- Audio Note ANE Spe HE Signature speaker: 98.5 dB when placed in the corner (and that is how it's setup in my room). I believe the impedance of the speaker is above 6 ohm for most of the frequency band.
- Audio Note M3 preamplifier: gain of 15dB with input sensitivity specified as "126mV for 1V output".
- My source/DAC puts out 2V signal.

Given the above, a low gain amp with input sensitivity of 2V for full output would work in my system? The stepped attenuator of M3 has 36 steps. 
radiohead99
9 responses Add your response
kijanki's avatar
kijanki
4,428 posts
 
1V output for 126mV input is 18dB (not 15dB)

If your DAC produces 2V nominal, then preamp output will be 2V x 1/0.126 = 15.9V - way too much for an amp with 2V nominal input.
Perhaps your DAC has jumpers to reduce gain by 10dB (like in my Benchmark DAC), otherwise you can insert 10dB attenuator.  Best place would be between amp and preamp, assuming that your preamp can output 15.9Vrms - if not, then between DAC and preamp.


radiohead99 OP
79 posts
 
Thank you @kijanki for your helpful response. Correct, that the preamp gain is 18dB, not 15dB. I don't know which position of the attenuator will represent the unity gain on my  preamp. But there should be enough steps to attenuate the signal such that the amp input sees a reasonable voltage. But don't know if the usable range will be idea.

It sounds to me that if anything I may have to worry about too much gain rather than too little gain, right?
erik_squires
16,046 posts
 
Almost all amps have 26 dB of gain I believe.  IMHO, better to have a low gain preamp.  Less noise.
kijanki's avatar
kijanki
4,428 posts
 
@radiohead99   Voltage gain of your preamp is about 8x.  In order to obtain 0dB gain (2V input, 2V output) you need to set wiper at about 50% (12 O'Clock) position (to divide by 8).  Since ideal position would be around 2 O'Clock (with extra gain for soft recordings) you are not much off.  It is all assuming that you have logarithmic audio pot (most likely).  Some companies use linear pot with loading resistor (Benchmark DAC1) - a little bit different characteristic.
lowrider57's avatar
lowrider57
5,417 posts
 
Maybe an email to Audio Note UK is required...they do reply to queries.
The output voltage of AN DACs is 2.5V (unbalanced). All AN preamps are built to handle this amount of gain. The volume control on my M2 Special sits at 12:00 while using an AN DAC 2.1x Signature. There must be more at play here than the spec sheet.




lowrider57's avatar
lowrider57
5,417 posts
 
M3 gain is 15dB @ 1kHz.

kijanki's avatar
kijanki
4,428 posts
 
@lowrider57   They had two versions of M3: pre i post October 2013.  Both have gain of 18dB

Here is user manual that reflects it:  

https://d1b89e86-9572-4311-9f80-60009b280608.filesusr.com/ugd/3e7c3b_cb9f60cb6a26418992b53df75192a77...
lowrider57's avatar
lowrider57
5,417 posts
 
You're correct, it's 18dB. I still read it as 15, my vision is poor.
jond's avatar
jond
5,780 posts
 
@lowrider57 Is right check with AN also an AN amp would be a natural partner with your other gear and they make all of their amps in both high and low gain versions.
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