MDAC First Listen (part 00011110)

[PhilCTTE]

Well I was going to post some measurements of the Quad 520F, but the performance is so unbelievably bad, that I need to regain my composure.

Its not a problem as the intention is to totally redesign the unit - serving as a prototype on the MAMP / MIMP etc. I guess I'm just so surprised that the product was ever approved and sold like this... Quad must have been going though some very bad times to have such a poor level of engineering... I must say, I've lost a lot of respect for them after seeing this design.

I thought my Quad 240's where bad, this design is even worst... basically poor PCB design, but the circuits not great, but no reason why it should be any worst then a Quad 606 etc - in fact it has a larger PSU / Heatsink so it could have been better...

Eek and I've bought 2 of them. I have total faith so basically I've bought a large psu and a case lol

Perhaps the sock will come in useful when you listen to it ...

Will you listen to it before dissecting? The none serviced one you have sounded rougher at both ends but a fuller bass. At first I thought it was better and more solid bass but decided that there was just more of it, as I noted previously. I level matched it by ear and turned the input trim down, so it want just the volume at play.
Hope it helps with your design implementation.

 

[JohnW]

Eek and I've bought 2 of them. I have total faith so basically I've bought a large psu and a case lol

Well it was always going to be stripped - indeed when you look at it that way its the Case / PSU / Connectors etc that are going to be reused - The internal Electronics is not a problem for me - Mechanical is the issue.

Perhaps the sock will come in useful when you listen to it ...

Yes - my Left ears still a little blocked by my recent bout with the Flu / Cold - so I can just stuff the SINGLE sock into my Right ear!!!

Will you listen to it before dissecting? The none serviced one you have sounded rougher at both ends but a fuller bass. At first I thought it was better and more solid bass but decided that there was just more of it, as I noted previously.

The measured noise floor at 1W is truly terrible - its being modulated by shot noise of the Zener diodes used to regulate the power to the DC Servo Op-amp - the ground plane is being heavily contaminated by the "Zener injected noise" due to bad PCB layout - this will make a mess of the Bass response - and I bet inject RF crud at the top end...

Years ago I would have done anything to work for a company such as Quad - but being "unknown" it would have been near impossible from me to get a job with them - yet when you see the level of engineering they produced at that time its truly disgraceful - even at such a young age (back when the unit was produced) I would have been able to design without such basic mistakes... I say this with a heavy heart as I'm so fond and aware of Quads legacy and contribution to the British Hi-Fi industry.

The original idea was to compare your unit both in standard and modified form with the 520F I won via Ebay (which I've paid for, but not yet arranged collection)... But it hardly seems worthwhile to pay the GBP100 pounds shipping asked by the seller just for a "comparison unit" - so I'll listen to your unit maybe against my lab Amp to form a "mental picture" of its sound quality - and see how its sounds by comparison after redesign

Once I've completed the MDAC2 Analogue board PCB design - I'll spin an Amplifier PCB design which I'll build into your unit I need a good amp to test the MDAC2 with

 

[PhilCTTE]

Okay I wondered how this was going to fit in with the timescales of the Mdac2 design and production. Certainly didn't want to hinder any progress.

I can ship my other 520f if you need a second ? Only cost me £30 un-insured

I,ve found that if I drink alcohol headphone listening is bearable , otherwise they irritate the hell out of me. So not a problem losing the second quad. Especially if I can at a later date forward funds to upgrade that one as well

Did Nick collect the other quad or do need assistance with the pick up from Coventry?

 

[jirij]

John, if you happen to have some extra amp lying around, please let me know. I'll be buying some bookshelves (probably Dynaudio DM2/6, demo @ Olomouc) and would like something as neutral as possible to power them (optimally 75W per channel).
Thanks, Jiri.

 

[JohnW]

John, if you happen to have some extra amp lying around, please let me know. I'll be buying some bookshelves (probably Dynaudio DM2/6, demo @ Olomouc) and would like something as neutral as possible to power them (optimally 75W per channel).
Thanks, Jiri.

Jiri,

I have x4 Quad 240's I plan to use as "salvaged units" - I'll hope to capitalise on the design work on Phils Quad 520 and the Quad 240's... these will form prototype MIMP / MAMP chassis... (you can borrow one of these units for free as I'll not be doing much with them until I complete the MDAC2 Analogue board design).

Or I also have a Audiolab M-PWR that I've turned into a Mini Super Amp that now I've had my fun confirming Computer simulations - I'd like to sell the Super MPWR to convert it back to cash... The MPWR is Black and will match your MDAC...

