db attenuators on the amp. Keep it low or high?

[celo]

Please reply in plain language

So, I have this pro amp ( https://www.mc2-audio.co.uk/wp-content/uploads/t1000_datasheet.pdf ) with db attenuators.

It starts from 30db I guess from the knobs the way they are marked. I assume it is negative 30db.

My streamer/DAC is Logitech Transporter which has 3V output XLR connection which I directly connect to the amp.

When I do this, I cannot put the db attenuator more than -12db because it gets too loud on my desktop.

I also have a preamp with 1V output and when I connect it between the amp and the DAC, then I can go easily to 6db even 4db.

When set to 6db the amp gets hotter and when 12db, it does not get as hot. When I say hot, still normal operating temp, nothing excessive.

My question is this, what are those db attenuators for? Is it better to keep them as low as possible such as running a source with 3V or bring them to close to 0db with a lower output voltage such as my preamp with 1V.

If I keep it at 12db, am I limiting the power of my amp or am I doing good to the amp by not getting near to 0db?

It is all technical to me so I am trying to figure out which setting is most ideal for the db attenuators on the amp.

My amp has 1.2V sensitivity, 32db gain and 20K ohm impedance, and more specs at the link above.

 

[Old_School_Brad]

As long as you're not clipping the amplifier's inputs, it's best to run the source at the highest possible voltage and handle attenuation at the amplifier. Pro amps can sometimes introduce a bit of noise.

What you want to do is set the attenuators so you can achieve both your maximum and minimum desired volume levels -while keeping the input voltage as high as possible.

 

[celo]

So, what I understand is you are saying, keep using my 3V source directly connected to the amp and ditch the preamp.
Set the attenuator where it is best level and change the volume from the Logitech if needed.

So my second question then, would getting something like Topping Pre90 improve noise and/or sound technically? In other words, would a preamp improve things technically in general? This way I can keep my Logitech at 100% at all times (even set it to fix) and change the volume from the Pre90.

 

[Old_School_Brad]

So, what I understand is you are saying, keep using my 3V source directly connected to the amp and ditch the preamp.
Set the attenuator where it is best level and change the volume from the Logitech if needed.

So my second question then, would getting something like Topping Pre90 improve noise and/or sound technically? In other words, would a preamp improve things technically in general? This way I can keep my Logitech at 100% at all times (even set it to fix) and change the volume from the Pre90.

Your questions aren’t easily answered without doing direct measurements on each component.

That said, in general, the fewer components in the signal chain, the less noise you'll introduce.

Connecting the 3V source (what exactly is it?) directly to the power amplifier is totally doable. Before settling on that setup, though, I’d make sure the source’s maximum output level won’t damage anything if it spikes accidentally. A practical approach is to turn the amp’s attenuators fully counter-clockwise (maximum attenuation), then crank your source volume to its absolute maximum. From there, gradually turn the amp’s attenuators clockwise until you hit your maximum listening level -the loudest you plan to listen.

 

[celo]

That's how exactly I was using like you explained but then I was thinking maybe the source voltage should not be double the amp sensitivity but I guess the more voltage from the source the better is. My thinking was wrong. I was just thinking the amp does. not give the advertised wattage if not turned on all the way to 0db or at least close to it.

This is my source.

https://downloads.lms-community.org/docs/Transporter%20Owners%20Guide.pdf

 

[Wayne A. Pflughaupt]

Never heard of that amplifier, but a little digging found that the MC2 brand was founded by principals of the high-respected Klark-Teknik pro audio brand (which is now owned by Behringer). So it should be a solid piece – overkill for a desktop system, really. The MC2 amps get good reviews from professional users at the Pro Sound Web ( https://forums.prosoundweb.com/index.php?topic=73982.0 ).

My question is this, what are those db attenuators for?

