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

[nagster]

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.

Does low gain (12.8dB) bypass the input buffer?
Or does it flow through the 0dB input buffer?

 

[boXem]

Does low gain (12.8dB) bypass the input buffer?
Or does it flow through the 0dB input buffer?

Bypassing would imply changing the input impedance, which doesn't comply with the target of having an "easy to drive" amplifier. So flow through.

 

[nagster]

Thank you for your prompt reply.

 

[restorer-john]

View attachment 177509

Surely that is just an attenuator pot up front on the input stage like a million other power amps?

Edit: Dual gang 100K pots up front.

BTL mono is incorporated by feeding signal into the inverting input of the differential FET front end or grounding the feedback R divider (NFB) in normal stereo. The actual gain of the power amp is not variable. That's what I was driving at.

 

[Rottmannash]

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? My VTV Purifi runs ice cold, even at ludicrous levels driving F208s.

 

[Rottmannash]

Is anyone else having issues when replying to posts using Firefox? Instead of the quoted section appearing up top in the box my reply appears at the tail end of the quote with no dileneation between them. very frustrating and misleading .

 

[VintageFlanker]

So you do not care about air flow and thermal management??

From my own experience, both ET400A amps and ADI-2 DAC (when not using headamp) are running dead cold hours after hours...

View attachment 176661

Damned, I took your M16s for Evoke 20s...

 

[restorer-john]

Using Firefox. No problems with the quote box, although editing afterwards can sometimes be a pain if you have several quotes.

Is anyone else having issues when replying to posts using Firefox? Instead of the quoted section appearing up top in the box my reply appears at the tail end of the quote with no dileneation between them. very frustrating and misleading .

You do need to put the cursor on the first letter of a quote in a box and hit enter to get a line above in order to type above the quote.

Like this:

Then hit enter.

 

[Deleted member 23424]

Damned, I took your M16s for Evoke 20s...

Would you like to buy some Dynaudio? Very reasonable price.

 

[VintageFlanker]

Would you like to buy some Dynaudio?

No thanks. I switched to some other Danish poison...

 

[Deleted member 23424]

No thanks. I switched to some other Danish poison...View attachment 177744

Nice. I'm currently on the hunt for some big ol' teak monsters. Really interested to hear what all this clean power, control and grip will be like through some Kef Concerto/104AB, Celestion Ditton 66 etc.

 

[BrokenEnglishGuy]

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? My VTV Purifi runs ice cold, even at ludicrous levels driving F208s.

Yeah the vtv purifi runs very cold, even my headphone amp / pre amp class A 8w runs hotter lol

 

[ririt]

No thanks. I switched to some other Danish poison...View attachment 177744

can you please provide any feedback on them?

 

[VintageFlanker]

can you please provide any feedback on them?

I did countless times. Use the search button.

 

[ririt]

I did countless times. Use the search button.

Ok thanks. sorry to not did it before asking…I will have a look

 

[JeyElDee]

Went to pick up my new Arthur 4215/E2 last friday. First impressions are very well.
Very transparent, open and musical sound, almost to forget there is an amp...
I have a slight impression it could beat my McIntosh MC252 on all fronts. It certanly drives the JBL Ti5000 speakers very well.
TBC ...

 

[nstzya]

The gain switch on the rear helps put my mind at ease with regard my better half blowing any speakers up. My Revel M16 can handle full power from the amp on the medium gain setting without issue.

You've mentioned this a few times - that you can run the amp at "full power", etc. How are you determining it is at full power? How are you using that term? Do you push it the clip indicator and back off slightly? Or are you just using the term loosely? Because on medium gain, you aren't technically using it at full power, per se... Not trying to be a stickler. Just curious if you've pushed it to clipping.

It's a well executed amplifier and beautifully crafted. Should serve you well.

 

[Deleted member 23424]

Not trying to be a stickler.

I think you've answered your own question there, Mr Stickler.

 

[nstzya]

Sort of. Stickling and semantics aside... you refer to "even at full power". Are you running up against clipping (albeit at medium gain)?

 

[daniboun]

Without being slanderous, I've always found that Boxem has a serious concern for design... their amp looks like a cash drawer. It's a shame because the rest is better.