more smps

[ed]

didn't want to tack this on the end of the previous smps thread as it's a different subject.....

moving on from PB's series connected cisco supples, whereby he cut the earth because it was connected to the negative output, and thus caused a short if connecting 2 in series........

can anybody who has the metal caged variety tell me if the metal cage is connected to output negative?? I know there is an earth terminal where the mains terminals are located, which I don't intend to use...but if the metal body is connected to output negative it's more trixy to implement a truly floating supply.....The ones I intend to buy are quite expensive so I thought I'd cover this one before I fork out the dosh......I'm terriifed of this project as it's already cost me £150 in wasted transformers....

it's very hot this afternoon and perhaps my brain has shutdown, causing a stupid question....feel free to abuse me if that is the case.

[IslandPink]

On the contrary this is a very good question Ed, and while I can't advise you, I am very interested in the answer . I assume the 'cage' is connected to mains earth ?
The laptop ones only have two input wires, so I am assuming ( but could ask this question ) there's no problem in having the output conections sat at 50 to 100V ?

[davebms]

[quote="ed"]didn't want to tack this on the end of the previous smps thread as it's a different subject.....



can anybody who has the metal caged variety tell me if the metal cage is connected to output negative?? I know there is an earth terminal where the mains terminals are located, which I don't intend to use]

on my 2 no its not ,,, the mains earth term is.. tested with fluke on diode
test,,ie beep beep or not

[Nick]

On the ones I have used, the case is connected to the earth point, but both the input and output are floating WRT it.

RS: 680-2815

[ed]

thanks chaps that sounds encouraging.....

I was going to feed Rod Coleman's board with a 12v 12a or 15a version. As he always recommends grounding down the positive leg it might have been unsatisfactory if the negative was connected to the case and the case was bolted to the chassis.......

I might even try the raw 12v into the ecc82/83s.

If this works I might try it with one of my 2A3s as I have a couple of Rod's low power kits lurking in a bit box somewhere. The 5v 5a smps seem to be readily available.

I hope this will be much the same as the RS version:

http://www.ebay.co.uk/itm/Universal-DC- ... vi-content

[Dave the bass]

The laptop ones only have two input wires

Not that clear cut IME TBH Mark, Dell and others sometimes use a 3 core mains i/p cable. The screening case is then usually tied to mains earth in the few we've had through the 'shop that we've used on various jobs.

Floating o/p has caught me out a few times. I once used an old Iomega Zip drive (remember them...?!) 5V SMPS to supply a bass headphone amp/FX pedal/looper I used to jam with at lunchtimes. That 5V sat on approx 40V AC... I got a tingle when I touched the bass strings and any earthed or class 1 appliance!

DTB

[IslandPink]

Thanks Dave for the heads-up.
The Sony one ( which I'm most likely to use ) definitely has two input connections, it has a removable mains lead with one of those small '8'-shaped mains plugs .
I should check what the Dell one does -
I wonder what is the easiest way to check ?
Would it be as simple as testing continuity from the plug earth wire to the outer braid on the output wires, I wonder ?

[ed]

aha!

I might finally be getting somewhere with sv572 dc heaters.

I was orginally looking for a direct connection between smps and filament but after 6 months I gave up looking for 6v at 8 amps.....so I opted for 12v 12amps into the Coleman boards which I had been using previously.

The smps arrived from hong kong this morning so I wired one up straightaway. I've been calibrating the Coleman units with a 25w motorbike bulb before committing a valve, which is what is glowing in the picture. I'm pretty pleased so far....after 30mins the smps is the same temperature it arrived at....exactly 6v across the bulb..1mv ac at the bulb..exactly 11.7v across the board input....the heatsink is just cosy......the maplin monitor says 53 watts at the wall socket so 25 watts in the bulb means 25 watts lost through the heat sink........

I was reluctant originally cos the only 12v smps I could find were £30...these were £6 so if they sound as good as they promise then Rod's elaborate dc power supply with its ourageous transformer requirements and high current caps might be redundant.

so far I'm a happy bunny, now to put the breadboard back together and have alisten

[pre65]

so far I'm a happy bunny

Well that is good to hear Ed.

