Hi,
I have a MF A3.24 DAC with a failure of the coaxial digital input. The Optical input work OK and the DAC works and sounds great. My only problem is the coaxial input.
Anyone has experienced this problem? Can you recommend how to approach this repair?
If someone on the forum has the schematic for the A3.24 DAC that would be great.
Thanks,
Ronen
I have a MF A3.24 DAC with a failure of the coaxial digital input. The Optical input work OK and the DAC works and sounds great. My only problem is the coaxial input.
Anyone has experienced this problem? Can you recommend how to approach this repair?
If someone on the forum has the schematic for the A3.24 DAC that would be great.
Thanks,
Ronen
I would guess that the problem is the IC10 the DS266L532CM as it it the only active device that would stop the coax input as the optical comes in after this.
Also are you sure it's not the coax output of your transport before you start ripping into this?
Cheers George
Also are you sure it's not the coax output of your transport before you start ripping into this?
Cheers George
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I have the same unit. Sometimes the signal fails to "lock" unless one cycles power. As you probably know, the bright blue LED in front indicates signal lock. Is it on?
If cycling power does not fix the problem, you'll need to get inside the unit to troubleshoot. For that you'll need a #10 Torx security wrench/bit.
As far as the schematics ... good luck. I've tried to obtain these myself but this company -- like many "high-end" audio/video companies -- are highly protective of their designs and only supply circuit schematics to official dealers or repair facilities. (Check MF's web site for more info on this.)
Frankly, my disgust with companies like this -- and all the high-end magazine kiss-*** politics that promote their so-so over-priced products -- is why I pretty much went DIY. It's way less $, way more fun/rewarding, the camaraderie/support (via DIY forums) and open availability of info and schematics is unparalleled, and (IMO) the end product actually performs better. An example of this is mod'ing one of the latest Toshiba CD/DVD players (see this page for more info)). For about $90 -- that includes the price of a new player ($40), readily-avail. schematics ($20), and a few upgrade parts ($30: op-amp, rope caulk, etc.) -- I have attained Red Book playback that sounds better than the A3-24. I also have a decent DVD player, whose performance also improved via the mod. And I don't need a special $10 bit to get inside it!
Okay … I'm stepping off my soapbox, now
If cycling power does not fix the problem, you'll need to get inside the unit to troubleshoot. For that you'll need a #10 Torx security wrench/bit.
As far as the schematics ... good luck. I've tried to obtain these myself but this company -- like many "high-end" audio/video companies -- are highly protective of their designs and only supply circuit schematics to official dealers or repair facilities. (Check MF's web site for more info on this.)
Frankly, my disgust with companies like this -- and all the high-end magazine kiss-*** politics that promote their so-so over-priced products -- is why I pretty much went DIY. It's way less $, way more fun/rewarding, the camaraderie/support (via DIY forums) and open availability of info and schematics is unparalleled, and (IMO) the end product actually performs better. An example of this is mod'ing one of the latest Toshiba CD/DVD players (see this page for more info)). For about $90 -- that includes the price of a new player ($40), readily-avail. schematics ($20), and a few upgrade parts ($30: op-amp, rope caulk, etc.) -- I have attained Red Book playback that sounds better than the A3-24. I also have a decent DVD player, whose performance also improved via the mod. And I don't need a special $10 bit to get inside it!
Okay … I'm stepping off my soapbox, now
Maybe it's the way you ask, I receieved it (see previous post) this is only part of the circuit I have the rest if needed posted at other threads do a search under my name and you'll shall find all.
Also this dac is very good sounding out of the box, and if you do my dc coupling and I/V mods also in previos threads, it is so far unbeatable.
Cheers George
jean-paul said:
Yes: TR10.
An externally hosted image should be here but it was not working when we last tested it.
I ended up getting
this Security Torx Fold-Up Keys Sets , which actually cost more than the $10 I noted earlier. I think the $10 tool was/is avail at Lowe's or Wal-Mart.
georgehifi said:
I assume this is the thread you're referring to. Although I've already played around with swapping op-amps -- using AD8620, OPA627, etc. -- and still think the moded Toshiba sounds better, I did not remove/replace-with-better/short-out the output caps. To that end, some Q's...
- In the aforementioned thread you wrote "put a digital multimeter on the output and earth". Do you mean put one lead of meter on the output JACK (hot side)?
- Would you recommend this same mod (one that uses 5k cermet mini pots) for DACs in general?
Thx
hollowman said:
No the mod for DC coupling the output, only applies to this (A3.24) Dac as this DAC has a very powerfull low impedence discrete output stage.
The IC change is for the I/V stage which changes out the two NE5532's for 4 AD825's smd.
The DC coupling mod greatly enchances the sound, as does the I/V IC mod to a lesser degree.
