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:
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:
Attachments
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:
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:
Attachments
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 ?
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 ?
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
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
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.
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.
Power 5V
Hi Cobra,
Thank you for the information about all the modifications.
I purchased the DA-500 DAC from "Stofnest". He already did some modifications, he replaced the opamps and the diodes. Your little clock-"bug" was also introduced in this nice machine.
- I replaced the power capacitors by larger Panasonics FC
- Installed some bypass amps Vishay MKP 10nF near the mute relay.
- Installed a XY-capacitor in the power cord
- I improved some of the connections made by "stofnest"
This mods makes the DAC even more nice! Easy to do and great improvements.
Now I would like to do the 5V trick with the unused voltage line. The 7812 is getting very hot (is this because the opamps are changed?), so I think this trick is good to relieve the load. And if it sounds better it is even more nice!!
I was wondering where you connected the (-) from your mod?
Did you cut only one power supply line?
May be you can show your connections/ cuts into the attached image.
Thank you!
Hi Cobra,
Thank you for the information about all the modifications.
I purchased the DA-500 DAC from "Stofnest". He already did some modifications, he replaced the opamps and the diodes. Your little clock-"bug" was also introduced in this nice machine.
- I replaced the power capacitors by larger Panasonics FC
- Installed some bypass amps Vishay MKP 10nF near the mute relay.
- Installed a XY-capacitor in the power cord
- I improved some of the connections made by "stofnest"
This mods makes the DAC even more nice! Easy to do and great improvements.
Now I would like to do the 5V trick with the unused voltage line. The 7812 is getting very hot (is this because the opamps are changed?), so I think this trick is good to relieve the load. And if it sounds better it is even more nice!!
I was wondering where you connected the (-) from your mod?
Did you cut only one power supply line?
May be you can show your connections/ cuts into the attached image.
Thank you!
Attachments
Final stage
Hi Inertial,
I can imagine your envy, it has a nice sound, and seems easy to improve it.
I did not think to skip the I/V ic, what is the use of doing this?
- a XY-capacitor is also installed
- I connected the ground to the IEC socket and the XY capacitor
- Extra aluminum is attached to the radiators
- The PSU upgrade uses skottky's a large capacitor and a small bypass cap.
To be honest, i'm not sure if the sound made improvements. . . but The 12v unit doesn't get hot any more. So that is a plus.
When I installed the LME49720NA opamps in the center the dac was interrupted when I switched a light on or off, that is why I installed the XY cap. In the active filters is the Opa BB2134 used (thanks to Stofnest!) I have to change them in the future with the 49720 to check if the sound quality will change.
I think it is ready for now. I only have 2 digital inputs, but when I have more in the future may be I will change the optical ones to coax......
Hi Inertial,
I can imagine your envy, it has a nice sound, and seems easy to improve it.
I did not think to skip the I/V ic, what is the use of doing this?
- a XY-capacitor is also installed
- I connected the ground to the IEC socket and the XY capacitor
- Extra aluminum is attached to the radiators
- The PSU upgrade uses skottky's a large capacitor and a small bypass cap.
To be honest, i'm not sure if the sound made improvements. . . but The 12v unit doesn't get hot any more. So that is a plus.
When I installed the LME49720NA opamps in the center the dac was interrupted when I switched a light on or off, that is why I installed the XY cap. In the active filters is the Opa BB2134 used (thanks to Stofnest!) I have to change them in the future with the 49720 to check if the sound quality will change.
I think it is ready for now. I only have 2 digital inputs, but when I have more in the future may be I will change the optical ones to coax......
Attachments
inertial said:Hi pmd-audio,
I image you are a solid-state guy, I' m a triode guy
The I/V passive would be a step into targeting a modd ala Thoersten Loesch
Cheers,
Paolo
I'm a vacuum tube guy myself, and I've modified CD players that have DACs with I out with I/V passive (resistor) circuits that feed into triode buffers or amplifiers. See
my vacuum tube CD player mods page here
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