Beresford Bushmaster DAC

[StanleyB]

They are already running at 5mA per LED .
The (progarmmable )LED off function is already part of the features. But I probably won't have time to implement the LED dimming function. It appears to be quite difficult to be able to dim a LED in software.

[Martinh]

Hi Stan,

I'd like auto switching - if you can do the following, you have my order ( and my congratulations)

Input 1:

Optical from apple TV2 box - output comes on when you start playing media and stays on until the TV2 box switches itself off automatically (user selectable delay before auto switch off).

There is no "power off" button. It will only auto power off if the stop button has been pressed or the album has finished playing. If it's streaming radio, it will never auto switch off.

Input 2:

Optical out from Virgin media box. Output goes off when unit is put into standby.

Input 3:

Coax digital out from Marantz DV7600. Output goes off when unit is put into standby.


I'd like it to switch seamlessly between sources - my system is controlled via a harmony remote and devices are switched on and off automatically, depending upon the function required.

Id also like a variable out, but that isn't on the cards is it?

Cheers,

Martin

[StanleyB]

There is no variable output. That option is something for the future .

[Val33]

Stan

Is it a case of the Bushmaster definitely will not work with a passive pre, or that it might not work with some?

Any thoughts on using an isolation transformer if needed?

Thanks

Val

[StanleyB]

I can only go by whatever preamps I manage do borrow to test the Bushmaster with, and use that as a guide. But I stand corrected . No doubt time will throw up a list of passive preamps that have been successfully tested with the Bushmaster by enterprising owners.

[Labarum]

How do you think the Bushmaster might work into a step attenuator, Stan?

As I understand it the tiny DC offset in the output of the direct coupled Bushmaster is likely to degrade the track of a conventional pot volume control.

If I were to replace the left and right pots at the front of my Pro Power Amp with a switched step attenuator would those fixed resistors bear the tiny current?

I could then, as I do anyway, make adjustments of a few dB using the digital volume control in the Squeezebox, or in software when playing videos.

I rarely adjust the level controls on either the power amp or my Caiman - I live with up to 10dB of digital attenuation.

[StanleyB]

All active amps will work with the Bushmaster. It's the passive ones that could cause a problem. In an active amplifier the design already caters for an AC signal, with or without a DC component, to the volume control. It's a design rule. So there are no problems with operating the Bushmaster with your amp if you need to plug your amp into the mains before it will work.
But if you have a stand alone volume control pot or passive preamp, it is more than likely not to work properly with the Bushmaster.

[Labarum]

Stanley - my Quad Pro Amp has a 100k pot between the input socket and the first capacitor in the signal path - it has, is suppose a "passive pre-amp" built in.

I was asking if there is any point in replacing that pot with a step attenuator, using a rotary switch and fixed resistors.

[Clive]

I have sympathy Stan, there's no absolute rule about whether DC blockers are on inputs or outputs. It's crazy to end up with a capacitor on the output feeding into another at the input.....

As for assuming all powered amps have a DC blocker before the pot, I'm afraid you can't assume this (edit - just seen Brian's post a few mins before mine). One example I know of is the original Musical Fidelity A1, this has the DC blocker following the 50k pot, it's a passive pre feeding a power amp. I expect there will be more modern examples of this poor practice. I should add that anyone with a TVC will need to take care as DC will magnetise these.

[StanleyB]

The actual DC from the Bushmaster is less than 1mV, which works quite happily with any active amp. But the passive resistive networks could to be clamping the signal to ground on the input side, which upsets the output impedance of the DAC.