Cheers George
hollowman said:
Don't quite know how to put this, but if you need to ask this, I suggest not to do any of the mods. But yes the dc offset is measured in dcmv at the output, red lead hot and black lead ground, if it is capacitor coupled you will measure zero, if the cap is removed as per the mod you will measure 20-50 or more dcmv which then can be nulled out with the 5k cermet pots, but watch out for muting relay on the output, otherwise it will give wrong readings of zero if in mute condition. Hope this is clear enough, but suggest you get a tech to do the mods.
Cheers George
jean-paul said:
They call it a Security Torx bit. I think companies like MF use them so that it's harder for people to look under the hood at their family jewels. Same reason they do not sell/supply schematics to all but a select few.
Frankly, with all the great-sounding DAC DIY plans/designs on the Internet -- most avail for free on forums and private web sites -- I personally can't reasons to go to this anal level of security.
georgehifi said:
Hmm...I usually remove muting transistors from the CD players I mod. I've been cautioned by others about the potential hazards of doing this. But this mod is also suggested by other DIYers so I'm a bit tossed. Removing them from myriad players I've moded have, thus far, never given me any problems, even at power up/down. Other than power up/down, when else are the muting transistors/relays supposed to-- or do -- kick in? I.e. under which conditions?
hollowman said:
Muting transistors can have an effect on the quality of sound, but good quality double pole muting relays are a very good idea, they have no effect on the sound, and can save your poweramp if something goes wrong esspecially on the the A3.24 with it's huge output capability.
Cheers George
Update on MF A324 upgrade
I've been listening to the georgehifi-based A324 revamp for a few months now and I think it was quite a significant upgrade. I completed the project in phases, and then had to wait out the burn-in period before commenting!
Since you (George) have the schematics (post earlier in this thread), I was wondering if you also have the parts list for this model. The schematics are pretty hard to read; and even then, they don't list component values.
Also, in this post , you mentioned upgrading to a Tent Labs clock, but I'm not sure if you were specifically referring to replacing the A324's clock. If so, did you have any issues with the fact that the A324 originally uses a 50.000HHz clock, while the fastest Tent model, TTBOMK, is ~45MHz?
Any other tips you may have for this unit are also welcome.
I've been listening to the georgehifi-based A324 revamp for a few months now and I think it was quite a significant upgrade. I completed the project in phases, and then had to wait out the burn-in period before commenting!
Since you (George) have the schematics (post earlier in this thread), I was wondering if you also have the parts list for this model. The schematics are pretty hard to read; and even then, they don't list component values.
Also, in this post , you mentioned upgrading to a Tent Labs clock, but I'm not sure if you were specifically referring to replacing the A324's clock. If so, did you have any issues with the fact that the A324 originally uses a 50.000HHz clock, while the fastest Tent model, TTBOMK, is ~45MHz?
Any other tips you may have for this unit are also welcome.
Re: Update on MF A324 upgrade
This is the best I can do off the A3 service diagram, it has all the values, as for more mods, yes you can do the Tent XOdac mods, I have not done this yet but Guido Tent has and he told me it made a significate upgrade to the A3.24, he was very expressive on how good it sounded, it is expensive and time consuming mod.
I have been doing some more on the I/V stage, as I have found out that maybe all the you beaut voltage feedback opamps (Ne5532, AD825 OPA627's and such) that we are playing around with are not the ideal for I/V use from a current output dac.
What is needed in this position apparently is a current feedback opamps, which there has not been too much said about in these forums.
I have ordered the AD844 current feedback opamps to see what the apparent massive difference is all about, people like Krell have known this for some time and have been using it for their I/V stages. Here are couple of only a few postings about it. I cannot wait to hear what the differences are going to be.
http://www.essex.ac.uk/ese/research...Current steering transimpedance amplifier.pdf
http://www.pedjarogic.com/1541a/rev0.htm
http://www.pedjarogic.com/1541a/rev1.htm
Cheers George
hollowman said:
This is the best I can do off the A3 service diagram, it has all the values, as for more mods, yes you can do the Tent XOdac mods, I have not done this yet but Guido Tent has and he told me it made a significate upgrade to the A3.24, he was very expressive on how good it sounded, it is expensive and time consuming mod.
I have been doing some more on the I/V stage, as I have found out that maybe all the you beaut voltage feedback opamps (Ne5532, AD825 OPA627's and such) that we are playing around with are not the ideal for I/V use from a current output dac.
What is needed in this position apparently is a current feedback opamps, which there has not been too much said about in these forums.
I have ordered the AD844 current feedback opamps to see what the apparent massive difference is all about, people like Krell have known this for some time and have been using it for their I/V stages. Here are couple of only a few postings about it. I cannot wait to hear what the differences are going to be.
http://www.essex.ac.uk/ese/research...Current steering transimpedance amplifier.pdf
http://www.pedjarogic.com/1541a/rev0.htm
http://www.pedjarogic.com/1541a/rev1.htm
Cheers George
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