I would like to use the parts I have for DIY PSX, I have 25v & 35v Toroidal transformers. Below is the schematic I intend to use. My questions are
- 25v toroid will give me 35v DC, which is less than the original transformer voltage inside the Cyrus 2, and 5v less than PSX, will it be a pointless exercise building an external power supply like this?
- 35v Toroid will give me 50v DC, which is 10v more than supplied by PSX, will it blow the Cyrus 2?
Option 1 may work OK but make sure you have sufficient voltage headroom for the linear regulators for the preamp. The amp will run cooler and be more reliable. Check and adjust bias current if needed.
Option 2 will decrease reliability and may cause heat issues with linear regulators (you also need to check they can operate with the higher voltage differential across them) and it will noticeably increase dissipation in some areas of the power amp such as the voltage amplifier stages and of course the output transistors. I would have to say not recommended really. You also need to check any cap voltages that might be exceeded.
Bear in mind the voltages from the transformers will be higher than specified at low loading (amp idling and normal low power output). The secondary voltages are quoted at max loading. and you must figure in the regulation factor (a percentage given in the data sheets) to see what the increase will be.
Also a 230 volt toroid will have higher output on UK mains that could be in the 245 volt region at times.
Simple answer... get a 30 volt toroid 🙂
Option 2 will decrease reliability and may cause heat issues with linear regulators (you also need to check they can operate with the higher voltage differential across them) and it will noticeably increase dissipation in some areas of the power amp such as the voltage amplifier stages and of course the output transistors. I would have to say not recommended really. You also need to check any cap voltages that might be exceeded.
Bear in mind the voltages from the transformers will be higher than specified at low loading (amp idling and normal low power output). The secondary voltages are quoted at max loading. and you must figure in the regulation factor (a percentage given in the data sheets) to see what the increase will be.
Also a 230 volt toroid will have higher output on UK mains that could be in the 245 volt region at times.
Simple answer... get a 30 volt toroid 🙂
Hard to say. There will almost certainly be some HF noise (ripple) on the rails which is very hard to remove without adding dedicated filtering such as a combination of L/C and R/C networks.
Its an unknown tbh although there is nothing wrong with correctly designed and implemented SMPS. You also have to think of long term reliability if you are building it as a one off project. Plus points should be no 50./100Hz hum issues or mechanical buzzing noise.
Its an unknown tbh although there is nothing wrong with correctly designed and implemented SMPS. You also have to think of long term reliability if you are building it as a one off project. Plus points should be no 50./100Hz hum issues or mechanical buzzing noise.
Interesting. I have Smartpower+. I would like to get PSX also to my Cyrus. Is it realistic to assemble?
I have used the SMPS linked above, however there was no discernable difference in sound quality. The 40v supplies were sagging under load to 37.6v.
The answer to your question is it is doable.
HTH
The answer to your question is it is doable.
HTH
I meant to say, I have tried the smps, I have linked in post number 5 and did not notice any change in sound.
Smartpower +, if it gives +/- 40 v will not harm your Cyrus 2. Whether you like the sound is for you to decide.
Here is the link for the connector you need to use should you decide to go ahead
https://uk.rs-online.com/web/p/industrial-circular-connectors/7389041
Smartpower +, if it gives +/- 40 v will not harm your Cyrus 2. Whether you like the sound is for you to decide.
Here is the link for the connector you need to use should you decide to go ahead
https://uk.rs-online.com/web/p/industrial-circular-connectors/7389041
I have used a 2x30v 500VA transformer and a Chinese capacitor board from eBay with good results. To me it sounds like a different amplifier. It was well worth the effort.
Waiting for a case to arrive for safe installation now.
Waiting for a case to arrive for safe installation now.
I am still playing with the power supply, using an old NAIM 135 clone voltage regulator board, I have set the power supply to exactly +/- 40V. There is further refinement in sound, could be user bias.
I wish I had instruments or know how to objectively measure this effect!
I wish I had instruments or know how to objectively measure this effect!
Attachments
I'm always a bit skeptical about power regulator boards.
Not because they don't work, it's just that I view a power amplifier as a voltage controlled PSU: Look how similar your regulator board is compared to a regular power amplifier 🙂. They sort of do the same thing.. just one is controlled by an audio signal.
My own viewpoint is that the currents through the main output devices (in solid state anyway) should be fed by a different path than the rest of the amplifier.
Then the driver section (low current draw) can be regulated if needed, and remains unaffected by the voltage sag inherent on the supply rails from the music. Perhaps that's what the PSX does, I don't know. Certainly the 30,000uF per rail they throw at it (see schematic) smacks of desperation, not saying it's bad, just excessive in a good design, and other design issues come first IMO.
On the subject of Cyrus, I had a Cyrus One of similar vintage, and replaced it with some (Maplin lateral MOSFET based) monoblocks with huge isolated MOSFET supplies (as mentioned above) and it blew the Cyrus away - which was rapidly sold afterwards.
