How to control volume with 2 BTL mono block amps? (Sabaj A8)

[ninetylol]

Hey i ordered 2x Sabaj A8 and plan to use them as mono blocks to my Polk ES60. They do have volume knobs but I dont know how I should set them up for volume control and volume balance.

E.g. Set both amps to 100% and control volume with DAC? (probably bad because amp working at 100% would introduce distortion and DAC loses SINAD at lower signal.

So amps at about 50% and and using dac for volume control?

In other words what would the optimal volume position on the two A8s be?
And how would I ensure correct volume balance between both speakers.

Any tips would be appreciated.

 

[Deleted member 48726]

Well, that depends entirely on how loud you listen to music in general. I like to have fine control at low volume most often. So I have the gain turned down a bit. When I want to listen loud I turn the gain up. It also depends on you pre-amplifier's signal range/resolution.

 

[staticV3]

Set your DAC to 100% volume and your Amps to 0%.
Start playing music and slowly increase the Amps' volume until they're as loud as you'll ever realistically need.
Decrease your DAC a bit to spare your ears, then fine-tune the Amps' volume to get proper L/R balance.
Finally, leave the knobs on your Amps where they are and do all your volume control on the DAC.

That's how I'd do it.

 

[restorer-john]

I see the input sensitivity for the Sabaj is advertised as 280mV.

With respect to what, is the issue. If that spec is with respect to full power, you will need to use the attenuators to pull back a little, so you don't end up with too little fine control over your volume, particularly at low-medium levels.

People on ASR obsess over levels, and yet they fail to understand the massive variation in source levels and content. You need reserve gain and attenuation.

 

[ninetylol]

Set your DAC to 100% volume and your Amps to 0%.
Start playing music and slowly increase the Amps' volume until they're as loud as you'll ever realistically need.
Decrease your DAC a bit to spare your ears, then fine-tune the Amps' volume to get proper L/R balance.
Finally, leave the knobs on your Amps where they are and do all your volume control on the DAC.

That's how I'd do it.

Thats about what I was thinking too. But how would I ensure volume balance? By ears only?

 

[ninetylol]

I see the input sensitivity for the Sabaj is advertised as 280mV.

With respect to what, is the issue. If that spec is with respect to full power, you will need to use the attenuators to pull back a little, so you don't end up with too little fine control over your volume, particularly at low-medium levels.

People on ASR obsess over levels, and yet they fail to understand

Input sensitivity of 280mV means DAC should not send more than 280mV if the amp is set to 100%? But if i lower the volume on amps i can send full 4.0 volts balanced I guess?

 

[restorer-john]

Thats about what I was thinking too. But how would I ensure volume balance? By ears only?

Balance the amplifiers electrically, but understand, most recording are not remotely well balanced and without the ability to control gain in each channel in real time, your images will be all over the shop.

 

[staticV3]

Thats about what I was thinking too. But how would I ensure volume balance? By ears only?

If your MLP is at equal distance from each speaker, then you can use a multimeter and measure the output voltage of each Amp under load to ensure both speakers get the same signal amplitude. This only works if both speakers have the same sensitivity though.
Alternatively you could use a microphone, any microphone to measure SPL coming from each speaker separately and match volumes that way.
Or, just do it by ear. It's fine.

 

[restorer-john]

Input sensitivity of 280mV means DAC should not send more than 280mV IF the amp is Set to 100%? But if i lower the volume on amps i can send full 4.0 volts balanced I guess?

An input sensitivity is normally referenced to full rated power.

Example: 1.5V for 200wpc@8R. That equates to an amplifier voltage gain of 28.5dB- a typical number.

280mV is above typical line level (150-200mV) and well below typical power amp input levels (1.0-2.0V).

As we have really no idea exactly what output power these amps actually achieve (Chinese specs are a total joke in most cases) and their relative gain, it's all guesswork until someone bothers to put a unit on the bench.

 

[Zek]

But how would I ensure volume balance? By ears only?

Feed a 1kHz audio signal to both channels and adjust the volume on the amplifiers so that your sound comes from the center between the two speakers.