Read this description (see link below). It will answer your question, and should also be sufficient to show why the amp “responds” differently with your two devices with different output voltages.

https://www.hometheatershack.com/threads/gain-structure-for-home-theater-getting-the-most-from-pro-audio-equipment-in-your-system.35677/#post-317690

As you can see, it doesn’t matter which front end device you use; the amp can accommodate both. The only difference is that the Logitech with the hotter 3V output will utilize a lower gain setting on the amp, while the 1V preamp will require a higher gain setting. “Highest possible input signal” isn’t a factor, only matching the amp’s input stage to the output of the device in front of it. That is, if the goal is for the amp to achieve its maximum power. However...

If I keep it at 12db, am I limiting the power of my amp…

As noted in the above-referenced link, varying input levels (from different front end devices) have nothing to do with the amp’s maximum output.

But - do your desktop speakers really need 450 watts @ 8 ohms or 750 watts @ 4 ohms? Will they even take that kind of power without blowing? And if they can, do you really need 115 + dB from a speaker 3-4 feet from your ears?

If the answer to any of those questions is “no,” then you probably *do* want to limit the amp’s power output. This is easily done by setting the input gains lower than what’s needed to achieve maximum power.

So, assuming that achieving maximum power from the amp isn’t really needed, my advice would be to simply set the gains so that the volume (SPL) from the speakers is comparable to what you were getting from the amp / front-end device combination you were previously using.

Regards,
Wayne A. Pflughaupt

 

[Old_School_Brad]

The position of the attenuators doesn’t affect the core spec -the amplifier is rated to deliver maximum power with a 1.2 V input when the attenuators are set to 0 dB. If you turn the attenuators down, a higher input voltage will be needed to reach full output. It is capable of reaching full output with the attenuators set to anything other than 0 dB. (Disregarding potential input stage clipping.)

All amplifiers have a maximum input voltage threshold, beyond which the input stage will clip -but this particular spec isn’t mentioned in the documentation. That said, unless you actually need the full output power (which you probably don’t), there’s no issue continuing to use it as you are now -just keep the safeguard in place for any unexpected spikes in input level, as previously described.

 

[celo]

@Wayne A. Pflughaupt my amp is awesome. It beats my $4K MSRP amp which I won't name here out of respect. This amp is so powerful and balanced. Detailed yet not fatiguing. I know these terms are seen as BS but really this amp is clean. I have heard that Hans Zimmer himself uses MC2 amps. That tells you something.

What confused me was that I am not too familiar with pro amps and the attenuater sounded best at low level with my DAC but then I was thinking maybe I not getting the best out the of the amp.

I use this on my desktop temporarily, soon enough I will be using with some good floor standers if the local seller accepts my offer

 

[Old_School_Brad]

Pro amplifiers are seriously underrated. Many of them wipe the floor with McIntosh, Krell, Parasound, D’Agostino, and other audiophile heavyweights.
Even Purifi and Hypex are outclassed in terms of sheer power and continuous output capability.
Pro amps also feature robust protection circuits -unlike many consumer brands that often rely on something as simple as a rail fuse.

Go pro or go home!

 

[celo]

Pro amplifiers are seriously underrated. Many of them wipe the floor with McIntosh, Krell, Parasound, D’Agostino, and other audiophile heavyweights.
Even Purifi and Hypex are outclassed in terms of sheer power and continuous output capability.
Pro amps also feature robust protection circuits -unlike many consumer brands that often rely on something as simple as a rail fuse.

Go pro or go home!

I agree with everything you said. I myself was also staying away from pro amps. I once bought a Class D Crown pro amp but didn’t like it. But reading someone’s post online decided to try the MC2. Glad I did.

The only issue for me was the fan noise but this specific model can be set for the rear fan to be active when it goes above 90 Celsius and I haven’t made it turned on yet. The front fan I replaced with a quieter one and you can hear it from 4ft at night which is fairly close. Day time harder to hear obviously. The rear fan is more difficult to replace so I left it but it doesn’t kick in anyway.