For the sake of a few pence, you should replace them all!!! I cam also recommend replacing the caps in the filter section with styrene or maybe even smt pps could be an option. See post 1 for rays list. The filter mods are a definite worthwhile if you plan to retain an opamp output stage.
If you can do without the on/off switch Ben, you can fit a large transformer behind the transport, that way you could leave the original TX in situ?
Hi guys, i have been sticking the trafos on the back panel, it is getting really crowded. The last one to do for now is trafo for the servo. BTW-is the DOS upgrade is much better than the op-amp- LMA49720?.
Quan
Thanks for your replies about the filter section. I'm building the DOS board and I just ordered a pair of mundorf output caps and two super regulators. The whole idea is to make the DOS the output stage of my behringer SRC2496 and I'm almost there. I hope the results are good after all the effort. I'll post some pictures when I'm done.
Ben: Good news you managed to fit the tx, I'm curious to hear your improvements soundwise.
Ben: Good news you managed to fit the tx, I'm curious to hear your improvements soundwise.
Hi, definately worth spending the extra on decent mundorf output caps....a good choice.
What regulators are you using? Personally I've found that although the DOS doesn't actually need high current to run, it certainly sounds much better using regs that will react fast and deliver high current from an massively oversized transformer
What regulators are you using? Personally I've found that although the DOS doesn't actually need high current to run, it certainly sounds much better using regs that will react fast and deliver high current from an massively oversized transformer
Thanks Ian. Yes, I think you're just right about the regs. I was experimenting with LM317 regs (as explained on Ray's site) and found that they need a lot of load current (>100 mA) to have a good ripple rejection (reading the datasheet). I tried a load resistor but it became to hot. So that's why I decided to spent some money on super regulators, since that seems to be the ultimate solution anyway. I ordered 2 Belleson 15V super regs at pcx, because they offer 25% off this month. The regs can deliver 500mA current max. I hope I made a good choice, because I'm quite a newbie with diy audio and I also have to take care of the economics.
Last edited:
I listened for a couple of hours last night and a little more this morning. If there's an improvement then it's pretty subtle. I'm afraid at first listen, it doesn't come close to the big leap forward that I got from beefing up the smoothing caps and adding the separate 5v supplies with good local decoupling. There's also unfortunately some low-level mains hum coming through in stop mode that I'm certain wasn't there before. That's strange because I've kept the transformer and all new wiring comfortably over in the 'mains corner' of the box.
Ah, nope, I'm still on 8v regulators. If that's it then that's great - I'll pick some new regs up on the w/e. On the bright side, it's nice to get some affirmation that I'm not completely on crack when I do hear big improvements. The placebo effect of that meaty toroid and its celebrated benefits ought to have been pretty high. Any idea why I might have the new hum?
Hi Ian, the two ground wires from the new tx are connected to u309 and the secondaries either side. They're well soldered as far as I can tell. There's not a specific way round for them, is there? I'm guessing not. The only thing I did see was one of the yellow ground insulation sleeves from the original tx that's still connected to u309 appears to have two wires coming out of it, but only one is connected. The player sounds great, don't get me wrong, just not significantly improved as far as I can tell. The hum is only audible with the volume turned up high, but it's still worrisome.
What do you other transistorless guys hear when you max out your volume, if you don't mind me asking - is it just hiss from the DAC, or do you hear some mains noise as well?
What do you other transistorless guys hear when you max out your volume, if you don't mind me asking - is it just hiss from the DAC, or do you hear some mains noise as well?
Last edited:
I tried and it works. Measured the voltage after running for an hour and there
is no sag, only the regulator is hot but touchable
My xo clock is fed to pin 28 of DAC chip How do I feed the clock to decorder direct? Is it feed to pin 13 of the decoder and ground pin 13?
Appreciate help
Does it sound any better???
I'd be guessing that you are running a much lower va on that winding. You won't see voltage dips on a digital meter in any case. There is a reason for using a large va tx fir the servo section. It's greedy which is why the regs are getting warm!
With respect to the servo clock, you need half of the system clock if your clock can do it, you nee to send the feed to the xti or cki (clock in) pin. Check the device pin out at the start of the service manual.
@ben, id try reconnecting the servo to the original tx, disconnect the new tx from the mains and re test. Then connect the new tx to the mains only and re test. Then pair the tx output and re test. Then connect the centre tap to gnd and retest......you get the idea!!!
I'd be guessing that you are running a much lower va on that winding. You won't see voltage dips on a digital meter in any case. There is a reason for using a large va tx fir the servo section. It's greedy which is why the regs are getting warm!
With respect to the servo clock, you need half of the system clock if your clock can do it, you nee to send the feed to the xti or cki (clock in) pin. Check the device pin out at the start of the service manual.
@ben, id try reconnecting the servo to the original tx, disconnect the new tx from the mains and re test. Then connect the new tx to the mains only and re test. Then pair the tx output and re test. Then connect the centre tap to gnd and retest......you get the idea!!!