[ed]

more entertainment from planet 811/572..I am good to you guys....

version number 6, back on the board. I seem to have my mojo back as the aikido gain is now consistently 37. Same circuit but new components with the same valves, and obviously smps heating. Doesn't seem like anything in there to make the aikido jump from gain of 30 to gain of37....except I measure both input and output on the UNI-T scope....mmmmm

the smps have voltage adjustment which is adequate but tricky because they are very sensitive adjusters. I connected the coleman boards and the sv811s before finally adjusting for 12v out of the smps for the 12ax7 and 12au7s. I then calibrated the coleman boards for exactly 6.3v into the 811s.

ran just the heaters yesterday for 4 hours and the sinks got hot(not worryingly) and the smps got warm.

At the maplin wall meter the smps consume 140 watts. The amp consumes 74 watts.

heres the question for the experts...

I have floated the smps just to be sure..remember I asked about dc output connections to ground and Nick said his version had no connection.I checked these for any coninuity and there is no connection between the DC outputs and the earth terminal/case..well, In the config shown the mains earth is not connected at the moment and all is running ok....
except....there is 31v ac between the earth terminal/case and mains earth... Anybody any ideas why this might be.

so far so good...there is 2mv ac at the output and the aikido wave flattens at the bottom at about 3.7 watts at the output...going to have a listen this afternoon, fingers crossed

[James]

Hi Ed,

SMPS tend to be quite "leaky" and this will cause the PSU ground to lift if not connected to the mains (safety) ground. I think you will need to connect the earth for the EMC filter (Y) capacitors to function correctly

It may be worth checking outs Rod's comments on powering his regulators from a SMPS here:-

http://www.diyaudio.com/forums/tubes-va ... er-59.html

I have 2 of Rods regulators running in parallel to supply 10v/10A for 833a and these will be fed from a SMPS.

I just think there are some things to look out for. Some of the SMPS I have looked at put a Cap between the primary and secondary grounds. I am thinking about removing this. More thought needed.

Best Regards,

James.

[James]

Post 590

[pre65]

I have 2 of Rods regulators running in parallel to supply 10v/10A for 833a and these will be fed from a SMPS.

James.

Ooh, tell us more.

[ed]

Eureka!

It was over 6 years ago that I first put together a sv572 and thought I'd discovered nirvana.....the hum and the heat got to me and I tinkered....and tinkered....and tinkered.....sometimes the hum was less, sometimes more...... sometimes the heat was less, sometimes more...never recreated that magic that was present the first time I put it together...a/c heating, auto bias, cheap this and that..

I spent lots of money having transformers wound to try and satisfy the coleman board's insane desire for current.....I very nearly gave up....

today I may give up, but for different reasons...

Now then.....Pay attention at the back.....

no hum or buzz..fostex 206 inky black!!!...HT transformer cold and quiet! .... smps warm to hot - no problem.....coleman sinks hot - no problem.

spent 2 hours listening......drum kit rhythms..wow!!! rides now ring and ting instead of shhhushhing I can hear the beat(start and stop)...bottom end is tight, even with an underdamped pair of speakers....also starts and stops revealing rhythms that were hiding....

I have what I thought was a very good example of a magical 2A3, but it's no longer the yardstick......the king is dead, long live the king!

I'm just pondering about photographing the previous power supply line up that amounts to about £75, involves lots of messing about, not to mention loadsa angst.........in the end it doesn't work!! £12 of smps leaves nothing wanting.

rave on rave on....Mr business man, you can't dress like me...

diet: I forgot to mention....there was 7mv at 27khz on the dc exiting the coleman unit but it didn't seems to affect the audio...no other ac detected.
my measure is the inky black on the 206s...might write a song about it, It was probably easier finding the northwest passage than inky black on sv572.

[Cressy Snr]

Nice when you hit that sound you just know is right.
I was like that with the KT120 push pull......then they updated iTunes.

I need another music player.

Is this the big purple coloured amp you're talking about here.
The breadboard version of this amp IIRC was bloody good