Sudden MG Head DT Problem
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briantf27

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Hey all,

Been a while since I've on the forums here, and I wish I were back under better circumstances...

In any event, my 1.5 year old MG Head DT (not the OTL) has started acting up just today. It is basically distorting all over the place... It sounds like clipping to me.

Some info: I removed the NF loop about a year ago, but never made other mods (I meant to replace the coupling caps but never got around to it). I've reverted back to the original tubes (the Sovteks and JJ) since they have never been used. The problem is real (not a tube problem) :)

So I thought maybe there was a high voltage problem. I probed the board in a few spots, and the voltages seemed OK. I probed around R13, R14, R15, and R16. Also probed the plates of the 6BQ5s at pins 7, and on the 12AX7 pins 1 and 6. Everything seems to check out there.

What next? I doubt the mylar caps are bad (in fact I don't know what the failure mode of mylar caps would be). Perhaps the C7 and C8,C9,C10 10uF and 100uF caps?

Ideas?

Thanks!!!

Brian.
 
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briantf27

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Well it looks like I spoke too soon.... Turns out that the MG Head is just fine and dandy, but the Cambridge CD player is distorting badly. Must be a bad analog output driver. Haven't tried its digital outs yet...

Thanks for all the responses, though. LOL. j/k


Brian.
 
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ServinginEcuador

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Quote:

Originally posted by briantf27
Well it looks like I spoke too soon.... Turns out that the MG Head is just fine and dandy, but the Cambridge CD player is distorting badly. Must be a bad analog output driver. Haven't tried its digital outs yet...

Thanks for all the responses, though. LOL. j/k


Brian.


Brian,

I have had my D500se for about a week now, running 24 hours a day as I was concerned about problems like you are speaking about. How long did it take for this problem to surface it's head? I hope this thing isn't problem ridden!!!! I guess I will just keep it running a burning in components until I get ready to leave the country again. I would hate to have this thing go bad on me in Ecuador!!!
What is your overall impression of the CDP, not counting the recent problem? I ask as I noticed in your profile that you own a Rega also. After reading some things around the net I have sent away for some output op amp replacements to try and spruce the sound up a little bit. Hopefully it makes a realy good player even better!!!


Lord Bless,
doug p.
 
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briantf27

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Quote:

Originally posted by ServinginEcuador
Brian,

I have had my D500se for about a week now, running 24 hours a day as I was concerned about problems like you are speaking about. How long did it take for this problem to surface it's head? I hope this thing isn't problem ridden!!!! I guess I will just keep it running a burning in components until I get ready to leave the country again. I would hate to have this thing go bad on me in Ecuador!!!
What is your overall impression of the CDP, not counting the recent problem? I ask as I noticed in your profile that you own a Rega also. After reading some things around the net I have sent away for some output op amp replacements to try and spruce the sound up a little bit. Hopefully it makes a realy good player even better!!!


Lord Bless,
doug p.


To be honest, I've never done a head-to-head comparison of the Cambridge and the Rega. The Rega is in my home system (with speakers), and is basically just a transport since I've also got an outboard DAC.

The build quality of the Cambridge is poor, IMO. However the sound quality is not bad for a $300 unit. I think it does alot of things very well. BTW, where did you get these opamps? What kind are they?

Thanks.

Brian.
 
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ServinginEcuador

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Quote:

Originally posted by briantf27
The build quality of the Cambridge is poor, IMO. However the sound quality is not bad for a $300 unit. I think it does alot of things very well. BTW, where did you get these opamps? What kind are they?

Thanks.

Brian.


Brian,

I actually ordered some AD825s from www.upscaleaudio.com Look under Products| Listing of Products by Manufacturer | Ah! Tjoeb 4000 CD player | Other Products & accessories from the Ah! factory | and lastly Ah! Tjoeb Op-Amp flavor kits. This is the same LC Audio plug-in modules available from www.diycable.com BUT.... DIY charges $26.90 each while Upscale only charges $27 per PAIR for the same exact op amps. These are Module 4 branded single op amps that drop right in to replace of the NE5534Ns that are in the CA D500SE.

I also ordered some OPA627s from Burr Brown. I got three for free from them, so I might look into buying three more to compare the different op-amps. (If this is what I think it is, might we coin the term "chiprolling" to describe what I am trying to do!!)
Swapping out chips to achieve the best sound possible?????

Hope this helps in some way!! Maybe you could try some Burr Browns in your CDP to see how you like the sound as compared to the 5534s you currently have????


Lord Bless,
doug p.
 
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Wodgy

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[snip] Answered my own question...
 
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briantf27

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Quote:

Originally posted by ServinginEcuador
Brian,

I actually ordered some AD825s from www.upscaleaudio.com Look under Products| Listing of Products by Manufacturer | Ah! Tjoeb 4000 CD player | Other Products & accessories from the Ah! factory | and lastly Ah! Tjoeb Op-Amp flavor kits. This is the same LC Audio plug-in modules available from www.diycable.com BUT.... DIY charges $26.90 each while Upscale only charges $27 per PAIR for the same exact op amps. These are Module 4 branded single op amps that drop right in to replace of the NE5534Ns that are in the CA D500SE.

Lord Bless,
doug p.


OK, I looked at the Analog Devices modules too. That's a good deal from Upscale. Let me know how it goes, and what your impressions are. If I ever fix the clipping problem with my unit, I might look into it also.

PS... It looks a little tight for space on the PCB. Hopefully those modules fit in there OK without the need for a socket.

Good luck!

Brian.
 
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ServinginEcuador

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Actually, I am having the current 5534's removed and a set of sockets put in to facilitate easy chip swaps in the future!! It also makes sure that the modules fit!! I also found out there are only four op amps in the output path. The other two are for power filtering!! Now I have an extra pair of LC Audio modules to sell!! Anyone interested????


Lord Bless,
doug p.
 
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