I think the money concentrates on transformer, main caps and perhaps output transistors, and most commercial amplifiers appear to have saved quite a bit of 'peak current capability' - which depending upon speakers perhaps, seems to make them a bit weedy as stock (weedy as in thin and feeble - not like weeds in the garden that seem to thrive LOL!). They also appear to embrace the boring an IMO inadequate GlobalNFB loop, I'd far prefer to see something a bit more imaginative, such as current drivers outside of the loop.
There's also a rule of diminishing returns, so perhaps I'd not mod the Cyrus too much, but probably better and bigger caps, watch the diodes and input fuses though, if no soft start - and bypass any electro caps with film caps, package the PSX addition nicely - but at that point perhaps it's at it's limit.
Not because they don't work, it's just that I view a power amplifier as a voltage controlled PSU: Look how similar your regulator board is compared to a regular power amplifier 🙂. They sort of do the same thing.. just one is controlled by an audio signal.
My own viewpoint is that the currents through the main output devices (in solid state anyway) should be fed by a different path than the rest of the amplifier.
Then the driver section (low current draw) can be regulated if needed, and remains unaffected by the voltage sag inherent on the supply rails from the music. Perhaps that's what the PSX does, I don't know. Certainly the 30,000uF per rail they throw at it (see schematic) smacks of desperation, not saying it's bad, just excessive in a good design, and other design issues come first IMO.
On the subject of Cyrus, I had a Cyrus One of similar vintage, and replaced it with some (Maplin lateral MOSFET based) monoblocks with huge isolated MOSFET supplies (as mentioned above) and it blew the Cyrus away - which was rapidly sold afterwards.
I think the money concentrates on transformer, main caps and perhaps output transistors, and most commercial amplifiers appear to have saved quite a bit of 'peak current capability' - which depending upon speakers perhaps, seems to make them a bit weedy as stock (weedy as in thin and feeble - not like weeds in the garden that seem to thrive LOL!). They also appear to embrace the boring an IMO inadequate GlobalNFB loop, I'd far prefer to see something a bit more imaginative, such as current drivers outside of the loop.
There's also a rule of diminishing returns, so perhaps I'd not mod the Cyrus too much, but probably better and bigger caps, watch the diodes and input fuses though, if no soft start - and bypass any electro caps with film caps, package the PSX addition nicely - but at that point perhaps it's at it's limit.
A good power amplifier has enough PSRR to reject mains hum from the rails without needing regulated supplies. And the drivers ideally need more voltage, not less than the outputs, so regulating down for the drivers would simply throw away headroom as the regulated voltage would have to be less than the sagged rail voltage by a volt or two anyway.
The "boring" and "inadequate" global feedback does the job well, imagine all you like bettering 0.001% distortion in a power amplifier will involve use of feedback as its the tool that does the job. It may bore you, but its not inadequate. Guess what's used in those Maplin monoblocks?
The "boring" and "inadequate" global feedback does the job well, imagine all you like bettering 0.001% distortion in a power amplifier will involve use of feedback as its the tool that does the job. It may bore you, but its not inadequate. Guess what's used in those Maplin monoblocks?
Absolutely, designing to cost is how most commercial amplifiers are done, otherwise they'd go out of business. That is why SMPS and class D are the mainstream now.
If the higher voltage toroid is not potted you can remove turns. Or not depending on the construction 🙁
The PSRR is not just for mains hum, stick a scope probe into the supply rails and you'll see the music playing 🙂
Agreed, drivers can need more voltage, and even a seperate bridge rectifier can do this as the main supply rail voltage can dip quite a few volts when driven hard.
My view on GNFB is that it is usually used on a non-linear system, so it tends to simply move the distortion up the frequency scale. NFB doesn't need to be global, to reduce phase margin errors it really needs a fast amplifier - and always the seperate stages will be faster than the whole.
Opamps and chip-amps - being tiny inside, often IMO sound better simply because they are faster so the GNFB works better.
0.001% distortion is good, yes. But perhaps the discussion of THD relative to sound quality should be deferred to Lynn Olsen's writings on this, in which he goes into some depth 🙂
http://www.nutshellhifi.com/library/FindingCG.html
My own experience bears out Lynn's viewpoint, high GNFB amplifiers have for me a very 'small', 'confined' sound that I'm not really a fan of, and then of course there's stability issues too - 'solved', but still hiding behind the scenes. Just my viewpoint of course 😀
Agreed, drivers can need more voltage, and even a seperate bridge rectifier can do this as the main supply rail voltage can dip quite a few volts when driven hard.
My view on GNFB is that it is usually used on a non-linear system, so it tends to simply move the distortion up the frequency scale. NFB doesn't need to be global, to reduce phase margin errors it really needs a fast amplifier - and always the seperate stages will be faster than the whole.
Opamps and chip-amps - being tiny inside, often IMO sound better simply because they are faster so the GNFB works better.
0.001% distortion is good, yes. But perhaps the discussion of THD relative to sound quality should be deferred to Lynn Olsen's writings on this, in which he goes into some depth 🙂
http://www.nutshellhifi.com/library/FindingCG.html
My own experience bears out Lynn's viewpoint, high GNFB amplifiers have for me a very 'small', 'confined' sound that I'm not really a fan of, and then of course there's stability issues too - 'solved', but still hiding behind the scenes. Just my viewpoint of course 😀