Input Sensitivity Help with Mojo 2 to Singxer Sa-1

[adubg]

Hi All,

I have a Mojo 2 that I am using as a DAC to my Singer Sa-1 amp that is powering my Arya v3 Stealths.

The amps current configuration is SE in and Balanced Out.

My question is should I be using low or high gain on the Singxer Sa-1?

With the SA-1 @ low gain with 4.3v out on the Mojo 2, the maximum I ever get on the volume pot is 2 o'clock.
When I use SA-1 @ high gain with 2v out on the Mojo2 the volume POT rarely getting above 12 o'clock and sits pretty low.

I was trying to capture Mojo 2's best dynamic range by outputting 4.3v into the Singxer and using the low gain, but am I sacrificing more by using low gain since the sensitivities aren't matched?

Couldn't find a lot of information about have a lower voltage input vs input sensitivity on the forums and if it would work best for this application or if it would better to use SA-1 high gain with the Mojo 2 @ 2v out and match exactly, but sacrifice the Mojo 2's best dynamic range.

Does anyone have a good suggestion on which method I should be using to get the best performance out of my setup? Thanks in advance!

Some details about the equipment:

Mojo 2 has its best SINAD and dynamic range outputting at 3-4.3v.

SA-1:
Output wattage: 32Ω 5.5W

Input Senstivity (maximum input without distortion at the maximum volume):
Low gain: RCA 7.4V RMS;
High gain : RCA 2.1VRMS.

With Single-ended input, balanced output: low gain is 6db, high gain is 17db;

 

[staticV3]

Low gain on your Amp and high output level on your DAC will give you the best SNR.

 

[adubg]

Gotcha, any reason why high gain would have any advantage other than more head room? Am I loosing something by not directly matching the higher input sensitivity in low gain (4.3v from the Mojo 2 vs the 7.4v on the SA-1)?

 

[staticV3]

Gotcha, any reason why high gain would have any advantage other than more head room?

None. Only downsides (more hiss, higher probability of channel imbalance).

Am I loosing something by not directly matching the higher input sensitivity in low gain

No.

 

[adubg]

Thanks for helping!

 

[adubg]

None. Only downsides (more hiss, higher probability of channel imbalance).


No.

One last question. How much power output am I giving up / outputting in watts @32ohms by only using 4.3v output when the low gains input sensitivity is 7.4v?

 

[staticV3]

One last question. How much power output am I giving up / outputting in watts @32ohms by only using 4.3v output when the low gains input sensitivity is 7.4v?

Depends. Are you using the SA-1 V1 or SA-1 V2?

 

[adubg]

V1.3

Depends. Are you using the SA-1 V1 or SA-1 V2?

v1 (1.3).

 

[staticV3]

V1.3

v1 (1.3).

Ah I see.
A bit confusing then that you're quoting the SA-1 V2 specs in your post above:

With Single-ended input, balanced output: low gain is 6db, high gain is 17db;

According to the SA-1 V1 user manual, Low gain is unity gain (1x/+0dB):


4.3V in would therefore give you a maximum output power of 4.3^2/32=0.58W per channel at 32Ω.

Edit:
It seems like the manual is incomplete and only specifies SE->SE/Bal->Bal gain.

On the SA-1 V1 website, SE->Bal gain is specified as +6/+17dB, just like you said: http://www.singxer.com/pd.jsp?id=82

With 6dB of gain, 4.3V in will limit maximum output power to (4.3*10^(6/20))^2/32=2.3W per channel at 32Ω.

 

[adubg]

0db is for single to single and balanced to balanced. For the mojo 2 it would be 6db since I’m using single ended in and balanced out.

 

[staticV3]

View attachment 374481
0db is for single to single and balanced to balanced. For the the mojo 2 it would be 6db since I’m using single ended in and balanced out.

See the edit above

 

[adubg]

Thanks again!