Help me decide which ebay dac please?

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Nick
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#376

Post by Nick »

Interesting that you have 50hz and third harmonic of that. If it was from the DAC board supply, I would have expected 100hz.
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Dave the bass
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#377

Post by Dave the bass »

Thanks Andrew, I'm learning.

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#378

Post by Andrew »

Nick wrote:Interesting that you have 50hz and third harmonic of that. If it was from the DAC board supply, I would have expected 100hz.
Ah but, if you will allow an ah but moment, there's no rectifiers on the DAC board. Could it be from the bench DC PSU?

Hmm, suppose 50Hz is getting picked up form the unshielded board, after the bench PSU or the leads, then the balanced output stage would indeed give us a fundamental and a 3rd, just like its doing with the test signal. Does that make sense?

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Dave the bass
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#379

Post by Dave the bass »

:idea: Maybe the bench PSU has switcher circuitry and has some noise on top of the DC?

I've found that happening with Electrophoresis PSU's we repair at work when I've tried to use them as HT supplies for amps. (Well...you don't know unless you try do you :-) )

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Nick
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#380

Post by Nick »

Yes that was my thoight. I also wondered what 50hz getting into the reciever ppl would look like
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#381

Post by Andrew »

I guess I could put in in a box, which is the eventual plan anyway...
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Laurence
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#382

Post by Laurence »

Nick wrote:Centre tapped.
But where it is tapped there are two ends. You could ask bud to bring both ends out. Use a split bobbin and you have two equal in every way windings, where they are normally combined in the centre for the B+ keep them seperate. Two CCS's perfectly matched.

You would loose some signal, and if that "some" affects your stage gain beyond what is acceptable to you? Two decoupling caps will fix it.
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#383

Post by Andrew »

Changing the op amp does indeed seem to improve matters, but not as much as I had been led believe. Perhaps having a better PSU reduces some of the dependency on the op amp quality, that's assuming my PSU is indeed better.

In my humble, still not up with Toppsy's Nue Toob CD player (however, you spell it).

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Ali Tait
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#384

Post by Ali Tait »

Richard mentioned changing the SP/DIF input cap makes one of the biggest differences. Might be worth a try.
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#385

Post by Andrew »

Ali Tait wrote:Richard mentioned changing the SP/DIF input cap makes one of the biggest differences. Might be worth a try.
Thanks, Ali, but I think I've done that one but I'll double check. I pretty much followed the changes on DIY Audio minus the power supply cap changes, for that I just used the existing caps wired out the diodes, changed the regs to the suggested one and fed the thing +-15v and 12 v DC instead of AC.

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Ali Tait
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#386

Post by Ali Tait »

I've still to mod mine, not bought all the parts yet. I did like the way Richard's sounded at Owston. It would have been interesting to have tried his board in my dac.
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#387

Post by richardcooper2k »

Maybe we're expecting too much of this thing.
It's giving me the best sound from digital i've have in my system (although i haven't tried that many things)
My vinyl front end still beats it even with my old 834p phono stage with the volume turned to max as it doesn't have a step up transformer for my low output cartridge (and the wrong impedance input as well)

But it is cheap as chips so i'm not complaining
Let me know when something comes along that is a lot better and doesn't break the bank
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#388

Post by richardcooper2k »

Ali Tait wrote:Richard mentioned changing the SP/DIF input cap makes one of the biggest differences. Might be worth a try.
I was actually just repeating what i had heard Al Newal saying.
I've no reason to doubt it but i never listened to changing this component on its own
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#389

Post by Ali Tait »

If I get time I'll change mine this weekend. Still smarting over one of the landlord's kids deciding to have a poke at the nice shiny gold cone in one of my travelling speakers. At least he's offered to buy me a new pair of drivers.[/youtube]
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Paul Barker
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#390

Post by Paul Barker »

Yes I only changed the opamp which was a very worthwhile change. That was the first opamp change since when i was advised to try a burr brown for a more analogue sound. indeed this worked a treat. i was beginning to get a little tried of listening for long periods with the first changed opamp, which was much more powerful than the original with better bass larger soundstage. the burr Brown didn't give away any power bass or soundstage but removed some critically analytical top end sounds and made prolonged listening more enjoyable.

no it doesn't replace vinyl but it is the first time in my home system digitable has been good enough to actually use it routinely.
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