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MDAC First Listen (part 00110011)

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Mark Dirac said:
Thanks for suggesting that BigDog. If all the 120Vers offer to source their own (recommended) PSUs, then that will speed up delivery for everyone just a smidgen.
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I have no issue with that if it meets the JW seal of approval...and is readily available. I can even see preordering PS if and when it is convenient for you to make recommendation.

JohnW said:
A few hours ago I finally have the Detox electronics costing (14 items missing), but I have idea of pricing for these.... With the UK pound plunging against the US$ I'm still trying to meet the GBP150 cost - we are close....
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I assume that the GBP150 is on top of the GBP50 development cost.
 
good morning John

Can you please clean up your mailbox.
I had tried in vain to send you a PM ;-)
Thank you

greetings
F.S.
 
Fred,

Your MDAC was shipped out to you yesterday :) apart from the bad caps it was in almost new condition :)

Your unit was manufactured late 2011 - so its 5 years old now yet looks pristine :) although your MDAC did complain to me that you use her with RCA outputs and not balanced :)

Email Renata and she will pass you message to me...sorry my mail box is full as I have messages I'd like to keep for our records - I can download, but then its not easy to read through them... :(

I added a few extra PSU tweaks - and note it takes about a week for the new caps to run-in until then it will sound hard and thin.
 
Finally getting some traction on the Detox production, yesterday the electronics pricing and today samples from the manufacturer of the custom crystals.

When I built the prototypes I used crystals selected from the lab parts bin of "unknown origin" that worked very well.

During my trip to China last month I gave the Crystals to local vendors to use as "reference samples" so today I'll test the devices that arrived from China to see if they work as well as the originals used on the prototype.

https://dl.dropboxusercontent.com/u/86116171/Detox Crystals.JPG
 
JohnW said:
Fred,

Your MDAC was shipped back you yesterday :) apart from the bad caps it was almost in new condition :)...
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Hallo John

thank you for your work, short turnaround time and the tweaks !!
and yes my Croft Pre is RCA only....
Perhaps the situation will change with the FDAC ;-)

greetings
F.S.
 
JohnW said:
News on the FDAC's phono stage, for listening test I was kindly lent a Audio Research PH5 phono stage - hopefully it will work better then the Quad 24P... That said I'm not sure where the root problem is with my Vinyl replay. so maybe its not the fault of the Pre amp.

https://dl.dropboxusercontent.com/u/86116171/PH5 Phono.JPG
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It's a long time since I heard an AR stage but the PH5 has a good reputation I be live it uses principles from their reference design which costs an arm and a leg so it should be a good bit of kit to compare to yours.
 
Well I've not had good experiences with AR units in the past - but I'm trying to get to grips with my systems SQ - so every "experience" helps for better or worst :)

Apparently the PH5 is one of there better designs...

I'm going to have to add transformers on the front end for my MC cart.... I'm considering pulling my QC24P apart for its transformers but I will have a second listen to the LL1933's first...

I'll need the luxury of some spare time...
 
JohnW said:
Well I've not had good experiences with AR units in the past - but I'm trying to get to grips with my systems SQ - so every "experience" helps for better or worst :)

Apparently the PH5 is one of there better designs...

I'm going to have to add transformers on the front end for my MC cart.... I'm considering pulling my QC24P apart for its transformers but I will have a second listen to the LL1933's first...

I'll need the luxury of some spare time...
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One point why use transformers I can understand in a valve stage but a solid state pre stage should be possible it could be mounted on a daughter board for those that want the extra gain.Doesn't the AR stage use FETs for input and valves for the output.
 
GWM said:
One point why use transformers I can understand in a valve stage but a solid state pre stage should be possible it could be mounted on a daughter board for those that want the extra gain.Doesn't the AR stage use FETs for input and valves for the output.
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A quick look onside the AR shows 4 paralleled JFETs used on each input (the claimed 5th JFET is used in the current source which IMO is rather missleading).

I'm not sure why the AR's Gain is so low - maybe the JFETS are to noisy for much more...

The FDAC does support MC without transformers (in standard or I/V mode), but noise might be an issue with the lowest output MC Carts.

There is a chance that the support for MC transformers might be dropped altogether pending further listening tests.
 
The ph5 gain is moderately low at 57db, i'd expect 64db for a MC stage, 40-44for MM stage. Noise is stated as 76db below 1mv at 1khz input. It is quite low output voltage though.

If you want a proper MC stage, just say the word.
 
Zion is the new stage from team Paradise. Fully balanced.

Besides there are no more Paradise boards left, apart from maybe the two spares I have upstairs :)
 
JohnW said:
There is a chance that the support for MC transformers might be dropped altogether pending further listening tests.
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I think that would be good. I don't doubt your abilities to implement an excellent mm stage - which means those who want to play with step up transformers before the mm stage can do so if they wish.

But I also feel (way more than) comfortable with what you'd come up with for a (transformerless) MC stage

And anyone can always choose to use any external phono stage they wish at any time.

Treat the MC stage as the best mic preamp you can come up with. I'm still extremely interested in digital riaa above analogue riaa. After all I'm looking at this fundamentally as a DAC with DSP. If I want I can always choose/implement an external phono riaa stage
 
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