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MDAC first listen (part XVII)

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Oddly enough my MDAC is starting to play up regularly; more often than not now I can't get any sound out of it until I've switched it off and on and perhaps fiddled with different sources. Last night it took almost 5 minutes to get a sound out of it, despite it showing input signals at times. The speakers were silent (and, yes, they were turned on). Eventually got it to work. Most odd.

This happens with different sources and doesn't now appear to be related to the source selected - it wasn't playing on opt1 (tv), coax1 (cd) or USB (SBT) and I had a similar issue when the Mac Mini was connected on USB.

It seems to be getting worse; any ideas?
 
Oddly enough my MDAC is starting to play up regularly; more often than not now I can't get any sound out of it until I've switched it off and on and perhaps fiddled with different sources. Last night it took almost 5 minutes to get a sound out of it, despite it showing input signals at times. The speakers were silent (and, yes, they were turned on). Eventually got it to work. Most odd.

This happens with different sources and doesn't now appear to be related to the source selected - it wasn't playing on opt1 (tv), coax1 (cd) or USB (SBT) and I had a similar issue when the Mac Mini was connected on USB.

It seems to be getting worse; any ideas?

HI JTC,

Does it cause trouble after power-up or die during use?

What software version are you using?

Next time it causes issue try cycling though the filters to see if this restores sound.

I've pretty much nailed down the hardware updates we plan to perform on the MDAC Mainboard as part of the MPAX upgrade package. I could take a look at your unit while also upgrading your MDAC's Mainboard (so you have partial benifits of the upgrade in advance of the full PSU package).

This would mean that once the MPAX is ready you can perform the internal PSU PCB upgrade yourself - and at least I would have loosen the MDAC screws that can be a total pain to remove...

John
 
After power-up (or, should I say, when I return to it not having powered it down (I leave it on all the time)). Though resetting the power doesn't always help. It's on A08. Cycling filters doesn't help (have tried). Shall I just send it to you (I won't be without music as I still have my CDQ also)? As I'm planning to go down the MPAX route this might make sense. Would this be a sovereign-style update incidentally :grin: ???
 
After power-up (or, should I say, when I return to it not having powered it down (I leave it on all the time)). Though resetting the power doesn't always help. It's on A08. Cycling filters doesn't help (have tried). Shall I just send it to you (I won't be without music as I still have my CDQ also)? As I'm planning to go down the MPAX route this might make sense. Would this be a sovereign-style update incidentally :grin: ???

Yes - OK, lets get it over to me to see what's going on :)

I'll PM you with my details...

John
 
Sounds like a fair challenge.... Tiny MiniAmps verse the "The Black Monolithic Beasts" :eek:

:)

Just received everything I need to solder some XLR cables. Now all I need is a pair of MIMPs.

Can't wait to test your new amps. Only a few more weeks, I guess.

Michael
 
For the very best performance - we have decided to upgrade the MDAC's internal PSU PCB - while this is quite an easy procedure to perform - I can understand why many would have a problem opening there MDAC - so the MDAC's will need to be sent to Czech Rep. for upgrade.

We also plan to offer a Mainboard performance tweak to go with the upgrade - this makes a significant difference (as you already know :) )

Hi John

I have also missed this.

Does the MDAC's internal PSU PCB upgrade replace the need/benefit of the MPAX or would it still be required to provide additional improvement or would you gain all the benefit by just fitting the MPAX, when it becomes available?

What is involved with replacing/upgrading the internal PSU PCB for somebody who is reasonably competent and can the Mainboard performance tweak only be done if the MDAC is sent to Czech Rep? In either/both cases are they just simple swap outs or would setting up and/or other checks be require after the upgrades have been made?

What is the cost for the DIY option (if possible/practicable) or for sending back to the Czech Rep for you to do in-house?

What would be the position with the remaining warranty?
 
Yes, indeed - but for those who are not based in Europe the above unit might be ideal :)

Also, its available now... :rolleyes:

Hi John,

I continue to be amazed by the VFM products that you have created, such as the mdac. While I understand your refusal to sell your new products outside of Europe, this sale restriction is a huge disappointment for folks from the rest of the world, who have seen and experienced the amazing products that you created. I am even prepared to accept all shipping and custom charges both ways, and have a UK shipping address, but that will amount to nothing if you plan to not sell to anyone outside Europe.

I hope one day, perhaps overseas distributors will be appointed, or that customs authorities in your part of the world will be in better shape.

Best,
Leon
 
V0.96 does sound different to me but it is very small, much bigger change when going from the 0.9x to A.xx.
V0.99 also has the best voicing which can be a treat to use every now and again. None of the A.xx attract me at all.

My opinion is that 0.96 is better than 0.90.

PS: John, do you use RCA or XLR for your SQ comparisons?
 
Sprint,
There's a main board upgrade replacing a few op-amps and jfets. Then there's a mooted rectifier smoother board upgrade (not finalised yet) and the external MPax.

