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MDAC First Listen (part XXVI)

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It'd take him longer to analyze the process than any gains he could possibly make from doing so.
 
Morning John,

I've just PM'ed you. Paid my due's for the new MDAC, but forgot to tell you me PFM ID. Hopefully, it all makes sense.

Sorry for the hassle.
 
Hi John and all,

Would the MDAC 2 digital pre output have a higher output of say,.. up to 5V.

Perhaps we could have a 3 gain select (lo, med, hi) on MDAC 2 ? This would accommodate those low gain power amps.
 
Hi John,
do you think my integrated amp (Arcam A18) and my speakers (Kef R100) will be able to expose MDAC2 sound quality or I need to upgrade something?
 
For me... not much, I rarely use headphones, but, as the MDAC is the best headphone amp I've used, it would be reassuring if it was the best possible.

I know I keep going on about it, but a volume controlled analogue path would be my nirvana...

+1 for the option of a volume controlled analogue input.

Personally, I also don't use headphones, but I've certainly no objection to a delay of a few days to accommodate improvements for those that want it.
 
Dear John,
in July you posted:

"Been thinking about it - I'm going to try to design-in the option to add an Analogue Pre-amplifier board at a later date to the MDAC2... maybe with two pairs of Analogue input with with level control - RCA only inputs due to rear panel space...

The board can be added later - I'll not have time to complete the design before the MDAC2 Mainboard released..."

I wonder if this option is still in your mind. If possible it might be great for all the vinyl lovers around us (no extra preamp needed...).

In any case, thank you so much for discussing all this stuff with the crowd...

Jansen
 
Hi John and all,

Would the MDAC 2 digital pre output have a higher output of say,.. up to 5V.

Perhaps we could have a 3 gain select (lo, med, hi) on MDAC 2 ? This would accommodate those low gain power amps.

Brian,

The MDAC2 will retain MDAC's +3dB option so can swing 3VRms... can I ask what application you need such a High level?

Analogue Gain scaling is a hat full of compromises - We plan too use "Gain Scaling" within the matching amplifiers where the extra Gain is used to improve performance rather then just being wasted as heat (as with analogue attenuation).
 
Morning John,

I've just PM'ed you. Paid my due's for the new MDAC, but forgot to tell you me PFM ID. Hopefully, it all makes sense.

Sorry for the hassle.

Thank you :)

No problems about the missing information, I've forward your PM to Renata I'm sure she can match the details together.
 
Dear John,
in July you posted:

"Been thinking about it - I'm going to try to design-in the option to add an Analogue Pre-amplifier board at a later date to the MDAC2... maybe with two pairs of Analogue input with with level control - RCA only inputs due to rear panel space...

The board can be added later - I'll not have time to complete the design before the MDAC2 Mainboard released..."

I wonder if this option is still in your mind. If possible it might be great for all the vinyl lovers around us (no extra preamp needed...).

In any case, thank you so much for discussing all this stuff with the crowd...

Jansen

The most likely route we will take is to have the AV Bypass RCA's mounted on a separate PCB which is mounted above the MDAC2 mainboard - this can be 'User' replaced later with an Analogue input board with Level control - or even an ADC board... who knows what the future will bring :)
 
...with the sliding bias circuit modulating the standing current if required

Fascinating. How does this configuration "know" when the bias must be adjusted up to real class A? Insertion of a plug into the headphone socket? I can see that you could use the secondary contacts on a jack to achieve that, but most other connectors don't offer that facility.
 
The most likely route we will take is to have the AV Bypass RCA's mounted on a separate PCB which is mounted above the MDAC2 mainboard - this can be 'User' replaced later with an Analogue input board with Level control - or even an ADC board... who knows what the future will bring :)

Thank you for replying! The future sounds very promising...

Jansen
 
Fascinating. How does this configuration "know" when the bias must be adjusted up to real class A? Insertion of a plug into the headphone socket? I can see that you could use the secondary contacts on a jack to achieve that, but most other connectors don't offer that facility.

The Sliding bias circuit operation is transparent to which output is used - basically Bias is set at say 50mA which is then actively increased (Modulated) with the signal content insuring that the output stage is never operated into ClassB (that both halves never switch off over the cycle even into very low impedances).

I'm designing for an 15 Ohm* minim load impedance and a 3VRms swing- the output stage will remain in Class A under these conditions.

*This allows the use of 30 Ohms balanced Headphones with a resultant 6Vrms - in ClassA!!! - hence making the MDAC2 a very decent headphone amplifier!
 
Does a meat holder come with this grill? :D

Considering the Winter months approach - I'm insuring no cold spots on the lab bench...

The real dissipation (heat output) will be low as the peak energy of Music is low... 99.9% of the time the Bias will be idling at the nominal 50mA... Could you image how loud 6Vrms would be on a pair of headphones!

In for low listening levels you could connect a pair of speakers directly to the MDAC2 output.
 
Considering the Winter months approach - I'm insuring no cold spots on the lab bench...

The real dissipation (heat output) will be low as the peak energy of Music is low... 99.9% of the time the Bias will be idling at the nominal 50mA... Could you image how loud 6Vrms would be on a pair of headphones!

In for low listening levels you could connect a pair of speakers directly to the MDAC2 output.
Great combination! Listening via speakers without a dedicated power amp while enjoying the warm air around the MDAC2 (and saving money on a regular heater), now that's something! :)

We probably shouldn't try that at home.
 
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