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Old 14th February 2007, 04:23 PM   #1
Cobra2 is offline Cobra2  Norway
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Default A little Denon DAC mod

The Denon DA-500 is a simple & fairly cheap DAC, and I found one used for the right price.
It has the BB PCM1702 dac-chips, so it should be possible to modify it into something reasonably well...?

Well, the masters of "don't waste parts", did not sleep in the KISS class.

PSU supply-decoupling is no problem; there are non...

Well, I started with the clock, or, "how to kill the clock".
Since it has a Yamaha YM3623B, I used the suggestion posted here some time ago.
Looks like this:
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Old 14th February 2007, 04:24 PM   #2
Cobra2 is offline Cobra2  Norway
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In dead-bug version, the added parts look like this:
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Old 14th February 2007, 04:25 PM   #3
Cobra2 is offline Cobra2  Norway
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Mounted, it will look something like this:
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Old 14th February 2007, 04:32 PM   #4
Cobra2 is offline Cobra2  Norway
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Then there is the PSU...you can do as much as you want...
Stock it is 7812/7912 for +/- 12v(analog), the 12v is further reduced thru 7805x2/7905 for dac & digital use.

And, wait...there are a unused secondary wire-pair..in mine it gave ~8,5V ac. So I put a bridge on it, a cap, and wired it up to the digital/control-7805, and cut the pcb-trace it used to have.

These few parts were well spent, and made a big difference!
My way:
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Old 14th February 2007, 04:34 PM   #5
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Op-amps were swapped, a few extra caps mounted, DC-blocking caps exchanged...it sounds much better.
If you have a similar unit, Try it!

Arne K
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Old 15th February 2007, 04:33 AM   #6
wa2ise is offline wa2ise  United States
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Question Re: A little Denon DAC mod

Quote:
Originally posted by Cobra2


Well, I started with the clock, or, "how to kill the clock".
Since it has a Yamaha YM3623B, I used the suggestion posted here some time ago.
Looks like this: [/B]

So what does this clock killer circuit do for you? in other words. why do it? Just want to know.
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Old 15th February 2007, 09:59 AM   #7
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Denon DCD-S 10 II clock

http://www.diyaudio.com/forums/showt...491#post282491

Arne K
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Old 17th February 2007, 04:21 PM   #8
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Hi, I did the "clock-shutdown" mod as well, replaced the 4 opamps with opa2134 on sockets, replaced the 4 standard diodes in the psu with skottkey ones, replace the powercord with a iec socket.

Before the mods the sound was nice but a bit dull, and the soundstage had not much depth, it was only wide. Now it has some depth in it.

My questions:
- how can I check if the clock mod did work (I only got a simple multimeter)?
- Do I have to use extra decouple caps on the opa2134's ?
- Can I swap the opa2134 with LM4562NA's (and wich one's as there are 4 of them, say you only got 2 LM4562NA)?
- how can I change the optical inputs to coax inputs ?
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Old 17th February 2007, 05:32 PM   #9
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Check voltage at pin 6, when input is locked, this should be lowered towards 0, as the transistor will be "on", and short the E-C connection, shorting the cap, and "killing" the clock.

I would not waste expensive op-amps everywhere, the 2 closest to DAC (the centre ones), are the output buffers.
The other two are just active filters. Use the "low-noise" 4570 here.
There are 2 DC-blocking caps, close (one on each side) to the mute-relay. Exchange the simple el-lytic caps, or bypass with good film-cap.

Coax instead of optical: do as the other coax-inputs...: add a 7404 (2 ports is used for 1 input)

Now, do the psu-upgrade!

Arne K
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Old 17th February 2007, 08:42 PM   #10
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You can stop the clock on YM3623B with just one 1N4148 diode too ( like Elektor did on their PCM1710 MiniDAC ). Elektor claimed the diodemod to stop the clock makes an improvement of 6 dB in THD+N , measured with a bandwidth of 30 kHz. They also used 16 MHz cristals but this was not enough, although it has no relation with the samplefrequencies it still interfered. Please see Elektor magazine of july/august 1996.

I had one of these DA500s too and modded it to the max as it really suffers from a severe conflict between engineers and the marketing department

I recall the same mods as you did Arne with the spare winding on the transformer but I also recall cutting traces to separate an 78xx that got overheated by design ( just like you did ). It comes to my mind I added an extra one for 5V in the middle of the PCB. You have to check that yourself as it was a long time ago I had the DA500. I also added larger heatsinks and adequate decoupling to the regs.

It became quite good after the mods were done but not too special like most DACs with PCM1702.
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