The main board stuff works with anything, mpax will work with anything and the Rectifier smoother board will likely just work with an external DC psu, (Mpax)

i think that's it.
 
I'm so perturbed by there transient "distortions" that I cannot shake my bias against them (the non Optimal Transient filters) - so I'm not very keen to spend much time listening.. we will release a Beta soon for user feedback :)

John

Hi John, would you describe non-techically what "transient distortions" sounds/feels like in real, daily listening? :) I'm looking forward very much to testing the beta too. :)
 
Hi John, would you describe non-techically what "transient distortions" sounds/feels like in real, daily listening? :) I'm looking forward very much to testing the beta too. :)

A very good CD (Music) for identify what I consider "FIR" Filter type "Distortions" is "The Wailin Jennys 40 days" this has well recorded stringed instruments and female vocals.

If you listen to the above CD's paying attention to the "resolution" of the Stringed instruments you can hear that the Optimal Transient filters clearly allow you to hear each string "vibrate" as the bow slides across them - while this "transient" type signal is smeared with the other filters. Once you start to recognise this effect it becomes obvious when listening to other filters.

I believe you can "train" your brain to identify a deficiency (distortion) in the replay process - and once "Trained" its very unforgiving...

Layered Female Vocals are also an area where the optimal transient filters excel... (The Wailin Jennys 40 days) being a very good disc.

You need a High resolution system - the speakers are very important here....

At IAG we used a pair of Monitor Audio speakers which where very good (normally I'm weary of metal dome tweeters)... Oddly, the Quad ESL's we tried where really poor (atleast the pairs we tried to use in China)... While the CLSII where like a magnifying glass...

John
 
Hmm... but MPAX will output DC or AC? I'm confused :)

The MPAX is a "Current source output" - in fact 5 current sources - 4 for the analogue stages and the last for the Digital stage.

The upgraded PSU PCB in the MDAC converts the Current inputs from the MPAX into 5 ultra low noise / Low impedance voltage sources.

By implementing current sources, the resistance of the Mini-Din interconnect between the MPAX and MDAC is no longer detrimental to performance - in fact it adds additional isolation and RF attenuation - which is now beneficial instead of being detrimental to performance if conventional voltage output was used.

John
 
A very good CD (Music) for identify what I consider "FIR" Filter type "Distortions" is "The Wailin Jennys 40 days" this has well recorded stringed instruments and female vocals.
Hi John, thanks for your explanation, I've just listened to some tracks of "The Wailin Jennys 40 days" on Youtube and discovered that it is actually quite my kind of thing, quality of recording aside. :)
 
Does the MDAC's internal PSU PCB upgrade replace the need/benefit of the MPAX or would it still be required to provide additional improvement or would you gain all the benefit by just fitting the MPAX, when it becomes available?

The Upgrade PSU card in the MPAX can only be use with the MPAX as its a five input / output Current to voltage converter.

What is involved with replacing/upgrading the internal PSU PCB for somebody who is reasonably competent.

1. Removing the 8 screws holding the Front and Rear panels of the MDAC together. (on some units these are so tight it can take significant time to remove them - one unit I recently worked on damaged 4 Torx tool bits!!!)

2. Partially remove front panel, unplugging the Flex Foil cable to the front panel. Once unplugged fulry remove front panel.

3. Slide-out Main PCB / PSU PCB with Rear panel (sliding out rearwards). As you slide out the PCB's, note how they are held within "Grooves" in the MDAC extrusion, when reassembling you will need to insure that both the Mainboard and PSU PCB slide back, held within these "Grooves / rails"...

4. Undo the two screws holding the PSU PCB to the rear panel.

5. Unplug the power connector from the PSU PCB to the Mainboard PCB

6. Remove power switch cap (Black or silver) from original PSU PCB and fit to the new upgrade PSU PCB

7. Reassemble the MDAC in reverse order, but fitting the replacement PSU PCB. (Do not forget to reconnect the power connector cable from PSU board to Mainboard + front Panel flex-foil cables).

8. Upload the new software to the MDAC via USB...

Can the Mainboard performance tweak only be done if the MDAC is sent to Czech Rep?

Yes the Mainboard upgrades can only be performed in Czech Rep. as we have to replace SMD components, carefully add Wiring modifications and test on an FFT analyser.

What is the cost for the DIY option (if possible/practicable) or for sending back to the Czech Rep for you to do in-house?

No Discount for the MPAX package - but you save on the cost of shipping. The Mainboard upgrades are extra - I'm thinking GBP199 without the MPAX, GBP 100 extra with the MPAX... Lets see what JTC and SQ think about the performance of the Mainboard upgrade without MPAX) - figures will be crossed here!...

What would be the position with the remaining warranty?

We take on the warranty obligations for the MDAC "package"

John
 
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