The "Super" MPWR is now better sound quality then the Quad 240 in standard form (amongst other tweaks, the "Super" MPWR has been biased into ClassA operation for the first 0.5 Watts or so)... but of coarse I plan that once modified the Quad240's will be in a reference league... but dont hold your breath on there time-scales...

If anyone interested in the "Super MPWR" as a temporary solution until the MAMP / MIMPs are ready than I'll offer the MAMP or MIMP "at cost" to the buyer of the S-MPWR....

 

[JohnW]

Okay I wondered how this was going to fit in with the timescales of the Mdac2 design and production. Certainly didn't want to hinder any progress.

I can ship my other 520f if you need a second ? Only cost me £30 un-insured

I,ve found that if I drink alcohol headphone listening is bearable , otherwise they irritate the hell out of me. So not a problem losing the second quad. Especially if I can at a later date forward funds to upgrade that one as well

Did Nick collect the other quad or do need assistance with the pick up from Coventry?

Nick has kindly offer to collect the 520 - But I've not given Nick the details as I feel very embarrassed to put anyone out... apparently its about a 20 Minute drive... and I just feel bad...

If you can solder a XLR lead, then I might have an idea that could improve your units SQ, also is your second unit a 520 or 520F??? maybe if you could lift the lid and take internal pictures...

 

[jirij]

Jiri,

I have x4 Quad 240's I plan to use as "salvaged units" - I'll hope to capitalise on the design work on Phils Quad 520 and the Quad 240's... these will form prototype MIMP / MAMP chassis... (you can borrow one of these units for free as I'll not be doing much with them until I complete the MDAC2 Analogue board design).

Or I also have a Audiolab M-PWR that I've turned into a Mini Super Amp that now I've had my fun confirming Computer simulations - I'd like to sell the Super MPWR to convert it back to cash... The MPWR is Black and will match your MDAC...

Thanks a lot for the offers, I'd go for one of the 240's as I'd still like to buy one or two of your own amps, once they're ready. It would just be nice to have something in the meantime.

 

[JohnW]

Thanks a lot for the offers, I'd go for one of the 240's as I'd still like to buy one or two of your own amps, once they're ready. It would just be nice to have something in the meantime.

they are quite light so no problem to carry

 

[Malyq]

If anyone interested in the "Super MPWR" as a temporary solution until the MAMP / MIMPs are ready than I'll offer the MAMP or MIMP "at cost" to the buyer of the S-MPWR....

Hi John,

I need a solution until your amps are ready, hence I'm interested in your offer to buy the S-MPWR - what is the price for it?

Regards
Malyq

 

[PhilCTTE]

Nick has kindly offer to collect the 520 - But I've not given Nick the details as I feel very embarrassed to put anyone out... apparently its about a 20 Minute drive... and I just feel bad...

As you are doing me a favour , I have no problem returning one ...
I used parcel2go std service which cost £30 which was collected from my work ... If seller is not willing to wait for the collection I could go get it and send it on ?

 

[giannitom]

Hello John,
can you summarize the status of the MDAC2 development? What about the analog stage?What has been decided about the development in two phases of the digital stage?

Thanks.

 

[JohnW]

Hi John,

I need a solution until your amps are ready, hence I'm interested in your offer to buy the S-MPWR - what is the price for it?

Regards
Malyq

Hi Malyq

A standard MPWR sells for GBP500 - how about GBP400 + Postage? (and you get the MAMP or MIMP "at cost" once they are ready) - and I'll also include a Pair of decent quality 50cm XLR cables so your ready to go

Its far better sound quality then a standard MPWR - but I don't think the standard MPWR offers good value for money.... and at the end of the day you can get an MAMP or MIMP at cost once they are ready

Its heavily modified (as part of the modifications the RCA inputs have been disabled - only the XLR inputs are functional for best performance with the MDAC) - it also gets slightly warm as its operating higher then normal in ClassA - so its a good idea to leave space above the Amp and the MDAC - although the XLR leads are only 50cm long... (the MPWR has vents on its top lid, maybe best to put the MDAC under the MPWR or above it on a second shelf if the leads can reach)...

It would go well with your Fusioned MDAC which has bundles of detail, the S-MPWR gets you foot tapping - its a fun little amp

 

[Nick1881]

Nick has kindly offer to collect the 520 - But I've not given Nick the details as I feel very embarrassed to put anyone out... apparently its about a 20 Minute drive... and I just feel bad...

If you can solder a XLR lead, then I might have an idea that could improve your units SQ, also is your second unit a 520 or 520F??? maybe if you could lift the lid and take internal pictures...

John, It's really not a problem, I have a company car too so it's not like you need to worry about that either

 

[JohnW]

Hello John,
can you summarize the status of the MDAC2 development? What about the analog stage?What has been decided about the development in two phases of the digital stage?

