BOXEM Audio | Arthur 4215/E2 Purifi Amplifier | Owners' Thread

[Deleted member 23424]

Most valuable function of the RME is the fully adaptive loudness - I do correct my room- impacts with a MiniDSP SHD studio using Dirac - the result is perfect at normal / high listening volumes but sounds too thin at low volumes- this is why the loudness feature is a must at least for me...

My issue is that Camila/PEQ on my Pi only works for streaming audio. Not that I'm overly concerned about the TV audio but it'd be nice to be able to tweak it as required.

 

[restorer-john]

Can confirm that mine lives in a cupboard and is barely above room temperature after pushing my speakers hard enough to move things on shelves in the adjoining room.

Do other purifi builds have a tendency to run warmer?View attachment 176661

That's a nice room.

 

[restorer-john]

Do other purifi builds have a tendency to run warmer?

Only in Australia, in summer, playing AC/DC.

 

[Deleted member 23424]

Only in Australia, in summer, playing AC/DC.

That'll be all the spiders nesting inside.

 

[JSmith]

That'll be all the spiders nesting inside.

I breed venomous snakes inside mine... and always tip cows.


JSmith

 

[charleski]

Those feet are incredible. They really do make everything sound so much better, though sometimes it's best to use 8 of them. Hic!

Have you compared them to the upgraded version?

I hear this upgrade gives you a real “We Are All In The Gutter But Some Of Us Are Looking At The Stars” feeling ...

"Please Drink Responsibly" ...

 

[Deleted member 23424]

Have you compared them to the upgraded version?

I hear this upgrade gives you a real “We Are All In The Gutter But Some Of Us Are Looking At The Stars” feeling ...

"Please Drink Responsibly" ...

8 of those would certainly increase the damping factor, in my underpants.

 

[Tacrolim]

Interesting combination. Revel M16 (Max120W speakers) with the Boxem 4215 (210W at 8ohm). I think (correct me if I am wrong) the rough pairing rule is to go for an amp with 1.5x the maximum recommended speaker power to allow for headroom and satisfy sufficent dynamic range for all genres of music, without clipping. This is more. Surely Revels drivers are well built. How safe is this (practically) and can this be extended to other speakers in general. And how goes that gain switch work? does it limit the out power like an attenuator? or does it act like a loudness switch?

 

[Deleted member 23424]

Running the amp at max on the middle gain setting has never clipped. It's plenty loud enough so haven't even tried the highest gain setting. I checked with various purifi amp makers before purchasing and all recommended said amp/speaker pairing.

I'll leave the explanation of the design to
@boXem | audio.

 

[boXem]

As it's name implies, the switch changes the gain of the amplifier. Low=12.8dB - Mid=20.8dB - High=27.2dB
If the input of the amp is 1.8 V RMS, it's output will be:
High gain: 41V RMS, i.e. 280W in 6 Ohm
Mid gain: 19.7V RMS, i.e. 65W in 6 Ohm
Low gain: 7.8V RMS, i.e. 10W in 6 Ohm
If the purpose of the gain switch is to adapt the sensitivity of the amplifier to the upstream component, it can also be used as power limiter as demonstrated above.

 

[Tacrolim]

As it's name implies, the switch changes the gain of the amplifier. Low=12.8dB - Mid=20.8dB - High=27.2dB
If the input of the amp is 1.8 V RMS, it's output will be:
High gain: 41V RMS, i.e. 280W in 6 Ohm
Mid gain: 19.7V RMS, i.e. 65W in 6 Ohm
Low gain: 7.8V RMS, i.e. 10W in 6 Ohm
If the purpose of the gain switch is to adapt the sensitivity of the amplifier to the upstream component, it can also be used as power limiter as demonstrated above.

Thank you. Well illustrated. I guess this is a fine example of how dexterous the unit can be with a range of speakers.

 

[Deleted member 23424]

Thank you. Well illustrated. I guess this is a fine example of how dexterous the unit can be with a range of speakers.

It's why I bought it. For my ears it's an end-game solution in terms of sound quality, and the flexibility afforded by the gain switch allows me plenty of scope to flit between speakers. Not that there's anything fundamentally wrong with the M16, but my room size would probably suggest larger would be better.

 

[restorer-john]

As it's name implies, the switch changes the gain of the amplifier. Low=12.8dB - Mid=20.8dB - High=27.2dB
If the input of the amp is 1.8 V RMS, it's output will be:
High gain: 41V RMS, i.e. 280W in 6 Ohm
Mid gain: 19.7V RMS, i.e. 65W in 6 Ohm
Low gain: 7.8V RMS, i.e. 10W in 6 Ohm
If the purpose of the gain switch is to adapt the sensitivity of the amplifier to the upstream component, it can also be used as power limiter as demonstrated above.

But let's be totally honest here shall we?

The gain of the amplifier itself is unchanged. It is the gain of the buffer stage up front of the amplifier that is adjusted.

 

[boXem]

But let's be totally honest here shall we?

The gain of the amplifier itself is unchanged. It is the gain of the buffer stage up front of the amplifier that is adjusted.

People buy a box called "amplifier". The switch changes the gain of the box . Inside the box, you are right, it is the buffer stage gain that is modified.

 

[tw99]

People buy a box called "amplifier". The switch changes the gain of the box . Inside the box, you are right, it is the buffer stage gain that is modified.

Think restorer-john got out of the wrong side of the bed again today

 

[storing]

Still, as an engineer I find this an interesting implementation detail.

 

[boXem]

Still, as an engineer I find this an interesting implementation detail.

I am not crazy enough to modify the self-oscillation loop gain on the fly, so no other choice than modifying the buffer gain.

 

[pma]

I am not crazy enough to modify the self-oscillation loop gain on the fly,

….. and you would be crazy to do so. The smart design of the FB loop is the key of the success and parameters of nCore and Purifi modules.

 

[restorer-john]

People buy a box called "amplifier". The switch changes the gain of the box . Inside the box, you are right, it is the buffer stage gain that is modified.

I know, I'm just having fun.

I can't think of any class AB amplifiers where the gain of the actual power stage is adjusted. Some VCA based preamps perhaps. Usually amps are fixed gain, with attenuators up front to give variable "gain".

Plenty of inexpensive Class AB integrated amplifiers with tone controls in the NFB loop of the power amp...

 

[pma]

I can't think of any class AB amplifiers where the gain of the actual power stage is adjusted