C17 and C18 are rail-to-ground, and should be omitted. However, you can squeeze in a bypass cap from rail-to-rail using one pad each from C17 and C18. I haven't bypassed C4, since I already have a very good film cap (Wima MKP10 or similar) at that location. There's no harm in trying an axial styroflex or similar to bypass C4 - any bypass at that location has to be more linear than C4 itself, which doesn't leave too many choices.
Myref with SMPS?
Has any one tried, or would any one care to comment about the possibility of using an SMPS with the MyRef?
The cost and space savings are quite significant, but I wonder if there would be any drawbacks?
I plan to bi-amp with 4 x linuxguru's 1.4 premium kits. The price of 8 x PS caps + 2 x 225VA transformers is about $260AUD from RS Components. (+ soft start if required)
I can get a single 300W SMPS from Connexelectronic for $55......
Edit: I'm not overly concerned about the cost and am almost inclined to go with the transformer setup regardless, just to keep it as close to Mauro's original design as possible. Would be interesting to hear some opinions though....
Has any one tried, or would any one care to comment about the possibility of using an SMPS with the MyRef?
The cost and space savings are quite significant, but I wonder if there would be any drawbacks?
I plan to bi-amp with 4 x linuxguru's 1.4 premium kits. The price of 8 x PS caps + 2 x 225VA transformers is about $260AUD from RS Components. (+ soft start if required)
I can get a single 300W SMPS from Connexelectronic for $55......
Edit: I'm not overly concerned about the cost and am almost inclined to go with the transformer setup regardless, just to keep it as close to Mauro's original design as possible. Would be interesting to hear some opinions though....
Last edited:
MyREF and the clones upto 1.3 all have the PSU built into the amp PCB. All that is needed is a transformer.
I think linux' 1.4 is similar.
I think linux' 1.4 is similar.
and foregoing the integrated star/audio ground, which has been properly designed.
And there we have it. After reading as many posts as possible in this thread, I figured AndrewT would be the one to set me straight regarding any potential issues with the power supply.
Thanks!!!
Is a soft start actually recommended in a MyRef system?
I get a half second hum if I turn on the amp with the volume up. It clears completely but is slightly annoying. I had assumed the relay components/system were supposed deal with this.
I get a half second hum if I turn on the amp with the volume up. It clears completely but is slightly annoying. I had assumed the relay components/system were supposed deal with this.
The relay circuit is supposed to delay connection to the speakers until the amplifier has stabilized. I get no hum or noise at all upon power up. Maybe your relay circuit is not working correctly.
Is there half-second hum after the relay clicks on? (Obviously, there should be no sound before the relay clicks on)
I'm unclear about the source of this hum in your setup, but I haven't encountered it in any build so far, V1.2 to V1.4. What are the trafo specs, and the main PSU caps? Is the relay a Goodsky or Omron?
Thanks Guys, I think I got my answer. I went back to my messages from Uriah and found his suggestion that the Lighter Note may need a jumper to earth ground. As I still haven't mounted this system in a metal case, it's quite possible that jumper will solve the problem.Again, the momentary hum does not effect the amp output - just a minor annoyance. I'll report back after I finish the chassis,.
Thanks for the confirmation messages.
Thanks for the confirmation messages.
I am building a 4 channel amplifier powered by two separate toroids of 25-0-25v around 100-150W each. Both transformers are powered via the same fuse built-in into the IEC. The fuse always blows if all channels are powered at the same time. If only one pair of amps are powered using one toroid then the fuse survives a few trys (transformer produces a soft hum for less than a second in this case). I tested each amp separately and every one of them worked just fine independently. Since there is no soft-start built in into the circuit what should be the rating on the power line fuse? Any suggestions are welcome. Thanks!
Try using an inrush-current limiting thermistor in series with each trafo on the primary side. This current surge is most probably being caused by the initial inrush charging current into the secondary filter caps, reflected by the trafos to the primary side. The reason the fuse doesn't always blow is that it depends on the point in the cycle when it is switched on - if it happens near zero-crossing, then the cap may charge without blowing the fuse.
Last edited:
That's a good idea. What should be the cold resistance of current limiting thermistor? Will 2.5 or 5 ohms work?
Here is one group with a well develop in-rush delay for Toroidal transformers.
http://www.diyaudio.com/forums/grou...tart-toroidal-transformers-3.html#post2601069
This is another option I was look at but did not try yet.
http://www.amperite.com/assets/Documents/st1.PDF
They run about $35 for the relay. You need to select the relay most appropriate for your use.
I would also suggest you add in a relay to delay the power to your circuits until the soft start is completed, then turn on DC power to your amp circuits.
If you have a dead PC SMPS lying around, pull out the thermistor and check - I think about 10 ohms cold is the typical value for SMPSes up to 300W (which should be fine for a 2-channel MyRef), but it may be lower for higher powers. A CL60 isolator/thermistor may do the trick.
After building one monoblock and failing to figure out why was it producing a loud hiss. I decided to build the other monoblock hoping this one will work like it should. Well, I must have the worst luck because it is doing exactly the same thing as the first one I put together. I already tried all kinds of input leads, I tried testing the amps on a piece of wood. At this point I am certain it is not a shielding problem. I swapped out 8 different 318, I swapped out the 3886. I did notice a few things that are not normal, first the 3886 chip gets very hot just idling. I tried the NS318 and the TI318. Now the strange this is that the TI318 powers up the relay without any input signal. The NS318 will not power up the relay unless I connect a signal to the input. Also I am getting 2.48 volts between Vout and VGND. Anyone have any suggestions?
- Status
- Not open for further replies.