The switched PSU chirps

To all participants of the "green" offer made at Rockgrotto forum.

As I've stated above, all SM-PS plug top power supplies produce noise. The very idea of forcing a distorted squarewave through an inductor, which in the simplest of terms is what these EU preferred SM-PS do, causes ringing. If I did replace an SM-PS I would be in effect dealing the same card again. This will be the case where I have exchanged the three units so far because although they may be slightly quieter in two weeks of testing, they may also result in the same noise, which is within reason IMO when compared to similar SM-PS sold by other manufacturers. The "green" offer was made based on a product pilot and that means each unit was effectively a prototype. Each person taking part paid me for the value of the parts and labour without any profit, and obtained a good experimental amplifier using a "green" technology power supply. I had voiced my opinions about such power supplies on numerous threads at the forum where the offer was made. The offer was made to members only of that same forum. The offer wasn't made anywhere else because to do that could have been to mislead, for such people would not have been able to read my views (or should I say: I could not be certain that non-members would not be conversant with my views). Therefore my conclusion is that all those who partook of the offer were aware of the limitations of the SM-PS?

If each person who took part is now going to expect a replacement SM-PS or other satisfactory replacement after explaining the gist of that offer, I would think that was against the spirit of the offer. However, if it could be shown that even after stating that this was a product pilot, I have been in error with this offer, then it may take me a few years to replace each power supply because the average cost including shipping will be in the region of 30 GBP each. With over 100 of these offers having been taken up all around the globe the cost will therefore be in the region of 3,000 GBP. Apart from the final few "green" Solo's, I did the offer out of my own pocket, so that will mean I personally would have to pay some £3,000 out of my own pocket. People reading this may think I would find that easy, but unfortunately that isn't the case on my salary.

I have placed the above on record here for all participants of the offer to decide whether I forfit 3,000 GBP of my own income or whether they accept that it was part of the bargain? Fair?

As for an alternative, any half decent DC supply capable of supplying 24 volts (nameplate rating) to 35 volts (measured offload maximum) DC at 250mA or above will power the "green" Solo. As these units are comparatively cheap, users may find they can try a few and post their thoughts.

For anyone wanting to upgrade their "green" Solo to a PSU1, this would only be a good idea if the output stage bias resistors are changed to value 1k6. We will not be offering this service so it will be a DIY decision. I will publish information about this modification shortly.

I feel I must now announce that the "green" Solo offer is now suspended for the reasons as set out above.

dc2 wrote: Graham, Tried a Mascot 2183, 24VDC 1A linear regulated PSU (centre +ve) PDF document Measured offload voltage 23.752 volts LED barely lit no sound output? 250mv? what's wrong? # 0110-010

Does it still work with the SM-PS?

Maybe the DC plug isn't making good contact?

The little socket on the end of the wire can be problematic on these things - if we use them we squash or bend the pins on the DC plug part to ensure good contact, but be careful...

Another thing: Manufacturers often kindly protect metal parts from corrosion without thinking it also impedes electricity. We have to degrease some of the DC plugs we buy (and a sod it is too).

None of these things may apply to you dc2, but they could be of benefit to others.