Thanks.

Now I've come to terms with the idea that the MDAC2 will be based on two PCB's with the "Analogue section" which includes the twin ESS DACS, Clock, Analogue stage, and PSU on one PCB with the Digital section on a totally separated (and Isolated) PCB above, I can now optimise the layout of the Analogue board with a "Dual Mono" type arrangement .

I've been going back and forth with the design of the analogue stage - the MDAC2 ClassA stage and the power amplifiers share the same topology so as I work on one it feedbacks to the other design - its why I've been slightly distracted on the Amplifiers as feedback from simulations and listening results are applied to the MDAC2 design - I'm now in the process of updating the MDAC2 schematic with lessons I've learnt while experimenting with the Amps - small but important changes.

The "Analogue" board should be ready in 2 months while, the MDAC1.5 Digital board will be design in parallel by Dominick to help speed up the release of a working design, helping to alleviate pressure.

We also will design the MDAC2 with consideration to future "Upgrade" to the Tube output stage based on recent successful measured performance tests.

 

[JohnW]

As you are doing me a favour , I have no problem returning one ...
I used parcel2go std service which cost £30 which was collected from my work ... If seller is not willing to wait for the collection I could go get it and send it on ?

Worth considering (thank you), but you live even further then Nick... I worry about the amp sitting with the seller (now that I paid for it)...

 

[JohnW]

John, It's really not a problem, I have a company car too so it's not like you need to worry about that either

OK Nick, thank you, Ill forward the details of the seller and you can arrange with him the collection time - thank you

As I say, I don't need the Amp at this time, so I'm more then happy for you to hold onto it and try it out

 

[Malyq]

Hi Malyq

A standard MPWR sells for GBP500 - how about GBP400 + Postage? (and you get the MAMP or MIMP "at cost" once they are ready) - and I'll also include a Pair of decent quality 50cm XLR cables so your ready to go

Its far better sound quality then a standard MPWR - but I don't think the standard MPWR offers good value for money.... and at the end of the day you get an MAMP or MIMP at cost once they are ready

Its heavily modified (as part of the modifications the RCA inputs have been disabled - only the XLR inputs are functional for best performance with the MDAC) - it also gets slightly warm as its operating higher then normal in ClassA - so its good to leave space above the Amp and the MDAC - although the XLR leads are only 50cm long... (the MPWR has vents on its top lid, maybe but the MDAC under the MPWR or above on a shelf)...

It would go well with your Fusioned MDAC which has bundles of detail, the S-MPWR gets you foot tapping - its a fun little amp

That's a really great offer, which I cannot other than accept, thanks a lot, John
How do we proceed? Postage to Germany was 30£, if I remember correctly? Should I pay you the amount of 430£ via PayPal? Please submit me the details per PM! Thanks you very much!

 

[JohnW]

Malyq,

Your unit has been shipped

As part of the modifications I reduced the Gain of the amplifier so that under normal listening levels you don't require high levels of digital attenuation - I found normal listening levels where about -18dB, and the loudest we listened to was at -3dB, the MDAC can be set to +3dB so we could have still gone twice as loud - but it was already at "Party Levels" at -3dB.

If you find that the level is too low for your system / speakers then I can increase the level by an extra +6B... but it would need to be shipped back to Czech Rep.

I'm missing the unit already - I really need to sort out my lab Power Amps....

Interest what you think of your new Amp once you get to listen to it

I realised that the Power lead included was a UK version - so I swapped for a power lead from my Lab (Sorry its not new).... The Balanced interconnects are packed in the smaller white box.

 

[Malyq]

Malyq,

Your unit has been shipped

As part of the modifications I reduced the Gain of the amplifier so that under normal listening levels you don't require high levels of digital attenuation - I found normal listening levels where about -18dB, and the loudest we listened to was at -3dB, the MDAC can be set to +3dB so we could have still gone twice as loud - but it was already at "Party Levels" at -3dB.

If you find that the level is too low for your system / speakers then I can increase the level by an extra +6B... but it would need to be shipped back to Czech Rep.

I'm missing the unit already - I really need to sort out my lab Power Amps....

Interest what you think of your new Amp once you get to listen to it

I realised that the Power lead included was a UK version - so I swapped for a power lead from my Lab (Sorry its not new).... The Balanced interconnects are packed in the smaller white box.

Great - many thanks, John I'm so curious about it and about how it will perform in my system. I'll report next week, when I've had the time to give the amp an extensive listen!

 

[PhilCTTE]

It was sold as a 520f.
I will take a peek under the hood and take photo later tonight.

Cheers